Objective: To identify risk factors associated with Neospora caninum infection in dairy herds in Québec and to estimate seroprevalence in case and control herds.
Design: Herd-based case-control and seroprevalence study.
Animals: 3,059 cows from 24 case and 22 control dairy herds in Québec.
Procedure: Blood samples were obtained from each cow, and sera were tested, using an ELISA, for antibodies to N caninum. Owners of herds answered questionnaires requesting information on demographics and herd management practices. Seroprevalence was compared between case and control herds, using the Mann-Whitney test. Risk factors were compared between case and control herds, using logistic regression.
Results: All case herds and 73% of control herds had at least one seropositive cow. Median seroprevalence was significantly greater among case herds (22.5%) than among control herds (7.5%). Dogs were found most often and in greatest numbers on farms housing case herds compared with control herds during the past 3 years.
Clinical implications: Although the exact role that dogs have in transmission of N caninum in dairy herds needs to be elucidated, dogs should have limited access to barns and cattle.