"So, naturalists observe, a flea has smaller fleas that on him prey; and these have smaller still to bite ’em; and so proceed ad infinitum."
- Jonathan Swift

February 2, 2010

February 2 - Eimeria monacis

Because today is Groundhog Day, it seemed only fitting to highlight a parasite of Marmota monax, the groundhog or woodchuck. Eimeria monacis is a coccidial parasite – a group of parasites that are thought to be very host specific. Eimeria is an apicomplexan, like Toxoplasma, Plasmodium, and Cryptosproridium. Their life cycle contains many of the same stages and processes, but unlike vector-borne apicomplexans like malaria, Eimeria and other coccidians only use one host and are transmitted from host to host via oral-fecal pathways. (You can see a nice animation of the life cycle here, albeit in a goat, not a groundhog.) The picture is from Frederick Fish's original 1930 description of E. monacis. Fish was a parastiologist from Johns Hopkins University, who caught the type host outside of Washington D.C.


  1. What is their persistence in the environment like? Could any species be theoretically eliminated by eliminating the wild host, captive-raising the survivors in a clean environment, and subsequent reintroduction?

  2. The oocysts of coccidians are very durable and can survive for months in the environment. I don't think that eliminating a parasite in the manner you describe is a good idea for many reasons.