Iowa State University


Ted Kramer, Veterinary Medicine, (515) 294-3090
Steve Jones, News Service, (515) 294-4778


AMES, Iowa -- A poultry vaccine that could reduce the incidence of salmonella-tainted eggs has been developed by an Iowa State University researcher. Veterinary microbiologist Theodore Kramer said the vaccine could improve food safety.

The vaccine prevents hens from spreading salmonella to their eggs. It also significantly reduces the likelihood of the bacteria spreading to other chickens through feces, Kramer said. Use of the vaccine by egg producers still requires additional tests and U.S. Department of Agriculture approval.

The vaccine targets bacteria called Salmonella Enteritidis, organisms which cause food poisoning in humans called salmonellosis. The bacteria are found in the intestinal tracts of animals and humans and are easily spread. They hospitalize thousands in the United States annually and can cause death, according to Kramer. He added that chicken eggs account for about half of the U.S. human salmonellosis cases.

Kramer developed the vaccine using technology similar to what he and another ISU researcher used five years ago to create a swine salmonellosis vaccine. Both vaccines use live salmonella bacteria that have been stripped of their disease-causing capabilities. The new vaccine is administered to hens in their drinking water.

Kramer has been working on the poultry vaccine since 1995.

The vaccine could benefit egg producers around the world because salmonella-contaminated eggs are a global problem. Egg-borne human salmonellosis is most common in the United States along the East Coast.

"Salmonella costs the United States $2.5 billion a year," Kramer added.

Iowa is among the nation's top five egg-producing states, according to Janet Anderson, executive director of the Iowa Egg Council in Ames. She said Iowa has 20 million laying hens that produce 5.5 billion eggs annually. Anderson also said the Iowa egg industry is growing rapidly.

Humans who contract salmonellosis from eggs usually do so by eating products such as ice cream, mayonnaise or salad dressing made with contaminated raw eggs. Salmonellosis symptoms include attacks of abdominal cramps, nausea, vomiting and diarrhea. The attacks may be more serious for infants, pregnant women, the elderly and the ill.

"The effects of salmonellosis can be far-ranging," Kramer said. "A contaminated food product produced in a large quantity and distributed widely can cause illness in several states."

Salmonellosis is normally not a health problem for consumers who properly store and cook their eggs, Kramer said.

Kramer said it is important to keep chicken flocks from being infected with Salmonella Enteritidis. The bacteria are difficult to detect in chickens. Infected hens usually do not appear ill and current tests for the bacteria are time consuming and costly, Kramer explained.

"In a unit of 10,000 hens, it would be difficult to test every bird," Kramer said. "If salmonellosis is found, about all the producer can do is destroy all of the hens. That can be financially ruinous to the producer."

ISU has applied for a patent for the vaccine.


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