Johne's disease is devastating to the United States dairy industry, costing about $200 million per year due to reduced milk production. Estimates indicate that the disease is present in approximately 25 percent of Minnesota's dairy herds. Because the bacterium that causes Johne's disease, Mycobacterium avium subspecies paratuberculosis, is slow growing in the laboratory, previous tests often took between 6 and 18 weeks to process. The current study shows how genomic information may be used to develop highly specific, sensitive, and rapid tests for the detection of infected animals.
These new tests, which enable detection of the bacterium in fecal matter or milk, can be completed in 72 hours or less with an accuracy that was not possible without knowledge of the complete genome of the bacterium. Since animals shed the bacteria in their milk, faster diagnosis will likely help monitor and improve the quality of dairy foods.
"Since the results of this new test are available much sooner, infected animals can be identified and isolated more quickly, thereby providing an opportunity to minimize economic losses to the herd, and breaking the chain of transmission from animal to animal," said Vivek Kapur, BVSc., Ph.D., principal investigator, faculty member of the University's Medical School and College of Veterinary Medicine, and director of the Biomedical Genomics Center. In 2003, Kapur and his colleagues at the University of Minnesota were also awarded one of the largest research grants by the USDA to form a national consortium to study Johne's disease in cattle.
Mycobacterium avium subspecies paratuberculosis is also implicated as a factor in Crohn's disease, an inflammatory bowel disease in humans. Infection with this bacterium in humans and all animals is generally believed to occur at an early age, with clinical manifestations of the disease only showing up after several years. In the future, researchers are likely to be able to use this information to work on a test to detect these bacteria in blood or tissue of patients with Crohn's disease and ulcerative colitis.
"This research both advances knowledge of the basic science issues surrounding the disease as well as applies that knowledge for immediate benefits to animal and potentially human, health," said Sagarika Kanjilal, associate professor of medicine, and a co-author of the paper.
Funding for the project was provided in part by grants from the U.S. Department of Agriculture Cooperative State Research, Education, and Extension Service National Research Initiative, and the Agricultural Research Service.