Johne's Disease research gains steam at UM

St. Paul, Minn.—The United States Department of Agriculture (USDA) awarded University of Minnesota's (UM) College of Veterinary Medicine $4.4 million to study Johne's, thereby naming the institution the national research site for testing the disease in cattle.

The grant is the largest funding ever awarded by USDA's Cooperative State Research, Education and Extension Service to a university for research.

Johne's, considered one of the most destructive diseases found in dairy cattle, has infected at least 25 percent of Minnesota dairy herds, UM officials say. It is estimated that in herds with more than 300 dairy cows, at least 40 percent are infected and anywhere between 8 percent to 15 percent of beef cattle might have the disease, which spreads rapidly, officials add.

The research team includes several UM faculty members from the College of Veterinary Medicine, Agriculture, Food and Environmental Sciences and the Institute for Technology. A total 72 researchers from 23 other universities, state and federal governmental agencies also are participating in the research.

Human element

The destruction of Johne's disease might not end with dairy cattle, as research shows a possible zoonotic link causing Crohn's disease in humans, says Vivek Kapur, BVSc, PhD, professor of microbiology at the medical school and co-director of the university's Biomedical Genomics Center and Johne's disease program director.

"Pathogens have been discovered in retail milk samples," he says. "The Marshfield Clinic in Wisconsin found 2.5 to 3 percent of the 700 samples they collected from different states had a live organism, or 1 in 25 samples."

A prime goal of the researchers is to determine how the bacterial organism M. paratuberculosis, causes the disease.

"The organism grows slowly; what genes are indicated by the host are important to identify," Kapur says. However, there is not strong scientific evidence that, M. paratuberculosis, the bacteria that causes Johne's disease also causes Crohn's disease, he adds.

Due to transmission concerns, the Minnesota Dairy Leaders Roundtable has identified controlling Johne's disease a legislative priority.

Research goals

Scientists involved with the project hope to sequence the genome of

M. paratuberculosis

, to provide understanding for the developing new vaccines and treatments for the disease as well as diagnostic reagents.

"There are many questions about the virulence and pathogenicity of M. paratuberculosis," Kapur says. "There have been great strides in completing the sequencing project and DNA sequences that enabled us to design new tests for the disease."

Developing improved diagnostic tests are imperative in order to detect infected herds, he says, and determining herd level testing strategies will improve weeding out infected from non-infected herds as well as evaluate sensitive diagnostic approaches to detect the pathogen in individual animals. "A DNA-based PCR test already has been developed; it is planned to use an improved DNA-based PCR test using new information from the bacteria sequencing project," Kapur says. "When an animal has immunity to the disease, the bacteria may be eliminated with tools formed by researchers."

Disease management

Different immune responses to

M.

paratuberculosis

have been identified compared to other mycobacterium species.

"We want to develop some kind of control of the disease through herd-management," Kapur says. "Pasteurization of colostrums and waste milk at the farm, housing pregnant cows and mothers with calves separately to reduce transmission is necessary."

Kapur estimates that in two years there will be a reliable vaccine against Johne's disease. Various projects are taking place in effort to propel findings on the bacteria.

Nine cattle herds are being used in a project that changes management practices to more risk-conscious efforts, and disease reduction outcomes, if any, are being measured. In a separate project, 90 dairy farms are participating in a study to evaluate the role of wildlife and the environment in the transmission of the disease.

"It is unclear how many new animals can contract and pass the disease," Kapur says. "Rabbits, humans, primates, rodents, sheep, goats and small ruminants are all suspect."

The potential for fecal shedding also is being considered with the goal of identifying a way to slow the transmission and reduce the economic impact of Johne's disease, Kapur adds.

"Giving farmers information on how to protect their herds is important," he says. "Meetings with dairy veterinarians and producers to discuss the new information will become more common as new discoveries are presented."