Bovine neosporosis: comparison of serological methods using outbreak sera from a dairy herd in New Zealand

Serological methods developed to detect Neospora caninum specific bovine antibodies were compared using Sera from an abortion outbreak on a dairy farm in New Zealand. These methods included four ELISAs, IFAT and immunoblot. The abortions (n = 16) on the farm were restricted to one of two groups of the herd which consisted of 194 adult dairy cows. All ELISAs, IFAT and immunoblot (applying stringent cut-off levels) revealed a statistically significant association between seropositivity and abortion among the adult cows from the afflicted group I. The strength of this association varied between different tests, and different seroprevalences were determined for various animal groups. Among the different ELISAs, the strength of the relationship between single test results was characterised by a considerable variation in the determinants of correlation. Discrepancies in positive-negative classification between the two commercial ELISAs and one of the in-house ELISAs were due mainly to differences in the cut-off selection.