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Number of harvested foxes (dashed lines) and prevalence of sarcoptic mange (bars) in foxes collected from hunters in Gävleborg county. Data on the prevalence of sarcoptic mange are not available after 1982.
Source publication
Rapid declines in red fox Vulpes vulpes populations have followed outbreaks of epizootic mange caused by the mite Sarcoptes scabiei. In Sweden, the first outbreak of sarcoptic mange started in 1977/1978 and affected the whole country by 1984. Here we used data on the number of harvested red foxes (51 480) from Gävleborg county (18 199 km²) in Swede...
Citations
... As the mange disease progresses, the host may experience secondary infections, sepsis, and eventually death [3,5]. High mortality rates are frequently seen following sarcoptic mange infection in wildlife, especially among wild canids [6][7][8]. While sarcoptic mange is an enzootic disease fully established in some species, novel outbreaks are still periodically reported [9,10]. ...
Background
Sarcoptic mange is a skin disease caused by the contagious ectoparasite Sarcoptes scabiei, capable of suppressing and extirpating wild canid populations. Starting in 2015, we observed a multi-year epizootic of sarcoptic mange affecting a red fox (Vulpes vulpes) population on Fire Island, NY, USA. We explored the ecological factors that contributed to the spread of sarcoptic mange and characterized the epizootic in a landscape where red foxes are geographically constrained.
Methods
We tested for the presence of S. scabiei DNA in skin samples collected from deceased red foxes with lesions visibly consistent with sarcoptic mange disease. We deployed 96–100 remote trail camera stations each year to capture red fox occurrences and used generalized linear mixed-effects models to assess the affects of red fox ecology, human and other wildlife activity, and island geography on the frequency of detecting diseased red foxes. We rated the extent of visual lesions in diseased individuals and mapped the severity and variability of the sarcoptic mange disease.
Results
Skin samples that we analyzed demonstrated 99.8% similarity to S. scabiei sequences in GenBank. Our top-ranked model (weight = 0.94) showed that diseased red foxes were detected more frequently close to roadways, close to territories of other diseased red foxes, away from human shelters, and in areas with more mammal activity. There was no evidence that detection rates in humans and their dogs or distance to the nearest red fox den explained the detection rates of diseased red foxes. Although detected infrequently, we observed the most severe signs of sarcoptic mange at the periphery of residential villages. The spread of visual signs of the disease was approximately 7.3 ha/week in 2015 and 12.1 ha/week in 2017.
Conclusions
We quantified two separate outbreaks of sarcoptic mange disease that occurred > 40 km apart and were separated by a year. Sarcoptic mange revealed an unfettered spread across the red fox population. The transmission of S. scabiei mites in this system was likely driven by red fox behaviors and contact between individuals, in line with previous studies. Sarcoptic mange is likely an important contributor to red fox population dynamics within barrier island systems.
Graphical Abstract
... Due to their proximity to humans and domestic animals, such as dogs, they can potentially act as reservoirs for infectious and zoonotic agents [5]. Orphanhood is the most common cause of death in young foxes, while other categories of foxes most frequently die as a result of trauma or mange [6,7]. While these factors contribute to the mortality of different age categories of foxes, it is noteworthy that neoplastic diseases emerge as the primary cause of death in dogs in developed countries [8]. ...
The red fox, found on all continents except Antarctica, occupies diverse habitats. In Croatia, it is an indigenous wild species with a population density of 0.7 animals per square kilometer. While tumors in wild animals from the Canidae family are scarce, the true prevalence and diversity of tumors are likely underestimated due to limited research. So far, a limited number of tumors have been observed among the red fox population, either in their natural habitat or in captivity. As part of the National Rabies Control Program, we examined 1890 red fox carcasses over a four-year period. Our focus was on identifying abnormalities on the skin and internal organs that suggest potential neoplastic proliferation. Five red foxes, three males and two females, were found to have growths resembling potential tumors. Their age distribution spanned from 2 to 7 years. Microscopic investigation revealed two collagenous hamartomas, two Meibomian gland adenomas, and one intra-abdominal teratoma within a cryptorchid testis. This retrospective study aims to provide a comprehensive description of tumor and tumor-like lesions observed in free-range red foxes from Croatia, marking the first research of its kind in Croatia.
... Due to their proximity to humans and domestic animals such as dogs, they can potentially act as reservoirs for infectious and zoonotic agents [5]. Orphanhood is the most common cause of death in young foxes, while other categories of foxes most frequently die as a result of trauma or mange [6,7]. While these mentioned factors contribute to the mortality of different age categories of foxes, it is noteworthy that neoplastic 2 diseases emerge as the primary cause of death in dogs [8]. ...
The red fox, found on all continents except Antarctica, occupies diverse habitats. In Croatia it is an indigenous wild species with a population density of 0.7 animals per square kilometer. While tumors in wild animals from the Canidae family are scarce, the true prevalence and diversity of tumors are likely underestimated due to limited research. So far, a limited number of tumors were observed among the red fox population, either in their natural habitat or in captivity. As part of the National rabies control program, we examined 1,890 red fox carcasses over a four-year period. Our focus was on identifying abnormalities on the skin and internal organs that suggest potential neoplastic proliferation. Five red foxes, three males and two females, were found to have growths resembling potential tumors. Their age distribution spanned from 2 to 7 years. Microscopic investigation revealed two collagenous hamartomas, two Meibomian gland adenomas and one intra-abdominal teratoma within a cryptorchid testis. This retrospective study aims to provide a comprehensive description of tumor and tumor-like lesions observed in free-range red foxes from Croatia, marking the first research of its kind in Croatia.
... dispersal habits or variable daily range, facilitate the spread of the pathogen outbreaks (Carricondo-Sanchez et al., 2017;Soulsbury et al., 2011). Consequently, the sarcoptic mange is endemic in many red fox populations across Europe with some isolated outbreaks associated with important population decreases, even close to extinction, and cascading ecological impacts (Henriksen et al., 1993;Lindström, 1991;Soulsbury et al., 2007;Willebrand et al., 2022). ...
... Like the present study, a host range reduction was also documented [7], and very low numbers of wombats continue to occur there [23]. Host population declines associated with S. scabiei are widespread in affected mammals, such as red-fox [30][31][32], kit fox [33], vicuña [34,35], ibex [36,37], chamois [38], grey wolf [11] and coyote [15]. Importantly, this research is the first to test for the effect of density in mange epizootics where transmission is principally environmental [9]. ...
Invasive environmentally transmitted parasites have the potential to cause declines in host populations independent of host density, but this is rarely characterized in naturally occurring populations. We investigated (1) epidemiological features of a declining bare-nosed wombat (Vombatus ursinus) population in central Tasmania owing to a sarcoptic mange (agent Sarcoptes scabiei) outbreak, and (2) reviewed all longitudinal wombat-mange studies to improve our understanding of when host population declines may occur. Over a 7-year period, the wombat population declined 80% (95% CI 77-86%) and experienced a 55% range contraction. The average apparent prevalence of mange was high 27% (95% CI 21-34), increased slightly over our study period, and the population decline continued unabated, independent of declining host abundance. Combined with other longitudinal studies, our research indicated wombat populations may be at risk of decline when apparent prevalence exceeds 25%. This empirical study supports the capacity of environmentally transmitted parasites to cause density independent host population declines and suggests prevalence limits may be an indicator of impending decline-causing epizootics in bare-nosed wombats. This research is the first to test effects of density in mange epizootics where transmission is environmental and may provide a guide for when apparent prevalence indicates a local conservation threat.
... A notable aspect of the literature in this study is the occurrence of research themes in pathogen impacts assessed among host species, especially for well-studied host species. For example, red foxes were commonly used to assess population and community-level efects of infection [60][61][62]. In contrast, studies on bare-nosed wombats, Iberian ibexes, and Japanese raccoon dogs were often used to assess the immunological and physiological efects given infection [38,[63][64][65][66][67][68][69], whereas coyotes and grey wolves were more frequently used to assess the behavioural and social efects of infection [70][71][72][73]. ...
... Te red fox was ranked towards the middle of the conservative AIS ranking (0.737), indicating that the immunopathology associated with its S. scabiei infection is not as severe on average as some other host species, yet it has received the most attention within the literature. Te red fox has experienced occasional marked population declines throughout much of its range due to sarcoptic mange, with the disease persisting in relatively high prevalence [62,88]. Sample Size per Impact (log + 1) Figure 4: Free-living Sarcoptes scabiei host species (27) plotted against the average impact score (AIS) for S. scabiei impacts, with conservative criteria applied and the average range of AIS also shown. ...
Most pathogens infect more than one host species, and given infection, the individual-level impact they have varies among host species. Nevertheless, variation in individual-level impacts of infection remains poorly characterised. Using the impactful and host-generalist ectoparasitic mite Sarcoptes scabiei (causing sarcoptic mange), we assessed individual-level variation in pathogen impacts by (1) compiling all documented individual-level impacts of S. scabiei across free-living host species, (2) quantifying and ranking S. scabiei impacts among host species, and (3) evaluating factors associated with S. scabiei impacts. We compiled individual-level impacts of S. scabiei infection from 77 host species, spanning 31 different impacts, and totalling 683 individual-level impact descriptions. The most common impacts were those affecting the skin, alopecia (130 descriptions), and hyperkeratosis coverage (106). From these impacts, a standardised metric was generated for each species (average impact score (AIS) with a 0-1 range), as a proxy of pathogen virulence allowing quantitative comparison of S. scabiei impacts among host species while accounting for the variation in the number and types of impacts assessed. The Japanese raccoon dog (Nyctereutes viverrinus) was found to be the most impacted host (AIS 0.899). We applied species inclusion criteria for ranking and found more well-studied species tended to be those impacted more by S. scabiei (26/27 species AIS < 0.5). AIS had relatively weak relationships with predictor variables (methodological, phylogenetic, and geographic). There was a tendency for Diprotodontia, Artiodactyla, and Carnivora to be the most impacted taxa and for research to be focussed in developed regions of the world. This study is the first quantitative assessment of individual-level pathogen impacts of a multihost parasite. The proposed methodology can be applied to other multihost pathogens of public health, animal welfare, and conservation concern and enables further research to address likely causes of variation in pathogen virulence among host species.
... Predicting outcomes under uncertainty is one thing, predictions without understanding uncertainty can result in unexpected surprises (Allen and Gunderson 2011, Seville et al. 2015). For example, the effects of the sarcoptic mange on the fox population and many of its prey populations when it first entered Sweden came as a surprise (Lindström et al. 1994, Willebrand et al. 2021. I think we need more emphasize on explaining knowledge, uncertainty and surprise to stakeholders and students (Tobias and Everson 2002). ...
THIS IS NOT AN ABSTRACT This is not a traditional manuscript and is a result of my thoughts on wildlife research since NKV decided to start Wildlife Biology to replace the national journals 30 years ago. I am not sure that this is a format suitable for Wildlife Biology but it would be interesting to know what you think. Best wishes, Tomas Willebrand
