Methods for detecting Babesia microti infection in wild rodents.

We compared various methods for detecting Babesia microti infection in white-footed mice (Peromyscus leucopus) captured in enzootic regions of Massachusetts. The most sensitive method tested involved inoculating blood from wild rodents into hamsters. One month postinoculation proved to be the optimal time for microscopically examining blood of inoculated hamsters. With this method, as few as 300 organisms produced patent infection. Prior splenectomy of hamsters did not increase susceptibility to infection. For direct study of captured animals, a Giemsa-stained, thin blood-film prepared from the animal's tail was the most convenient method tested. However, this method detected only 61% of infections identified by hamster inoculation.