Neosporosis-associated bovine abortion in Pennsylvania.

Neospora caninum was found in fetal tissues of 34 of 688 cases of bovine abortion submitted to the Pennsylvania Animal Diagnostic Laboratory System during the period from May 1994 to November 1996. The aborted fetuses ranged in gestational age from 3 to 8 months. Microscopic lesions consisted primarily of encephalitis and myocarditis. A labeled (strept) avidin-biotin staining procedure using anti-N. caninum polyclonal rabbit serum revealed N. caninum organisms within the fetal brain (27 of 27), heart (10 of 13), placenta (5 of 6), kidney (2 of 2), liver (1 of 4) and skeletal muscle (1 of 1).