Association of Neospora caninum with reproductive performance in dairy cows: A prospective study from Iran

There is no prospective study from Iran to estimate the direct risk of Neospora caninum for pregnancy loss or reproductive factors. In addition, there is no report in the literature concerning the association of N. caninum with dystocia and sex of calves. Therefore, this study was conducted on a group of dairy cows in a large intensive production system during 2011 to 2013 in southern Iran to evaluate the impact of neosporosis on reproductive performance. A total of 253 cows which were diagnosed as pregnant during the first six months of the study were followed until calving or abortion. Reproductive data were collected and N. caninum serostatus was determined using ELISA. To investigate the association of abortion with N. caninum, survival analysis was performed using Cox proportional hazard model. The N. caninum seroprevalence in the study group was 30.40% (95% CI: 27.40, 36.10). The overall abortion rate was 12.25%, significantly higher in seropositive animals (20.80%) than seronegative ones (8.50%). Results of Cox model showed that serostatus of animal for N. caninum and season had significant associations with abortion (p < 0.01). Neospora caninum did not show significant association with other factors such as dystocia and sex of calves. In conclusion, neosporosis is responsible for 12.00% excess abortion risk in infected group and more than 30.00% of abortions could be preventable by control of Neospora in study population. Therefore, control of N. caninum would reduce the economic losses caused by parasite mainly due to pregnancy loss.