Submitted to: Journal of Wildlife Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 20, 1996
Publication Date: N/A
Interpretive Summary: Infection by the protozoan (single-celled) parasite Toxoplasma gondii is widespread in humans and livestock in the U.S. It causes mental retardation and loss of vision in congenitally infected children and abortion in livestock. Humans become infected by ingesting food or water contaminated with oocysts excreted by cats or ingesting meat infected with tissue cysts. The role of wildlife in the epidemiology of toxoplasmosis is not well known. Scientists at the Beltsville Agricultural Research Center and the Alaska Department of Fish and Game have found antibodies to T. gondii in 25% of grizzly bears from Alaska. The results indicate widespread exposure of bears to Toxoplasma infection. Therefore, all bear meat should be cooked thoroughly before human consumption.
Blood samples were collected from 887 grizzly bears (Ursus arctos) in Alaska from 1973 to 1987. Sera were tested for evidence of exposure to Toxoplasma gondii by means of the modified agglutination test. Six hundred seventy-two sera (75%) had titers <25. Twenty-four samples (3%) had titers of 25. One hundred thirty-two specimens (15%) had titers of 50. Sixty-four sera (7%) had titers greater than or equal to 500. Antibody prevalence increased from 9% (18 positive of 196 tested) in southern areas to 37% (162/433) in northern areas. There is no readily apparent explanation for these discrepancies in location-specific prevalence.