The significance of Blastocystis as a cause of human and animal disease remains unknown. It has been

suggested that the organism is zoonotic. This study was undertaken to determine the prevalence of

Blastocystis sp in stray dogs, which may be implicated as a reservoir for human infection.

During the period April-September 2007, 50 stray dogs were collected from different parts of urban Sari,

in Mazandaran Province, Iran. They were immediately transported to Sari Medical School, where they were

necropsied; the gastrointestinal tract was opened completely and searched for Blastocystis sp The specimens

were examined by wet mount and formalin-ether concentration methods.

Blastocystis sp were found by light microscopy in 14 (28%) of 50 fecal samples from the youngest (2

months) to the oldest (4 years) dogs in this study. Six of 21 male (28.6%) and 8 of 29 female (27.6%) dogs

had Blastocystis sp in their fecal matter. No correlation between the presence of Blastocystis sp and the age

or sex of the host was found in dogs studied. The high prevalence of the organism in dogs indicates that

stray dogs may be an important source of Blastocystis sp infection for humans

اتحاد, غلامحسین

دریانی, احمد

شریف, مهدی

ضیایی, هاجر

عمویی, افسانه

گوهر دهی, شعبان

English

ArUMS Digital Repository (سامانه اطلاعات زیست پزشکی و سلامت)

Available online at www.ptat.thaigov.net
59P r o c  o f  t h e  3 r d  A S E A N  C o n g r  o f  T r o p  M e d  a n d  P a r a s i t o l .  P a r a s i t e s :  a  H i d d e n  T h r e a t  t o  G l o b a l  H e a l t h
Blastocystis Sp: a Neglected Zoonotic Protozoan
A Daryani1, M Sharif1, A Amouei1, GH Ettehad2, H Ziaei1,  
SH Gohardehi1, R Bastani1
1 Department of Parasitology and Mycology, School of Medicine, Mazandaran University of Medical Sciences, 
PC 48168-95475, Sari, Mazandaran;
2 Department of Basic Sciences, School of Medicine, Ardabil University of Medical Sciences, Ardabil, Iran
ABStRAct
The significance of Blastocystis as a cause of human and animal disease remains unknown. It has been suggested that the organism is zoonotic. This study was undertaken to determine the prevalence of 
Blastocystis sp in stray dogs, which may be implicated as a reservoir for human infection.
 During the period April-September 2007, 50 stray dogs were collected from different parts of urban Sari, 
in Mazandaran Province, Iran. They were immediately transported to Sari Medical School, where they were 
necropsied; the gastrointestinal tract was opened completely and searched for Blastocystis sp The specimens 
were examined by wet mount and formalin-ether concentration methods.
 Blastocystis sp were found by light microscopy in 14 (28%) of 50 fecal samples from the youngest (2 
months) to the oldest (4 years) dogs in this study. Six of 21 male (28.6%) and 8 of 29 female (27.6%) dogs 
had Blastocystis sp in their fecal matter. No correlation between the presence of Blastocystis sp and the age 
or sex of the host was found in dogs studied. The high prevalence of the organism in dogs indicates that 
stray dogs may be an important source of Blastocystis sp infection for humans.
Keywords:  Blastocystis sp, protozoan, zoonosis, human health, parasite, dog
Introduction
 Blastocystis sp is an anaerobic protozoan 
that occurs in the intestines of humans and other 
mammals [1]. B. hominis has been traditionally 
regarded as a non-pathogenic parasite of humans. The 
pathogenic potential of B. hominis has been reported 
in the literature since 1899 [1], and studies reporting 
its association with human disease have been 
increasing [2-9]. Pathogenicity appears to be related 
to the numbers of parasites. Reports of symptomatic 
individuals with fewer than five parasites per ×400 
field have been documented. More severe symptoms 
have been noted with increased numbers of parasites 
[6,10].
 Many B. hominis-like organisms have been 
isolated from various animals, especially from many 
species of birds and mammals [11-18]. Salim et al 
[19], in a study of B. hominis among humans, showed 
that animal handlers had significantly higher rates of 
infection than normal healthy individuals who did not 
work with animals. The presence of zoonotic strains 
isolated from a chicken and a guinea pig has shown 
the transmissibility of the organism between humans 
and animals [20,21].
 Although there are few reports of Blastocystis 
sp from cats and dogs [22-24], there is no report 
of Blastocystis sp from dogs in Iran; this study was 
correspondence:
 Ahmad Daryani
Proc ASEAN Congr Trop Med Parasitol. 2008;3:59-62.	 	
60
undertaken to determine the prevalence of Blastocystis 
sp in stray dogs, which may be implicated as a 
reservoir for human infection.
Materials and methods
Study area
 Samples were taken in 7 different regions of 
Sari; this city, in the center of Mazandaran Province, 
northern Iran, has a population around 196,000 and 
lies between the parallels 35º58’ and 36º50’ north, 
and 52º56’ and 53º59’ east. The mean annual relative 
humidity is 85.83%, with rainfall in all seasons, and an 
average temperature of 17ºC.
collection and examination of dogs
 During the period April-September 2007, with 
the approval of the Ethics Committee of Mazandaran 
University of Medical Sciences, 50 juvenile (< 6 months) 
and adult (> 6 months) stray dogs (males 21; females 
29) were shot and collected from different urban areas 
in Sari city, Mazandaran Province, Iran. They were 
transported immediately to Sari Medical School, where 
they were necropsied and the gastrointestinal tracts 
opened along their entire length. The mucosa, scraped 
with a scalpel, and fecal specimens, were examined 
by formalin-ether concentration method.
Statistical analysis
 Statistical analysis used SPSS 15. Chi-square 
testing was used to assay the prevalence of Blastocystis 
sp relative to host age and gender.
Results
A total of 23 juvenile and 27 adult stray dogs were 
examined for the presence of Blastocystis sp 
Evaluation of the feces samples indicated that, 
overall, 28% of dogs were infected with at least one 
Blastocystis sp.
 There was no significant different in the overall 
prevalence by gender (males 6/21 = 28.6%; females 
8/29 = 27.6%) (Table 1).
 With respect to the ages of the dogs, 6/23 (26.1%) 
of juvenile dogs and 8/27 (29.6%) of adults were 
infected with Blastocystis sp There was no statistically 
significant association between Blastocystis sp and 
age range among the stray dogs (Table 2).
 The distribution of the positive dogs over the 
locality indicated that differences in terrain did not 
influence infection rates.
table 1  Prevalence of Blastocystis sp in stray dogs, 
by sex..
Sex Positive No. (%) Negative No. (%)
Male 6 (28.6) 15 (71.4)
Female 8 (27.6) 21 (72.4)
Total 14 (28.0) 36 (72.0)
 
P > 0.05; df = 1; χ2 = 0.006
table 2  Prevalence of Blastocystis sp in stray dogs, 
by age.
Age group Positive No. (%) Negative No. (%)
Juvenile 6 (26.1) 17 (73.9)
Adult 8 (29.6) 19 (70.4)
Total 14 (28.0) 36 (72.0)
P > 0.05; df = 1;  χ2 = 0.077
Discussion
 Although Blastocystis studies started in the early 
20th century [25,26], the significance of this protozoan 
as a cause of human and animal disease remains 
unknown. It has been suggested that the organism 
is zoonotic [27], but there is insufficient evidence to 
either support or refute this.
 This study, the first epidemiological survey of 
Blastocystis in dogs in Iran, found that 28% of dogs 
were infected with at least one Blastocystis sp. This 
parasite has been reported in the feces of a number of 
economically important animals, including cattle and 
pigs [11,14,28,29]. Several studies have determined 
prevalence rates in large numbers of animals 
[11,14,28]. Data on the presence of this organism in 
cats and dogs are extremely limited [22-24]. A high 
prevalence (70%) was found in the feces of the dogs 
and nearly 70% of cats examined in Australia [23]. 
In contrast, no Blastocystis sp were found among 
dogs and cats in Germany, Malaysia and Japan 
Blastocystis Sp: a Neglected Zoonotic Protozoan
61
[15,24,30]. It is unclear why the prevalence varies, 
but one explanation may be the housing conditions 
of the animals. Abe et al [24] reported that carnivores 
and herbivores, including lions, camels, deer, and 
hares, housed in a city zoo, were not infected with 
Blastocystis sp. Meanwhile, circus animals that were 
housed together, or caged close to other animals, 
were found to be infected, and the infection could 
have been transmitted within circus animal facilities 
[29]. It is important to consider the sanitary conditions 
of animals in epidemiological surveys; generally, the 
prevalence of Blastocystis sp infection among stray 
animals, such as dogs and cats, is high. Blastocystis 
organisms were identified microscopically by direct 
examination of fecal samples. This parasite is very 
fragile, so that detection using this method alone 
requires immediate collection and a relatively large 
number of organisms. As a result, it appears that in 
many studies its prevalence is higher than the present 
data indicate. No relationship was found between the 
presence of Blastocystis sp. in dogs and urban area, 
or dog sex or age. The prevalence of the organism 
appears similar in juvenile and adult dogs of both 
sexes. Duda et al [23] showed that sex- and age-
related differences were insignificant.
 Although Duda et al [23] showed that nuclear 
morphology does not appear sufficiently distinctive 
to allow differentiation between Blastocystis sp from 
dogs and B. hominis from humans, Yoshikawa et al 
[31] reported that all animal isolates classified into 
the known genotypes appeared zoonotic, and may 
possess zoonotic potential.
 In conclusion, regarding possible zoonotic 
transmission, a Blastocystis sp prevalence rate of 
28% in dogs indicates that stray dogs may be an 
important source of infection for domestic dogs and 
humans. Therefore, animal health and human health 
education are recommended in these communities. 
Veterinarians and physicians should play an important 
role in increasing the level of awareness of zoonotic 
dog parasites, thus helping prevent or minimize 
zoonotic transmission.
References
 1. Zierdt CH. Blastocystis hominis–past and future. 
Clin Microbiol Rev. 1991;4:61-79.
 2 Zierdt CH. Blastocystis hominis, a protozoan 
parasite and intestinal pathogen of human beings. 
Clin Microbiol Newslett. 1983;5:57-9.
 3 Garcia LS, Bruckner DA, Clancy MN. Clinical 
relevance of Blastocystis hominis. Lancet, i. 
1984:1233-4.
 4 Ricci N, Toma P, Furlani M, Caselli M, Gullini 
S. Blastocystis hominis: a neglected cause of 
diarrhoea? Lancet. 1984;1(8383):966.
 5 Lebar WD, Larsen EC, Patel K. Afebrile diarrhea 
and Blastocystis hominis. Ann Intern Med. 
1985;103:306.
 6 Garavelli PL, Orsi P, Scaglione L. Blastocystis 
hominis  infect ion dur ing AIDS. Lancet. 
1988;2(8624):1364.
 7 Tasova Y, Sahin B, Koltas S, Paydas S. Clinical 
significance and frequency of Blastocystis hominis 
in Turkish patients with hematological malignancy. 
Acta Med Okayama. 2000;54:133-6.
 8 Chen TL, Chan CC, Chen HP, Fung CP, Lin CP, 
Chan WL, et al. Clinical characteristics and 
endoscopic findings associated with Blastocystis 
hominis in healthy adults. Am J Trop Med Hyg. 
2003;69:213-6.
 9 Minvielle MC, Pezzani BC, Cordoba MA, Deluca 
MM, Apezteguia MC, Basualdo JA. Epidemiological 
survey of Giardia spp. and Blastocystis hominis 
in an Argentinian rural community. Korean J 
Parasitol. 2004;42:121-7.
 10 Kain KC, Noble MA, Freeman HJ, Barteluk RL. 
Epidemiology and clinical features associated with 
Blastocystis hominis infection. Diagn Microbiol 
Infect Dis. 1987;8:235-44.
 11 Pakandl M. Occurrence of Blastocystis sp. in pigs. 
Folia Parasitol. 1991;38:297-301.
 12 Teow WL, Ng GC, Chan PP, Chan YC, Yap EH, 
Zaman V, et al. A survey of Blastocystis in reptiles. 
Parasitol Res. 1992;78:453-5.
 13 Zaman V, Ng GC, Suresh K, Yap EH, Singh M. 
Isolation of Blastocystis from the cockroach 
(Dictyoptera: Blattidae). Parasitol. Res. 1993;79: 
73-4.
 14 Quilez J, Clavel A, Sanchez-Acedo C, Causape 
AC. Detection of Blastocystis sp. in pigs in Aragon 
(Spain). Vet Parasitol. 1995;56:345-8.
 15 König G, Müller HE. Blastocystis hominis in 
Blastocystis Sp: a Neglected Zoonotic Protozoan
62
animals: incidence of four serogroups. Zbl Bakt. 
1997;286:435-40.
 16 Chen XQ, Singh M, Ho LC, Moe KT, Tan SW, Yap 
EH. A survey of Blastocystis sp. in rodents. Lab 
Anim Sci. 1997;47:91-4.
 17 Lee MG, Stenzel DJ. A survey of Blastocystis 
in domestic chickens. Parasitol Res. 1999;85: 
109-17.
 18 Yoshikawa H, Morimoto K, Nagashima M. Isolation 
and characterization of Blastocystis spp. isolated 
from anuran amphibians. In: Tada I, Kojima S, Tsuji 
M, editors. Proceedings of the Ninth International 
Congress of Parasitology 1998. International 
Proceedings Division, International Congress of 
Parasitology, Bologna, Italy; 1998. p. 1075-9.
 19 Salim HR, Kumar GS, Vellayan S. Mak JW, Anuar 
AK, Init I, et al. Blastocystis in animal handlers. 
Parasitol Res. 1999;85:1032-3.
 20 Yoshikawa H, Nagano I, Yap EH, Singh M, 
Takahashi Y. DNA polymorphism revealed by 
arbitrary primers polymerase chain reaction 
among Blastocystis strains isolated from humans, 
a chicken, and a reptile. J Euk Microbiol. 
1996;43:127-30.
 21 Clark CG. Extensive genetic diversity in Blastocystis 
hominis. Mol Biochem Parasitol. 1997;87:79-83.
 22 Knowles R, Das Gupta BM. On the nature of 
Blastocystis hominis. Ind J Med Res. 1924;12: 
31-8.
 23 Duda A, Stenzel DJ, Boreham PFL. Detection of 
Blastocystis sp. in domestic dogs and cats. Vet 
Parasitol. 1998;76:9-17.
 24 Abe N, Nagoshi M, Takami K, Sawano Y, 
Yoshikawa H. A survey of Blastocystis sp. in 
livestock, pets, and zoo animals in Japan. Vet 
Parasitol. 2002;106:203-12.
 25 Alexeieff A. Sur la nature des formations dites 
‘kystes de Trichomonas intestinalis’. CR Soc Biol. 
1991;71:296-8.
 26 Brumpt E. Coˆlite a `Tetramitus Mesnili Wenyon 
1910 et coˆlite a `Trichomonas intestinalis 
Leuchart 1879. Blastocystis hominis n. sp. et 
Formes voisines. Bull Soc Pathol Exot. 1912;5: 
725-30.
 27 Garavelli PL, Scaglione L. Blastocystosis. 
An epidemiological study. Microbiologica 
1989;12:349-50.
 28 Burden DJ, Anger HS, Hammet NC.  Blastocystis 
sp. infections in pigs. Vet Microbiol. 1978-
79;3:227-34.
 29 Stenzel DJ, Cassidy MF, Boreham PFL. Morphology 
of Blastocystis sp. isolated from circus animals. 
Int J Parasitol. 1993;23:685-7.
 30 Chuong LS, Suresh K, Mak JW, Init I, Kathijah 
O. Prevalence of Blastocystis in animals from 
domesticated surroundings. Southeast Asian J 
Trop Med Public Health 1996;27:850-2.
 31 Yoshikawa H, Abe N, Wu Z. PCR-based identification 
of zoonotic isolates of Blastocystis from mammals 
and birds. Microbiology. 2004;150:1147-51.
Blastocystis Sp: a Neglected Zoonotic Protozoan


A survey of Blastocystis in domestic chickens. Parasitol Res.

A survey of Blastocystis in reptiles. Parasitol Res.

A survey of Blastocystis sp. in livestock, pets, and zoo animals in Japan. Vet Parasitol.

A survey of Blastocystis sp. in rodents. Lab Anim Sci.

Afebrile diarrhea and Blastocystis hominis.

An epidemiological study.

Blastocystis hominis in Blastocystis Sp: a Neglected Zoonotic Protozoan62 animals: incidence of four serogroups. Zbl Bakt.

Blastocystis hominis infection during AIDS.

Blastocystis hominis–past and future. Clin Microbiol Rev.

Blastocystis hominis, a protozoan parasite and intestinal pathogen of human beings.

Blastocystis hominis: a neglected cause of diarrhoea?

Blastocystis in animal handlers. Parasitol Res.

Blastocystis sp. infections in pigs. Vet Microbiol.

Clinical characteristics and endoscopic findings associated with Blastocystis hominis in healthy adults.

Clinical relevance of Blastocystis hominis.

Clinical significance and frequency of Blastocystis hominis in Turkish patients with hematological malignancy. Acta Med Okayama.

Coˆlite a `Tetramitus Mesnili Wenyon

Detection of Blastocystis sp. in domestic dogs and cats. Vet Parasitol.

Detection of Blastocystis sp. in pigs in Aragon (Spain). Vet Parasitol.

DNA polymorphism revealed by arbitrary primers polymerase chain reaction among Blastocystis strains isolated from humans, a chicken, and a reptile.

Epidemiological survey of Giardia spp. and Blastocystis hominis in an Argentinian rural community.

Epidemiology and clinical features associated with Blastocystis hominis infection. Diagn Microbiol Infect Dis.

et coˆlite a `Trichomonas intestinalis Leuchart 1879. Blastocystis hominis n. sp. et Formes voisines. Bull Soc Pathol Exot.

Extensive genetic diversity in Blastocystis hominis. Mol Biochem Parasitol.

Isolation and characterization of Blastocystis spp. isolated from anuran amphibians.

Isolation of Blastocystis from the cockroach (Dictyoptera:

Morphology of Blastocystis sp. isolated from circus animals.

Occurrence of Blastocystis sp. in pigs. Folia Parasitol.

On the nature of Blastocystis hominis.

PCR-based identification of zoonotic isolates of Blastocystis from mammals and birds.

Prevalence of Blastocystis in animals from domesticated surroundings.

Sur la nature des formations dites ‘kystes de Trichomonas intestinalis’.

Blastocystis Sp: a Neglected Zoonotic Protozoan

http://eprints.arums.ac.ir/568/1/Blastocystis.pdf

Blastocystis Sp: a Neglected Zoonotic Protozoan

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