Submitted to: Research Workers in Animal Diseases Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 11/12/1996
Publication Date: N/A
Technical Abstract: Winter dysentery (WD) is a disease of cattle characterized by acute diarrhea rapidly affecting many adult animals in a herd. We studied the relationship of individual cow's exposure to bovine coronavirus (BCV), bovine viral diarrhea virus, Salmonella spp., Cryptosporidium spp., and other cow-level factors with the occurrence of clinical illness from 229 individuals within 12 WD affected herds, using case-control methodology. Diagnostic samples were collected during the outbreak and 3 weeks later. A multivariate conditional logistic regression model was built by manual forward selection to identify important risk factors, while adjusting for herd effects. The odds ratio (OR) for being a WD case increased as the amount of BCV antigen present in feces increased, evidenced by each 0.100 increase in BCV antigen ELISA value (OR=2.94, p=0.031). Animals confirmed pregnant were only half as likely to be WD cases compared to nonpregnant herdmates (OR=0.49, p=0.016). A statistical interaction was found between the acute BCV IgG antibody log2 titer and whether or not an individual showed a greater than or equal to 4-fold convalescent seroresponse with the same assay (p=0.013): for animals that did not serorespond, each unit of increase in the acute BCV IgG antibody ELISA log2 titer was associated with less (OR=0.81) risk. However, for animals that did respond, lower acute BCV IgG antibody log2 titers were associated with being control animals, whereas higher log2 titers were associated with being WD cases. This interaction may be due to the dynamics of the assay rather than a biologic effect in the animal. We conclude that, within herds affected with WD, clinically ill cows are more likely to shed BCV in feces and pregnancy status may be a predictor of which cows become clinically ill.