Associations of Neospora caninum seropositivity with gestation number and pregnancy outcome in Danish dairy herds

The prevalence and distribution of seropositivity towards the protozoan par asite Neospora caninum were studied in single blood samples from 1561 cows from 31 Danish dairy herds. Blood samples were analysed by an indirect enzy me-linked immunoassay and an indirect fluorescent-antibody test, Seropreval ence in 15 herds with previous abortions assigned to neosporosis ranged fro m I% to 58%, with a mean frequency of 22%. In eight out of 16 herds without a history of N. caninum related abortions, no seroreactors were found. In the remaining eight herds, the seroprevalence ranged from 6% to 59%. The pr evalence and distribution of seropositivity, gestation number prior to samp ling, and breed were related to abortions and perinatal deaths using a rand om-effects logistic-regression model. Abortion risk was significantly incre ased in seropositive animals (OR=3) and in greater than or equal to 2nd-ges tation cows (OR=3). Perinatal death was significantly influenced by gestati on number and breed, but not by serostatus, Reproductive performance and cu lling risk of cows were not affected by serostatus. Seropositivity increase d with "age" (i.e, gestation number) (P=0.02). In open cows, seropositivity tended to decrease with distance from calving (P=0.05). The proportion of seropositive pregnant cows increased with trimester (P=0.02). (C) 1999 Else vier Science B.V. All rights reserved.