Neosporosis in Mexican dairy herds: lesions and immunohistochemical detection of Neospora caninum in fetuses.

Of 211 aborted bovine fetuses collected from Mexican dairy herds between January 1996 and March 1999, 73 showed microscopical lesions consistent with neosporosis. Of these 73 fetuses, 58 (79%) showed lymphocytic myocarditis, 39 (53%) showed microgliosis and multifocal necrosis in the brain, 39 (53%) showed lymphocytic hepatitis, and 19 (26%) showed lymphocytic myositis. Immunohistochemical examination of brain, myocardium and liver from 53 of the same 73 fetuses demonstrated Neospora caninum antigens in 41 (77%), of which 19 (46%) gave positive results in one of the three sites, 15 (37%) in two, and seven (17%) in three. The results indicated the presence of neosporosis in a number of the main dairy farming regions of Mexico. Copyright Harcourt Publishers Ltd.