A vaccine that prevents liver abscesses in cattle could help restore consumer confidence and save processors and packagers millions, according to researchers in the US.
The vaccine, which was recently given approval by the United States Department of Agriculture, could provide the meat industry with a much-needed guarantee of safety and quality. The discovery of another case of bovine spongiform encephalopathy (BSE) in Canada has again raised fears that public confidence in beef could be further undermined.
The scientific breakthrough by T.G. Nagaraja, a professor of diagnostic medicine and pathobiology in K-State's College of Veterinary Medicine, and M.M Chengappa, department head of diagnostic medicine and pathobiology, therefore represents some much-need good news for the industry.
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 per cent of the grain-fed cattle in feedlots are afflicted with abscesses, which cannot be detected until the animals are slaughtered.
Abscesses are a significant economic liability to producers, packers and consumers. Liver condemnation, which Nagaraia 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.
"If you look at the animal you can't tell if they're abscessed or not," said Nagaraja. "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 defence 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 neutralising 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 neutralise 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," said Nagaraja. "But it was new for this organism that we were able to identify strains that are able to optimise conditions for production of large amounts of leukotoxins."
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.