Seroprevalence of Neospora caninum and abortion in dairy cows in northern Spain

The seroprevalence of Neospora caninum infection was estimated from a sample of 889 cattle from 43 dairy herds in three counties in the Asturias region of Spain. The true prevalence of infection was estimated to be 30-6 per cent (95 per cent confidence interval (ci) 27-6 to 33-6). Seropositivity was associated with abortion during the previous year (odds ratio (OR)=3-31, P<0-001) and was slightly higher among purchased cattle (37-6 per cent), than among cattle raised on the farm (29-1 per cent) (P=0-078). Seropositive cows were more likely than seronegative cows to have had a seropositive dam (OR=2-3, P=0-011), suggesting that congenital transmission contributed to about 56 per cent of the infections. Herds with a true seroprevalence above 10 per cent had more dogs on the farm, than herds with a lower prevalence (P=0-032). The ORS relating abortion to seropositivity in individual herds ranged from 0-7 to 19, indicating that some herds experienced few abortions caused by N caninum, while others experienced more abortions due to the organism. Overall, 38-7 per cent of the abortions were estimated to have been attributable to N caninum.