K-State professors develop vaccine to prevent abscess in liver of cattle

01/14/05

MANHATTAN, KAN. - It's a pretty safe bet you won't hear this request from your kids: "More liver, please."

If by chance you do, they'll be no shortage of the iron-rich delicacy most kids love to hate, thanks to a vaccine developed by a Kansas State University professor.

T.G. Nagaraja, a professor of diagnostic medicine and pathobiology in K-State's College of Veterinary Medicine, and M.M Chengappa, university distinguished professor of microbiology and department head of diagnostic medicine and pathobiology, have developed a vaccine that prevents liver abscesses in cattle. The vaccine was recently given approval by the United States Department of Agriculture.

The KSU Research Foundation and Schering-Plough, a global science-based health care company, have a licensing agreement to market the vaccine. Schering Plough Animal Health corporation further developed the product and worked with USDA to get license approval for the vaccine.

According to Nagaraja, abscesses are a common malady found mostly in grain-fed cattle, the result of an aggressive feeding program. He said about 20 to 40 percent of the grain-fed cattle in feedlots are afflicted with abscesses, which can not be detected until the animals are slaughtered. While the organ is condemned and not used for sale, in most instances the remainder of the carcass is approved for sale.

"If you look at the animal you can't tell if they're abscessed or not," Nagaraja said. "They look normal, so they don't show any clinical signs. The only time we see the problem is when animals are slaughtered."

The abscesses are caused by a bacteria that is present in the rumen, the first of four compartments that comprise a cow's stomach. That compartment contains numerous microorganisms which are beneficial in assisting the animal digest food .

According to Nagaraja, who began researching the vaccine 14 years ago, the liver is a very well defended organ. So much so that he calls it the "Pentagon" because it has "so many systems" of defense to protect it. However, under certain conditions, when this bacteria crosses the stomach wall and gets into the blood stream, it is trapped inside the liver, producing a toxin which kills white blood cells or leukocytes, which generally defend the body from germs or infections.

The vaccine prevents abscesses from occurring by neutralizing the toxin, which is a protein. Once injected into the animal, antibodies are produced that act on the protein. When the bacteria goes into the liver and produces the toxin, antibodies would neutralize it and allow the leukocytes to survive. These white blood cells can in turn kill the bacteria.

"That's not a new concept; it's been done with other bacteria," Nagaraja said. "But it was new for this organism that we were able to identify strains that are able to optimize conditions for production of large amounts of leukotoxins."

According to Nagaraja, abscesses are a significant economic liability to producers, packers and consumers. He said the liver condemnation, which he estimates to cost about $5 per head, is just one of the economic losses of this disease. Occasionally, the entire carcass must be condemned because the abscess on rare instances causes adhesions to other organs or ruptures and spill the pus into other organs. In addition to the liver condemnation, economic impact includes reduced feed intake, reduced weight gain decreased feed efficiency and decreased carcass yield. According to Nagaraja, reduced animal performance is the major economic impact of the problem.

Source: Eurekalert & others

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