Pneumocystis cariniiin arvicoline rodents: seasonal, interspecific, and geographic differences

We studied the seasonal prevalence of Pneumocystis carinii in Microtus agrestis (n = 289, two locations), Clethrionomys glareolus (n = 37), and Myopus schisticolor (n = 31) in southern and central Finland, in C. glareolus (n = 406) and Microtus oeconomus (n = 167) in Finnish Lapland, and in Lemmus lemmus (n = 35) in a fall sample in northern Norway. All material came from populations at peak and declining densities. The highest prevalence of P. carinii in M. agrestis in both locations in southern and central Finland was observed in November (30 and 10%). Two M. oeconomus were infected with P. carinii. No individual of the other species examined was positive for P. carinii. The prevalence and intensity of P. carinii infection in M. agrestis fed experimental low-protein diets were similar to those found in the field material.