Herd-level risk factors for infection with Mycobacterium paratuberculosis in US dairies and association between familiarity of the herd manager with the disease or prior diagnosis of the disease in that herd and use of preventive measures

Objective-To evaluate associations among herd infection status, herd manage ment practices, and familiarity of the herd manager with Mycobacterium para tuberculosis (Johne's disease) or prior disease diagnosis in that herd to s upport development of Johne's disease-control programs. Design-Population-based cross-sectional study. Sample Population-1,004 US dairies, each with greater than or equal to 30 c ows, representing 79.4% of US dairy cows. Procedure-Questionnaires were administered to dairy managers, and blood sam ples were collected from cows during herd visits. Sera were tested for anti bodies to M paratuberculosis, using a commercially available ELISA. Multiva riable logistic regression analyses were used to evaluate associations betw een use of management practices, herd disease status, and familiarity of th e manager with Johne's disease or prior diagnosis of Johne's disease in tha t herd. Results-Results from serologic testing revealed that 3.4% of cows and 21.6% of dairy herds were infected with M paratuberculosis. Factors associated w ith infection included number of cows in herd, region of country, percentag e of cows born at other dairies, group housing for periparturient cows, and group housing for preweaned calves. Few preventive practices were positive ly associated with prior diagnosis of Johne's disease (time of separation o f newborn calf from dam) or familiarity of the manager with the disease (te ats and udder washed before colostrum collected). Conclusions and Clinical Relevance Risk factors associated with Johne's dis ease in this study confirmed those management practices generally recommend ed for disease control. An educational problem, however, is the finding tha t herd managers familiar with Johne's disease generally use management prac tices similar to those used by managers unfamiliar with the disease.