The most common
genera of coccidian parasites are Isospora
and Eimeria (Oklahoma State University).
You know a little about Eimeria
of heteromyid rodents from reading the original article by Ford et. al (1990). Species of Eimeria
are most commonly found in ruminants, birds, and rodents (University of New Mexico). The Isospora
genus is found in humans and domestic dogs and cats. Being very species-specific, Isospora is not zoonotic and therefore
cannot be passed from dog or cat to human.
It also cannot be passed from dog to cat and vice versa (UC Davis: University of California).
You are not only worried about yourself being exposed to coccidia, but also Kit
Kat and Beau, your adorable dog and cat. So you decide that Isospora is a more
appealing genus, and branch off toward that direction with your
research. Isospora species are found throughout the world, thus climate must
not be a distribution factor. Carnivores, especially
canines and felines, and some omnivores, such as humans, and birds are the main
hosts for infection. Coccidian
species usually only parasitize a single host species, thus they are referred
to as being oioxenous. As an exception
to that rule, some species in birds and reptiles can also parasitize close
relatives, and are stenoxenous, while yet others infect unrelated hosts and are
euryxenous. Certain hosts are vulnerable
to more than one species of Isospora,
which can have variable morphologies, lifecycles, and pathogenicity. It is clear that Kit Kat and Beau cannot pass
the parasite to you or you to them, and it is more likely for them to contract
the infection than for you to (Australian
Society for Parasitology Inc.).
Species of Isospora
infect a host through ingestion of food or water contaminated with sporulated
oocysts containing sporozoites.
Sporozoites penetrate into intestinal cells where they feed, mature, and
asexually reproduce by a process called schizogony. Merozoites result from schizogony and some
infect new cells. Other merozoites
sexually reproduce and develop into micro- and macro-gametes. Upon fertilization, a zygote, or oocyst is formed. The oocyst passes through the intestine and
is released along with feces allowing the cycle to continue (Oklahoma State University).
Most species of Isospora are mildly pathogenic, causing temporary symptoms such as
diarrhea, colic, dehydration, anemia, appetite loss, weight loss, and
fever. In extreme cases, death will result. When the parasite is
mature, it lyses epithelial cells that line the small intestinal villi of the
host. The destruction of the intestinal
epithelium and underlying tissue of the mucosa is associated with hemorrhaging
into the lumen of the intestine, inflammation of the mucous membranes in the
head and throat, villous atrophy, and crypt hypertrophy. Young animals are most susceptible to disease
caused by Isospora (Isosporiasis),
but acquire a strong protective immunity (Australian
Society for Parasitology Inc.). Therefore,
Kit Kat and Beau, both being of adult age may have been infected by Isospora in their early years, but
likely have immunity to it now. You’re
interested in finding out how Isospora
is diagnosed and what precautions can be taken to protect humans and pets from
this coccidian, but for now it’s time to call it a day.
References
Oklahoma State University Center for Veterinary Health
Sciences. (n.d.). Coccidia and coccidia-like parasites. Retrieved from
http://instruction.cvhs.okstate.edu/kocan/vpar5333/5333iii.htm
UC Davis: University of California. (n.d.). Isospora spp.
Retrieved from http://vetpda.ucdavis.edu/parasitolog/Parasite.cfm?ID=81
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