Parasitic Organisms in the Blood of Arvicoline Rodents in Alaska

A Grahamella-like organism (Schizomycetes: Bartonellaceae) was found in erythrocytes of laboratory-reared northern voles, Microtus oeconomus Pallas, which had been inoculated intraperitoneally with a saline suspension of ground fleas, Megabothris abantis (Roths.), from wild northern voles captured at Lower Ugashik Lake, Alaska Peninsula. A live-trapped northern vole from the same locality harbored trypanosomes referable to T. microti (Mastigasida: Trypanosomatidae). Two morphologically similar but biologically different strains of piroplasms (Piroplasmasida: Theileriidae) of uncertain generic status were isolated from northern voles of Ugashik Lake origin and from northern red-backed voles, Clethrionomys rutilus Pallas, from the vicinity of Anchorage, Alaska. In the natural host, these piroplasms seemed to reproduce principally by schizogony in the spleen and bone marrow, but inexperimentally infected hosts from populations occurring outside the enzootic area, intraerythrocytic fission was a common method of reproduction. The vector of these piroplasms is evidently a tick, Ixodes angustus Neumann, whose geographic distribution in Alaska coincides with that of piroplasm-induced splenomegaly in arvicoline rodents. The piroplasms have been successfully transmitted from host to host in the laboratory via ticks of this species.