Objective: To test the association between exposure to bovine coronavirus (BCV) and outbreaks of winter dysentery (WD) in dairy herds and to examine other risk factors for outbreaks of WD in dairy herds.
Animals: 12 dairy herds in Ohio affected with WD (case herds). For each case herd, 2 unaffected herds from the same area were concurrently used as control herds.
Procedure: A case-control study was conducted, using herds as the unit of investigation. Multivariate logistic regression modeling was used to identify risk factors for contracting disease.
Results: 4 factors appeared to increase a herd's risk for WD: increase in herd prevalence of adult cows that had a fourfold or more increase in BCV serum IgG antibody titer; increase in herd prevalence of adult cows that had a fourfold or more increase in bovine viral diarrhea virus (BVDV) titer; housing cattle in tiestall or stanchion barns rather than free-stall facilities; and use of equipment to handle manure and subsequently handle feed. The adjusted population-attributable risk for these variables was 71, 43, 53, and 31%, respectively, and 99% overall, indicating that these variables had considerable impact on WD outbreaks for the study population.
Conclusions and clinical relevance: In dairies in Ohio, recent herd exposure to BCV appeared to increase the risk for WD outbreaks. Some WD outbreaks might have been associated with acute BVDV infection. Certain housing and management practices may have increased the risk of an outbreak of WD.