Objective: To determine seroprevalence of Neospora caninum infection in beef herds and the association between serologic status and rate of abortion, stillbirth, calf mortality, and reproductive failure.
Design: Longitudinal study.
Animals: 419 cows from 8 beef herds in central Alberta.
Procedure: 1,391 serum samples from a serum bank were analyzed, using ELISA, and results were compared, using logistic regression, with productivity data on individual cows obtained from a database established during a 4-year period.
Results: 30% of cows were seropositive at some point during the 4-year period. Risks of abortion (odds ratio [OR], 5.7) and stillbirth (OR, 2.8) in seropositive cows were significantly greater than in seronegative cows. Risks of being culled for any reason (OR, 1.9) or for reproductive failure (OR, 2.5) in seropositive cows were also significantly greater than in seronegative cows. Changes in titer with time in individual cows and a lack of association between serologic status of dam versus daughter suggest that postnatal transmission was possible in these herds. However, horizontal transmission did not appear to play a substantial role in abortions that occurred in these herds.
Clinical implications: Neosporosis should be investigated as a potential source of economic loss to the beef industry.