Johne’s Disease Tool Now Patented

By Linda McGraw
December 21, 1999

A diagnostic tool for identifying dairy cattle in the early stages of a costly disease has been patented by Agricultural Research Service scientists in Ames, Iowa. An article in the December millennium issue of Agricultural Research magazine highlights this and other ARS advances in animal research.

The new test detects Johne’s disease, which costs U.S. dairy producers more than $200 million annually. The newly patented gene probe is based on a genetic sequence discovered by ARS researchers. The probe can pinpoint Mycobacterium paratuberculosis--the organism that causes Johne’s disease in dairy cattle--in blood, tissue and fecal samples.

Using this genetic sequence and another previously discovered genetic sequence for M. paratuberculosis in a DNA-based test allows diagnosticians to accurately identify animals infected with the organism even in the early stages of infection. Current tests can detect the presence of an antibody, but it takes years before an infected animal’s immune system produces antibodies to M. paratuberculosis.

Early diagnosis is critical to eliminating the disease because the primary control method is removing infected animals from the herd. Infected animals often don’t show signs of disease, but they can still pass the organism to healthy animals. Johne’s is spread within and among dairy herds in three ways: by an infected cow passing the organism to an unborn fetus, by calves coming into contact with bacteria-laden manure, and by calves nursing an infected cow.

The patent was issued to ARS microbiologist Judith H. Stabel at ARS’ National Animal Disease Center in Ames and to Jay L.E. Ellingson, formerly with ARS. Other accomplishments cited in the article include:

• Advances in gene marker selection by scientists at ARS’ Meat Animal Research Center in Clay Center, Nebraska. These advances will help researchers select genes that impart disease resistance as well as quality characteristics, such as size, reproductive capability or leanness.

• A way to predict which Holstein bulls will sire daughters more susceptible to mastitis, a bacterial infection that costs U.S. dairy producers more than $2 billion annually

• An automated chicken inspection system developed by a Beltsville, Md., researcher. The computerized system scans up to 140 birds a minute, alerting a human inspector with a red light to indicate that a particular bird warrants closer inspection. The payoff for this research: safer poultry products, with less Salmonella and Campylobacter.

• An oral vaccine for shipping fever developed by ARS scientists in Ames, Iowa. Commercialization of this vaccine is still about 3 years away, but it will help U.S. cattle producers cut losses that add up to more than $1 billion annually.

ARS is USDA’s chief research arm. A more detailed story on this research appears in Agricultural Research magazine. To read the story online click here.

Scientific contact on Johne’s disease: Judith H. Stabel, ARS Zoonotic Diseases Research, National Animal Disease Center, P.O. Box 70, Ames, IA, 50010, phone (515) 663-7304, fax (515) 663-7458, jstabel@nadc.ars.usda.gov. To contact other scientists whose work appears here, contact Linda McGraw, ARS Information Staff, Peoria, Ill., phone (309) 681-6530, lmcgraw@asrr.arsusda.gov.