Serological differences in Neospora caninum-associated epidemic and endemic abortions

A sandwich enzyme-linked immunosorbent assay (ELISA) for the sensitive and specific detection of bovine antibodies to Neospora caninum was developed a nd evaluated using sera from cattle experimentally infected with N. caninum . Toxoplasma gondii. Sarcocystis cruzi, Sarcocystis hominis, Sarcocystis hi rsuta, Eimeria bovis, Cryptosporidium parvum, Babesia divergens. and field sera from naturally exposed animals. Field sera were classified using a gol d standard that included the results from an indirect fluorescent antibody rest (IFAT) and an immunoblot (IB). Based on these gold standard results, i .e., IFAT-IB results, an equal relative sensitivity and specificity of 94.2 % (theta(0),) was reached when a cutoff of 0.034 (d(0))was employed. The an alysis of IFAT-IB-positive held sera showed that within groups of aborting and nonaborting dams, the animals from herds with endemic N. caninum-associ ated abortions had significantly higher ELISA indices than animals from her ds with N. caninum-associated, epidemic abortions. By contrast, IFAT-IBposi tive aborting dams from herds with endemic N. caninum,-associated abortions had significantly lower IFAT titers than IFAT-IBpositive abetting dams fro m herds with epidemic N. caninum-associated abortions. This is the first ti me that statistically significant serological, differences between herds ex hibiting epidemic and endemic N. canimum-associated abortions are described .