Comparative Parasitology 67(2) 2000 - Peru State College

Comp. Parasitol.
67(2), 2000 pp. 197-201
Hymenolepis nana in Pet Store Rodents
LAURA M. DUCLOS AND DENNIS J. RICHARDSON'
Department of Biological Sciences, Box 138, 275 Mount Carmel Avenue, Quinnipiac University, Hamden,
Connecticut 06518, U.S.A. (e-mail: dennis.richardson@quinnipiac.edu)
ABSTRACT: The rodent tapeworm, Hymenolepis nana, is a zoonotic pathogen transmissible through the ingestion
of eggs in feces or cysticercoids in arthropods. Since data addressing the potential for acquiring human infections
of H. nana from pet rodents are lacking, a survey of pet stores in southern Connecticut, U.S.A., was conducted.
Fecal flotation analysis revealed 9.1% overall prevalence in 110 samples collected weekly from cages holding
group-housed small animals, from 3 stores for 4 weeks. Of 11 species, only cages holding rats (3 of 22 samples),
mice (6 of 30 samples), and prairie dogs (1 of 2 samples) were positive. Necropsies of 38 rats, 72 domestic
mice, and 39 golden hamsters purchased from 9 stores showed prevalences of 31.6%, 22.2%, and 10.3%,
respectively. Mean intensity was 66 worms per rat, 14 worms per mouse, and 15 worms per hamster. Overall,
75% of surveyed pet stores were selling infected rats, mice, or hamsters, indicating that pet store rodents pose
a potential threat to public health.
KEY WORDS: Hymenolepis nana, pets, rodents, survey, zoonosis.
Hymenolepis nana Siebold, 1852, infects 75
million people worldwide (Crompton, 1999), of
whom the majority are children (Little, 1985;
Markell et al., 1999). Hymenolepis nana has a
cosmopolitan distribution, with human, Old
World monkey, and rodent definitive hosts becoming
infected through ingestion of infective
cysticercoids within beetle or flea intermediate
hosts or through ingestion of eggs in feces. In
the latter route, cysticercoids develop in intestinal
villi, with worms later reemerging and attaching
to the mucosa (Roberts and Janovy,
2000). Direct transmission through the ingestion
of eggs may be the most common route of infection
in humans (Turner, 1975).
It has been suggested that 2 morphologically
identical subspecies of H. nana exist, yet this
tapeworm is typically classified as a zoonotic
and is capable of horizontal transmission between
human and nonhuman animals (Fox et al.,
1984; Jacoby and Fox, 1984; Chomel, 1992).
Human infections "produce either no symptoms
or vague abdominal disturbances. In fairly heavy
infections, children may show lack of appetite,
abdominal pain with or without diarrhea, anorexia,
vomiting, and dizziness" (Neva and
Brown, 1994). Such nondescript symptoms may
account for the low number of reported clinical
cases, and many subclinical infections may go
undiagnosed. Available prevalence data regarding
human populations were obtained in most
cases from fecal surveys conducted in develop-
1 Corresponding author.
197
ing nations. For example, H. nana was found in
20.5% of Australian aborigines (Meloni et al.,
1993), 8-10% of oncology patients in Mexico
(Guarner et al., 1997), 16% of Egyptian school
children (Khalil et al., 1991), and 0.6% of Thai
laborers (Wilairatana et al., 1996). In developed
regions such as Western Europe and North
America, human infections are seldom identified
or acknowledged, and survey data are often
patchy and scarce (Croll and Gyorkos, 1979; Jacobs,
1979; Seaton, 1979; Cooper et al., 1981).
Still, H. nana is estimated to be an important
cause of cestodiasis in the southeastern United
States, with infections found in approximately
1% of school children (Roberts and Janovy,
2000) and 4% of pediatric clinic patients (Flores
et al., 1983). In 1987, 34 state diagnostic laboratories
identified H. nana in collected stool
samples (0.4%), with Connecticut reporting a
prevalence of 0.8%, Massachusetts 0.4%, and
Rhode Island 1.6% (Kappus et al., 1991).
Most studies focus on human infection, but
fail to adequately address potential zoonotic
sources of the infection. In Turkey, 5.6% of surveyed
wild mice and rats harbored H. nana (Sahin,
1979), and in Saudi Arabia, H. nana was
reported from baboons living in close proximity
to humans (Ghandour et al., 1995). In the United
States, Stone and Manwell (1966) reported infection
in 21% of mice and 9% of hamsters from
Syracuse University, Syracuse, New York,
U.S.A., animal rooms and various commercial
vendors. In the same study, pet mice and ham-
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