Balantidium coli

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GLOBAL WATER PATHOGEN PROJECT
PART THREE. SPECIFIC EXCRETED PATHOGENS: ENVIRONMENTAL AND
EPIDEMIOLOGY ASPECTS
BALANTIDIUM COLI
Francisco Ponce-Gordo
Complutense University
Madrid, Spain
Kateřina Jirků-Pomajbíková
Institute of Parasitology Biology Centre, ASCR, v.v.i.
Budweis, Czech Republic

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Citation:
Ponce-Gordo, F., Jirků-Pomajbíková, K. 2017. Balantidium coli. In: J.B. Rose and B. Jiménez-Cisneros, (eds)
Global Water Pathogens Project. http://www.waterpathogens.org (R. Fayer and W. Jakubowski, (eds) Part
3 Protists) http://www.waterpathogens.org/book/balantidium-coli Michigan State University, E. Lansing, MI,
UNESCO.
Acknowledgements: K.R.L. Young, Project Design editor; Website Design
(http://www.agroknow.com)
Published: January 15, 2015, 11:50 am, Updated: October 18, 2017, 5:43 pm

Balantidium coli
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Summary
To date, Balantidium coli is the only ciliate protozoan
reported to infect the gastrointestinal track of humans.
During its life cycle, two stages exist: the active trophozoite
stage which inhabits the hindgut, and the resting/resistant
cyst stage which is shed with the feces and is the
transmissible stage to new hosts. The parasite can infect a
wide range of mammals, pigs being the main reservoir. The
organism has also been found in some birds.
In most cases, B. coli is not considered a public health
problem because infections are usually asymptomatic;
however, in some (still not clearly determined)
circumstances the parasite could invade the intestinal
mucosa causing a disease known as balantidial dysentery
(balantidiasis) which could be fatal. Transmission from one
infected individual to others is by a fecal-oral route in
which contaminated drinking water or food are the main
modes of transmission. Close contact with pigs and poor
condition of the water sources are the main risk factors
associated with the infection by the parasite.
Control measures includes the identification and treatment
of infected people, the safe disposal of excreta (both of
human and animal origin), avoiding the use of night soil as
fertilizer for vegetables to be consumed raw, and the
improvement in the quality of the water sources. There
have not been any specific studies about B. coli cyst
survival time in the environment or about specific
inactivation processes during wastewater or drinking water
treatment.
The protozoan ciliates of the genus Balantidium are
transmitted by a fecal-oral route in which cysts are the
infective stage. Balantidium cysts can be present in
temperate and tropical surface waters worldwide. Among
the species in this genus, there is only one infecting
humans, Balantidium coli, and no subspecies, serotypes, or
genetically diverse types have been named to date. The
main reservoir of this species is swine. Human infections
are related worldwide in relation to low sanitation or to
contamination of drinking water sources with human and
animal (especially swine) feces. Worldwide prevalence is
low, estimated less than 1%, with most cases reported in a
few endemic areas in which prevalence could rise up to
30%. Most infections are asymptomatic, but the organism
could in some cases produce a severe infection and even
the death of the host, usually associated with other
concurrent illness. Waterborne transmission has been
documented in some cases
1 Epidemiology of the disease and
pathogen
1.1 Global burden of disease
1.1.1 Global distribution
Balantidium coli is reported worldwide although it is
more common in temperate and tropical regions (Areán and
Koppisch, 1956). The Philippines, Papua New Guinea, some
Pacific Islands, some regions of Central and South America
and central Asia are considered endemic areas (Fletcher et
al., 2012; Kline et al., 2013; Owen, 2005; Schuster and
Ramirez-Avila, 2008; Zaman, 1978).
In humans, the overall prevalence is estimated to be
0.02 to 1% (Areán and Koppisch, 1956; Boonjaraspinyo et
al., 2013; Schuster and Ramirez-Avila, 2008; Walzer and
Healy, 1982). It is possible that these numbers are an
underestimation of the real situation as the parasite is
considered usually asymptomatic and most reports and
statistics are based on data from symptomatic or
compromised patients (Cooper and Guderian,
1994; McCarey, 1952; Nuti et al., 1979; Walzer et al.,
1973). In endemic areas of South America the prevalence
has been reported to be 1 to 12% (Areán and Koppisch,
1956; Devera et al., 1999; Esteban et al., 1998), and even
near 30% in Oceania (Kline et al., 2013; Walzer and Healy,
1982).
1.1.2 Symptomatology
It remains undetermined whether B. coli alone is
pathogenic. Trophozoites inhabit the intestine, feeding on
bacteria and other intestinal contents. In most cases,
infections are asymptomatic and the infected host shows no
clinical signs, suggesting that this ciliate is an opportunistic
parasite that could take advantage of the weakened status
of the host caused by other infections, lesions, or diseases.
In such cases, the parasite could invade the intestinal wall
causing the disease known as balantidiasis or balantidial
dysentery. In the chronic form of the disease, the symptoms
varied from unspecific abdominal disorders (diarrhea,
abdominal pain) to cramping rectal pain, nausea and
vomiting, whereas in the acute form these symptoms can be
accompanied by mucus and blood in feces, and in severe
cases, hemorrhages and perforation could occur resulting
in parasite dissemination to other tissues or even in the
death of the host (Areán and Koppisch, 1956; Neafie et al.,
2011; Zaman, 1978). In most of the human patients with
extraintestinal balantidiasis, a concurrent intestinal
infection was usually not diagnosed (Anargyrou et al.,
2003; Dhawan et al., 2013; Sharma and Harding, 2003;
Vasilakopoulou et al., 2003) but a common characteristic
was that they suffered from another illness such as
diabetes, hepatic disorders, pulmonary and renal
disorders, HIV infection or cancer (e.g. Anargyrou et al,.
2003; Clyti et al., 1998; Ferry et al., 2004; Karuna and
Khadanga, 2014; Sharma and Harding, 2003;
Vasilakopoulou et al., 2003). In the last few years, several
cases have described the presence of B. coli in urine (Maino
et al., 2010; Bandyopadhyay et al., 2013; Karuna and
Khadanga, 2014; Khanduri et al., 2014), which stresses the
importance of the examination of the urinary specimens.
The economic importance of balantidiasis is not well
determined. In different studies it has been suggested that

Balantidium coli
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B. coli infections in animals could affect the development of
the offspring directly (by causing mortality or reducing the
weight gain; (Bauri et al., 2012; Bilic and Bilkei, 2006) or
indirectly (i.e., by affecting the milk composition in the
mother; Hinde, 2007). There are no data regarding the
economic status of balantidiasis in humans.
1.2 Taxonomic classification of the agent
1.2.1 Taxonomy
Balantidium coli, the first intestinal protozoan formally
identified in humans, is the largest protozoan inhabiting the
human intestine and the only ciliate known to infect
humans. The first formal description of this organism was
reported as Paramecium coli by Malmsten in 1857
(Malmstein, 1857) but soon afterwards it was renamed as
Balantidium coli by Stein in 1863 (Stein, 1863). Some
proposals to change this name were made during the 20th
century but they were not accepted until recently. Based on
genetic analysis, Pomajbiková et al. (2013)(Pomajbíková et
al., 2013) proposed to reclassify the human species in a
new genus, as Neobalantidium coli for the homeothermic
clade. Chistyakova et al. (2014) (Chistyakova et al., 2014)
considered this name as a junior synonym of Balantioides
coli, which was proposed by Alexeief (1931) (Alexeief,
1931). Because the nomenclature is under revision and to
avoid confusion for the readers, we use the name that
remains accepted worldwide and is commonly used in the
scientific and medical literature - Balantidium coli.
The parasite has been described in a large number of host
species (see “Reservoirs”). Based on morphological
differences of specimens gathered from different host
species, or from results of cross-infection studies, some
researchers proposed that isolates from pigs, guinea pigs,
camels and several non-human primates were different
species (e.g., (Hegner, 1934; McDonald, 1922). Such
morphological differences could be related to differences in
growth conditions (Levine 1961); this nutrient-related
variability has been also observed in in vitro cultures
(Barbosa et al., 2015; Levine, 1940). Failures by some
authors in cross-infections studies (i.e., see Awakian,
1937; Schumaker, 1930) have also led to the implication
that an isolate was host specific and therefore a separate
species. But most of these species have been considered
synonyms of B. coli (Levine, 1961; Levine, 1985). However,
Balantidium suis from pigs and Balantidium caviae from the
guinea pig have infrequently been used in publications until
recently (Schuster and Ramirez-Avila, 2008). Recent
genetic analysis with isolates from pigs, gorillas, and
humans (Ponce-Gordo et al., 2008; Ponce-Gordo et al.,
2011) have shown some genetic variability within the
species, but this is not related to the origin of the isolates
from a particular host species; in fact, these results and
others obtained with isolates from different mammalian
hosts including elk, African buffalo, several suid species
(i.e., domestic pig, red river hog and South American tapir)
and non-human primates (Pomajbíková et al., 2013; Ponce-
Gordo et al., unpublished) and from ostriches and rheas
(Ponce-Gordo et al., 2008; Ponce-Gordo et al., 2011; Ponce-
Gordo et al., unpublished) indicate that only one species
infects warm-blooded animals (mammals and birds),
Balantidium coli.
1.2.2 Physical description (morphology)
Balantidium coli has two stages in its life cycle: the
active, feeding, replicating stage (the trophozoite) that is
found most commonly in the lumen of the large intestine,
and the nonreplicating encysted stage (the cyst) that
develops in the lower colon and is excreted in the feces.
Trophozoites (Figure 1) are large (usually 100-150 µm in
length; the size range varies somewhat according to
different authors) and ovoid, with the entire cell surface
covered by cilia. A mouth-like opening, the cytostome, is
located in the anterior part of the cell. There is an elongate
or kidney-shaped macronucleus usually located in the
posterior part of the cell and a smaller, round micronucleus
which usually overlaps the macronucleus and is not easily
observable. Some vacuoles can also be seen in the
cytoplasm. The cysts (Figure 2) are also large (40-60 µm in
diameter); they are round and contain a single cell
surrounded by a thick cyst wall. In stained cysts the
macronucleus and some vacuoles can be easily identified
and, occasionally, cilia can be seen.
Figure 1 Balantidium coli trophozoite from a pig
sample, unstained. Scale bar: 50 μm.

Balantidium coli
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Balantidium coli has two stages in its life cycle: the active, feeding, replicating stage (the trophozoite) that is found most
commonly in the lumen of the large intestine, and the nonreplicating encysted stage (the cyst) that develops in the lower colon and is
excreted in the feces. Trophozoites (Figure 1) are large (usually 100-150 µm in length; the size range varies somewhat according to
different authors) and ovoid, with the entire cell surface covered by cilia. A mouth-like opening, the cytostome, is located in the
anterior part of the cell. There is an elongate or kidney-shaped macronucleus usually located in the posterior part of the cell and a
smaller, round micronucleus which usually overlaps the macronucleus and is not easily observable. Some vacuoles can also be seen in
the cytoplasm. The cysts (Figure 2) are also large (40-60 µm in diameter); they are round and contain a single cell surrounded by a
thick cyst wall. In stained cysts the macronucleus and some vacuoles can be easily identified and, occasionally, cilia can be seen.
Figure 1 Balantidium coli trophozoite from a pig sample, unstained. Scale bar: 50 μm.
Figure 2 Balantidium coli cysts from a pig sample.
Scale bar: 50 μm. Left: Unstained cyst. Right: Cyst stained
with Lugol's iodine; an egg of Trichuris suis also shown for
comparison purposes.

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Figure 2 Balantidium coli cysts from a pig sample. Scale bar: 50 μm. Left: Unstained cyst. Right: Cyst stained with Lugol's
iodine; an egg of Trichuris suis also shown for comparison purposes.
1.3 Transmission
1.3.1 Routes of transmission
Balantidium cysts are found in the feces of infected
individuals. Balantidiasis is considered a waterborne and
foodborne disease. The parasite is transmitted by the fecal-
oral route, with the cysts, and possibly but less likely the
trophozoites, being ingested with fecally-contaminated
water and food. Transmission by coprophagia could occur
in animals, and this possibility has been suspected for some
human infections, especially in asylums, orphanages,
prisons and mental institutions (Areán and Koppisch, 1956;
Giacometti et al., 1997; Schuster and Ramirez-Avila, 2008).
It has been considered that the trophozoites of B. coli
cannot survive passage through the stomach (Schuster and
Visvesvara, 2004) and the cysts were the only infective
stage (Schuster and Ramirez-Avila, 2008). However, recent
studies on captive great apes infected with B. coli suggest
that trophozoites might also be infective (Pomajbíková et
al., 2010). This possibility should be further investigated; if
confirmed, trophozoites would likely need to be ingested
within a few hours after excretion of the stools as their
survival in the environment is limited (Areán and Koppisch,
1956), whereas cysts can survive with in the environment
for ten days at room temperature (Rees, 1927) and for
several weeks in pig feces, particularly if kept moist and
away from direct sunlight (Schuster and Visvesvara, 2004).
The cyst wall provides protection from stomach acid.
Outbreaks of balantidiasis are rare. Apart from two
reports in mental institutions (Areán and Koppisch, 1956;
Giacometti et al., 1997), only two other outbreaks were
reported from southern Persia (McCarey, 1952) and from
the Pacific island of Truk (Walzer et al., 1973; Walzer and
Healy, 1982). In Persia, 87 cases were thought to be caused
by human-to-human transmission among Muslims in an oil
refinery town, whereas the outbreak in Truk affected 110
persons after a devastating typhoon that caused
widespread contamination of water supplies with pig feces.
As a waterborne parasite, B. coli could be transmitted
by drinking water but also by recreational water. In
countries with high sanitation standards, transmission is
mainly due to an occasional contamination (i.e., in
swimming pools) or a process failure within water utilities
(Bellanger et al., 2013), while in the developing world it
could be the consequence of inadequate or insufficient
sewage treatment and water supply systems that can be
affected by adverse environmental conditions (e.g., the
typhoon in Truk) (Plutzer and Karanis, 2016; Thompson and

Balantidium coli
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Smith, 2011).
1.3.2 Reservoirs
Balantidiasis is a zoonotic disease. The parasite has
been described in a wide range of mammalian hosts other
than humans, including non-human primates, pigs and wild
boars, cattle, sheep, goats, camels, equids and rodents
(Hegner, 1934; Levine, 1961; Levine 1985); Balantidium
infecting ostriches and rheas might also be B. coli ( Ponce-
Gordo et al., 2008; Ponce-Gordo et al., 2011). On the other
hand, Balantidium species from poikilothermic hosts have
been erroneously reported as B. coli and their hosts (i.e.,
turtle, cockroaches) have been incorrectly listed as suitable
hosts of B. coli (i.e., Areán and Koppisch, 1956; Neafie et
al., 2011).
The most important reservoirs are the domestic pig and
wild boars. Other hosts potentially important in the
transmission of B. coli to humans are rodents, wild boars,
sheep, goats, camels and horses. Domestic pigs are infected
worldwide with B. coli, with prevalence ranging from 50 to
100% of the animals examined (Hindsbo et al., 2000; Ismail
et al., 2010; Schuster and Ramirez-Avila, 2008; Weng et al.,
2005; Yatswako et al., 2007; Yin et al., 2015). In pigs, these
ciliates are non-invasive and non-pathogenic (Schuster and
Visvesvara, 2004). Among the studies, prevalence and the
intensity of infection varied between gender and age
groups and in some cases opposite results were found
between the studies, but probably the main factors
affecting infection rates were the management practices at
each farm and the veterinary care (Schuster and Ramirez-
Avila, 2008). In general, facilities with cement floors,
adequate cleaning protocols, and sewage disposal reduced
the prevalence among pigs (Ismail et al., 2010; Giarratana
et al., 2012; Weng et al., 2005; Yatswako et al., 2007; ).
There are very few studies on the prevalence of B. coli
in wild boars and feral pigs. The data available indicate that
prevalences are lower than in domestic pigs, ranging from
4 to 70% depending on the study (Navarro-Gonzalez et al.,
2013; Solaymani-Mohammadi et al., 2004). Other suids
such as the Central American tapir has been found infected
with B. coli (Cruz Aldan et al., 2006), but its
epidemiological importance in relation to the transmission
of B. coli to humans is unknown.
The epidemiology of B. coli in some Muslim countries
has not been clearly determined, but reservoirs other than
pigs have been proposed to be of local importance.
Although pig farming is forbidden in Muslim countries,
human balantidiasis exists in some regions, such as Iran
(Solaymani-Mohammadi et al., 2005a; WHO 1979). It has
been proposed that wild boars might act as the main
reservoirs (Solaymani-Mohammadi et al., 2005a;
Solaymani-Mohammadi et al., 2005b); other authors have
suggested camels (Cox 2005), donkeys (Khan and Fallon
2013), and sheep and goats (Jamil et al., 2015). In Iran and
neighboring countries, the parasite has been found in cattle
and buffaloes (Mirzaei and Khovand 2015; Samad,
2011; Tarrar et al. 2008) but most of the reports have been
based on the cyst stage, which is indistinguishable from the
cattle ciliate Buxtonella sulcata (Sultan et al., 2013) so the
importance of ruminants (cattle and buffaloes) as reservoirs
of B. coli should be considered with caution.
Balantidium coli has been found in several rodent
species. Rats have been considered as a possible source of
infection of B. coli for humans and as a source of spreading
the cysts in the environment (Awakian, 1937; Bogdanovich,
1955; Schumaker, 1930). Other rodents, such as the
lowland paca (Cuniculus paca) which is raised as a source
of proteins in some Central American countries, can harbor
this ciliate Matamoros et al. (Matamoros et al., 1991) gave
a prevalence of 5.7% in farmed pacas in Costa Rica and
may play a role in the transmission of the parasite to
humans in these regions.
1.3.3 Incubation period
There are no data on prepatent and incubation periods
of B. coli in humans. According to experimental infections
in piglets and non-human primates, the incubation period
ranges from 3 to 6 days (Yang et al., 1995).
1.3.4 Period of communicability
The infectious dose or dose-response for trophozoites or
cysts is not known. The disease is communicable
(infectious) for as long as organisms are excreted, but it
should be noted that in chronic balantidiasis the parasite is
identified in the stools only sporadically (Areán and
Koppisch, 1956). Cysts can survive much longer (weeks)
outside the host body whereas trophozoites die at a faster
rate (hours) (Areán and Koppisch 1956; Schuster and
Visvesvara, 2004). This information is important for
understanding human-to-human transmission, because
cysts are rarely detected in human feces and trophozoites
are often found in cases of dysentery (Areán and Koppisch,
1956; Kennedy and Stewart, 1957).
1.3.5 Population susceptibility
Persons working with animals appear at greatest risk of
acquiring balantidiasis, especially those in contact with
pigs (the main reservoir host of B. coli). Pig-to-human
transmission was recorded in areas where humans live in
close proximity with domestic pigs and even share
habitation (Ferry et al., 2004; Sharma and Harding, 2003).
In most cases, people at greatest risk live in poor hygienic
conditions (Barnish and Ashford, 1989; Esteban et al.,
1998; Owen, 2005). Others at risk work in abattoirs where
pig intestines are handled; farmers working with pig feces;
zookeepers working with apes carrying B. coli infections, or
are veterinarians or veterinary students (Anargyrou et al.,
2003; Schuster and Visvesvara, 2004). In regions where
pigs are not reared such as Muslim countries, the contact
with other reservoirs such as wild boars, camels, small
ungulates or equids could be the source of infection. In all
cases, a poor hygienic environment or poor personal
hygiene (see below – hygiene measures) would facilitate
both the animal-to-human and the human-to-human
transmission.
Another important factor is the health status of the

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8
person, which is of paramount importance for the onset of
the infection and of the disease. This includes the physical
condition, concurrent pathologies, immunological status
and immunodepression (Anargyrou et al., 2003; Maino et
al., 2010; Vasilakopoulou et al., 2003; Yazar et al., 2004; )
and diet (nutritional status) of each person (Schovancová et
al., 2013). Balantidium coli is usually detected in persons
with other infectious agents (other protozoa, helminths,
bacteria, viruses), with systemic diseases, or suffering
malnourishment. All of these conditions complicate the
medical management and the prognosis (Walzer and Healy,
1982). Although there is no conclusive evidence that these
other infections render the host more susceptible to B. coli
(Schuster and Ramirez-Avila 2008), the extraintestinal
locations of the parasite are usually associated with other
concurrrent illness (e.g., Anargyrou et al., 2003; Clyti et al.,
1998; Ferry et al., 2004; Karuna and Khadanga, 2014;
Khanduri et al., 2014; Sharma and Harding, 2003;
Vasilakopoulou et al., 2003). Other factors that might
facilitate balantidiasis include the virulence of B. coli
subpopulations (still not confirmed) and the number of
infecting forms ingested (Schuster and Ramirez-Avila,
2008).
1.4 Population and individual control measures
The populations at greatest risk are people living in
close contact with reservoir hosts (as in many rural areas),
people living in poor sanitation environments with limited,
unconditioned, or absent adequate infrastructures for
water supply and sewage disposal; people with poor
hygienic habits, those at low socio-economical levels, and
those residents and workers in institutions (as asylums,
orphanages, prisons and mental institutions) where
hygienic supervision is inadequate (Schuster and Ramirez-
Avila, 2008; Yatswako et al., 2007). Human infection is rare
in temperate areas and in industrialised countries (Ferry et
al., 2004). In France a clinical case of balantidiasis in a not
immunocompromised patient, who lived alone, with no
history of travel or chronic inflammatory bowel disease was
recently reported (Bellanger et al., 2013). The patient was
not working in contact with animals. He reported having
been on a hike the previous weekend during which he had
drunk water through a polyurethane hydration pouch
bladder. The patient insisted that he did not refill the
hydration system during the hike. In the authors´ opinion,
the persistence of residual water in the patient’s hydration
pouch bladder was the source of the contamination
(Bellanger et al., 2013).
1.4.1 Hygiene measures – hand washing, disinfection
The best means of protection against B. coli infection is
by providing adequate clean water for drinking and other
uses (Schuster and Ramirez-Avila, 2008). Because it is
unrealistic to attempt to render reservoir animals (mainly
pigs) B. coli-free, the best option is to keep animals and
their feces away from contaminating water sources used for
human consumption.
Chlorine, at concentrations normally used for ensuring
water safety, is not effective against cysts of B. coli
(Schuster and Ramirez-Avila, 2008). Water boiling is
acceptable. Individual hygiene measures include washing
hands with soap and clean water after being in contact with
reservoir hosts or before handling food, and washing fruits
and vegetables with clean water.
1.4.2 Drug therapy
Until the 1950s, about one third of persons with severe,
acute balantidiasis would die (Areán and Koppisch, 1956).
Since then, the use of antibiotics has clearly improved the
prognosis and now most fatal cases are associated with
another concurrent pathology. Balantidium coli infections
are easily treated with antibiotic therapy, provided that the
correct diagnosis is made in time (Knight, 1978). For
humans, treatment consists of tetracycline (500 mg four
times daily for 10 days; not recommended for pregnant
women or for children under 8 years old), metronidazole
(750 mg three times daily for 5 days) or iodoquinol (640 mg
three times daily for 20 days). It is advisable to give the
patient a starch-free diet (Areán and Koppisch, 1956;
Schovancová et al., 2013). Pigs (the main reservoir of B.
coli) can be treated with oxytretracycline.
2 Environmental Occurrence and Persistence
2.1 Detection methods
Trophozoites of B. coli rapidly disappear outside the
host (Areán and Koppisch, 1956) and only the cysts can be
found in environmental samples. There are no specific or
standardized methods for detection and those applied for
other enteric protozoa and helminths can be used with B.
coli.
In fecal samples, trophozoites can be easily detected by
microscopy in saline smears by their size and their slow
motion; in fixed samples, the morphology of the
macronucleus can be easily recognized in both trophozoites
and cysts in temporary smears stained with iodine. Other
staining methods such as hematoxylin-eosin or trichrome
are also useful. Cysts can be recovered using common
coprological techniques (i.e., centrifugation methods for
concentration). In samples from cattle and buffaloes, the
diagnosis based on the identification of cysts should not be
considered confirmatory because other ciliates (namely B.
sulcata) with morphologically identical cysts could also be
present. Complementary genetic analysis should be made
in this case. For this purpose, the sequences corresponding
to the ribosomal genes (the small subunit rDNA and the
5.8s rDNA, and the internal transcribed spacers –ITS– 1
and 2), although showing some genetic heterogeneity, can
be used (Pomajbíková et al., 2013; Ponce-Gordo et al.,
2008; Ponce-Gordo et al., 2011).
In environmental samples, the B. coli trophozoites
would not be detectable (they disappear soon after the
passage of the stools; Areán and Koppisch, 1956) and only
the cysts would be found. However, it is not possible to
differentiate on morphological grounds the cysts of B. coli
from those of other Balantidium species (i.e., amphibian or
fish balantidia), or even from those of other ciliates (as B.
sulcata from cattle), and genetic analysis should be made to

Balantidium coli
9
correctly identify the species.
2.2 Data on occurrence in the environment
2.2.1 Feces
Only very little data are known about intensity of
infection of B. coli in pig or human samples, because
generally it is difficult to choose an appropriate
quantification method for ciliates. The only study by
Růžicová et al. (2014) reported a few data on the intensity
of infection of B. coli during calibration of the diagnostic
and quantitative method FLOTAC® on both stages
(Růžicová et al., 2014). The cysts were quantified in pig
feces, whereas trophozoites in chimpanzees, which
similarly as human feces contain trophozoite stages of B.
coli. Despite it is optimized on chimpanzee feces, it can be
used also for the detection and quantification of human
infections.
2.2.2 Sewage and sludge
Few data are available on the presence of B. coli cysts
in environmental samples, and care should be taken when
interpreting the data available to date because they are
based on unreliable cyst morphology (see “Detection
methods”).
The presence of the parasite has been reported in large
numbers in sludge from a wastewater processing facility in
Bahrain but the origin was uncertain, because prevalence
among the residents served by the processing facility was
found to be negligible (two positive patients out of over
18,000 samples examined) and pigs were absent (Amin,
1988). In another report, Balantidium cysts were found in
the sewage water in Bangladesh; the samples were
collected from different places and B. coli cysts were found
in three places although in low intensity ranging between 5
to 7.5 × 104 stages cysts per liter (Khanum et al., 2012).
2.2.3 Drinking waters
The balantidiasis outbreak of Truk followed a typhoon
affecting an island with primitive catchment water supplies,
low hygiene standards, and high numbers of pigs in close
contact with humans. The combination of these factors
resulted in the contamination of the water supplies (Walzer
et al. 1973). Apart from this outbreak derived from a
catastrophic situation, there are no published outbreaks of
balantidiasis in relation to water supplies. However, several
authors have raised concerns about the risk of epidemics.
In Australia, B. coli was detected in feral pig populations
that were foraging and wallowing in major public drinking
water catchments (Hampton et al., 2006). The authors
speculated that chances of pathogens reaching the main
water supply might be high.
In Hyderabad, India, B. coli cysts were detected in 61 of
232 water samples (26.3% positive) collected in hostels,
small restaurants, households, and various public places.
The source of the contaminated samples was the water
stored in overhead tanks and various other containers
(Jonnalagadda and Bhat, 1995). In three districts in
Pakistan, B. coli cysts were detected in all three sources of
drinking water used for examination (tap water, ponds, and
drain water) with total prevalence 5.78% (26/450) (Ayaz et
al., 2011). A recent case report of a patient suffering from
dysentery caused by B. coli related to water was reported
in France by Bellanger et al. (Bellanger et al., 2013).
2.2.4 Soil
The only information about the occurrence of B. coli in
the soil is from Nigeria where B. coli cysts were found in
water and soil samples in two out of the seven pig farming
areas (Yatswako et al., 2007). The prevalence of B. coli in
pig population in the studied area ranged between 35.3 and
75.7 % (207 samples positive for B. coli out of 402 collected
samples in total).
In southwestern Nigeria, intestinal parasites, including
B. coli, were detected on selected vegetables from open
markets; the contamination was attributed to contaminated
soil (Ogbolu et al., 2009). In Brazil several protozoan and
helminth species including B. coli, were detected on field-
grown strawberries although the prevalence was quite low
(da Silva et al., 2014).
2.3 Persistence
There are few published data on the survival and
viability of B. coli cysts in the environment. As mentioned
above, the cysts could survive for several weeks in moist
feces away from direct sunlight (Schuster and Visvesvara,
2004). Early studies in parasitology sugggest that the cysts
survive in the environment for at least ten days at room
temperature (Rees, 1927), whereas trophic ciliates can
survive for as long as ten days in the environment (Zaman,
1978).
3 Reduction by sanitation management
There are no data available about the inactivation or
removal of B. coli cysts by sanitation treatment processes.
Because of their larger size (40-60 µm in diameter) it is
possible that cysts are removed by sedimentation or
filtration more so when compared to the removal of smaller
protozoan cysts and helminth eggs. This suggests that the
cysts will end up in the sludge and would remain an
indicator of sanitation effectiveness for solid fecal waste
treatment technologies.

Balantidium coli
10
References
E. Aldan, C, I. Torres, L, Andrade, D.MGuiris, D. Sarabia, O and Quintero, M.M (2006). [Parasites of the Central American
tapir Tapirus bairdii (Perissodactyla: Tapiridae) in Chiapas, Mexico]. Revista de Biología Tropical. 54, pp. 445- 450.
Alexeief, A. (1931). Sur quelques particularités de structure de Balantioides (nom. nov.) coli (Malmsten). Comptes Rendus
des séances de la Société de BiologieComptes Rendus des séances de la Société de Biologie. 107, pp. 210-211.
Amin, O.M (1988). Pathogenic micro-organisms and helminths in sewage products, Arabian Gulf, country of Bahrain.
American Journal of Public HealthAmerican Journal of Public Health. 78, American Public Health Associationpp. 314-315.
Anargyrou, K., Petrikkos, G.L, Suller, M.TE, Skiada, A., Siakantaris, M.P, Osuntoyinbo, R.T et al. (2003). Pulmonary
Balantidium coli infection in a leukemic patient. American Journal of HematologyAmerican Journal of Hematology. 73,
Wiley-Blackwellpp. 180-183.
Areán, V.M and Koppisch, E. (1956). Balantidiasis: a review and report of cases. American Journal of HygieneAmerican
Journal of Hygiene. 32, pp. 1089-1115.
Awakian, A. (1937). Studies on the intestinal protozoa of rats. II. Rats as carriers of Balantidium.. Transactions of the Royal
Society of Tropical Medicine and HygieneTransactions of the Royal Society of Tropical Medicine and Hygiene. 31, Oxford
University Press (OUP)pp. 93-98.
Ayaz, S., Khan, S., Khan, S.N, Bibi, F., Shamas, S. and Akhtar, M. (2011). Prevalence of zoonotic parasites in drinking
water of three districts of Khyber Pakhtunkhwa Province, Pakistan. Pakistan Jouranl of Life and Social SciencesPakistan
Jouranl of Life and Social Sciences. 9, pp. 67-69.
Bandyopadhyay, A, Majumder, K. and Goswami, B.K (2013). Balantidium coli in urine sediment: report of a rare case
presenting with hematuria. Journal of Parasitic Disesaes. 37, pp. 283-285.
Barbosa, Ada Silva, Bastos, OMachado Pe, Uchôa, CMAntunes, Pissinatti, A, Filho, PRicardo Fe, Dib, LVerdan et al.
(2015). Isolation and maintenance of Balantidium coli (Malmsteim, 1857) cultured from fecal samples of pigs and non-
human primates. Veterinary ParasitologyVeterinary Parasitology. 210, Elsevier BVpp. 240-245.
Barnish, G. and Ashford, R.W (1989). Occasional parasitic infections of man in Papua New Guinea and Iran Jaya (New
Guinea). Annals of Tropical Medicine and ParasitologyAnnals of Tropical Medicine and Parasitology. 83, pp. 121-135.
Bauri, R., Ranjan, R, Deb, A. and Ranjan, R. (2012). Prevalence and sustainable control of Balantidium coli infection in pigs
of Ranchi, Jahrkahnd, India. Vet.erinary WorldVet.erinary World. , ScopeMed International Medical Journal Management
and Indexing Systempp. 94.
Bellanger, A.P, Scherer, E., Cazorla, A. and Grenouillet, F. (2013). Dysenteric syndrome due to Balantidium coli: a case
report. New Microbiologica. 36, pp. 203-205.
Bilic, H.R and Bilkei, G. (2006). Balantidium, Cryptosporidium and Giardia species infections in indoor and outdoor pig
production units in Croatia. Veterinary RecordVeterinary Record. 158, BMJpp. 61-61.
Bogdanovich, V.V (1955). Spontaneous balantidiasis in rats. Meditsinskaia Parazitologiia I Parazitarnye
BolezniMeditsinskaia Parazitologiia I Parazitarnye Bolezni. 24, pp. 326-329.
Boonjarsapinyo, S., Boonmars, T., Kaewsamut, B., Ekobol, N., Laummaunwai, P., Aukkanimart, R. et al. (2013). A cross-
sectional study on intestinal parasitic infections in rural communities, northeast Thailand. Korean Journal of Parasitology.
51, pp. 727-34.
Chistyakova, LV, Kostygov, AYu, Kornilova, OA and Yurchenko, V (2014). Reisolation and redescription of Balantidium
duodeni Stein, 1867 (Litostomatea, Trichostomatia). Parasitology ResearchParasitology Research. 113, Springer Science +
Business Mediapp. 4207-4215.

Balantidium coli
11
Clyti, E., Aznar, C., Couppie, P., M. Guedj, el, Carme, B. and Pradomaid, R. (1998). Un cas de conifection par Balantidium
coli et VIH en Guyane Française. Bulletin de la Société de Pathologie ExotiqueBulletin de la Societe de Pathologie
Exotique. 91, pp. 309-311.
Cooper, P.J and Guderian, R.H (1994). Grastrointestinal illness associated with Balantidium coli infection in rural
communities in Ecuador. Parasitología al DiaParasitologia al Dia. 18, pp. 51-54.
Cox, FEG (2005). Human balantidiasis in Iran: are camels reservoir hosts?. Trends in ParasitologyTrends in Parasitology.
21, Elsevier BVpp. 553.
Da Silva, S.RM, Maldonade, I.R, Ginani, V.C, Lima, S.A, Mendes, V.S, Azevedo, M.LX et al. (2014). Detection of intestinal
parasites on field-grown strawberries in the Federal District of Brazil. Revista da Sociedade Brasileira de Medicina
TropicalRevista da Sociedade Brasileira de Medicina Tropical. 47, pp. 801-805.
Devera, R., Requena, I., Velasquez, V., Castillo, H., Guevara, R., De Sousa, M. et al. (1999). Balantidiasis in a rural
community from Bolivar State, Venezuela. Boletín Chileno de ParasitologíaBoletin Chileno de Parasitologia. 54, pp. 7-12.
Dhawan, S, Jain, D and Mehta, VSingh (2013). Balantidium coli: an unrecognized cause of vertebral osteomyelitis and
myelopathy. Journal of Neurosurgery: SpineJournal of Neurosurgery: Spine. 18, Journal of Neurosurgery Publishing Group
(JNSPG)pp. 310-313.
Esteban, J.G, Aguirre, C., Angles, R., Ash, L.R and Mas-Coma, S. (1998). Balantidiasis in Aymara children from the northern
Bolivian altiplano. American Journal of Tropical Medicine and HygieneAmerican Journal of Tropical Medicine and Hygiene.
59, pp. 922-927.
Ferry, T., Bouhour, D., De Monbrison, F., Laurent, F., Dumouchel-Champagne, H., Picot, S. et al. (2004). Severe peritonitis
due to Balantidium coli acquired in France. European Journal of Clinical Microbiology and Infectious DiseasesEuropean
Journal of Clinical Microbiology and Infectious Diseases. 23, Springer Science + Business Mediapp. 393-395.
Fletcher, SM, Stark, D, Harkness, J and Ellis, J (2012). Enteric protozoa in the developed world: a public health
perspective. Clin Microbiol Rev. 25, pp. 420–449.
Giacometti, A, Cirioni, O, Balducci, M, Drenaggi, D, Quarta, M, De Federicis, M et al. (1997). Epidemiologic features of
intestinal parasitic infections in Italian mental institutions. Eur. J. Epidemiol. 13, pp. 825–830.
Giarratana, F., Muscolino, D., Taviano, G. and Ziino, G. (2012). Balantidium coli in pigs regularly slaughtered at abattoirs
of the province of Messina: hygienic observations. Open Journal of Veterinary MedicineOpen Journal of Veterinary
Medicine. 02, Scientific Research Publishing, Incpp. 77-80.
Hampton, J, Spencer, PBS, Elliot, AD and Thompson, R.CAndrew (2006). Prevalence of Zoonotic Pathogens from Feral Pigs
in Major Public Drinking Water Catchments in Western Australia. EcoHealthEcoHealth. 3, Springer Science + Business
Mediapp. 103-108.
Hegner, R.W (1934). Specifity in the genus Balantidium based on size and shape of body and macronucleus, with
descriptions of six new species. American Journal of HygieneAmerican Journal of Hygiene. 19, pp. 38-67.
Hinde, K. (2007). Milk composition varies in relation to the presence and abundance of Balantidium coli in the mother in
captive rhesus macaques (Macaca mulatta). American Journal of PrimatologyAmerican Journal of Primatology. 69, Wiley-
Blackwellpp. 625-634.
Hindsbo, O., Nielsen, C.V, Andreassen, J., Willingham, A.L, Bendixen, M., Nielsen, M.A et al. (2000). Age-dependent
occurrence of the intestinal ciliate Balantidium coli in pigs at a Danish research farm. Acta Veterinaria ScandinavicaActa
Veterinaria Scandinavica. 41, pp. 79-83.
Ismail, H.A.H.A., Jeon, H.-K., Yu, Y-M.n, Do, C. and Lee, Y.-H. (2010). Intestinal parasite infections in pigs and beef cattle in
rural areas of Chungcheongnam-do, Korea. Korean Journal of ParasitologyKorean Journal of Parasitology. 48, Korean
Society for Parasitology (KAMJE)pp. 347.

Balantidium coli
12
Jamil, M, Ijaz, M. and M. Ali, M (2015). Prevalence, hematology and treatment of Balantidium coli among small ruminants
in and Around Lahore, Pakistan. Kafkas Universitesi Veteriner Fakultesi Dergisi. 21, pp. 123-126.
Jonnalagadda, P.R and Bhat, R.V (1995). Parasitic contamination of stored water used for drinking/cooking in Hyderabad,
Southeast Asian. Journal of Tropical Medicine and Public HealthJournal of Tropical Medicine and Public Health. 26, pp.
789-794.
Karuna, T. and Khadanga, S. (2014). A rare case of urinary balantidiasis in an elderly renal failure patient. Tropical
ParasitologyTropical Parasitology. 4, Medknowpp. 47.
Kennedy, C.C and Stewart, R.C (1957). Balantidial dysentery: A human case in Northern Ireland. Transactions of the Royal
Society of Tropical Medicine and HygieneTransactions of the Royal Society of Tropical Medicine and Hygiene. 51, Oxford
University Press (OUP)pp. 549-558.
Khan, A.R. and Fallon, P.G. (2013). Helminth therapies: Translating the unknown unknowns to known knowns.
International Journal of Parasitology. 43, pp. 293- 299.
Khanduri, A, Chauhan, S., Chandola, I., Mahawal, B. and Kataria, V. (2014). Balantidiosis: a rare accidental finding in the
urine of a patient with acute renal failure. Journal of Clinical and Diagnostic Research for doctors. 8, pp. DD03-4.
Khanum, H., Khanam, S.S, Sultana, M., Uddin, M.H, Dhar, R.C and Islam, M.S (2013). Protozoan parasites in a wastewater
treatment plant of Bangladesh. Univ. j. zool. Rajshahi Univ.Univ. j. zool. Rajshahi Univ.. 31, Bangladesh Journals Online
(JOL)
Kline, K, McCarthy, JS, Pearson, M, Loukas, A and Hotez, PJ (2013). Neglected tropical diseases of Oceania: review of their
prevalence, distribution, and opportunities for control. PLoS Neglected Tropical DiseasesPLoS Neglected Tropical
Diseases. 7, Public Library of Science (PLoS)pp. e1755.
Knight, R. (1978). Giardiasis, isosporidiasis and balantidiasis. Clinics in GastroenterologyClinics in Gastroenterology. 7, pp.
31-47.
Levine, N.D (1985). Veterinary Protozoology. Iowa State University Press, Ames..
Levine, N.D (1940). Changes in the dimensions of Balantidium from swine upon cultivation. American Journal of
HygieneAmerican Journal of Hygiene. 32, pp. 1-7.
Levine, ND (1961). Protozoan parasites of domestic animals and of man. , Smithsonian Institution
Maino, A, Garigali, G., Grande, R., Messa, P. and Fogazzi, G.B (2010). Urinary balantidiasis: diagnosis at a glance by urine
sediment examination. Journal of Nephrology. 23, pp. 732-737.
Malmsten, P.H (1857). Infusorien als Intestinal-Thiere beim Menschen. Archiv für pathologische Anatomie und Physiologie
un für klinische MedicinArchiv für pathologische Anatomie und Physiologie un für klinische Medicin. 12, Springer Science
+ Business Mediapp. 302-309.
Matamoros, Y., Velazquez, J. and Pashov, B. (1991). Parásitos intestinales del tepezcuinte, Agouti paca (Rodentia:
Dasyproctidae) en Costa Rica. Revista de Biología TropicalRevista de Biologia Tropical. 39, pp. 173-176.
McCarey, A.G (1952). Balantidiasis in South Persia. BMJBMJ. 1, BMJpp. 629-631.
McDonald, J.D. (1922). On Balantidium coli (Malmsten) and Balantidium suis (sp. nov.) with an account of their neuromotor
apparatus. University of California Publications in ZoologyUniversity of California Publications in Zoology. 20, Smithsonian
Institutionpp. 243-300.
Mirzaei, M. and Khovand, H. (2015). [An investigation on the prevalence of Balantidium coli in traditional farms of the
Darab city in Fars Province (Iran)] (in Persian with English abstract). Journal of Experimental Animal BiologyJournal of
Experimental Animal Biology. 4, pp. 79-86.

Balantidium coli
13
Navarro-Gonzalez, N., Fernández-Llario, P., Pérez-Martín, J.E., Mentaberre, G, López-Martín, J.M., LavÃn, S et al.
(2013). Supplemental feeding drives endoparasite infection in wild boar in Western Spain. Veterinary
ParasitologyVeterinary Parasitology. 196, Elsevier BVpp. 114-123.
Neafie, R.C, Andersen, E.M and Klassen-Fischer, M.K (2011). Balantidiasis. Meyers, W.M., Firpo, A., Wear, D.J. (Eds)
Topics on the Pathology of protozoan and invasive arthropod diseases.. , Armed Forces Institute of Pathology,
Washingtonpp. 6 pp..
Nuti, M., Sanguigni, S. and de Bac, C. (1979). Osservazioni su di un focolaio endemico di balantidiasi (studio di 80 casi).
Annali di Medicina NavaleAnnali di Medicina Navale. 196, pp. 641-646.
Ogbolu, D.G, Alli, O.A, Ongunleye, V.F, Olusoga-Ogbolu, F.F and Olaosun, I. (2009). The presence of intestinal parasites in
selected vegetables from open markets in south western Nigeria. African Journal of Medicine and Medical SciencesAfrican
Journal of Medicine and Medical Sciences. 38, pp. 319-324.
Owen, I.L (2005). Parasitic zoonoses in Papua New Guinea. Journal of HelminthologyJournal of Helminthology. 79,
Cambridge University Press (CUP)pp. 1-14.
Plutzer, J. and Karanis, P. (2016). Neglected waterborne parasitic protozoa and their detection in water. Water Research.
101, pp. 318- 332.
Pomajbíková, K, Petrželková, K.J, Profousová, I. and Modrý, D. (2010). Discrepancies in the occurrence of Balantidium coli
between wild and captive African great apes. Journal of Parasitology. 96, pp. 1139-1144.
Pomajbíková, K., Oborník, M., Horák, A., Petrželková, K.J., Grim, J.N., Levecke, B. et al. (2013). Novel insights into the
genetic diversity of Balantidium and Balantidium-like cyst-forming ciliates. PLoS Neglected Tropical DiseasesPLoS
Neglected Tropical Diseases. 7, Public Library of Science (PLoS)pp. e2140.
Ponce-Gordo, F., Fonseca-Salamanca, F. and Martínez-Díaz, R.A. (2011). Genetic Heterogeneity in Internal Transcribed
Spacer Genes of Balantidium coli (Litostomatea, Ciliophora). ProtistProtist. 162, Elsevier BVpp. 774-794.
Ponce-Gordo, F., Jimenez-Ruiz, E. and Martínez-Díaz, R.A (2008). Tentative identification of the species of Balantidium
from ostriches (Struthio camelus) as Balantidium coli-like by analysis of polymorphic DNA. Veterinary
ParasitologyVeterinary Parasitology. 157, Elsevier BVpp. 41-49.
Rees, C.W (1927). Balantidia from pigs and guinea-pigs: their viability, cyst production and cultivation. ScienceScience. 66,
American Association for the Advancement of Science (AAAS)pp. 89-91.
Růžicová, M, Petrželková, K.J, Kalousová, B., Modrý, D. and Pomajbíková, K. (2014). Validation of Flotac for the detection
and quantification of Troglodytella abrassarti and Neobalantidium coli in chimpanzees and pigs. The Journal of
Parisitology. 100, pp. 662-670.
Samad, M.A (2011). Public health threat caused by zoonotic diseases in Bangladesh. Journal of Veterinary Medicine. 9, pp.
95-120.
Schovancová, K, Pomajbíková, K.,, Modrý, D., Bolechová, P. and Petrželková, K.J (2013). Preliminary insights into the
impact of dietary starch on the ciliate, Neobalantidium coli, in captive chimpanzees. Plos One. 8,
Schumaker, E. (1930). Balantidium coli: host specificity and relation to the diet of an experimental host. American Journal
of HygieneAmerican Journal of Hygiene. 12, pp. 341-365.
Schuster, F.L and Ramirez-Avila, L. (2008). Current world status of Balantidium coli. Clinical Microbiology ReviewsClinical
Microbiology Reviews. 21, American Society for Microbiologypp. 626-638.
Schuster, F.L. and Visvesvara, G.S. (2004). Amebae and ciliated protozoa as causal agents of waterborne zoonotic disease.
Veterinary ParasitologyVeterinary Parasitology. 126, Elsevier BVpp. 91-120.
Sharma, S. and Harding, G. (2003). Necrotizing lung infection caused by the protozoan Balantidium coli. Canadian Journal

Balantidium coli
14
of Infectious DiseasesCanadian Journal of Infectious Diseases. 14, pp. 163-166.
Solaymani-Mohammadi, S., Rezaian, M. and Anwar, M.A. (2005). Response to Cox: Human balantidiasis in Iran: wild boars
or not?. Trends in ParasitologyTrends in Parasitology. 21, Elsevier BVpp. 554-555.
Solaymani-Mohammadi, S., Rezaian, M. and Anwar, M.A. (2005). Human balantidiasis in Iran: an unresolved enigma?.
Trends in ParasitologyTrends in Parasitology. 21, Elsevier BVpp. 160-161.
Solaymani-Mohammadi, S., Rezaian, M., Hooshyar, H., Mowlavi, G.R, Babaei, Z. and Anwar, M.A (2004). Intestinal
Protozoa in Wild Boars (Sus scrofa) in Western Iran. Journal of Wildlife DiseasesJournal of Wildlife Diseases. 40, Wildlife
Disease Associationpp. 801-803.
Stein, F (1863). Ueber Paramecium (?) coli Malmsten. Amtl Berl Dtsch Chem Ges. 37, pp. 165.
Tarrar, M.A, Khan, M.S, Pervez, K., Ashraf, K., Khan, J.A and Rehman, Z.U (2008). Detection and chemotherapy of
Balantidium coli in buffaloes around Lahore, Pakistan. Pakistan Journal of Agricultural SciencesPakistan Journal of
Agricultural Sciences. 45, pp. 163-166.
Thompson, RCA and Smith, A (2011). Zoonotic enteric protozoa. Veterinary Parasitology. 182, pp. 70–78.
Vasilakopoulou, A., Dimarongona, K., Samakovli, A., Papadimitris, K. and Avlami, A. (2003). Balantidium coli pneumonia in
an immunocompromised patient. Scandinavian Journal of Infectious DiseasesScandinavian Journal of Infectious Diseases.
35, Informa UK Limitedpp. 144-146.
WHO (1979). Parasitic zoonoses. Report of a WHO Expert Committee with the participation of FAO. World Health
Organization Tecnical Report Series nº 637, Geneva. pp. 107 pp.
Walzer, P.D and Healy, G.R (1982). Balantidiasis. CRC Handbook Series in Zoonoses. Section C. Parasitic Zoonoses Editor
in Chief: J. J. Steele. Vol. I. Ed. L. Jacobs and P. Arambulo. , CRC Press, Inc., Boca Raton, Floridapp. 15-24.
Walzer, P.D, Judson, F.N, Murphy, K.B, Healy, G.R, English, D.K and Schultz, M.C (1973). Balantidiasis outbreak in Truk.
American Journal of Tropical Medicine and HygieneAmerican Journal of Tropical Medicine and Hygiene. 22, pp. 33-41.
Weng, Y.B, Hu, Y.J, Li, Y., Li, B.S, Lin, R.Q, Xie, D.H et al. (2005). Survey of intestinal parasites in pigs from intensive farms
in Guangdong Province, People's Republic of China. Veterinary ParasitologyVeterinary Parasitology. 127, Elsevier BVpp.
333-336.
Yang, Y., Zeng, L., Li, M. and Zhou, J. (1995). Diarrhoea in piglets and monkeys experimentally infected with Balantidium
coli isolated from human faeces. Journal of Tropical Medicine and HygieneJournal of Tropical Medicine and Hygiene. 98,
pp. 69-72.
Yatswako, S., Faleke, O.O, Gulumbe, M.L and Daneji, A.I (2007). Cryptosporidium oocysts and Balantidium coli cysts in
pigs reared semi-intensively in Zuru, Nigeria. Pakistan Journal of Biological SciencesPakistan Journal of Biological
Sciences. 10, Science Alertpp. 3435-3439.
Yazar, S, Altuntas, F., Sahin, I. and Atambay, M. (2004). Dysentery caused by Balantidium coli in a patient with non-
Hodgkin's lymphoma from Turkey. World Journal of Gastroenterology. 10, pp. 458-459.
Yin, D.M, Lv, C.C, Tan, L., Zhang, T.N, Yang, C.Z, Liu, Y. et al. (2015). Prevalence of Balantidium coli infection in sows in
Hunan province, subtropical China. Tropical Animal Health and Production. 47, pp. 1637- 1640.
Zaman, V. (1978). Balantidium coli. Paratic Protozoa. 2, New York, USA, Academic Presspp. 663-653.