Antibody Accurately IDs Johne’s Disease

USDA scientists find a way to identify a disease that affects ruminant farm animals without disrupting tests for other diseases.

by Dani Yokhna
USDA scientists discover a way to accurately detect Johne's disease in cows, goats, sheep and other ruminants. Photo courtesy iStockphoto/Thinkstock (
Courtesy iStockphoto/Thinkstock

The contagious Johne’s disease, also known as Paratuberculosis, is estimated to cost the U.S. dairy industry more than $220 million each year. It also affects sheep, goats, deer and other animals, causing diarrhea, reduced feed intake, weight loss and sometimes death. USDA microbiologist John Bannantine and his colleagues at the Agricultural Research Service’s National Animal Disease Center in Ames, Iowa, have discovered an antibody that’s 100-percent specific in detecting Johne’s disease, meaning detecting the disease could be easier than ever before.

This is the first discovery of a specific antibody that binds only to Mycobacterium avium subspecies paratuberculosis (MAP), the pathogen that causes the disease. The scientists were awarded a patent for the antibody, which could help improve diagnostic tests that confirm MAP’s presence.

Previous efforts to detect Johne’s disease were hindered because all antibodies used to identify MAP strains also reacted to environmental mycobacteria, says Bannantine, who works in NADC’s Infectious Bacterial Diseases Research Unit. Some of those antibodies also reacted to the disease pathogen responsible for bovine tuberculosis and caused false-positive results.

Other research, conducted by NADC microbiologist Judy Stabel, focused on ensuring that Johne’s disease vaccines don’t cross-react with tests for bovine tuberculosis, a disease afflicting states where wild deer infect cattle.

Stabel and her team vaccinated calves with an effective commercial Johne’s vaccine to test cross reactivity with tuberculosis tests. They took blood samples for one year and then measured immune and serological responses of calves using novel tuberculosis tests.

Scientists found no cross reactivity with the tuberculosis serology tests, demonstrating that animals could be vaccinated against Johne’s disease without interfering with bovine tuberculosis testing. Similar results were found with the skin test used to detect tuberculosis in cattle.

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Read more about this research in the April 2013 issue of Agricultural Research magazine.


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