Toxoplasmosis in beluga whales (Delphinapterus leucas) from the St Lawrence estuary: two case reports and a serological survey.

Toxoplasmosis was diagnosed in two free-ranging beluga whales from the St Lawrence estuary, Quebec, Canada, in 1988 and 1998. Histologically, tachyzoites and bradyzoites were present in the brain, spleen, lymph nodes, adrenals and lungs of both animals, and in the thymus of one. These organisms were readily labelled by an indirect immunohistochemical method for Toxoplasma gondii antigens. In the lymph nodes, spleen and lungs the organisms were associated with histiocytic infiltration. In the brain of one animal they were associated with mild multifocal gliosis and haemorrhages. There was no evidence of concomitant morbillivirus infection. Serum samples were collected from 22 beluga whales stranded between 1995 and 1998 on the shores of the St Lawrence Estuary and examined for antibodies to T. gondii by the modified agglutination test. Antibody titres of s25 were found in six (27%) of the animals. This is the first confirmed report of toxoplasmosis in beluga whales.