Johne's Disease

Key Information about Johne's Disease

Background:

• Minnesota's dairy industry generates over $1 billion each year in gross farm income from milk production, making it the largest livestock source of farm income in the State. In addition, beef production from dairy and beef cattle operations generate another $800 million in gross farm income to the State.
• Johne's disease has been recognized as an important economic loss in dairy cattle herds, with losses in heavily infected herds estimated at over $200 per cow in inventory.
• Available estimates indicate at least 25% of Minnesota dairy herds are infected with Johne's disease. In dairy herds with over 300 milk cows, at least 40% of dairy herds are already infected. Due to the ongoing expansion of dairy herds and widespread movement of cattle, the disease is spreading rapidly.
• While the scientific support for disease in humans is not strong, concern has arisen that M. paratuberculosis, the bacteria causing Johne's disease, may be a cause of Crohn's disease in humans.
• Because of these concerns, the Minnesota Dairy Leaders Roundtable has recently identified the control of Johne's disease as a top legislative priority.

Research Goals:
The Minnesota Johne's Working Group has undertaken the challenge of finding effective ways to control Johne's disease in Minnesota cattle herds. This group consists of a multidisciplinary group of basic and applied researchers at the University of Minnesota and diagnosticians at the CVM Minnesota Veterinary Diagnostic Laboratory, working with the Minnesota Board of Animal Health and Minnesota cattle producers and veterinarians.

Goals include:

• To sequence the genome of M. paratuberculosis. This approach will not only provide a rational basis for the development of new and effective diagnostic reagents, vaccines, and treatments, but also facilitate future research on important questions relating to the virulence and pathogenicity of M. paratuberculosis. 

  Status: Work is underway to complete the sequencing project, and several unique DNA sequences that could lead to new tests have already been identified.

• To develop improved diagnostic tests and more efficient methods of detecting infected herds. This includes evaluation of different herd-level testing strategies the will enhance the ability to distinguish infected from uninfected herds, and to develop and evaluate novel sensitive diagnostic approaches to rapidly detect the pathogen in individual animals. These developments are expected to enhance diagnostic capacity within the CVM Minnesota Veterinary Diagnostic Laboratory to support herd testing, monitoring, and control efforts. 

  Status: The group has already developed and evaluated an experimental DNA-based PCR test. With additional funding, plans are underway to develop an improved DNA-based PCR test using information from the sequencing project. In addition, the use of testing pooled samples to detect infected herds is being evaluated.

• To define key components of an effective immune response that result in successful elimination of M. paratuberculosis infection. Once these components are known, these tools can be used to identify susceptible and resistant cattle.

  Status: Different immune responses to M. paratuberculosis compared to that for other Mycobacterium species have been identified

• To develop effective control programs for Johne's disease in Minnesota cattle through implementation of risk assessment-based herd management changes, in collaboration with the Minnesota Board of Animal Health. Specific on-farm control measures including pasteurization of colostrum and waste milk, separate maternity housing, and segregated heifer rearing to reduce the transmission of M. paratuberculosis to dairy calves are being evaluated.

  Status:
  Project 1. Nine Minnesota cattle herds are currently participating in demonstration herd control project. Through changes in management practices on the farm (based on a risk assessment approach, reductions in disease and infection are being measured.

  Project 2. Ninety dairy farms throughout Minnesota are participating in a study to evaluate the potential role of wildlife (deer and rabbits) and the environment in the transmission of Johne's disease.

  Project 3. Two large Minnesota dairy farms are visited every two weeks to evaluate factors related to onset of fecal shedding and clinical disease in dairy cattle. The goal is to identify management practices that could slow the onset of clinical disease in infected herds. The economic impact of Johne's disease (milk production, reproduction, longevity) in affected cattle will also be evaluated.

• To deliver new information gained to Minnesota dairy producers through the University of Minnesota, Minnesota veterinary practitioners, the Minnesota Board of Animal Health, and dairy extension personnel across the state of Minnesota.

  Status: Meetings are taking place this spring across Minnesota with dairy veterinarians and producers to discuss new information regarding interpretation of Johne's test results, transmission of the disease, and changes in the Board of Animal Health.