Neosporosis in Cattle

Abstract

Bovine neosporosis has emerged as an important reproductive disease since its first association with an abortion storm in 1987 on a dairy in New Mexico.⁴⁶ Numerous reports of Neospora abortion have confirmed this infection as a significant cause of abortion, particularly among dairy cattle.^{2,7,18,23,25,26,36,45,46,47,48,55} It has a worldwide distribution, having been diagnosed in many countries from six continents, and is prevalent throughout North America. Bovine neosporosis is probably not a new disease, but rather a newly recognized one. Retrospective studies in California have confirmed that the parasite has been endemic since 1984, and a decade earlier the infection was identified retrospectively in a stillborn calf in Australia.²³ Surveys in California, the Netherlands and New Zealand indicate that approximately 20% of all aborted bovine fetuses submitted to the diagnostic laboratory are diagnosed with this infection. In abortion submissions from dairy herds with a history of Neospora abortion, the proportion of Neospora infection in aborted fetuses is as much as 44%.⁴ Since fetal infection can result in either fetal death or the birth of a live congenitally infected calf, there are questions about what factors determine the clinical outcome of fetal infection and what are the appropriate methods to diagnose Neospora abortion. This will be discussed.