Parasites of Small Mammals in Grand Teton National Park: Babesia and Hepatozoon

Abstract

Babesia microti, a parasitic protozoan, is endemic in the Microtus montanus of Grand Teton National Park. It is transmitted by the tick Ixodes eastoni and reproduces in the erythrocytes of its vole host. A second protozoan parasite, Hepatozoon sp., which is widespread in small mammals in Europe, is also found in reptiles throughout the world. The record of Hepatozoon in North American small mammals is not extensive. Hepatozoon, unlike Babesia, may be a two-host or a three-host parasite. Also unlike Babesia, for which the intermediate host is always a tick, the intermediate host of Hepatozoon may be a tick, a mite, a flea, or a mosquito. The method of transmission by the vector also differs in the two parasites. Babesia is transmitted in the tick's saliva when it bites, whereas Hepatozoon infection requires the vertebrate host to ingest a vector. In our 1996 studies, we sought more data on these two parasites. The objectives for 1996 focused on Hepatozoon: to sample specific populations of M. montanus, in which we have previously documented Hepatozoon infections; to determine whether differences exist in the infection rates at different study sites in the park; and to search for any additional vectors of Hepatozoon sp. infections in M. montanus by examining ectoparasites. These studies contributed to our long-term objectives of documenting the effects and cost of parasitism on M. montanus populations.