American scientists develop vaccine for liver abscesses in cattle
T.G. Nagaraja, a professor of diagnostic medicine and pathobiology, and M.M Chengappa, professor of microbiology and department head of diagnostic medicine and pathobiology, developed the vaccine that was recently given approval by the United States Department of Agriculture. According to Nagaraja, abscesses are a common malady found mostly in grain-fed cattle, the result of an aggressive feeding programme. He said about 20 to 40% of the grain-fed cattle in feedlots are afflicted with abscesses, which cannot 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."
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 into other organs. In addition to the liver condemnation, economic impact includes reduced feed intake, reduced weight gain, decreased feed efficiency and carcass yield.
The abscesses are caused by bacteria 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 well-defended organ. So much so that he calls it the "Pentagon" because it has "so many systems" of defence to protect it. However, under certain conditions, when these bacteria cross the stomach wall and get 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 KSU Research Foundation and Schering-Plough, health care company, now have a licensing agreement to market the vaccine.
