Isolation and characterization of Sarcocystis from brain tissue of a free-living southern sea otter (Enhydra lutris nereis) with fatal meningoencephalitis

protozoan was isolated in cell culture from the brain of a free-ranging sea otter with fatal meningoencephalitis. The biological history of this otter , a study animal being monitored via an intraperitoneal radio transmitter, is summarized. Histologically, protozoal parasites were associated with are as of brain inflammation and necrosis in the cerebrum and cerebellum. Morph ology and measurements of fixed, Giemsa-stained protozoal zoites growing on coverslips were consistent with Sarcocystis. These parasites reacted only with polyclonal antisera raised against S. neurona on immunohistochemistry. Cell culture-derived zoites reacted strongly with polyclonal antiserum to S. neurona on indirect fluorescent antibody tests. Amplification of portion s of the 18S ribosomal DNA and the adjacent first internal transcribed spac er were performed. The resulting sequences were compared with published seq uences from similar apicomplexan protozoa. This isolate (SO SN1), was indis tinguishable from S. neurona, based on parasite morphology, antigenic react ivity and molecular characterization.