Intraerythrocytic parasites in rodent populations of Connecticut: Babesia and Grahamella species.

A total of 612 Peromyscus leucopus, 11 Microtus pennsylvanicus, 21 Clethrionomys gapperi, and 4 Tamias striatus was collected in Connecticut and examined for Babesia and Grahamella during 1976 and 1977. Babesia antibodies were detected in sera of 9 P. leucopus collected from 4 sites. Babesia parasites were not detected in the blood smears of captured rodents. Subsequent splenectomy and subinoculation of blood from these rodents into susceptible animals failed to induce disease and no Babesia was isolated. Six of 10 P. leucopus inoculated with a Shelter Island, New York strain of B. microti remained infected for 3 1/2 months. Indirect fluorescent antibody titers of experimentally infected P. leucopus ranged from 1:8 to 1:256. Prevalence of Grahamella peromysci infection, as determined from examinations of blood smears of P. leucopus, was 13%. This infection rate is a conservative estimate because parasitemia is difficult to detect in intact animals. Twenty of 58 P. leucopus, taken at 2 sites and with negative blood smears for G. peromysci, developed parasitemia after splenectomy.