Diagnosis, epidemiology and fecal shedding of Mycobacterium paratuberculosis in Ontario dairy cattle

In a cross-sectional study, 686 cows from nine dairy herds with a high prevalence of Johne's disease were evaluated with a milk and serum ELISA and mycobacterial culture of feces. The level of agreement and proportion of cattle positive on each of these three assays were compared. The milk ELISA results were in closest agreement to those of a single fecal culture.; Associations between the paratuberculosis status and several production outcomes were evaluated for the cattle enrolled in the above study. Fecal culture and milk ELISA positive cows produced less milk, fat and protein as compared to their test negative herd mates. Survival analysis demonstrated that cows positive on any of the three tests were at higher risk of being culled than test negative cows. Johne's disease status was not associated with milk somatic cell count.; In a case-control study, 94 selected herds had a management questionnaire completed. Composite milk samples were evaluated with an ELISA for M. paratuberculosis. Regression analysis was used to determine the management factors associated with milk ELISA status of cattle. Herds with a history of Johne's disease were at increased risk of having cows test positive on a milk ELISA. The use of monensin sodium or calf hutches, and a higher test-day milk production, all reduced the odds of a cow testing milk ELISA positive.; The prevalence of milk and serum antibodies to M. paratuberculosis was determined for the 50 randomly chosen herds in the case-control study. The cow and herd-level prevalence as determined by the milk and serum ELISA was 1.6%,2.6% and 18%,30% respectively. The level of agreement between the milk and serum ELISA at both the cow and herd-level was low to moderate.; A clinical trial was completed using 233 cows from 13 herds infected with M. paratuberculosis. Cattle were randomized to receive a monensin controlled release capsule (CRC) or a placebo bolus. Fecal and blood samples were collected over a period of 98 days. Mixed effect models were used to determine that cows treated with a monensin CRC shed 1.8 cfu per tube less than placebo treated cows (P = 0.08).{09}The biological significance of this reduction is unknown.