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Corso di laurea magistrale in ANALISI E GESTIONE DELL’AMBIENTE
A PRELIMINARY STUDY FOR THE QUEST, RETRIEVAL, AND DISPOSAL OF WILD
BOAR CADAVERS AT THE ONSET OF AN AFRICAN SWINE FEVER EPIDEMIC
Tesi di laurea in MONITORAGGIO E PIANIFICAZIONE DEL TERRITORIO
Relatore
Prof. DINO SCARAVELLI
________________________________
Correlatore
Dott. CARLO VITTORIO CITTERIO
________________________________
Controrelatore
Prof. CRISTIAN TORRI
________________________________
Presentata da
ROBERTO CELVA
_______________________________
Sessione Unica Anno Accademico 2022/2023
A preliminary study for the quest, retrieval, and disposal of wild boar cadavers at the onset of an African Swine Fewer epidemic
Celva Roberto | Environmental Assessment and Management | 2022-23
SUMMARY
1. INTRODUCTION .................................................................................................................................................. 1
1.1. WILD BOAR ......................................................................................................................................................... 1
1.2. AFRICAN SWINE FEVER (ASF) .................................................................................................................................. 3
1.2.1. Aetiology and symptomatology ................................................................................................................... 3
1.2.2. Biological cycle ............................................................................................................................................ 4
1.2.3. Epidemiology in WB ..................................................................................................................................... 6
1.2.4. Distribution in Europe .................................................................................................................................. 7
1.3. STRATEGIES AGAINST ASF IN THE WILD .................................................................................................................... 11
1.3.1. EU legislation ............................................................................................................................................. 11
1.3.2. Zoning ....................................................................................................................................................... 12
1.3.3. Fencing ...................................................................................................................................................... 13
1.3.4. Wild boar management ............................................................................................................................ 14
1.3.5. Surveillance ............................................................................................................................................... 15
1.3.6. Handling and disposal of cadavers ............................................................................................................ 16
1.4. NATIONAL CONTEXT ............................................................................................................................................ 17
1.4.1. Wild boar population ................................................................................................................................. 17
1.4.2. ASF occurrence .......................................................................................................................................... 18
First reports of ASF in continental Italy ..................................................................................................................................21
1.4.3. Legislation and operational hierarchy ....................................................................................................... 22
1.4.4. ASF management strategy ........................................................................................................................ 25
2. AIM OF THE STUDY ............................................................................................................................................29
3. STUDY AREA ......................................................................................................................................................30
3.1. ENVIRONMENTAL CONTEXT ................................................................................................................................... 30
3.2. MANAGEMENT OF WILD BOAR ............................................................................................................................... 31
3.3. ASF PREPAREDNESS – CURRENT STATUS IN THE STUDY AREA ........................................................................................ 33
4. MATERIALS AND METHODS ...............................................................................................................................36
4.1. ENHANCED PASSIVE SURVEILLANCE ......................................................................................................................... 36
4.2. EXPECTED WILD BOAR MORTALITY FOLLOWING ASF INTRODUCTION ............................................................................. 37
4.3. SUPPORT FOR MANAGING CADAVERS IN THE FIELD...................................................................................................... 39
5. RESULTS ............................................................................................................................................................40
5.1. ENHANCED PASSIVE SURVEILLANCE ......................................................................................................................... 40
5.2. EXPECTED WILD BOAR MORTALITY FOLLOWING ASF INTRODUCTION ............................................................................. 43
5.3. SUPPORT FOR CADAVERS’ MANAGEMENT IN THE FIELD ................................................................................................ 45
6. DISCUSSION ......................................................................................................................................................47
6.1. ENHANCED PASSIVE SURVEILLANCE ......................................................................................................................... 47
6.2. EXPECTED WILD BOAR MORTALITY FOLLOWING ASF INTRODUCTION ............................................................................. 48
6.3. SUPPORT FOR CADAVERS MANAGEMENT IN THE FIELD ................................................................................................. 49
7. CONCLUSIONS ...................................................................................................................................................52
REFERENCES ...............................................................................................................................................................54
ANNEX 1: TRANSECTS FOR ENHANCED PASSIVE SURVEILLANCE IN PORDENONE EDR ...................................................62
ANNEX 2: FIELD NOTE FOR ENHANCED PASSIVE SURVEILLANCE ...................................................................................63
ANNEX 3: ZONING APPLIED TO ASF MANAGEMENT OF WILD BOAR IN ITALY ................................................................64
A preliminary study for the quest, retrieval, and disposal of wild boar cadavers at the onset of an African Swine Fewer epidemic
Celva Roberto | Environmental Assessment and Management | 2022-23
A preliminary study for the quest, retrieval, and disposal of wild boar cadavers at the onset of an African Swine Fewer epidemic
Celva Roberto | Environmental Assessment and Management | 2022-23
ABSTRACT
ASF is a potentially panzootic viral pig disease, which has recently affected the Italian territory with
multiple hotspots. According to the recent EU Regulation, immediate eradication measures must be
taken as soon as it is detected. As no vaccine or drugs are available against ASF, preventive measures
are crucial for disease management: in swine farms, these include depopulating, physically isolating
vulnerable holdings, contact tracing of animals and related products, and enforcing biosecurity
throughout the production chain. Outbreaks are managed by isolating the infected area, thus causing
extremely harsh socioeconomic effects on both individual farms and downstream economies,
exerted mainly by the restrictions applied on the commercialization of live swine and swine products.
A cornerstone of ASF prevention and management is the early detection and removal of viral
reservoirs: in Europe, this is mainly represented by the wild boar, whose management is considered
crucial for disease control: the measures to be implemented include the active quest and removal of
cadavers, an important demographic decrement, and the predisposition of an infrastructural network
for collecting, sampling and disposing of carcasses and cadavers.
Given the high resistance of ASFV, all these activities must be carried out observing stringent
biosafety measures throughout a precise territorial compartmentalization, requiring high level skills,
landscape expertise, coordination between different stakeholders, and the setup of an efficient
operational hierarchy.
The present work describes the setup of these measures in preparation of an ASF outbreak in
Pordenone EDR (ex-province), northeast Italy, and the main aspects to be considered for an efficient
management of wild boar and wild boar cadavers in case of ASF introduction. An overview of ASF
ecology and targeted legislation is given, in a view to draft a comprehensive framework of ASF
management in wild boar at an operational scale.
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1. INTRODUCTION
1.1. WILD BOAR
The Wild boar (Sus scrofa L., 1758) is an ungulate of the Suidae (GRAY, 1821) family indigenous to
Eurasia. Despite being the ancestor and a conspecific of the domestic pig, which is nowadays
distributed worldwide in both its farmed and feral (i.e. farmed animals reverted to a wild state) kinds,
the native form remains constrained to the Palearctic (Figure 1).
Figure 1: Distribution of wild boar in Afro-Eurasia (top left, IUCN data from KEULING & LEUS, 2023) and habitat suitability
model for wild boar in EU (data from ENETWILD-CONSORTIUM, 2022.) EPSG: 3857
The Wild boar is a generally sedentary social species which aggregates in family groups, whose mean
home range sizes is approximately 4.6±3.7 km2 (ENETWILD-CONSORTIUM, 2022). As the litter size is the
largest amongst ungulates (3-7 to 11-15 cubs, MASSEI & TOSO, 1993), local population densities show
a strong seasonality, ranging from 2.7±2.7 individuals/km2 in winter, to 28.4±25.7 individuals/km2 in
summer (ENETWILD-CONSORTIUM, 2022). Generally, sexual maturity occurs within the 10th month in
males, and a couple of month later in females (MASSEI & TOSO, 1993), with farrowing peaking during
winter and early spring (JORI ET AL., 2021). However, as both fecundity and fertility in females are
related to body mass rather than age, population productivity is constrained by environmental
factors, such as water and food availability, and winter temperature (JORI ET AL., 2021; PITTIGLIO ET AL.,
2018); thus, favourable conditions (e.g. warm winter, mast years) often coincide with earlier maturity
(e.g. 23% fertile females as young as 9 - 12 months old) and bigger litters (PIOL ET AL., 2022). Oestrus,
which normally takes place between November and January, is also environmentally modulated, so
that female reproductive season can extend all year round, allowing for the production of two breeds
per year (MASSEI & TOSO, 1993, but see also PIOL ET AL., 2022), and yearly population growth possibly
exceeding 200% (KEULING ET AL., 2013). Yearly natural mortality is often assumed to be approximately
10% (GUBERTI ET AL., 2022), raising to 15% if roadkill are included (TOÏGO ET AL., 2008).
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The wild boar population structure is generally reflected in the hunting bags, comprised by 50-60%
of piglets (< 1 year old), 20-30% of subadults (one and two y.o.), and 10-20% of adults (≥ three y.o.).
Such a population structure is often itself a consequence of the hunting policies.
Figure 2: Wild boar population density as estimated in PITTIGLIO ET AL., 2018. EPSG: 3857
Wild boar is an opportunistic omnivore, whose diet include both plant and animal matter (PAOLUCCI &
BON, 2022). Feeding occurs mainly through rooting, by which animals search for underground food
sources such as plant roots, fungi or soil fauna.
During the past century, different factors have concurred to increase the size of both wild boar
population and potential habitat throughout its distributional range, leading to an overall
demographic increase in most EU countries (KEULING ET AL., 2013; MASSEI ET AL., 2015); notably:
1. Climate warming, which allowed wild boar to settle in previously unoccupied habitats (VETTER
ET AL., 2015);
2. the development of industrial agriculture, that provided local populations with additional
feeding resources (GUBERTI ET AL., 2022; JORI ET AL., 2021);
3. measures to increase hunting productivity, such as reintroductions, control of predators and
supplementary winter feeding (MASSEI ET AL., 2015).
Given its general confidence towards anthropogenic habitats, this species is often regarded as
problematic, especially for agriculture: negative impacts are exerted mainly through the rooting
behaviour, with direct damages to the topsoil and the root apparatus of cultivated plants. As a
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consequence, populations are generally heavily managed through culling campaigns and targeted
hunting; however, as these activities are often inefficient, local overabundance is frequently
observed.
1.2. AFRICAN SWINE FEVER (ASF)
1.2.1. Aetiology and symptomatology
ASF is a viral disease caused by a double-strained DNA virus (ASFV) of the Asfarviridae family, genus
Asfivirus (KING ET AL., 2011), affecting pig species of the Suidae family; these include all breeds of Sus
scrofa (both domestic and wild) and various African species, such as warthogs (Phacochoerus spp.),
bushpigs (Potamochoerus spp.) and the giant forest hog (Hylochoerus meinertzhageni) (Figure 3).
Although all Suidae taxa can be infected, the disease manifests clinically only in Sus scrofa (SÁNCHEZ-
VIZCAÍNO ET AL., 2012): common symptoms include high fever, anorexia, vomiting, diarrhoea and
respiratory complications, leading to haemorrhages and neurological disorders, and finally death
(ARIAS & SANCHEZ-VIZCAINO, 2008).To date, twenty-four viral strains are acknowledged (QU ET AL., 2022),
with genotype-specific pathogenicity and clinical characteristics (namely, mortality, morbidity, case
fatality ratio), which varies greatly between strains.
ASFV Genotype II, which is currently circulating in the EU (see Distribution in Europe), is characterized
by a very high case fatality (i.e. the proportion of infected individuals that die within a certain
timeframe, THRUSFIELD ET AL., 2018), assessed at 94.5-100% in both domestic and wild suids (GERVASI &
GUBERTI, 2021). Although estimates of prevalence (i.e., the proportion of infected individuals overall
the population, THRUSFIELD ET
AL., 2018) are hardly achievable
in wild populations, wild boar
demographic declines
exceeding 80% are attributed
to ASF (MORELLE ET AL., 2020).
However, as the contagiosity
of ASF is likely dose-
dependent, a high viral
transmission is bound to an
exposure of high viral loads, as
can be found in the bodily
fluids (blood, especially) of
infected animals; in situations
where exposure to bodily fluids
(e.g., high contact rate,
cannibalism) is avoided, ASF
transmission can be low
(CHENAIS ET AL., 2018).
Experimentally inoculated wild
boars develop clinical signs after an incubation period of 3 – 4 days, while virus shedding starts after
Figure 3: Some of the species targeted by ASFV: Sus scrofa (A: domestic pig; B: wild
boar); Phacochoerus africanus (C); Potamochoerus porcus (D). All images are CC0.
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a latent period of 2 - 6 days, leading to the death of all tested specimens in seven to nine days post-
inoculation (BLOME ET AL., 2012; GABRIEL ET AL., 2011).
ASFV is a very stable virus (MAZUR-PANASIUK ET AL., 2019): as its inactivation requires exposure to 60°C
for at least 20 minutes, it can survive in fresh, frozen, putrefied and cured meat, as well as inside the
lymph nodes and bone marrow of the few survivors, whose natural death and permanence in the
field as infected cadavers is likely to start a new disease hotspot (BELLINI ET AL., 2016; PENRITH & VOSLOO,
2009). At environmental conditions, the infectivity of biological tissues (spleen, kidney, lung) is highly
temperature-dependent, and spans from up to two years at -20°C, to 9-17 days at 23°C (MAZUR-
PANASIUK & WOŹNIAKOWSKI, 2020); viral survival and infectivity in soil has been shown to be negatively
impacted by acidic conditions (CARLSON ET AL., 2020).
1.2.2. Biological cycle
Depending on the presence of susceptible hosts, the characteristics of the pig production system,
and the availability of an arthropod vector, ASF life cycle can be ascribed to four different, although
non-exclusive, pathways (Figure 4).
1. Sylvatic cycle: prevalent in sub-Saharan Africa, where ASF is endemic in several countries
(BELLINI ET AL., 2016). It is sustained by argasid ticks of the genus Ornithodoros and the common
warthog (Phacochoerus africanus), which share burrowing sites. African suid hosts are mostly
indifferent to the disease.
2. Tick-pig cycle: described in parts of sub-Saharan Africa and during the early 60s and 70s
epidemics in Europe (BOINAS ET AL., 2011).
3. Domestic cycle: involved in the majority of oubreaks worldwide (PENRITH & VOSLOO, 2009); the
virus in transmitted exclusively amongst domestic pigs, both via direct contact, and via
contaminated porcine products, regardless of the arthropod host.
4. Wild boar-habitat cycle: characteristic of the current European outbreak, viral transmission is
both direct amongst wild boars, and indirect via the environment, which is manly
contaminated by infected cadavers.
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Figure 4: The biological cycles of African swine fever and main transmission agents. 1) Sylvatic cycle: the common warthog,
bush pig, and soft ticks of Ornithodoros spp. The role of the bush pig in the sylvatic cycle remains unclear. 2) Tick–pig cycle:
soft ticks and domestic pigs. 3) Domestic cycle: domestic pigs and pig-derived products (pork, blood, fat, lard, bones, bone
marrow, hides). 4) Wild boar–habitat cycle: wild boar, infected meat and contaminated habitat (CHENAIS ET AL., 2018)
The aforementioned life cycles represent adaptations of ASFV to the local hosts’ populations, at
various phases of its evolution: the virus is suggested to have developed in Ornithodoros ticks around
1.5 million years ago (FORTH ET AL., 2020), remaining endemic amongst tick and local suids, mostly
indifferent to the infection; the jump from African wildlife to disease-prone domestic pigs followed
the increase of local breeds, leading to the definition of a tick-pig cycle first, and the establishment
of a domestic cycle later; afterwards, the globalization of meat industry allowed ASFV to trespass
previously restraining geographical barriers, to leave the African continent, and to further spread in
Eurasian populations of domestic pig. The virus then gained the capability of surviving locally, often
without major involvement of the domestic pig population (SAUTER-LOUIS ET AL., 2021), by exploiting
the growing, free-ranging wild boar populations, and thus defining the wild boar-habitat cycle.
Although the wild boar-habitat cycle is independent of intermediate hosts, Ornithodoros ticks could
still play an important role where present. In fact, they can act both as a vector, and a reservoir, being
characterized by a long lifespan (up to 15 years), resistance to starvation and viral persistence (up to
5 years). However, their role in viral spread is considered negligible in most of Eurasia (EFSA, 2010).
The virus can spread either directly or indirectly: direct transmission occurs by close contact between
healthy and sick animals, whereas indirect transmission takes place through infective environmental
matrices (EFSA, 2014; PENRITH & VOSLOO, 2009), such as carcasses and offal, blood, faeces and urine,
oral/nasal excretions/secretions, soil, grass and crops, raw meat, food/kitchen waste, fomites (e.g.
clothes, tools, car tires), scavenging insects, hematophagous arthropods.
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Contacts between living animals and infected carcasses is a particularly important source of indirect
transmission, exerted mainly through specific behaviours such as sniffing, poking and cannibalism
(CUKOR, LINDA, VÁCLAVEK, MAHLEROVÁ, ET AL., 2020; PROBST ET AL., 2017) (Figure 5).
Figure 5: Wild boar (left) poking on the cadaver of a conspecific, likely feeding on diptera larvae. At the time the picture
was taken, the cadaver underwent six days of environmental degradation. Courtesy of IZSVe (ongoing research project
“RC IZSVe 06/22 - Deathboars”)
1.2.3. Epidemiology in WB
Typically, the spread of the ASFV amongst a naïve wild boar population follows four steps (Figure 6):
1. Incursion: is the introduction of the virus in a naïve population. It can occur either by natural
spread from a neighbouring endemic, or by the importation of viral particles from non-
adjacent territories. The former case is generally bounded to wild boar spatial behaviour
(namely, home range size and dispersal distance), and particularly to the movement patterns
of infected animals. The latter is mostly attributable to anthropogenic factors, such as
transport and disposal of infected meat or meat products (CHENAIS ET AL., 2019); in this case,
long distance “jumps” can be observed, which represent a major factor in ASF spatial
dynamics (PEPIN ET AL., 2020). Viral incursion is unrelated to population size and density.
2. Invasion: represents the initial successful spread of the virus. It is strictly dependent on
intraspecific contact, and is thus theoretically bounded to a host density threshold (Nt),
representing the minimum population density to sustain the spread. However, the resistance
of ASFV to environmental degradation sets this threshold virtually to zero, and makes a
reliable estimation practically unattainable (EFSA, 2018).
3. Epidemic: represents the progressive spread of the infection to the susceptible population.
At an early stage, the epidemic curve usually follows an exponential growth, whose shape is
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mostly determined by the basic reproductive number R0 (i.e. the average number of
secondary cases determined by one infected individual, during its entire infectious period, in
a fully susceptible population, DIEKMANN ET AL., 1990), which for ASF Genotype two averages
1.67±0.22 (LOI ET AL., 2022; MARCON ET AL., 2020). Naturally, the speed of the epidemic spread
ranges approximately from 1 km/month to 1 km/week (GUBERTI ET AL., 2022; LICOPPE ET AL.,
2023; PODGÓRSKI & ŚMIETANKA, 2018).
4. Endemicity: is local persistence of the virus. It is supported by the host’s critical community
size (CCS), which represent the minimum population size with which a pathogen has 50%
probability of fading out spontaneously (BARTLETT, 1960).
Figure 6: Hypothetical example of the four phases of the infection dynamic in a population of wild boar, measured through
the number of carcasses detected weekly (GUBERTI ET AL., 2022)
Due to ASFV lethality, both Nt and CSS are often unrealized in the leftover wild boar population;
however, the viral transmission can still be supported indirectly through the contaminated habitat.
The long lasting viability of the virus largely outmatches the lifespan of infected animals: in fact, the
role of cadaver-based transmission increases at decreasing population densities (PEPIN ET AL., 2020),
making it possible to the virus to persist at very low prevalence (usually around 1%, GERVASI & GUBERTI,
2021), even in scanty host populations.
1.2.4. Distribution in Europe
To date, ASF has been reported almost exclusively in Afro-Eurasian countries, the only exception
being the island of Hispaniola, where the virus has been reported in farmed animals; where both wild
and domestic hosts are present, ASF affected both populations almost invariably. ASF affected
countries based on WOAH case reports (https://wahis.woah.org/#/home, July 1st, 2005 – December
31st, 2023 data) is given in Figure 7.
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Figure 7 Afro-Eurasia and Indonesian countries affected by ASF in wildlife and domestic/farmed animals. Countries which
had been affected before 2023, but were not during 2023, are shaded, while countries affected during 2023 (Jan 01st-
Dec31st) are represented in bright tones. EPSG: 4326.
ASF is endemic in most countries of sub-Saharan Africa, where it was first reported in colonial Kenya
in 1921 (EUSTACE MONTGOMERY, 1921), and where the highest genotypic richness is currently found
(Figure 8).
In Europe, recurring Genotype I outbreaks have occurred during the second half of 1900; all of them
have been successfully eradicated, except in the Italian island of Sardegna, where it remained
endemic since 1978 (BELLINI ET AL., 2016; MUR ET AL., 2016) (see ASF occurrence).
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A second ASFV strain (Genotype II) is affecting
Eastern Europe since 2007 (BELLINI ET AL., 2016;
BLOME ET AL., 2012; GUINAT ET AL., 2014).
Compared to ASFV Genotype I, Genotype II is
more virulent and lethal, and appears to be
highly wild boar density-dependent (GUBERTI ET
AL., 2022). The European spread started from a
spill-over event, likely originating from
improper waste disposal by international ships
in the Georgian docks of Poti (BELTRAN-ALCRUDO
ET AL., 2008). During the first stages of the
epidemic, ASF infections were detected mostly
in domestic pig farms with generally low
biosecurity: arguably, the similarities with the
predominantly “domestic” Genotype I
outbreaks lead to overlook the role of wild
boar in sustaining the epidemiological cycle of
the virus (SAUTER-LOUIS ET AL., 2021).
After occasional spill-overs to the wild boar
population, ASF transmission pattern assumed
the characteristics of a typical wild boar-
habitat cycle (CHENAIS ET AL., 2018). During the
subsequent years, the epidemic wave moved
eastward affecting both farmed and wild
hosts, through the Caucasus and the Russian
Federation, with a pace ranging between 1
km/month to 1 km/week (GUBERTI ET AL., 2022). In 2014, ASF reached Lithuania and the EU borders,
where it currently represents a constant threat to the livestock sector (BELLINI ET AL., 2016).
To date, ASF has infected thirteen EU countries: Estonia, Lithuania, Latvia, Poland, Czech Republic,
Bulgaria, Belgium, Romania, Hungary, Slovakia, Germany, Italy and, on early September 2023,
Sweden. Among these, only two have achieved viral eradication: Czech Republic, which was declared
ASF-free in 2019 after 21 months from the index case (OIE, 2019), and Belgium, which regain ASF-
free status in November 2020 after 26 months of management (LICOPPE ET AL., 2023; OIE, 2020). In
both instances, ASF index case developed at more than 300 km from the nearest cases (SAUTER-LOUIS
ET AL., 2021), leading to ascribe the incursion to human transport. During December 2022, new
outbreaks have been reported in Czech Republic, which likely followed the epidemic wave coming
from Poland, while Belgium remains, to do date, ASF-free.
WOAH records for European ASF outbreaks in wild and domestic animals are represented in Figure 9
and Figure 10, respectively. Given that disease reports are the outcomes of voluntary surveillance
activities, the distribution of cases must be interpreted with caution.
Figure 8: Distribution of ASF genotypes in Africa and Europe.
Differently coloured roman numbers identify different
genotypes (overlapping labels in genotypically rich countries
have been removed). Data relative to Africa was obtained from
NJAU ET AL., 2021, while European data (December 2023) was
downloaded from WOAH webGIS at
https://wahis.woah.org/#/home. EPSG: 4326
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Figure 9: ASF outbreaks in wild boar (WB) in Europe (west to Ural mountains, 31/12/2023
data). Feature count is shown in square brackets in the map legend. Overlapping data.
EPSG: 3857
Figure 10: ASF outbreaks in domestic suids in Europe (west to Ural mountains,
31/12/2023 data). Feature count is shown in square brackets in the map legend.
Overlapping data. EPSG: 3857
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1.3. STRATEGIES AGAINST ASF IN THE WILD
1.3.1. EU legislation
All EU member States are members of the World Organization of Animal Health (WOAH), for which
ASF is as “notifiable” disease; this includes “transmissible diseases that have the potential for very
serious and rapid spread, irrespective of national borders, that are of serious socio-economic or public
health consequence and that are of major importance in the international trade of animals and animal
products” (OIE-WOAH, 2011 Art. 1.3.5.). WOAH member States can self-declare disease-free status
after one year of absence of the virus, as proved through monitoring (OIE-WOAH, 2011).
In the EU, REGULATION (EU) N. 429, 2016 (“Animal Health Law”, AHL hereafter) provides the structure
for prioritising and categorising diseases of Union concern. ASF is included amongst the five most
important listed animal diseases, which include ASF, classical swine fever, foot and mouth disease,
highly pathogenic avian influenza, and African horse sickness (AHL, art. 5). As a listed disease, ASF is
subjected to categorization, provided through IMPLEMENTING REGULATION (EU) N. 1882, 2018; ASF is
ascribed to three categories:
1. Category A: a disease that does not normally occur in the Union and for which immediate
eradication measures must be taken as soon as it is detected (AHL, Article 9(1)(a));
2. Category D: a disease for which measures are needed to prevent it from spreading on
account of its entry into the Union or movements between Member States (AHL, Article
9(1)(d))
3. Category E: a disease for which there is a need for surveillance within the Union (AHL, Article
9(1)(e))
As such, EU Countries must report ASF outbreaks to the EU Commission via a dedicated tool, the
Animal Disease Information System (ADIS) (REGULATION (EU) N. 429, 2016, Art. 22). Once ASF is
detected, the area should be declared as infected, and subjected to zoning restrictions as per
DELEGATED REGULATION (EU) N. 687, 2020, Artt.63-64-65 (see Zoning). IMPLEMENTING REGULATION (EU) N.
594, 2023 also include specific measures for ASF control, according to the zoning status of the area.
Based on the EU experience, the success of ASF eradication strategy highly depends on prevention
and early detection (BELLINI ET AL., 2016), and must consist of an integrated approach based on zoning,
population control, effective surveillance and removal and safe disposal of infected cadavers (EFSA,
2022); so far, none of this activity have single-handedly proven successful in stopping the viral spread
(LICOPPE ET AL., 2023). To carry on such an integrate strategy, an overall coordination amongst
stakeholders is essential throughout the process (LICOPPE ET AL., 2023).
To be effective, the management strategy must be timely and tailored to the epidemiological stage
of the disease (GUBERTI ET AL., 2022). As the large number of infectious individuals makes ASF
management a prohibitive task during the epidemic phase (GUBERTI ET AL., 2022), outbreak control
should be reached ideally during the incursion and the invasion phases. However, as the former (i.e.
the “patient zero”) is virtually undetectable (GERVASI ET AL., 2020), the very first finding of an infected
carcass is likely to mark the invasion phase, if not the onset of a latent epidemic, with a large number
of infected and undetected carcasses already present in the field (GUBERTI ET AL., 2022).
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Within 90 days from the ASF index case, the competent Authorities of affected member States should
draft national surveillance and eradication programmes to be approved by EU Commission
(REGULATION (EU) N. 429, 2016, Art. 31); this programmes should account for dedicated guidelines, as
provided in SANTE/7113/2015, REV. 12, 2020, and should include a including a risk analysis of viral
introduction.
1.3.2. Zoning
After the detection of the index case, and having assessed the spatial pattern of infections around
the index case through on the active search of wild boar cadavers (see Surveillance), three
“operational zones”, as per LICOPPE ET AL., 2023 (Figure 11), should be defined:
1. Infected area: an area in which positive carcasses are found, and in which all ASF containment
and eradication measures must be applied. This area must preferably be shaped according to
the presence of artificial or natural barriers, to slow the viral spread. It includes the area of
viral circulation, represented by a convex polygon around detected cases, plus a surrounding
area which should be at least double in “size” (GUBERTI ET AL., 2022).
2. White area: a wild boar-free buffer zone, where the quasi-extinction (non-viability) of the host
population should be looked forward
3. ASF free area: an external land strip in which usual hunting activities can be carried out,
improving hunting efforts (e.g. double the previous year’s hunting bag), and targeting adult
and sub-adult females
Inside the infected area, a restriction on non-ASF related activities should be imposed to minimize
the risk of spreading the virus through anthropogenic media, lifting the access ban only at the end of
the epidemic phase (JORI ET AL., 2021). Culling and trapping activities must be carried out avoiding
environmental exposure to infected biological ASFV matrices, especially blood, through the
displacement of wounded animals or bloody carcasses. Every wild boar inside the infected area,
either hunted or found dead, should be analysed for ASF, and thus be handled using stringent
biosafety measures.
In the EU, the establishment of the infected area following an outbreak in wild animals is due for all
AHL Category A diseases, (DELEGATED REGULATION (EU) N. 687, 2020, Artt.63-64-65); in addition, based
on the epidemiological state of a territory, a second regionalization scheme (“restriction zoning”,
Figure 12) is also provided. Restriction zoning aims at regulating activities in and around the infected
area, in particular the movement of animal and animal products, in a view to prevent the spread of
the disease to naïve territories and commercial activities (IMPLEMENTING REGULATION (EU) N. 594, 2023;
SANTE/7112/2015, REV. 3, 2019)
ASF affected territories are categorized into three Restriction Zones (RZs):
1. RZ I: ASF-free areas bordering with RZ II or RZ III
2. RZ II: areas in which ASF is found exclusively in wild boar
3. RZ III: areas in which ASF is found in domestic pigs, with or without cases in wild boar
Territories falling under these restriction zones (generally, at municipality level) are listed in Annex I
of Implementing Regulation (EU) n. 594, 2023, which is regularly updated to account for new
outbreak notifications and changes in the epidemiological situation of affected areas.
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Although restriction zones and operational zones may overlap, they pursue different objectives:
eventually, RZ II and RZ III will coincide with the Infected Area, and RZ I with the White area, thus
making the institution of the Infected Area a provisional measure. However, the maintenance of an
operational zoning system in parallel with EU zoning can facilitate the implementation of the ASF
response strategy (LICOPPE ET AL., 2023). An updated, interactive map on ASF restriction areas in the
EU can be found at
https://santegis.maps.arcgis.com/apps/webappviewer/index.html?id=45cdd657542a437c84bfc9cf1
846ae8c.
1.3.3. Fencing
In the context of ASF
management in wildlife, fencing
can be adopted to isolate
infected areas, and to facilitate
wild boar population
management, by hindering
animal movements. In
particular, the creation of the
“White zone” (see Zoning)
requires an intense effort to
prevent animal migration either
in and out the ASF-free area
(LICOPPE ET AL., 2023). “Ad hoc”
or "focal” fencing can be
implemented to increase the
fragmentation of the habitat, in
a view to slow down wildlife-
mediated ASF spread (JORI ET AL.,
2021).
Figure 11: Operational zoning
Figure 12: Restriction zoning
Figure 13: Fencing system around ASF cases in wild boar in Belgium (Jori et al.,
2021)
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To be effective, wild boar fences should provide an electrical shock, be buried at 50 centimetres
below ground, and be regularly checked for breaks and impediments to the electric flow (JORI ET AL.,
2021); as this is often too costly and too demanding to be implemented promptly, some compromise
can be considered: for example, above-ground wire fences facilitated ASF management in Belgium,
where approximately 300 km of 1.2 m high, unburied fences were laid down, resulting in
approximately 270 m of fence per km2 (Figure 13) (LICOPPE ET AL., 2023; ŠATRÁN, 2019). In fact, the
Belgian solution was a compromise between efficiency and rapid installation, as compared to electric
and buried fences, respectively. To further facilitate this operation, fencing could be carried out by
enforcing existing barriers, such as highways, large rivers etc.
Despite being highly recommended for ASF management, the use of fencing for wildlife disease
control is controversial, given to both scarce efficacy in containing indirect or human-mediated
spread, and to various adverse ecologic and economic impacts (MYSTERUD & ROLANDSEN, 2019).
1.3.4. Wild boar management
After the introduction, the invasion stage on an ASF outbreak is mostly sustained by direct
transmission; thus, the risk of developing an ASF epidemic in the wild could theoretically be
minimized by maintaining populations in ASF-free areas below the host density threshold. Similarly,
in areas characterized by an endemic persistence of the virus (which is mostly transmitted indirectly),
this threshold would be represented by the critical community size (see Epidemiology). However, the
resistance of ASFV to environmental degradation sets these thresholds virtually to zero, and makes a
reliable estimation of both practically unattainable (EFSA, 2018). Furthermore, considering the high
productivity of wild boar populations, such low numbers would probably be unreachable (GUBERTI ET
AL., 2022; MASSEI ET AL., 2015; REICHOLD ET AL., 2022).
Conversely, an overall demographic decrease of wild boar in ASF free areas is considered desirable
as a preventive measure (SANTE/7113/2015, REV. 12, 2020), aiming at slowing down an eventual ASF
spread in the future. This includes culling, possibly targeted on sub-adult (i.e., one to two years old
animals) and adult (≥ three y.o.) females (GUBERTI ET AL., 2022), avoiding supplementary feeding and
limiting attractive baiting (e.g. SANTE/7113/2015, REV. 12, 2020).
As the demographic growth of wild boar populations can exceed 200% per year, inducing a decrease
in the short term may require the removal of 65% of individuals from the local population (KEULING ET
AL., 2013). However, this would likely determine compensatory migrations from nearby regions, and
should therefore be implemented in a coordinated manner, possibly at a regional scale (JORI ET AL.,
2021). At this conditions, achieving a substantial reduction is often unrealistic (GUBERTI ET AL., 2022;
KEULING ET AL., 2016; MASSEI ET AL., 2015); however, this effort can be effective when applied in
conjunction with supplementary measures, such as zoning, fencing and trapping (GUBERTI ET AL., 2022;
JORI ET AL., 2021).
While a demographic decline of wild boar as a preventive measure against ASF is suggested overall,
improving hunting in disease-ridden areas is controversial (APOLLONIO ET AL., 2017); the reason behind
this lies in the operational aspects of killing, processing and transporting animals, which inherit a high
risk of human-induced viral spread through infected bodily fluids; moreover, hunting chases are likely
to induce dispersal of possibly infected animals towards ASF-free areas (PEPIN ET AL., 2020; SCILLITANI ET
AL., 2010).
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Therefore, the removal of animals for disease control should be strictly tailored on each ASF
management area, as identified through the process of zoning (see Zoning). At first, hunting and
feeding should be entirely banned inside the infected area, in a view to avoid viral spread; meanwhile,
an intense hunting effort should aim at creating an area virtually free of all wild boars around the
infected area (i.e., the “white zone”). Hunting practices should minimize animal movement; hence,
driven hunting should be avoided in favour of standing hunts overall the surrounding areas (KEULING
ET AL., 2008).
Once the virus has decimated most of the wild boars inside the infected area, an intensive hunting
campaign should pursue the elimination of all of the few survivors. Given that hunting only slightly
affects the high mortality induced by ASF (MORELLE ET AL., 2020), aids such as night visors and trapping
devices are often suggested and implemented (LICOPPE ET AL., 2023).
1.3.5. Surveillance
In the context of animal health, surveillance is the systematic and ongoing production of data related
to animal health and welfare, used to describe health hazard occurrence and to contribute to the
planning, implementation, and evaluation of risk mitigation actions (HOINVILLE ET AL., 2013).
As regard to ASF, surveillance is performed by testing dead animals, both domestic and wild.
Diagnosis for ASF is usually carried out by biomolecular (PCR) analysis on a spleen sample, but other
tissues (kidney, lymph nodes, tonsils, blood, or bone marrow) and tests (antigenic test, RT-PCR, ELISA,
immunoperoxidase) can be used, according to the state of the dead animal.
In wild boar, surveillance is carried out on animals which are either hunted (active surveillance) or
found dead (passive surveillance), with the latter strategy largely outperforming the former in terms
of efficacy (GERVASI ET AL., 2020).
To date, the vast majority of ASF outbreak in EU has been detected through passive surveillance
(EFSA, 2022). However, wild boar density and viral prevalence may be too low to provide the required
sample size (e.g. at the end of the epidemic phase): this can lead to overlook a latent endemic
situation, where wild boar demographic recovery give rise to re-emerging ASF cases. Therefore, a
combination of both active and passive surveillance is often required (GERVASI ET AL., 2020; NIELSEN ET
AL., 2021).
In a particular case of passive surveillance, cadavers are actively looked for (enhanced passive
surveillance, HOINVILLE ET AL., 2013). The scope of enhanced passive surveillance for ASF is twofold: it
provides data for epidemiological surveillance, allowing to adjust management strategies accordingly
(e.g. LICOPPE ET AL., 2023), while enforcing disease control through the removal of contaminating
sources; to this point, a delay in detecting and removing infected cadavers impedes the early
detection of the virus, thus favouring the development of ASF endemic contexts (GERVASI ET AL., 2020).
Therefore, enhanced passive surveillance is considered a pillar for the eradication of ASF in wild boar
(BOUÉ ET AL., 2017; GUBERTI ET AL., 2022; MORELLE ET AL., 2019; PROBST ET AL., 2017; ŠATRÁN, 2019).
To maximize surveillance outcomes, enhanced passive surveillance should target suitable habitats.
More than 80% of wild boars die in forests, suggesting that sick animals perceive this environment as
safe and comfortable (CUKOR, LINDA, VÁCLAVEK, ŠATRÁN, ET AL., 2020). Given the feverish symptoms
induced by ASF, moribund and dead infected animals are often found around cool and moist
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environments, near water bodies (MORELLE ET AL., 2019), in young broad-lived forests or in meadows
with significant vegetation (CUKOR, LINDA, VÁCLAVEK, ŠATRÁN, ET AL., 2020; PODGÓRSKI ET AL., 2020).
As for disease control, the quest for cadavers should aim to re-define the borders of the ASF
management area, in a view to promptly concentrate management efforts where most needed;
therefore, during the epidemic phase, enhanced passive surveillance should be focused inside and
around the infected area.
These activities should be sustained during both disease-free and escalation periods (GUBERTI ET AL.,
2022): given the effort they require, local authorities should well in advance identify dedicated
personnel, develop all the protocols for carcass testing, collection and disposal, and be ready to
promptly implement all of the strategies aimed at containing and extinguishing the virus.
Given the implications of manipulating, removing and destroying a possibly infected cadaver (see
Carcass handling and disposal), a definition of “suspect case” must be clearly stated; given the ASF
situation in Eurasia, however, it is largely considered that this definition should include “any found
carcass out of the context of hunting, including road killed animals and any diseased wild boar shot
for sanitary reasons” (GUBERTI ET AL., 2022; JORI ET AL., 2021). In practice, however, the definition of
suspect case is largely dependent on local governments, which must provide the logistics for
retrieving and disposing of each suspect case following adequate biosafety protocols (JORI ET AL.,
2021).
The reliability of the enhanced passive surveillance system can be measured through the number of
dead wild boar reported (GUBERTI ET AL., 2022): as natural mortality in wild boar (excluding roadkill) is
approximately 10% of the population (KEULING ET AL., 2013; TOÏGO ET AL., 2008), the report of 10% of
those is suggested as a threshold for an efficient passive surveillance (i.e. 1% of the whole estimated
wild boar population, GUBERTI ET AL., 2022).
1.3.6. Handling and disposal of cadavers
Once sampling for ASFV had occurred, all cadavers and carcasses coming from the ASF management
zone should be transported at a rendering plant using a dedicated truck (e.g., LICOPPE ET AL., 2023).
At the onset of an ASF outbreak, an intense effort should be spent looking for cadavers in the field,
which should be tested for ASF in a view to define the infected area (SANTE/7113/2015, REV. 12,
2020). Afterwards, ASF management strongly relies on wild boar depopulation.
Both the retrieval of infected cadavers, and the act of killing a possibly infected animal, pose a high
risk of spreading ASFV: to minimize this risk, all dead animals should be regarded as suspect ASF cases
until the diagnostic results are available, and therefore treated with strict biosafety measures both
during passive surveillance, and during hunting (GUBERTI ET AL., 2022).To this aim, all operators
involved in manipulating cadavers should be trained, wear disposable clothing and undergo
systematic disinfection at the end of the activities (LICOPPE ET AL., 2023). The use of private cars should
be avoided, dedicating trucks to be used exclusively inside the infected area or, whether not possible,
to be thoughtfully disinfected after each activity To avoid habitat contamination due to leakage of
bodily fluid, ASF sampling should be carried out in a controlled environment, where the dead animals
could be stored until diagnostic results are available. To this aim, intermediate collection point(s)
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between the killing ground/finding spot should be prepared, following biosafety protocols during the
transport of dead animals, using plastic or metal tanks to transport the body.
In intermediate collection points, animals should be stored in batches, and released only when the
entire batch is tested ASF negative. The equipment used for sampling and dressing should be
disinfected after each use, and not leave the dressing facility. Disposal of offal must be regulated, and
each hunting ground should be provided with one or more facility dedicated to animal dressing. Such
facilities should be placed on permanently dry soil, and should be fenced against scavengers and
unauthorized access. Water and a locked-up pit or container for offal and waste must be provided.
If transport of the dead animal is unfeasible, sampling can be provided on site, given that the area is
thoughtfully disinfected, and the remains disposed of on site and made unavailable to scavengers.
This can be accomplished either by incineration, local burning, single or mass burial (GUBERTI ET AL.,
2022) or composting (CARRAU ET AL., 2023).
Given the high mortality of ASF, the means for disposing of a large number of cadavers must be
prepared, especially in areas where wild boar population density is high. The logistics of disposal relies
on the road network for transporting potentially infected material to the appropriate treatment
plant, the availability of intermediate collection point(s), and the possibility of local disposal if
rendering is considered unfeasible.
1.4. NATIONAL CONTEXT
1.4.1. Wild boar population
Wild boar had been largely absent from the Alpine territories between the 17th and the first half of
the 20th centuries, persisting locally at a metapopulation state in central and southern Italy (APOLLONIO
ET AL., 1988); the recolonization of the peninsula begun in the 1920s (Piemonte region: Torino, Cuneo
and Imperia provinces) and the 1950s (Friuli-Venezia Giulia region: Udine province), proceeding from
bordering States, and was favoured by both climate warming, and the rewilding of marginal habitats
abandoned by humans (APOLLONIO ET AL., 1988).
Wild boar population size and distributional range have gradually increased during the second half of
the 20th century, favoured by massive restocking of eastern European animals for hunting purposes
(APOLLONIO ET AL., 1988; HAUFFE ET AL., 2007; PAOLUCCI & BON, 2022). At the national level, restocking of
wild boars has been banned only in 2015, while supplementary feeding is allowed exclusively for
controlled culling (LAW N. 221, 2015); nonetheless, although prohibited, supplementary feeding to
facilitate hunting is still a common practice.
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Currently, the Italian wild boar post-reproductive
population is estimated at a plausible minimum
of 1.5 million individuals (ISPRA, 2023, 2021
data); as its presence is reported in all Italian
regions (Figure 14) (PAOLUCCI & BON, 2022), this
species is the most widespread and abundant
ungulate on the National territory. Locally,
overabundance is often reported, representing a
threat to both natural and agricultural
ecosystems. As a consequence, its proliferation is
contrasted by most administration. As a game
species, the wild boar is hunted according to LAW
N. 157, 1992, art. 18, and as a conflictive species
is subjected to culling campaigns, which are
regulated by means of specific quadrennial plans,
as per LAW N. 157, 1992, art. 19. In the latter case,
both administrative personnel and private
hunters are involved in culling actions. During the
period 2015-2021, overall wild boar harvest
attributable to hunting and control activities
were calculated at 86% (1.8 mln) and 14%
(630000), respectively (ISPRA, 2023).
1.4.2. ASF occurrence
During the past century, Italy has been affected by multiple ASF Genotype I outbreaks, mostly linked
to anthropogenic introduction. While viral eradication was achieved in all hotspots developed in the
continental territory (DANZETTA ET AL., 2020), ASF Genotype I has been considered endemic in the
island of Sardegna from 1978, up until very recently (October 25th, 2023). The persistence of the
Sardinian hotspot was linked to traditional farming practices, frequently adopting free ranging of
domestic pigs (MUR ET AL., 2016), and it has been regarded as the last remnant of ASF Genotype I in
Europe.
In continental Italy, the first ASF National Surveillance and Prevention Plan (Piano di sorveglianza e
prevenzione in Italia, NSPP hereafter) was adopted in 2020, as a consequence of the progressive
expansion of the epidemic front in Eastern Europe (Figure 15), and in consideration of the risk
represented by anthropogenic viral spread. Although most sectors were subjected to restrictions due
to COVID-19 pandemic, the actions prescribed in the NSPP were deemed prerogative
(https://resolveveneto.it/wp-content/uploads/2020/02/Nota-MS-su-Piano-sorveglianza-
PSA_150420.pdf, in Italian), and lead to the detection of ASF index case through passive surveillance.
The ASF virus was first detected in Italy in a wild boar cadaver found on December 29th, 2021 in Ovada
municipality, Piemonte region (northwest Italy, Figure 15). The sample tested positive for ASF on
Figure 14: Wild boar population density in Italy (PITTIGLIO
ET AL., 2018). EPSG: 32632
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January 5th, 2022, confirmed as
ASFV Genotype II by the national
reference lab two days later, and
thus reported to EU Commission
and WOAH (ISCARO ET AL., 2022),
where the report was dated as
January 3rd, 2022. The Italian
index case was detected at
approximately 800 km from the
active epidemic front in Eastern
Europe, thus suggesting the
anthropogenic source of the
introduction (Figure 15). Since
then, three additional hotspots
developed in central (Lazio
region, 4th may, 2022) and
Southern Italy (Calabria and
Campania regions, April 27th and
May 5th, respectively).
Moreover, ASF Genotype II has been recently detected in a pig farm in Sardegna, and although the
outbreak has been declared resolved in January 2024 (https://wahis.woah.org/%23/in-review/5491),
the island could face further ASF developments (DEI GIUDICI ET AL., 2024).
Table 1: Summary of ASF Genotype II cases in Italy based on WOAH reports (Jan 23rd, 2024 data)
Hotspot
Region (NUTS 2)
ASF GEN II
INDEX CASE
ASF GEN II
LAST REPORT
N ASF CASES (22/01/2024)
WILD
DOMESTIC
TOT
PL
Piemonte
05/01/22
10/01/24
566
0
566
Liguria
07/01/22
12/01/24
648
0
648
Lombardia
19/06/23
16/01/24
34
19809
19843
Emilia-Romagna
08/11/23
16/01/24
21
0
21
TOT (PL)
1269
19809
21078
LA
Lazio
04/05/22
01/08/23
91
2
93
CAM
Campania
22/05/23
03/07/23
26
0
26
CAL
Calabria
27/04/23
14/11/23
17
413
430
SA
Sardegna
19/09/23
19/09/23
3
3
TOT
1406
20224
21630
Figure 15: ASF cases (wild boar and domestic pig) in Europe at the times the
Italian index case was found (January 3rd, 2022) (overlapping data). EPSG: 3857
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A brief overlook of the first
outbreaks up to January 2024 is
summarized in Box 1; currently,
four hotspots of ASF Genotype II
are identified (Figure 16), tallying
up to more than 1400 positive
cases in wild boar only (Table 1,
Figure 16).
Both the distance from the east-
European epidemic front, and the
spatial distribution of ASF
hotspots on the national territory,
indicate that a human-mediated
incursion is highly plausible
(EUROPEAN COMMISSION, 2022). This
hypothesis is further supported by
biomolecular data, which allowed
to identify two different viral
strains for the Piemonte-Liguria
and Lazio outbreaks
(https://www.izsplv.it/it/notizie
/308-peste-suina-africana/1493-
peste-suina-africana,-i-focolai-
laziale-e-piemotese-ligure-
hanno-origine-diversa.html, in
Italian).
Figure 17: Weekly reports of ASF in wild boar from the ASF hotspots in continental Italy (Jan 23rd, 2024)
Figure 16: ASF hotspots and index cases in Italy (Jan 23rd, 2024 data),
restriction zones and infected areas. PL = Piemonte-Liguria; LA = Lazio; CAL =
Calabria; CAM = Campania; SA = Sardegna. EPSG: 32632
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First reports of ASF in continental Italy
On January 5th, 2022, a wild boar carcass found during passive surveillance in Ovada (AL, Piedmont region) tested
positive to ASF analysis, carried out by the local IZ. Two days later, the results were confirmed by CEREP as ASF
Genotype II virus, and thus reported to EU Commission and WOAH. A Local Crisis Unit meeting was held, and the
Central Crisis Unit was instituted. As ASF Expert Group identified the infected zone as comprising 63 municipalities,
suspect case number two (Isola Del Cantone, GE, Liguria region) and three (Franconalto, AL, Piemonte region)
were found.
On January 10th, 2022, cases two and three were confirmed ASF positive. Pending the amendment of 2021/594,
Implementing Decision (EU) 2022/28 instituted the infected area as RZ II. The day after, three additional cases
were found inside the RZ II (Voltaggio and Tagliolo-Monferrato, AL, Piemonte region).
On January 14th, 2022, Implementing Decision (EU) 2022/62 expanded RZ II to 115 municipalities, and two days
later Implementing Regulation (EU) 2022/440 amended 2021/594.
On May 4th, 2022, CEREP confirms ASF in a dying wild boar found in Parco dell’Insugherata (Rome, Lazio region),
approximately 450 km from the first outbreak. On June 9th, the virus entered a small free-range pig holding in the
outskirt of Rome. No further ASF reports came from the Lazio hotspot since August, 2023.
On June 1st, 2022, as 136 ASF positive cases were already reported, fencing operations began in Ponzone-Voltri
territories (GE, Liguria region).
On May, 5th, 2023, an infected wild boar was found in the hinterland of Reggio Calabria (RC, Calabria region),
approximately 500 km from the nearest outbreak. The focus expanded in the Aspromonte area, involving also
domestic pigs.
On May 22th, 2023, five wild boars were confirmed SAF positive in Cerreta Cognole forest (SA, Campania region),
approximately 230 km from the nearest outbreak. EU RZs were instituted on September 19th by Implementing
Regulation (EU) 2023/1799.
On June 19th, 2023, the PL hotspot northward expansion reached Lombardia region, where ASF was detected in
wild boars. Between August and October, multiple farms in Lombardia were affected by the disease.
On August 27th, 2023, ASF was detected in a pig farm in Zinasco (PV, Lombardia); allegedly, the holding had been
infected since early August, having experienced an important increase in mortality (apx. 400 deaths) that was kept
from the Authorities; possibly infected animals would therefore have been sent towards multiple butcheries in
Lombardia and other regions (Veneto and Emilia-Romagna), thus allowing the virus to spread with the meat trade.
An investigation on these events is currently on the way.
On September 20th, 2023, ASF genotype II has been detected in a pig farm in Dorgali (NU, Sardegna region). As no
further ASF cases have followed on the Island, the outbreak was declared resolved during January, 2024.
On November 8th, 2023, ASF was found in a wild boar in Ottone (PC, Emilia-Romagna region), following the
eastward expansion of the PL hotspot.
Box 1: First ASF reports in continental Italy (January 2024 data)
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1.4.3. Legislation and operational hierarchy
In Italy, REGULATION (EU) N. 429, 2016 (“Animal Health Law”, AHL hereafter) was implemented by EU
DELEGATION LAW N. 53, 2021, Art. 14, prescribing the adoption of further acts to fit AHL in the national
legislation; in large part, this is accomplished by, LEGISLATIVE DECREE N. 136, 2022.
With regards to ASF, the central competent Authority as per AHL is the Ministry of Health, through
the National Centre for Animal Diseases (Centro Nazionale di lotta ed emergenza contro le malattie
animali, CLEMA hereafter), while the local competent Authority as per AHL is the Local Health Unit
(Azienda Sanitaria Locale, ASL hereafter) (LEGISLATIVE DECREE N. 136, 2022).
The strategies and operational hierarchy for intervening in case of epidemic emergencies and
outbreaks of Category A diseases (which include ASF) are detailed in the National Contingency Plan
(“Piano Nazionale per le emergenze di tipo epidemico" – ITAVETPLAN hereafter, ITALIAN MINISTRY OF
HEALTH, 2014), which prescribes the institution of three crisis units: at the national level (CLEMA), the
central crisis unit (unità di crisi centrale, UCC hereafter) coordinates the emergency on the basis of
the scientific support given by specific expert groups (gruppo operativo degli esperti, GOE hereafter),
by the Italian Institute for Environmental Protection and Research (Istituto Superiore per la Protezione
e la Ricerca Ambientale, ISPRA hereafter) and by the Reference Lab for Pestivirus and Asfivirus
diseases (Centro di Referenza Nazionale per lo studio delle malattie da Pestivirus e da Asfivirus, CEREP
hereafter). After the detection of ASF index case, the CLEMA drafted a National Emergency and
Eradication Plan (Piano nazionale di sorveglianza ed eradicazione, NEEP hereafter, EUROPEAN
COMMISSION, 2022), according to LEGISLATIVE DECREE N. 136, 2022 and AHL, Art. 31. The NEEP includes
the norms for ASF surveillance and eradication in infected Regions, as well as the measures to be
undertaken in newly infected areas; these measures must be implemented in accordance with
ITAVETPLAN and EU zoning strategy (see Zoning), and are further specified in the Operational Manual
of Swine Flus (“Manuale Operativo Pesti Suine”, MOPS hereafter, ITALIAN MINISTRY OF HEALTH, 2022).
At lower levels of the operational hierarchy, the regional crisis unit (unità di crisi regionale, UCR
hereafter) coordinate the corresponding ASLs at a regional (NUTS 2) scale, and the local crisis unit
(unità di crisi locale, UCL hereafter) implements the strategic plans on the territory of each ASL
(generally corresponding to a NUTS 3 territorial unit). Once the NEEP had been promulgated, each
UCR had to articulate the actions prescribed therein in a specific Regional Plan of Urgent
Interventions (Piano Regionale di Interventi Urgenti, PRIU hereafter), drafted in cooperation with
ISPRA and CEREP. Each PRIU must be adopted by each UCL and enacted locally by each ASL through
a specific ASF Territorial Operative Group (Gruppo Operativo Territoriale, GOT hereafter), which
coordinate the UCL (ORDER N. 4, 2023). PRIUs are exempted from SEA and Natura 2000 EIA procedures
(LAW N. 29, 2022).
Since 2022, a ASF Commissioner is instituted (LAW N. 29, 2022) to coordinate the strategy against ASF
at national level, to approve the PRIUs in conjunction with the UCC, and to draft the eradication plans
for ASF-infected regions; moreover, it coordinates the UCRs and the network of administrations
responsible for implementing these actions. In the context of Italian jurisdiction, the Commissioner
exerts derogative power through targeted extra ordinem acts (“Orders”).
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Figure 18: Schematization of ASF operational hierarchy in Italy. Sources of law are highlighted in red, while sources of
scientific support are highlighted in green.
Following the NEEP, diagnosis for ASF must be carried on every wild boar found dead, and on every
ASF suspect case. The definition of “suspect case” is not clearly stated in any piece of legislation, but
it can de described in general terms as “an animal showing ASF-like symptomatology, or a carcass
found in the context of an overall enhanced mortality” (e.g., NSPP, ORDER N. 5, 2023). However, what
cases should be treated as “suspects” depends by the zoning status of the finding location: in Infected
Areas, RZ II and RZ III, the aforementioned definition applies, while in buffer zones and RZ I, “every
suid cadaver showing symptoms ascribable to ASF” must be regarded as suspect (ORDER N. 5, 2023).
Finally, in ASF-free regions, DELEGATED REGULATION (EU) N. 689, 2019 definition of “suspect case” is
adopted (ORDER N. 5, 2023); this includes animals or group of animals when:
a) clinical, post-mortem or laboratory examinations conclude that clinical sign(s), post-mortem
lesion(s) or histological findings are indicative of that disease;
b) result(s) from a diagnostic method are indicating the likely presence of the disease in a sample
from an animal or from a group of animals; or
c) an epidemiological link with a confirmed case has been established.
The test for ASF is carried out by RT-PCR on (preferably) spleen, kidney, lymph nodes or, in case of
advanced decomposition, long bone tissue. Sampling from the dead animal is carried out by ASL,
eventually supported by trained Personnel (Figure 19). If a finding is considered an ASF suspect case,
ASL must immediately report it as such on SIMAN, while ASF test will be carried out at CEREP. For
non-suspect cases, ASF test can be carried out by the local Zooprophilactic Institute (Istituto
Zooprofilattico, IZ hereafter): in case of a positive result, a second test must be provided, carried out
either by the local IZ (infected regions) or by CEREP (ASF-naïve regions). CEREP must communicate
the results of the test to the Ministry of Health as soon as they are available (MOPS) (Figure 20).
NEEP
UCC DS GOE
UCR (Region )PRIU
UCL (ASL )
GOT
ISPRA
CEREP
CLEMA (Ministry of Health )
ASF commissioner
Implementation of ASF management strategy
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Figure 19: spleen identification for ASF sampling on domestic pig (above) and wild boar (below). Courtesy of IZSVe
Data regarding local outbreaks, collected by ASL, are channelled towards the EU Animal Disease
Information System (ADIS, REGULATION (EU) N. 429, 2016) through the National Animal Disease
Information System (“Sistema Informativo Malattie Animali Nazionale”, SIMAN), hosted on
Veterinary Information System (VETINFO) portal. SIMAN notifications comply for both EU disease
surveillance, and WOAH requirements for disease-free status declaration.
Sa mple flo w
ASF - noti fica tion
ASF + notif icati on ( provis ion al )
ASF + notif icati on ( defi niti ve)
LEGEND
ASL
IZ
ASF -
ASF +
SIMAN
CEREP
NON-SUSPECT report
SINVSA
Ministry of Health
EC, WOAH
ASL
IZ
ASF -
ASF +
CEREP
SUSPECT report
SINVSA
Region
SIMAN
Figure 20: Notification flow for non-suspect (left) and suspect ASF cases (right)
The results of surveillance activities are published on VETINFO portal through the National Veterinary
Information System (Sistema Informativo Veterinario per la Sicurezza Alimentare, SINVSA hereafter)
Both SIMAN and SINVSA are accessible to restricted accounts only.
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1.4.4. ASF management strategy
In case of an ASF outbreak, the infected area must be identified, delimited, and signalized. Pending
the institution of EU restriction zones (IMPLEMENTING REGULATION (EU) N. 594, 2023), a preliminary
infected area is defined by the area of active circulation (i.e., the minimum convex polygon around
outbreaks, plus a 6 km buffer to account for wild boars movement pattern), plus a “high risk area”
(MOPS), whose size should at least equal to that of the area of active circulation (GUBERTI ET AL., 2022).
Around that, an area of improved passive surveillance (“surveillance area”) should be identified
(MOPS). Ecological barriers for fencing the RZs (see Fencing) must be identified and reinforced.
After EU zoning is instituted, ASF management activities must be undertaken accordingly; inside the
infected area (RZ II and RZ III), specific activities must be carried on to improve disease surveillance,
to thin the wild boar population, and to eradicate the virus, as detailed in Annex 3.
Once ASF virus has been eradicated, a proposal for scaling back the RZs can be advanced by the
Ministry of Health to EU Commission, according to the outcomes of surveillance activities.
ASF surveillance is carried out by testing dead animals, which can be either hunted or culled (active
surveillance), found opportunistically (passive surveillance) or actively searched for (enhanced passive
surveillance) (see Surveillance). A summary of the main outcomes of these activities for Italian ASF
hotspots (February 07th, 2024 data) is outlined in Table 2, while a comparison of the performances in
terms of sample quality (i.e., proportion of samples yielding a reliable ASF diagnostic), and detection
of ASF infected animals (i.e., ASF sample prevalence), is provided in Figure 21.
Table 2: Number of animals retrieved and tested for ASF through passive surveillance in Italian ASF hotspot (excluding
Sardegna). CAM= Campania; CAL = Calabria; LA = Lazio; PL = Piemonte-Liguria
CAM
CAL
LA
PL
AS
PS
EPS
AS
PS
AS
PS
EPS
AS
PS
EPS
ASF -
1041
422
6
1353
67
1561
648
9
10361
2799
47
ASF +
0
27
0
0
17
12
79
0
286
989
106
ND
0
0
0
0
0
0
0
7
10
57
11
TOT
1041
449
6
1353
84
1573
727
16
10657
3845
164
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Figure 21: Aggregate performances of ASF surveillance strategies in Campania (CAM), Lazio (LA) and Piemonte-Liguria
(PL) infected areas. Sample quality and sample prevalence are represented on the secondary axis.
The destiny of wild boar cadavers (either hunted or found dead) is also bounded to ASF zoning (Figure
22); namely:
• Inside the infected area or the RZ II, they constitute a Category 1 animal by-product
(REGULATION (EU) N. 1069, 2009). By way of derogation, ASF negative animals and animal parts
derived from control activities can be commercialized outside the infected area and RZ II, only
after risk-mitigating treatments as per DELEGATED REGULATION (EU) N. 687, 2020, Annex VII are
provided. Otherwise, wild boar cadavers are destined to destruction.
• Inside RZ I, they constitute a Category 3 animal by-product, as per REGULATION (EU) N. 1069,
2009. By way of derogation. ASF negative animals and animal parts derived from hunting
and control activities can be destined to self-consumption, only inside RZI; otherwise,
commercialization outside RZI, by way of derogation, follows the same prescription as in
RZII.
RZII
(RZIII)
RZI
FOUND CADAVERS
HUNTED ANIMALS (INC. CONTROL)
EXPORT
SELF
CONSUMPTION
ASF test
ASF +
ASF -
DESTRUCTION
DESTRUCTION
NO ASF test
(derogation)
ASF test
COLLECTIO N POINT
ON-SITE DISPOSAL
COLLECTIO N POINT
ON-SITE DISPOSAL
ASF +
ASF -
TREATMENT*
(derogation)
Figure 22: Destiny of WB cadavers found in the field (left) and carcasses derived by hunting and control activities (right) in
Italy
0
0.2
0.4
0.6
0.8
1
1.2
0
2000
4000
6000
8000
10000
12000
14000
AS PS EPS
Sample quality / Prevalence
N. samples
N. samples Sample quality Prevalence
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As a measure to preventively slow down viral spread by direct contact amongst animals, a specific
national plan for 2023 - 2028
(https://www.salute.gov.it/portale/documentazione/p6_2_2_1.jsp?lingua=italiano&id=3357, in
Italian) encourage population thinning by setting the harvest quotas that Regions should reach,
prescribing for each a severe increase of harvest by hunting (+ 116 ± 126%), and particularly by
control (+ 468 ± 613%).
During peace time, passive surveillance should allow to detect suspect ASF cases. Nonetheless, as
pointed out by JORI ET AL., 2021, the definition of “suspect case” is often lacking or unclear: to their
point, in Italian legislation and guidelines, this concept is not well defined, being associated to
diseased/found dead animals whose clinical-pathological picture is ascribable to ASF (i.e., by the
intervening ASL operator), either in association with a context of “increased mortality”, or not. As an
example, ORDER N. 5, 2023 binds suspect cases to an increment of mortality inside the infected area
(RZs II and III), but not in RZ I, while regional guidelines often associate this definition to spatio-
temporally related” finding of more than two wild boar cadavers (e.g., https://salute.regione.emilia-
romagna.it/normativa-e-documentazione/materiale-
informativo/archivio/manuali/fauna_selvatica_2013.pdf, in Italian). This particular case not only is likely
to add uncertainty to the operator’s assignment, but also strikes as an epidemiological nonsense: in
fact, inside the infected area, both an increased mortality amongst wild boar, and a higher frequency
of ASF positive samples, are expected; conversely, in RZI, an increase in mortality should indeed be
linked to a spread from the neighboring ASF infected area, given that natural mortality is expected to
remain stable.
Sampling of dead animals (both carcasses, and cadavers) must be carried out in intermediate
collection centres (ICCs hereafter) between the finding location, and the rendering plant. The
transportation of the cadaver from the finding/culling location to the ICC must be carried out in strict
biosafety, using solid trays and dedicated vehicles, and eventually a winch. Burial is allowed in
extrema ratio, as per REGULATION (EU) N. 1069, 2009, Art. 19.
The characteristics of intermediate collection points are included in ORDER N. 2, 2023; in particular,
they must include:
• Detergent and disinfectants.
• Access to clean water and electricity.
• A refrigerator or a freezer; alternatively, a sealed container if carcasses are disposed of before
48 hours.
• Sampling tools.
• Fencing to preclude access to animals and unauthorized persons.
• A cleansing area for tools and clothing.
• Disinfections barriers at entry point (e.g., pools of disinfectant).
The intermediate collection point can be emptied, only after ASF test results for all carcasses stocked
therein is available. In case one carcass is ASF positive, all the stock must be considered infective. At
that point, the use of the intermediate point is suspended, and the carcasses must be disposed of by
ASL. All contaminated material, including the cadaver and the finding spot (“deathbed”), must be
disinfected using agents listed in the MOPS; these include:
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• Potassium peroxymonosulfate + malic acid + sulfamic acid + Sodium
dodecylbenzenesulfonate + Sodium hexametaphosphate 1% (Virkon S)
• Sodium hydroxide 2%
• Sodium carbonate 40%
• 2-Phenylphenol 1% (Environ D)
• 2-Phenylphenol 5% (Lysol)
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2. AIM OF THE STUDY
African Swine Fever (ASF) is a potentially panzootic viral pig disease, which has recently affected the
territory of continental Italy with multiple hotspots. In Europe, the virus spreads mainly through
transport of contaminated meat, then surviving locally in the wild boar population and in
contaminated environments.
Introducing ASF translates into harsh economic and social impacts in affected regions, which must
adopt severe countermeasures to eradicate the disease from both the domestic and the wild suid
population, and to minimize the risk of viral spread. Accordingly, EU Regulation denote ASF as “a
disease for which there is a need for surveillance within the Union”, and “a disease that does not
normally occur in the Union and for which immediate eradication measures must be taken as soon as
it is detected”.
In Italy, the competent Authority for the enactment of the ASF management strategy is the Local
Health Unit (ASL), whose territory usually correspond to one EU NUTS 3 level. This is the case of the
study area considered in the present work, which comprehends the ASF-free territory of Pordenone
EDR (former Pordenone province).
In a nutshell, the study described herein aims at:
• building/increasing the ASF surveillance system.
• assessing the preparedness to a possible ASF introduction.
• supporting the ASF management capacities.
Epidemiological surveillance for ASF is based on the active search for wild boar cadavers (enhanced
passive surveillance, EPS hereafter), an activity that should be undertaken in disease-free areas in
order to detect the virus as early as possible. In this work, the definition of a set of transects for EPS
is described, including a summary of the activities carried out during the last year, discussing the
outcomes and highlighting possible weak spots of the strategy adopted so far.
In case an ASF outbreak is detected, a timely implementation of an integrated strategy for the quest,
retrieval and disposal of possibly infected wild boar cadavers is crucial for disease management. This
strategy pivots on sampling, transporting and disposing of these cadavers, relying on an
infrastructural network that must be scaled to the number of dead animals it will have to cope with.
Unfortunately, the likely outcomes of an eventual ASF outbreak are seldom predictable, leading to
delaying decision making.
In the present study, a method for obtaining an indicative estimate of the expected wild boar
mortality is presented, based on routinely collected census data, and on the outcomes of the
successful ASF management experience carried out in Belgium. These bases allow to depict a likely
scenarios of an eventual ASF epidemic, allowing to forward some hypotheses regarding the spatial
distribution of the infrastructures needed for the management system.
.
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3. STUDY AREA
3.1. ENVIRONMENTAL CONTEXT
The study area (EPSG32633: 320872E, 5108678N) is the territory of the Regional Decentralization
Institution (Ente di Decentramento Regionale, former Province, EDR hereafter) of Pordenone, a 2273
km2 NUTS 3 (REGULATION (EC) NO 1059, 2003) territorial unit located in Friuli-Venezia Giulia region
(FVG), in northeaster Italy. Geographically, two macro areas can be distinguished: a northern
montane area, and a southern plain; in the context of the EU biogeographic regionalization (EEA,
2023), these two areas correspond to the “Alpine” and the “Continental” biogeographic region,
respectively (Figure 23).
Figure 23: Pordenone EDR: Corine Land cover aggregated classification and water courses. Hillshade based on TINITALY
DTM is used as a base layer. EPSG: 32633
The northern Alpine part spans over 992 km2 (apx. 44% of the overall territory of the study area); it
is characterized by a median altitude of 992 (IQR = 680) m a.s.l., and median terrain ruggedness index
(TRI hereafter, RILEY ET AL., 1999) of 16.82 (IQR=12.8). Land cover is mostly represented by forests and
seminatural areas (96%), out of which 351 km2 (37%) of broad-leaved forest and 313 km2 (33%) of
mixed forests. Approximately 25 km2 are dedicated to agriculture, most of which (14 km2)
interspersed with significant natural or semi-natural areas (CLC class 2.4.3).
The southern Continental portion of the study area spans over 1281 km2 of mostly plain territory,
with a median altitude of 56 (IQR=133.2) m a.s.l, and median TRI of 0.36 (IQR = 0.4). 72% of the land
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(916 km2) is used for agricultural
purposes, mainly non-irrigated
crops (CLC class 2.1.1, 64%).
Natural vegetation is found
almost exclusively in marginal
areas: forests are limited to the
foothills, spanning over a 78 km2
(6%) belt, while sparse shrub
vegetation and non-vegetated
natural areas occupy the
riverbanks of rivers Cellina and
Meduna, which converge halfway
down the plains. 15% of the
territory (187 km2) is occupied by
artificial surfaces, which consists
mostly of discontinuous urban
fabric (CLC class 1.1.2).
3.2. MANAGEMENT OF WILD BOAR
With regard to wildlife management, Pordenone EDR is subdivided in 56 hunting reserves (generally
matching municipality boundaries, corresponding to Local Administrative Units as per REGULATION (EC)
NO 1059, 2003), representing the territorial management units; these are grouped into four hunting
districts (Figure 25, Figure 26). The local competent Authority for environmental and forestry policing
is the Pordenone forestry inspectorate (Ispettorato forestale di Pordenone) of the Regional Forestry
Corp, which is organized in six forest Stations, attending to a corresponding portion of the territory.
Concerning wild boar specifically, Pordenone EDR is subdivided in a “hunting area”, and an
“eradication area” (Figure 26), which are characterized by different management policies. In the
hunting area, where wild boar is most abundant, wild boar management is directed towards the
conservation of a manageable, healthy population, based on yearly census data. Hunting is
implemented through the “selective” technique, which includes standing hunts (posta) and hunting
with a scent hound (girata), and is carried out from May 15th to January 15th, eventually extended to
April 1st (REGIONAL LAW N. 14, 1987). The hunting area includes the “Prealpi Carniche” and
“Pedemontana pordenonese” hunting districts, occupying the mountains and foothills in the
northern part of the study area.
In the eradication area, management aims at the eradication of residual, sporadic nuclei, whose size
is also estimated yearly. Hunting is enacted using the “traditional” technique, consisting of driven
hunts (battuta) which usually involve less than ten hunters, and is carried out from September 1st, to
Figure 24: Terrain ruggedness index (TRI) and EU biogeographic regions in
Pordenone EDR. EPSG: 32633
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December 31st. The eradication area consists of the “Alta Pianura pordenonese” and “Bassa Pianura
pordenonese” hunting districts, located in the southern plains.
Population abundance, age structure and sex ratio are assessed through yearly censuses. Censuses
are carried out by hunters during late winter through vantage point counts, which are performed
simultaneously for all hunting reserves in each hunting district. The census data is then used to assign
hunting quotas to each reserve, aiming at pursuing management goals. At the end of each season,
this data is published on the regional website
(https://www.regione.fvg.it/rafvg/cms/RAFVG/ambiente-territorio/tutela-ambiente-gestione-
risorse-naturali/gestione-venatoria/FOGLIA9/).
In 2022-23, census data included 820 individuals (0.48±0.71 ind/km2), corresponding approximately
to 16% of the overall FVG census population (Figure 26).
Figure 25: Hunting districts and forest stations. Hillshade
based on TINITALY DTM is used as a base layer. EPSG:
32633
Figure 26: Hunting districts, hunting reserves and census
data for 2022-23. Null values are not shown. EPSG: 32633
Wild boar hunting data for Pordenone EDR (2000-23) is represented in Figure 27. On average,
87±32% of the census population is assigned to harvest, out of which 51±14% is effectively harvested,
leading to an average harvest offtake of 44±18%. Over the past twenty years, the wild boar
population remained practically stable (β=-0.0002; R2=0.02). According to census (2020-23 data), the
population structure is based on a majority of juveniles, and a sex ratio slightly tilted towards males
(J=0.59±0.02; M=0.18±0.02; F=0.23±0.03).
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Figure 27: representation of Pordenone EDR overall hunting data (2000-2023).
Hunted animals are kept by hunters, either for auto consumption, for direct alienation or
commercialization. In the latter case, the hunter must forward the carcass to a registered Game
Handling Establishment (centri di lavorazione selvaggina), for veterinary control and further
slaughtering phases, accordingly with REGULATION (EC) NO 853, 2004; beforehand, carcasses can
eventually be gathered in collection centres (centri di raccolta), from one to five days accordingly to
the equipment (REGIONAL DELIBERATION N. 943, 2021).
In addition to hunting, control measures against conflictive species (LAW N. 157, 1992; REGIONAL LAW N.
14, 2007) are applied, following specific quadrennial plans. Culling is carried out either by the Region
Forestry Corp, or private trained operators (“selecontrollori” or “bioregolatori”) all year round. In the
case of carcasses arising from control measures, culled animals can either be destroyed, or destined
to self-consumption by the shooter (up to three animals/person/year).
Animals found dead for any reason cannot enter the meat market, while commercialization is allowed
for those that are culled (e.g. following a car crash)for which an ante-mortem examination, followed
by a post-mortem exam at a CLS, is provided by trained personnel, as per REGULATION (EC) NO 853,
2004.
3.3. ASF PREPAREDNESS – CURRENT STATUS IN THE STUDY AREA
As no ASF case was detected in FVG region, nor in adjacent municipalities, FVG constitutes a minimum
alert area (EUROPEAN COMMISSION, 2022; REGIONAL DELIBERATION N. 957, 2022). The ASF regional crisis unit
(UCR) was instituted, and the Regional Plan of Urgent Interventions (Piano Regionale di Interventi
Urgenti, PRIU hereafter) adopted, , on July 1st, 2022 (REGIONAL DELIBERATION N. 957, 2022).
0
200
400
600
800
1000
1200
1400
Wild boars (n)
CENSUS POPULATION (n) HUNTED (Selection) HUNTED (traditional) ASSIGNED
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In Pordenone EDR, the ASF local competent Authority is the Health Unit of Western Friuli (Azienda
Sanitaria del Friuli Occidentale, ASFO hereafter).
Passive surveillance activities started in 2022. These include the geo-referencing, sampling and ASF
testing of any wild boar which is either roadkill, found dead, or euthanized. Citizens can report wild
boar cadavers either through the National Emergency Number (112), or directly to wildlife rescue
agencies (https://www.regione.fvg.it/rafvg/cms/RAFVG/economia-imprese/agricoltura-
foreste/foreste/FOGLIA100/). To that purpose, a regional toll-free number is available since 2019. To
encourage citizen participation, a 10€ reward is offered for any case report (20€ if a sample is
conferred), as suggested in SANTE/2017/10186, REV. 4, 2020.
Passive surveillance also includes the active search of carcasses at monthly cadence (see Enhanced
passive surveillance), which should be carried out by the FVG Regional Forestry Corp.
FVG ASF strategy highly relies on wild boar management, prescribing a general thinning of the
population: as an increase of hunting effort is considered unattainable, this purpose will be pursued
by shifting hunting towards 0-12 month animals (60%) and adult females (65% of culled adults), as
indicated in national guidelines (https://www.izsum.it/index.php?id_sezione=171152); this would
induce a 3% increase of hunting harvest of adult females. Also, the intervention strategy includes the
withdrawal from existing culling limitations: these include shifting the end of the selective hunting
season from September 1st to December 31st, allowing to hunt more than 150% of the census
population inside the hunting area, and allowing to harvest adult females with cubs inside the
eradication area. Furthermore, night hunting using visors is allowed.
Furthermore, the PRIU plans to increase in the number of operators dedicated to population control,
by incentivizing hunters to partake in this activity; this will be accomplished by allowing culled animals
to enter the meat market, which was previously restricted to hunted animals, and by allowing hunters
to keep more than the current maximum of two preys/hunter/year.
Conversely, national guidelines for 2023-28
(https://www.salute.gov.it/portale/documentazione/p6_2_2_1.jsp?lingua=italiano&id=3357), which
were published after the latest FVG PRIU, prescribe for the region a more severe increase in wild boar
harvest; in particular, yearly quota should increase of 59.2% for hunting, and 828.8% for control
culling relative to the mean harvest of 2021-23 hunting seasons, reaching an overall expected harvest
of 9100 wild boars per year (which is approximately 180% of the census population).
As the study area is currently ASF free, the definition of “suspect case” is only applied in presence of
lesions or symptoms ascribable to ASF, and/or presence of two or more carcasses, and/or otherwise
suspect-inducing conditions.
If the case is confirmed as non-suspect by ASL (or ASL designated) personnel, ASF sampling is carried
on-site follows routinary biosecurity measures; the sampling material include:
• Dispensable gloves (nitrile/latex)
• Dispensable overshoes
• Airtight jar (primary sample container)
• UN3373 95KPa bags (secondary container)
• Biocide (sodium hypochlorite, Quaternary ammonium cation or similar)
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• Waste plastic bag
The cadaver must then be reasonably hidden from people and scavenging animals until ASF test
results are in; in case of a positive diagnosis, ASL operators must return on site, to dispose of the
cadaver accordingly.
If the case is considered suspect, the carcass must be handled only with the supervision of ASL, which
will provide sampling preferably at the collection point; the operators must then proceed as follows:
• Reach the target on an authorized vehicle; at the moment, one pick-up truck is available
• Wear the Personal protective equipment (PPE) before approaching the carcass
• Spread the carcass with disinfectant, as indicated in the MOPS
• Insert the carcass in a first bag (primary bag)
• Spread the bag with disinfectant
• Insert the primary bag containing the carcass in a secondary bag
• Load the bagged carcass on the authorized vehicle
• Remove the PPE and insert them in a bag, to be closed, disinfected and treated as 180202
EWC waste (Absolute Hazardous).
• Georeference the location
• Fill up the SINVSA sampling sheet, assigning a unique ID to the carcass
• Associate the carcass to the SINVSA sheet (i.e. writing the ID number on the bag)
• Bring the carcass to the rendering site/collection point
• Wash and disinfect the vehicle
As for the PRIU, the candidate endpoint of the cadavers retrieved in field activities from all FVG Region
was identified in the rendering plant of Morsano al Tagliamento (SALGAIM ECOLOGIC S.p.A.); there,
butchery waste is stabilized, and animal by-products (REGULATION (EU) N. 1069, 2009) are sold as
protein flours destined to incineration, and animal oils. As for a non-technical report published in
2014 (https://www.regione.fvg.it/rafvg/export/sites/default/RAFVG/ambiente-
territorio/valutazione-ambientale-autorizzazioni-contributi/FOGLIA3/DITTE/allegati/PN-AIA-
42R_sintesi.pdf), the plant treated 15000 tons of animal waste (corresponding, for example, to
300000 50kg cadavers per year, i.e. 822 cadavers per day), running at approximately 45% of its
capacity. Given that the entire wild boar population in FVG is estimated at approximately 5400
animals, for the purposes of the present work the proposed plant was assumed to be compliant for
the tasks required to it. Intermediate collection points have not been identified yet.
Sampling on the carcass is done by ASL at the rendering site or collection point; if the carcass can’t
be moved, sampling is conducted on site under ASL supervision, followed by burial or incineration on
site; if tools have to be used for carcass removal (e.g. a winch), these have to be accurately disinfected
afterwards.
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4. MATERIALS AND METHODS
4.1. ENHANCED PASSIVE SURVEILLANCE
To maximize the likelihood of finding wild boar cadavers, the areas on which to identify the transects
for enhanced passive surveillance were determined based the distribution of georeferenced
salmonellosis (Salmonella enterica serovar choleraesuis, var. Kunzendorf) cases in wild boar (LONGO
ET AL., 2019) (n=49, February 7th, 2012 - June 22nd, 2015 data). This choice was due to the
symptomatology of this particular disease, which highly resembles that of ASF (notably, high fever),
thus likely pushing infected animals to find relief in similar environments.
To highlight candidate areas, 3 km kernel density of Salmonellosis cases was calculated and plotted
using QGIS (QGIS DEVELOPMENT TEAM, 2022). The transects were finally identified by operators of
Pordenone Forestry Corp on their corresponding territory (forest stations), based on their prior
knowledge of the territory and expected effort.
Operators were asked to identify candidate transects preferably alongside shallow water courses.
This choice was based on recent literature, suggesting that these environments represent
preferential deathbeds for sick animals (MORELLE ET AL., 2019).
Enhanced passive surveillance activities begun in April 2022, surveying each transect every two
weeks; operators were asked to report and georeference all wild boar cadavers, to report any sign of
presence of the species encountered during the activity, and note the time each survey started and
ended, using a specific field note (Annex 2).
The outcomes of the surveys up to December 2023 are reported; these include the length of the
tracks, the number of surveys carried out, the time required by each survey and the sampling effort
(SE). The latter was calculated (for each transect and aggregated by forest station), as the product of
the time required by the surveys and number of operators involved in the activities (Equation 5).
Missing reports of sampling effort were replaced by the average value for the corresponding transect.
Equation 5
The efficiency of the system (sensu PORTA, 2014: “The effects or end results achieved in relation to the
effort expended in terms of money, resources, and time”) was evaluated by dividing the number of
cadavers found, by the sampling effort (Equation 6)
Equation 6
To evaluate the performances of the enhanced passive surveillance programme, its effectiveness
(sensu PORTA, 2014: “A measure of the extent to which an intervention or policy fulfills its objectives in
practice”) was calculated as the ratio between the number of wild boar cadavers found, and the 10%
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of the census population (representing the quota of natural mortality expected to be present in the
field, excluding roadkill, KEULING ET AL., 2013; TOÏGO ET AL., 2008) (Equation 7).
Equation 7
4.2. EXPECTED WILD BOAR MORTALITY FOLLOWING ASF INTRODUCTION
To provide an estimate of ASF incidence, data from the former ASF infected area in Belgium was
analysed. The choice of this particular area was due to the effectiveness of the management strategy
in extinguishing the ASF outbreak, which is likely indicative of the detection of (virtually) all infected
animals and cadavers.
Georeferenced ASF reports for Belgium were downloaded from WAHIS
(https://wahis.woah.org/#/home); in order to identify the data subset most representative of
epidemic stage of the outbreak, the cumulated dataset was visualized, setting a cut-off date at the
reaching of a “plateau” at right-hand tail of the cumulated curve. Then, the infected area
corresponding to the resulting subset (i.e. the convex hull containing all ASF cases) was determined,
using the Minimum Binding Geometry tool in QGIS (QGIS DEVELOPMENT TEAM, 2022).
The number of wild boars present in the infected area, and therefore exposed to the infection, was
derived from the 25 km2 raster file produced by PITTIGLIO ET AL., 2018, who estimated wild boar
population density on most of the European territory (Figure 2). Implicitly, an assumption of stability
of the wild boar population from the publishing date (2018) to the cut-off date of the WOAH dataset,
was made. The raster grid representing wild boar population density was resampled to a finer
resolution (2.5 km2) through bilinear interpolation using R package “terra” (HIJMANS R., 2023; R CORE
TEAM, 2023). Then, the corresponding population size was calculated by multiplying the population
density estimate, by the size of the infected area.
ASF cumulative incidence (CI) in wild boar over the epidemic period (x) for the chosen data subset
was calculated as the number of ASF reports, divided by the estimated number of exposed animals
(Equation 2).
Equation 2
This value was then extrapolated from the epidemic period (tx) to a general timeframe ty using
Equation 3 (THRUSFIELD ET AL., 2018).
Equation 3
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Then, the time period y during which half of the population is expected to get infected was calculated,
by solving Equation 2 for CIy = 0.5 (Equation 4). Considering that, in case of an ASF outbreak, all
diseased animals are actively looked for and eliminated, a 100% ASF case fatality rate was assumed:
therefore, this index will be referred to as “expected median lethal time” (expLT50).
Equation 4
The distribution curve of CI as calculated by Equation 3, and the corresponding expLT50, is plotted in
Figure 28.
Figure 28: distribution curve of the expected CI as calculated using Equation 3; expLT50 is highlighted.
To calculate the expected number of ASF positive cadavers to be disposed of in Pordenone EDR in
case of an ASF outbreak, wild boar census data for 2022 were downloaded, filtered and collated from
FVG region website (https://www.regione.fvg.it/rafvg/cms/RAFVG/ambiente-territorio/tutela-
ambiente-gestione-risorse-naturali/gestione-venatoria/FOGLIA9/). The corresponding expected
cumulate incidence at expLT50 was calculated, for each hunting reserve, by multiplying the incidence
estimated for the Belgian outbreak, by the number of wild boars present in the study area. A yearly
15% quota of the pre-existing wild boar population, representing animals that are expected to die by
natural and vehicle mortality (TOÏGO ET AL., 2008), was added to the result, thus obtaining the total
expected mortality in wild boar, accounting for both ASF-and non ASF-related deaths. This number
represents the number of dead animals that an efficient management strategy would need to test
for ASF and destroy in Pordenone EDR. These calculations were performed using R (R CORE TEAM,
2023), and the results were plotted using QGIS (QGIS DEVELOPMENT TEAM, 2022).
In a view to provide a further contextualization of ASF management based on an estimate of the wild
boar population, the size of the infected area in Gaume, and the cumulative incidence estimated
therein at expLT50, were compared to the corresponding outcomes of the Italian Piemonte-Liguria
(PL) ASF outbreak.
0
20
40
60
80
100
120
Infected animals (%)
Days since index case
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4.3. SUPPORT FOR MANAGING CADAVERS IN THE FIELD
Currently, in Italy, if an area is declared infected by ASF, all wild boar cadavers found in the field have
to be tested for ASF and destroyed; culled animal have to be tested as well, but only ASF positive
animals have to be destroyed. To lower the risk of spreading ASFV through transportation of possibly
infected cadavers, intermediate collection centres between the field and the rendering plant have to
be set up. These sites must be accessible to ASF dedicated vehicle(s), and must be provided with
electricity and water for conserving dead animals and disinfecting. Whether a safe transportation of
the cadaver to the collection centre is not possible (e.g., in areas less served by the road network,
“remote areas” hereafter), sampling of found cadavers can take place in the field, followed by in-situ
burial or incineration of cadavers (either single or collective).
The areas eligible for hosting intermediate collection centres in Pordenone EDR were individuated
based on the number of cadavers expected to be found as a consequence of ASF, natural mortality
and vehicle collision (see Expected Wild Boar mortality following ASF introduction). To include only
territories potentially occupied by wild boar from the computations, Corine Land Cover 2018 data
(CLC hereafter, https://doi.org/10.2909/71c95a07-e296-44fc-b22b-415f42acfdf0) and the digital
terrain model (DTM hereafter, TARQUINI ET AL., 2007) were analysed, retaining only habitats considered
suitable for wild boar: namely, CLC class 2 (Agricultural areas), class 3.1 (Forest) and class 3.2.4
(Transitional woodland/shrub), only when placed at an altitude below 1800 meters above sea level.
A representation of the road network serving the study area was obtained using OpenStreetMap
spatial data downloaded from GEOFABRICK (https://www.geofabrik.de/en/index.html), while data
regarding forest roads was downloaded from FVG WebGIS
(https://webgiscarnia.regione.fvg.it/it/map/viabilita_forestale/#); after removing overlapping data
and roads unfit for vehicles, the two datasets were merged using QGIS (QGIS DEVELOPMENT TEAM,
2022). To identify remote areas, the Euclidian distance of any point in Pordenone EDR from roads
was calculated at a resolution of 2.5 km2, using R package “rgeos” (BIVAND R. & RUNDEL C., 2023; R CORE
TEAM, 2023).
Finally, two raster images were obtained: one representing the expected number of wild boar
cadavers, excluding the habitats considered unsuitable for wild boar, and another representing the
inverse distance from the road network. After having standardized the two files by dividing the values
of the two grids by the corresponding maximum, the product of the two raster was obtained. The
candidate areas for intermediate collection points to be placed were identified by higher pixel values.
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5. RESULTS
5.1. ENHANCED PASSIVE SURVEILLANCE
A set of seventeen transects were identified (Figure 29; Annex 1), tallying up to 61.254 (4.38 ± 2.6)
km. Sixteen of them were included in the Pedemontana pordenonese hunting district, while only one
(transect FNA) fell entirely the in Alta pianura pordenonese hunting district.
Figure 29: Deployment of transects for passive surveillance activities based on kernel density of S. choleraesuis data from
LONGO ET AL., 2019 in Pordenone EDR. EPSG: 32633
Enhanced passive surveillance (EPS) activities begun in April 2022 and were carried out twice a month
by Pordenone Forestry Corp, inspecting transects falling in their corresponding forest station (FS
hereafter). Only for transect FNA (Pordenone FS), the surveys were undertaken by Claut FS personnel.
Descriptive statistics regarding the sampling effort is included in Table 3. After seven surveys, transect
BAL (2.98 km) of Barcis FS was replaced by MAS (7.20 km), as the growing crop became a visual
impediment; transect MAS was later removed from the set in September 2023, since no sign of
presence of the species was detected. Likewise, in Polcenigo FS, transect ART (2.48 km) was replaced
by CAV (1.90 km) after 13 surveys, as operators found evidence of wild boar passage alongside the
latter. Furthermore, since September 2023, transects MLI (2.43 km) and VAJ (2.41 km) of Maniago
FS were replaced by MED (8.06 km), given to frequent reports of wild boar presence in the latter
area.
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Overall, the number of surveyed transects shifted from fourteen (61.2 km, April 2022 - September
2023) to 12 (57.3 km, September 2023 – December 2023). All transects were inspected twice a
month, except for transects MAL and MAS (Barcis FS), for which only one survey was performed in
July 2022. During this period, 83 operators were deployed in the search activities (1.38±0.67
operators per survey/transect), which took approximately five hours per month/FS.
Missing reports of sampling effort affected 5% of surveys, while no wild boar cadaver was found
during the timeframe considered (April 2022 – December 2023), indicating that both efficiency and
effectiveness of the enhanced passive surveillance protocol were zero. Conversely, signs of presence
of the species were reported for all but four transects, confirming its presence of the surveyed
territory.
Figure 30: Livenza (LIV) transect, in Polcenigo FS
(September 23rd, 2022)
Figure 31: Artugna (ART) transect, in Polcenigo FS
(September 23rd, 2022)
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Table 3: Sampling effort from April, 2022 to December, 2023. Dismissed transects and aggregated data including dismissed transects is enclosed in squared brackets. *hours are
indicated in decimal form. BAL=Borgo Alzetta; GRI=Grizzo; MAL=Malnisio; MAS=Malnisio stradale; RCA=Rio Cavrezza; CAB=Cavasso-Arba; MLI=Maniago-Libero; MED=Meduno;
VAJ=Vajont; BCA=Bonifica Casarotto; CCR=Col Cravest; SFA=Strada fantasma; ART=Artugna; CAV=Cavrezza; ART=Artugna; LIG=Ligont; LIV=Livenza; FNA=Fontanafredda-Nave.
FOREST
STATION
OPERATORS
TRANSECT ID
LENGTH
LENGTH (FS)
SURVEYS
TOT LENGTH
TOT LENGTH (FS)
EFFORT
SAMPLING EFFORT
SAMPLING EFFORT (FS)
n
km
km
n
km
km
h (dec)*
h (dec)*
h (dec)*
BARCIS
9
(1.93 ± 0.79)
[BAL]
2.98
7.30
[17,48]
7
20.86
511.10
6.7
12.4
211.3
(10.06 ± 3.69)
(0.16 ± 0.35)
(0.59± 1.28)
GRI
3.79
34
128.76
39.7
77.6
(0.95 ± 0.15)
(3.69 ± 1.33)
MAL
3.51
33
115.83
42,2
83.6
(1 ± 0.26)
(3.98 ± 1.93)
[MAS]
7.20
33
207.86
19.8
37.8
(0.47 ± 0.42)
(1.8 ± 1.7)
CLAUT
7
(1.9 ± 0.29)
RCA
2.88
2.88
34
97.75
97.75
48
90.9
90.9
(4.33 ± 1.23)
(1.14 ± 0.33)
(4.33 ± 1.23)
MANIAGO
7
(1.85 ± 0.89)
CAR
8.70
16.76
[21.6]
34
295.73
594.39
34
63.4
125.6
(5.98 ± 1.93)
(0.82 ± 0.09)
(3.02 ± 1.08)
[MLI]
2.43
34
82.62
13.3
23.6
(0.32 ± 0.18)
(1.12 ± 0.7)
MED
8.06
8
64.48
7.8
15.7
(0.19± 0.4)
(0.75 ± 1.58)
[VAJ]
2.41
34
81.97
12.9
23
(0.31 ± 0.17)
(1.09 ± 0.69)
PINZANO
6
(1.95 ± 0.21)
BCA
8.32
17.23
34
282.71
585.92
45,9
90.7
306.7
(14.6 ± 9.23)
(1.09 ± 0.79)
(4.32 ± 3.18)
CCR
1.37
34
46.68
63
123
(1.50 ± 0.78)
(5.86 ± 3.2)
SFA
7.55
34
256.53
47.5
93
(1.13 ± 0.81)
(4.43 ± 3.25)
POLCENIGO
6
(1.52 ± 0.62)
[ART]
2.48
7.1
[9.58]
13
32.24
305.88
16.4
24.5
267.3
(12.73 ± 5.31)
(0.39 ± 0.62)
(1.17 ± 1.92)
CAV
1.90
34
72.14
38,7
52.8
(0.92 ± 0.66)
(2.52 ± 2.16)
LIG
2.21
34
75.07
55.4
80.3
(1.32 ± 0.34)
(3.82 ± 2.79)
LIV
2.99
34
101.80
64
109.7
(1.52 ± 0.37)
(5.22 ± 1.85)
PORDENONE
6
(2 ± 0.22)
FNA
6.00
6.00
34
204.10
204.10
50.2
100.5
100.5
(4.79 ± 1.75)
(1.19 ± 0.43)
(4.79 ± 1.75)
TOT
41
61.254
61.254
474
2071.92
2071.92
605.8
1102.4
1102.4
(mean ± sd)
(1.83 ± 0.65)
(4.38 ± 2.6)
(10.21 ± 5.66)
(33.86 ± 0.36)
(147.99 ± 87.78)
(345.32 ± 190.73)
(35.6 ± 19.2)
(64.8 ± 35.96)
(183.7 ± 91.4)
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5.2. EXPECTED WILD BOAR MORTALITY FOLLOWING ASF INTRODUCTION
The Belgian ASF outbreak lasted from September 09th, 2018, to March 04th, 2020 (543 days).
Cumulated ASF reports (n=833) are represented in Figure 32: after visual inspection, only data
collected up to June 21st, 2019 (286 days since the index case) was retained for downstream analysis.
This subset (n=824) comprises 99% of outbreak reports, all of which included in Gaume region (cfr.
LICOPPE ET AL., 2023).
Figure 32: Cumulate data of ASF epidemic in Belgium (September 09th, 2018-March 04th, 2020, n=833); the cut-off point
(21/06/2019, n=824) is indicated by a vertical line
On June 21st, 2019, ASF infected area in Gaume region extended 488,82 km2; there, wild boar
population density was estimated at 2.76 ± 1.4 ind/km2, or 1348 ± 683 individuals overall (Figure 33).
Over the 286-day period, ASF cumulative incidence was 0.61, and the expected median lethal time
(expLT50) as per Equation 3 was calculated at 211 days.
In Piemonte-Liguria (PL), where the index case occurred on January 3rd, 2022, expLT50 would have fall
on August 2th, 2022. At that time, PL infected area extended for 749.65 km2, where wild boar
population density averaged 2.91 ind/km2, thus leading to a population size of 2181 individuals
(Figure 34). 178 ASF positive cases were found in PL at expLT50, so that ASF cumulative incidence
results to be 0.0816; however, at expLT50, cumulative incidence is supposed to be 0.5 (i.e., 1090 ASF
reports): therefore, the outcomes of PL search efforts result to be approximately one sixth of those
expected by a Belgian-like ASF management strategy.
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Figure 33: WB density and ASF cases in WB (n=833) in Gaume infected area (Belgium). Data collected after the cut-off
date are represented as distinct features. Original density data from PITTIGLIO ET AL., 2018 is represented in the background
(grayscale). EPSG: 3035
Figure 34: WB density and ASF cases in WB (n=178) in the ASF infected area (Piemonte-Liguria, Italy). Original density data
from PITTIGLIO ET AL., 2018 is represented in the background (grayscale). EPSG: 3035
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In 2022-23, Pordenone EDR wild boar census data included 820 individuals (0.48±0.71 ind/km2).
Assuming an expLT50 of 211 days, as calculated on the basis of viral incidence found in the Belgian
infected area (CI = 0.61 over 286-day period), ASF management system in Pordenone EDR should
account for 411 infected wild boar cadavers over a 211-day period. Based on the indication of a 15%
annual mortality due to natural deaths and vehicle collisions, an additional quota of 8.67% of the wild
boar population should be included (n=71), thus tallying up to 482 wild boar cadavers for the whole
study area at expLT50. Given that 86% of the census population (n=706) occupies the northern
hunting area included in Prealpi Carniche and Pedemontana pordenonese districts, in which wild boar
population density reaches 0.93±0.85 ind/km2, 414 wild boar cadavers should be expected in this
area alone, averaging 18.8±13.5 cadavers per hunting reserve after 211 days from the index case
(Figure 35).
Figure 35: Expected number of cadavers at expLT50 (211 days from the detection of the index case) in Pordenone EDR. Null
values are not shown. Hillshade based on TINITALY DTM is used as a base layer. EPSG: 32633
5.3. SUPPORT FOR CADAVERS’ MANAGEMENT IN THE FIELD
The habitat that was considered suitable for wild boar according to Corine Land Cover (CCL hereafter)
and altitude is represented in Figure 36. Based on CLC classification and elevation data, 1797 km2
(79%) of the Pordenone EDR territory resulted suitable for wild boar, out of which approximately 52%
agricultural land, 43% forests and 5% transitional woodland and shrubs. 61 km2 of the study area is
located at more than 1800 m above sea level; however, the overlap between high elevation areas
and CLC unsuitable habitat was high (89%), so that only a negligible proportion of excluded territory
(0.4%) was due exclusively to altitude.
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Remote areas identified through linear distance from the road network are represented Figure 37.
Remote areas as identified by linear distance from the road network are found exclusively on the
northern part of the study area.
Site suitability for intermediate collection points based on habitat suitability, distance from the road
network and expected wild boar cadavers is represented in Figure 38. Candidate sites for ICCs
(suitability ≥ 0.75) were entirely determined on the territory of three hunting reserve (Aviano in
“Pedemontana pordenonese” hunting district, Andreis and Clauzetto in “Prealpi carniche” hunting
district)
Figure 38: Site suitability for ICCs, based on expected number of WB cadavers, WB habitat suitability and distance from
the road network. EPSG: 32633
Figure 36: WB habitat eligibility based on Corine Land
Cover classes. EPSG: 32633
Figure 37: Remote areas, road network and rendering
plant of Morasno al Tagliamento. EPSG: 32633
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6. DISCUSSION
6.1. ENHANCED PASSIVE SURVEILLANCE
Enhanced passive surveillance (EPS hereafter) is considered a pillar of ASF management in wild boar
(BOUÉ ET AL., 2017; GUBERTI ET AL., 2022; MORELLE ET AL., 2019; PROBST ET AL., 2017; ŠATRÁN,
2019), providing data for both epidemiological surveillance by actively looking for samples, and
disease control through the removal of viral reservoirs from the environment (LICOPPE ET AL., 2023,
GERVASI ET AL., 2020).. The detection of 1% of the overall wild boar population is considered an
indicative threshold to assess EPS reliability (GUBERTI ET AL., 2022), allowing to pinpoint an increase
in mortality which should raise awareness in ASF-free areas. For this reason, this threshold is often
used in the definition of “suspect ASF case”, as is the case in most Italian guidelines. However, if the
size of the wild boar population is unknown, the concept of “increased mortality” could be
misleading, and would benefit from a further refinement.
In Pordenone EDR, candidate sites for EPS were identified based on spatially clustered data (n = 49)
relative to a Salmonella epidemic, comprising sick animals died and found opportunistically between
February 7th, 2012, and June 22nd, 2015. Considering that the available data was not originally
integrated with field measurement, and its spatial accuracy was likely too low to pinpoint potential
deathbed sites, transects were ultimately individuated alongside suitable habitats by the field-expert
operators of Pordenone Forestry Corp, and were thus expected to bear positive results.
Unfortunately, this was not the case: in fact, no single wild boar cadaver was found during EPS
activities, which encompassed considerable search efforts, exerted during a lengthy timeframe, thus
leading to null efficacy and effectiveness of EPS activities. Such results were not expected in the study
area, all the more reason considering that dead wild boars had been consistently found during the
salmonellosis outbreak.
Although a mismatch between 2012-15 surveillance outcomes and the EPS activity reported herein
could be partially linked to sample frequency (i.e., to the increased mortality caused by Salmonella,
CONEDERA ET AL., 2014), and to different sampling conditions (i.e., to the longer span of surveillance
activities, and to the broader sampling strategy), the absence of any finding in Pordenone EDR could
be indicative of either an insufficient sampling effort for surveillance during peace times, or of the
presence of bias/biases in the surveillance strategy.
Undoubtedly, protracted periods of null findings could demotivate both the operators and local
administrations, whose workforce would seem to be negatively impacted by unfruitful search
activities. As increasing sampling effort is often made impossible by limited resources, EPS could be
improve by focusing search activities on potential deathbed sites. To this aim, spatial modelling could
be considered: as an example, species distribution models including ordinary passive surveillance
data could be implemented to highlight suitable areas. Data used for this purpose should be skimmed
from accidental mortality such as roadkill or predation, and should be accompanied by field
measurement in order to enhance spatial accuracy on a suitable scale. In fact, this activity has been
considered for Pordenone EDR, and it will be undertaken in the foreseeable future using SINVSA
notifications. Additionally, to quantify the reliability of human operators in detecting dead animals
alongside EPS transects, scent hounds could be deployed as a golden standard.
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However, it must be considered that in certain contexts (e.g., rugged territories, dense underwood),
the search for wild boar cadavers could turn out all the way ineffective (DESVAUX ET AL., 2021): to this
point, the wild boar population in Pordenone EDR is indeed located in the northern Alpine area, which
can present morphological obstacles to EPS activities. Nonetheless, EPS has proven to be an
important asset of ASF surveillance, and should be sustained during both disease-free and escalation
periods (GUBERTI ET AL., 2022); it is therefore worth pursuing an optimization of search efforts, until
the system is sensitive enough to detect suspicious shifts in mortality.
6.2. EXPECTED WILD BOAR MORTALITY FOLLOWING ASF INTRODUCTION
Knowledge regarding the size of a population affected by a disease is crucial for determining
epidemiological parameters, such as disease prevalence and incidence: unfortunately, this data is
often lacking, or missing altogether. In this study, in order to calculate cumulated incidence (CI
hereafter) of ASF in Belgium, a large-scale wild boar population density estimate was used. However,
this estimate was produced on the basis of spatially and temporally heterogeneous data, aiming at
providing a tool for large-scale epidemiological analyses (PITTIGLIO ET AL., 2018). While an improvement
in wild boar population assessment is undoubtedly desirable, the results presented herein should be
interpreted with caution, aimed at providing a parsimonious scenario for disease management.
The characteristics of an epidemic event are strictly bounded to the underlying factors that determine
the spread of the disease; notably, the demographic and behavioural dynamics of the affected
population. If a population is naïve to a particular disease and can be considered closed (i.e.,
unaffected by recruitment, deaths, and migration), CI is representative of the average individual risk
of developing that disease, during a certain timeframe. Considering the Belgian ASF outbreaks, the
assumption of closure was closely met in terms of migrations, given that the emergence of the
disease was followed by the implementation of severe restrictive measures. Conversely, both
infected and non-infected animals were certainly removed during the timeframe considered for
calculating CI, thus lowering the probability of viral transmission by direct contact: this has likely
biased, by deficiency, the calculation of epidemiological CI. Moreover, the most relevant sources of
infection (i.e, ASF positive cadavers) were actively removed from the field, thus further biasing CI
calculation towards lower values. In fact, the CI value calculated in the present work from the
beginning of the Belgian outbreak up to June 21st, 2019 (CI = 0.61), is highly similar to the “true”
values reported for the same area, in overlapping periods, by LICOPPE ET AL., 2023 (CI = 0.65±0.04 up
to March 19th, 2019; CI = 0.57±0.18 up to December 19th, 2019), whose calculations were affected
by the same biases.
As for Pordenone EDR, the absolute abundance of the wild boar population was assessed through
the technique of census by vantage point, which is susceptible to known biases (ENETWILD CONSORTIUM
ET AL., 2018). Nonetheless, the local data used by PITTIGLIO ET AL., 2018 to estimate population density
arose from the same technique: in fact, wild boar population census data obtained for 2021-22 in
Pordenone EDR (0.40 ± 0.67 ind/km2) was only slightly higher than the estimates available in PITTIGLIO
ET AL., 2018 for the same area (0.35 ind/km2). Given that the general trend of wild boar populations
all over Europe has either been stable or increasing compared to the source data used by PITTIGLIO ET
AL., 2018, the estimated effects of an ASF outbreak in Pordenone EDR in absolute terms (i.e., number
of cadavers) is likely underestimated.
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Considering all the above, integrating CI with a measure of the efforts to control ASF well adapts to
the purpose of the present study: indeed, CI as calculated herein should not be considered in
epidemiological terms, but rather as a parameter representing the proportion of ASF positive wild
boar that are likely to arise from an efficient ASF management system, allowing to depicting a likely
scenario and a baseline target for future strategies of disease management. As the both disease
incidence, and efficacy of the depopulation, are susceptible to local variability, a common reference
to evaluate the outcomes of different ASF management experiences, over different wild boar
populations, is needed.
Given that both CI, and the number of detected animals, show variable growth rates at different
stages of the outbreak, and especially near the beginning and the end of the emergency, it seems
reasonable to set this reference at the median point, thus representing the number of days since the
detection of the index case, after which half of the ASF positive wild boar population would have
died, either as a consequence of the disease, or harvesting. Considering that ASF virus is highly
resistant, remaining active in infected cadavers over a long period of time, the eradication of ASF
before endemicity will only be accomplished by inducing both ASF lethality and case detectability to
approach 100% (i.e., all infected animals die, are detected, and add up in assessing CI). As one of the
very few cases in which ASF eradication was attained, such scenarios were likely closely met in the
Gaume infected area (Belgium): therefore, in the present work, the reference timeframe spanning
from the detection of ASF index case, to 50% expected CI, was calculated from this area. As no similar
index was known to the authors, it is referred herein as “expected median lethal time” (expLT50),
based on the similarities with median lethal dose LD50.
The comparison of CI calculated at expLT50 in Piemonte-Liguria (PL, Italy) provides an example of the
application of this indices as a tool for assessing the quality of ASF management strategies; in this
case, the mismatch between the CI expected (0.5) and observed (0.08) suggest a high degree of
underdetection of ASF positive animals.
6.3. SUPPORT FOR CADAVERS MANAGEMENT IN THE FIELD
Once the ASF index case has been detected, the size of the area subjected to restriction will depend
on the distribution of positive animals, dead and alive, detected in the field The minimization of
impacts exerted by ASF eradication strategy is therefore bound to a timely early detection on one
hand (i.e., disease surveillance), and to prompt interventions on the other. To this second point,
advancing territorial planning is essential: this include the definition of the network for transporting
possibly ASF infected dead animals from the retrieval/culling site, to the rendering plant.
Although the transport outside Restriction Zones of dead animals derived from hunting and culling is
clearly advised against by guidelines (e.g. MOPS, GUBERTI ET AL., 2022), it is allowed by national
legislation. Accordingly, the sample for ASF testing from both cadavers retrieved from the field, and
carcasses derived from harvesting, must be withdrawn inside the restriction zone in which they
originated, and only then headed towards rendering or, eventually and exclusively for ASF negative
carcasses derived from harvesting, meat treatment (ORDER N. 5, 2023).
However, FVG PRIU prescribes the identification of only one regional intermediate collection centre
(ICC hereafter), which to date has not been identified yet: in a view to manage wild boar cadavers on
smaller territorial units, thus lowering the risk of viral spread to larger areas, the individuation of
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further candidate sites for setting up ICCs is therefore advisable. To this point, it could be indicative
to consider that the implementation of an efficient management strategy in Gaume (Belgium)
allowed to contain the ASF spread inside a 488 km2 infected area, which is approximately one quarter
the size of Pordenone EDR: therefore, more than one ICC could be identified.
Considering that animal products destined to consumption must be kept physically separated from
cadavers retrieved from the field, it follows that ICCs should include two distinct lines for sampling
and transporting dead animals. As that the number of dead animals that the system is expected to
produce is prone to changes, this network of infrastructures deployed to this end should allow for
some adaptability; nonetheless, it should pursue a minimum target of an efficient management of
expected ASF cases, of which an approximate indication was provided herein.
In the present work, considering that ICCs should be located where expected wild boar mortality is
higher, and that their deployment would be optimized by avoiding manual transportation of
carcasses for long distances, candidate sites for ICCs were identified based on census data, habitat
suitability for wild boar, and linear distance from the road network, keeping in mind the following
issues:
• Wild boar census data provided by vantage point is very likely affected by sampling bias:
notably, inconsistent effort amongst hunting reserves due to different number of operators
available (i.e., hunters and personnel of the Forestry Corp), and differential detectability of
animals due to territorial heterogeneity. Considering that the current ASF management
strategy pivots on wild boar depopulation, and that this activity relies upon the same
operators that provide census data, the aforementioned biases will eventually be reflected
on ASF management, unless additional resources are provided. Currently, a measure of these
biases is not available for the study area, and should be the target of further studies.
• The identification of habitat suitability based solely on Corine Land Cover and elevation is
certainly a rough methodological approach; nonetheless, given the ecological plasticity
exhibited by this species, aggregated CLC classes are likely to give an indicative approximation
of suitable territory, all the more reason when analysed in conjunction with census data.
• As a proxy of difficulty in transporting carcasses, linear distance from the road network can
be misleading: this is especially true when rough territories are considered, where steep
valleys and rock jumps can impede access to roads over small linear distances.
Three hunting reserves in Pordenone EDR resulted high suitable for ICCs (< 0.7): all three are located
in the northern part of the study area, which present several characteristics that support this
indication. Namely:
• it is densely populated by wild boar;
• it consist of mostly rough territory;
• it is far from the rendering plant.
Of course, a more precise definition of the ICC location(s) should take into account specific knowledge
of local resources (e.g., availability of public space, the presence of abandoned buildings/laboratories,
availability of electricity/water sources etc.) and available personnel. As an example, collection
centres already deployed for temporarily field stocking of hunted animals could be considered a
valuable option, whether they provide a suitable environment to apply the biosafety requirements
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of ICCs. However, a characterization of the number, size, type and distribution of these structures is
not currently available. On-site burial is allowed in extrema ratio by national legislation. Transporting
dead animals in rough areas can be arduous, implying a non-negligible risk of injury for the operators.
Moreover, it inherits a considerable risk of bodily leakage, and consequent viral spread. Therefore, it
seems appropriate to associate on-site burial with the distance from the road network. To this point,
remote areas identified in the present work could provide an approximate indication for the location
of burial sites, and could be integrated in the planning of ASF management strategy. Given that
excavating pits for single burials would likely be unfeasible as a routine method, remote areas
identified herein could represent approximate locations for mass burial trenches. In both cases, it
must be considered that that burying corpses inherits a high risk of soil and water contamination,
and should be pursued only after a fine characterization of the local environment: most importantly,
local hydrology and pedology should be considered, in order to minimize the spread of both the
bodily fluids leaking from the decomposing cadaver(s), and the disinfectants used to deactivate ASFV.
To the latter point, citric acid has been suggested for soil disinfection due to ASFV low tolerance to
acidic conditions (CARLSON ET AL., 2020), and could be considered as an alternative to traditional
products.
.
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7. CONCLUSIONS
ASF is currently an existential threat to the European swine industry. Given the role of wild boar as a
source of infection and viral reservoir, the activities of epidemic surveillance, population control and
removal of cadavers represent key aspects of disease control. These tasks represent a conspicuous
challenge, requiring solid bases for collaboration amongst stakeholders, information flow and
coordination between operators in the various steps of the emergency. In order to maximize their
efficiency and effectiveness, comprehensive territorial planning is necessary to identify the network
of infrastructures on which they rely upon. The present work focussed on a small part of these
requirements, while contributing in building the operative framework on which ASF preparedness is
based.
The Italian experience with ASF underlines how viral introduction is often anthropogenic, and
therefore unpredictable in time and space. The abundance of harsh territories will additionally
hamper both early detection, and removal of cadavers from newly discovered infected areas; in this
view, preparedness acquired during peace time is essential for eventually achieving ASF control and
eradication. The enhanced passive surveillance (EPS hereafter) activities carried out in Pordenone
EDR represent one of the few examples of active quest for wild boar cadavers implemented in ASF-
free areas in Italy, and were realized thanks to the commitment of the Officers and field operators of
the Pordenone forestry inspectorate. Despite having proven ineffective during the first 20 months of
implementation, the EPS protocol will undergo further adjustments in order to improve its
performances.
At the present state, the results presented herein stress the need for additional workforce for ASF
management, particularly for carrying out EPS, and very likely for wild boar demographic control. As
a rough comparison, the ASF outbreak in Belgium was controlled by deploying one operator each 20
hectares only to the quest for wild boar cadavers, while removal was carried out exclusively by
Authorities (forest services and Civil Protection), in a view to avoid viral spread (LICOPPE ET AL., 2023).
In Italy, wildlife management pivots on leisure hunting. However, when facing epidemic emergencies
such as ASF, the outreach of this activity will likely be insufficient: to this point, it is worth considering
that inducing a decrease in the wild boar population is rarely achieved, although highly incentivised,
even during peace times.
In a “One Health” perspective, the AHL encourages the participation of Veterinary Authorities in
wildlife management; nonetheless, their activity relies on accurate and updated population
assessments, which are rarely available for wild species, as underlined by the case of ASF in the wild
boar population. This problem is often linked to a lack of personnel dedicated to wildlife monitoring:
as an example, in the Italian context, this activity relies heavily on the voluntary efforts of leisure
hunters, which are spatially skewed. In Pordenone EDR this factor is, currently, not accounted for,
thus very likely leading to biased population assessments. To account for these biases, it seems
therefore advisable to undertake targeted studies aimed at correlating routinary census data with a
reliable estimate of population abundance.
Although describing the earliest steps required by ASF management in wild boar, many other are not
addressed by the present work. Notably, the importance of adopting physical measures to retain the
spread of the virus (i.e. fencing) seems self-evident, all the more reason considering the difficulties
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encountered in estimating and managing the wild boar population. These actions should follow
careful mapping of ecological barriers and weak spots, thus defining the territorial units for
downstream management actions. This would allow to anticipate the measures required by
restriction zoning, leading to a timely intervention after the detection of the index case. In this view,
further studies for identifying barriers and corridors in relation to wild boar movement are
encouraged.
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ANNEX 1: TRANSECTS FOR ENHANCED PASSIVE SURVEILLANCE IN PORDENONE EDR
Transects for EPS in Pordenone FS (FNA=Fontanafredda-
Nave)
Transects for EPS in Polcenigo FS (LIV=Livenza; LIG=Ligont;
ART=Artugna; CAV=Cavrezza)
Transects for EPS in Polcenigo FS, surveyed by Claut FS
(RCA=Rio Cavrezza)
Transects for EPS in Barcis FS (MAS=Malnisio stradale;
MAL=Malnisio; GRI=Grizzo; BAL=Borgo Alzetta)
Transects for EPS in Maniago FS (MLI=Maniago-Libero;
VAJ=Vajont; CAR=Cavasso-Arba; MED=Meduno)
Transects for EPS in Pinzano FS (BCA=Bonifica Casarotto;
CCR=Col Cravest; SFA=Strada fantasma)
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ANNEX 2: FIELD NOTE FOR ENHANCED PASSIVE SURVEILLANCE
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ANNEX 3: ZONING APPLIED TO ASF MANAGEMENT OF WILD BOAR IN ITALY
Since the publication of the ASF National Surveillance and Eradication Plan (NEEP hereafter), the
following activities must be carried out at regional level on all national territory:
• Adoption of Regional Plans of Urgent Interventions (Piani Regionali Iterventi Urgenti, PRIU
hereafter)
• Execution of enhanced passive surveillance surveys at monthly cadence
• Enforcement of mandatory reporting of dying or dead wild boars to the Local Health Unit (ASL
hereafter) (LAW N. 29, 2022)
• Enforcement of restrictions on the transportation of captured wild boars, as specified by
regions, and following ASLs authorization
• Execution of ASF diagnostic tests on all wild boar cadavers found in the field, and on all suspect
cases as per DELEGATED REGULATION (EU) N. 689, 2019
• Culling of all captured, illegally detained, or unidentified suids. Avoidance of wild boar
urbanization.
Once EU zoning is instituted, ASF management activities must be undertaken accordingly; inside the
infected area (RZ II and RZ III), these include:
• Active search of wild boar cadavers, focussing on peripheral areas.
• ASF testing for all wild boars found dead, moribund, captured, or culled.
• Adoption of a plan for management, sampling, and disposal of cadavers; setup of collection
points for sampling and temporary stocking.
• Depopulation of wild boar by means of control, favouring techniques that minimize animal
movement. Specific biosecurity measures must minimize the risk of viral spread.
• Setup of trapping devices to facilitate control activities.
• Ban on hunting on wild boar; ban on collective hunting (> 3 hunters) for all other species.
• Ban on export of wild suids and derived products.
• Ban on transportation and export of all living animal, except for culling.
• Restriction on all outdoors activities.
• Enforce the ban on attractive feeding for wild boar.
• Fencing, aiming at limiting animal movement and facilitate ASF eradication measures.
Inside RZ I, activities must be tailored to the results obtained in the infected area; these include:
• Enforcement of passive surveillance, including enhanced passive surveillance
• Unrestricted hunting and culling of wild boar, aimed at removing the maximum number of
animals possible.
• ASF testing of all culled animals, unless a derogation by the ASF Commissioner is provided.
• Ban on transportation and export of all living animal, except for culling and butchering.
