Blood parasites of wild voles, Microtus agrestis, in England

Abstract

1. Thirty-six of 70 Microtus agrestis captured near Oxford, England, between January and July, 1961, were infected with blood parasites—9 with Trypanosoma microti Laveran & Pettit, 1909, 18 with Babesia microtia (França, 1912) and 19 with Grahamella microti Lavier, 1921: some had more than one species.2. Morphologically indistinguishable parasites were found in 6 of 20 Clethrionomys glareolus (Babesia in 3, Trypanosoma in 2, and Grahamella in 1) and 2 of 4 Apodemus sylvaticus (Grahamella only). Hepatozoon sp. indet. was found in one C. glareolus.3. It is probable that the proportion of M. agrestis with patent infections of G. microti increased, and possibly that due to T. microti fell, during February–April, 1961.4. M. agrestis often have very enlarged spleens and it appeared that B. microtia (sometimes associated with T. microti) was commoner in the animals with the largest spleens.