CHARACTERIZATION OF PNEUMOCYSTIS-CARINII INFECTION IN SOREX-ARANEUS -A REVIEW

Pneumocystis carinii is a pulmonary pathogen causing a fatal pneumonia (PCP) in immunocompromised hosts. Notable interspecific differences i n the prevalence of P. carinii have been observed in small mammals in Finland. Although seasonal peaks (up to 30 %) occur in some species, p revalences usually are low (< 10 %). On the contrary, 40 % to 70 % of the common shrews, Sorer araneus, have the cyst form of P. carinii. Th e prevalence is high in all sex and age groups, in all seasons and thr oughout the country. Despite the high prevalence, no signs of PCP have been detected, and the infected shrews are apparently healthy. The oc currence of cysts has no significant relation to the histological chan ges detected in the lungs of the shrews. The number of cysts found per gram of lung tissue in wild S. araneus is low compared to those of cl inically ill rats, but seems on the average to be higher than those fo und in Microtus agrestis caught in the same area. The interspecific di fferences in the prevalence of P. carinii infection observed in shrews and other wild mammals are most likely due to the strong species spec ificity of P. carinii.