Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 12, 1999
Publication Date: N/A
Interpretive Summary: Neospora caninum is a single celled parasite of livestock and companion animals. It is a major cause of abortion in dairy cattle. Abortion is the only clinical sign in adult cows infected with N. caninum. In some dairy herds, up to 100% of cattle have been exposed to this parasite based on antibody testing. At present, there is no serologic test to distinguish acute versus chronically infected cattle. Scientists at the Beltsville Agriculture Research Center and the Institute of Virology in Berlin, Germany have developed a test to distinguish Neospora infected cows from herds with epidemic abortions (large numbers of abortions within 30 days) and endemic abortions. These results will be of interest to parasitologists, pathologists, and dairy cattle farmers.
A sandwich enzyme-linked immunosorbent assay (ELISA) for the sensitive and specific detection of bovine antibodies to Neospora caninum was developed and evaluated using sera from cattle experimentally infected with N. caninum, Toxoplasma gondii, Sarcocystis cruzi, S. hominis, S. hirsuta, Eimeria bovis, Cryptosporidium parvum, Babesia divergens and field sera from naturally exposed animals. Field sera were classified using a "gold standard", which included the results from an indirect fluorescent antibody test (IFAT) and an immunoblot (IB). Based on this "gold standard" results (i.e. IFAT-IB results) an equal relative sensitivity and specificity of 94.2% was reached when a cut-off of 0.034 was employed. The analysis of gold standard-positive field sera showed that within groups of aborting and non-aborting dams, the animals from herds with endemic N. caninum-associated abortions had significantly higher ELISA indices than animals from herds with N. caninum-associated epidemic abortions. By contrast, aborting cattle from herds with endemic N. caninum-associated abortions had significantly lower IFAT titers than the aborting cows from herds with epidemic N. caninum-associated abortions. This is the first time that statistically significant serological differences between herds exhibiting epidemic and endemic N. caninum-associated abortions are described.