Humans are Hosts Too

            Now that you’ve had several weeks to utilize your resources at the local library to gather some information on the mystery coccidian specimens and are attempting to learn the unique language of science, you’re ready to start analyzing.  You have learned that a coccidian is a specific type of parasite that causes diseases called coccidiosis and toxoplasmosis, so it is potentially harmful.  You also found that heteromyid mice are burrowing rodents adapted to desert conditions.  (This particular species will probably not be visiting New England anytime soon, phew!)  They belong to the family Heteromyidae, which includes pocket mice, kangaroo mice, and kangaroo rats.  Ok, so according to the study in the original article, these organisms cause disease and are infectious to pocket mice and kangaroo rats from California, New Mexico, Texas, and Mexico.  However, the three newly described parasites were only found in the mice from Texas.

Cyclospora angimurinensis was found in 1 of 20 mice collected for the original study you found (Ford, Duszynski & McAllister, 1990).  At the time of the study, there were six other described species of cyclospora in mammals, all from moles.  The new cyclosporan is different in that it has an oocyst residuum, that is, a mass of cytoplasmic material outside of the sporocyst and inside of the oocyst.  A sporocyst is the initial lifecycle stage of the parasite.  Sporocysts, when inside of oocysts, are the infective stage to mammals and birds.  An oocyst is essentially comparable to an egg of a female.  The new cyclosporan described also has different-shaped sporocysts with different length by width ratios. 

Eimeria chaetodipi was found in 3 of 20 mice collected.  This specimen has sporulated oocysts that are shaped like those of Eimeria liomysis, another coccidian parasite that infects heteromyid rodents, but is smaller.  Eimeria hispidensis was found in 4 of 20 mice.  This species has sporulated oocysts that are also similar to E. liomysis, but has an oocyst residuum that is not found in E. liomysis.

            Heteromyid rodents nest in underground burrows in which no more than one individual typically resides.  Its fecal matter is deposited in side tunnels away from the burrow.  This separation of territory could limit heteromyids from coccidian exposure, and infection prevalence is consequently moderate.  Heteromyids inhabiting the plains and prairie regions of the midwestern United States seem to have a high prevalence of infection due to greater amounts of humidity and precipitation unlike those inhabitants of desert areas (Ford, Duszynski & McAllister, 1990). 

            Some of the reported coccidians of heteromyid rodents are host-specific while others are not, which could be due to unique morphological and biochemical properties of the rodents or the diverse host range of coccidian parasites.  It appears that the three described species of coccidians are not much to worry about as they like warmer, humid climates and are partial to small mammals (Ford, Duszynski & McAllister, 1990).  On another note, the “diverse host range” sparks your interest, especially when you stumble upon a massive listing of hosts, unfortunately including humans and domestic animals under the mammals section (Duszynski, Upton & Couch, 1998).  Looks like you’re going to have to hit the books again and find out about the pathology and lifecycles associated with the human and pet species of coccidia.

 

 

 

References

 

Ford, P. L., Duszynski, D. W., & McAllister, C. T. (1990). Coccidia (apicomplexa) from heteromyid rodents in the Southwestern United States, Baja California, and Northern Mexico with three new species from Chaetodipus hispidus. Journal of parasitology, 76(3), 325-331.

Duszynski, D. W., Upton, S. J., & Couch, L. (1998). The coccidia of the world. Retrieved from http://biology.unm.edu/biology/coccidia/table.html