Herd-specific and age-specific seroprevalence of Neospora caninum in 14 British dairy herds

All the cattle in 14 dairy herds in England were tested for Neospora caninum-specific antibodies with a commercial ELISA. Three of the herds had had sporadic abortions, eight had had endemic abortions and three had had epidemic abortions associated with N caninum before the study. Of 4295 cattle tested, 17.1 per cent were seropositive and the herd-specific prevalence ranged from 7.3 per cent to 44.8 per cent. No significant effect of either herd size (P=0.988), endemic (P=0.869) or epidemic (P=0.138) patterns of abortion on herd-specific prevalence was found by using logistic regression analysis. There was no evidence in any herd of a significant increase in prevalence with age; the prevalence in seven- to 12-month-old cattle was not significantly different (P>0.400) from the prevalence in older cattle, except that there was a significantly lower prevalence (P=0.017) in 13- to 24-month-old cattle. The results of this study are consistent with vertical transmission being the major route of N caninum transmission in these herds.