A Retrospective analysis of risk factors associated with Johne's disease in Pacific Northwest dairy herds

Abstract

Data from 407 dairy risk assessments completed as part of the United States Department of Agriculture's Voluntary Bovine Johne's Disease Control Program in Washington and Oregon from November 2003 to August 2007 were evaluated to determine what management practices were associated with herd Johne's disease status, and what range of these management practices were in use in Pacific Northwest dairies. Overall, assessment scores between Johne's disease-positive and Johne's disease-negative herds did not significantly differ. A multivariate logistic regression analysis of the 32 individual management practices and two herd-level variables included in the overall risk assessment score found nine factors significantly associated with whether the assessment veterinarian reported at least one case of Johne's disease in the previous year. These nine factors were: (1) herd size, (2) addition of new animals during the previous year, (3) stocking density of the calving area, (4) degree of manure build-up in the calving area, (5) presence of Johne's disease suspects in the calving area, (6) degree of manure soiling of udders and legs of cows in the calving area, (7) exposure of bred heifers to adult cow manure, (8) pasture-sharing by bred heifers and adult cows, and (9) degree of contamination of adult cow feed with manure.