Longitudinal study of the distribution of Mycobacterium avium subsp. paratuberculosis in the environment of dairy herds in the Michigan Johne's disease control demonstration herd project.

The objective of this study was to describe the distribution of Mycobacterium avium subsp. paratuberculosis (MAP) in the environment of infected dairy farms over time. Johne's disease (JD) prevalence was monitored annually in 7 Michigan dairy herds.

Serologic evaluation of five unvaccinated heifers to detect herds that have cattle persistently infected with bovine viral diarrhea virus.

Objective: To determine whether serologic evaluation of 5 unvaccinated 6- to 12-month-old heifers is a valid method for identifying herds that contain cattle persistently infected (PI) with bovine viral diarrhea virus (BVDV).

Animals: 14 dairy herds with a history of BVDV infection, with health problems consistent with BVDV infection, or at risk for contracting BVDV infection.

Procedure: 5 unvaccinated 6- to 12-month-old heifers were randomly selected from each herd.