The Days of Salmonella May Be Numbered

A new vaccine for poultry may soon be able to prevent many of the more than 45,000 reported cases of food poisoning caused annually by salmonella bacteria.

Chickens are frequent carriers of Salmonella enteritidis, a type of bacteria that doesn’t make the birds sick but can cause cramps, fever and diarrhea in people. Raw or undercooked eggs (often used in mayonnaise or salad dressing) are the most frequent source of infection.

Contaminated chicken or turkey also can produce the illness, which is particularly dangerous for children, the elderly or people with weakened immune systems.

Because most cases of salmonella food poisoning are undiagnosed, the number of Americans who suffer from it annually may be as many as 4 million.

Roy Curtiss III, a professor of biology at Washington University at St. Louis, developed an oral vaccine for poultry that makes use of a weakened strain of a related bacterium, Salmonella typhimurium. The vaccine strain is missing two genes that the bacteria need in order to cause serious illness in birds.

When given the vaccine, adult chickens develop lifelong immunity to salmonella (including the strains that cause food poisoning in humans) and pass on this immunity to their eggs and to their chicks.

Curtiss presented results of initial trials of the vaccine at the International Veterinary Vaccines and Diagnostics Conference in Madison, Wis. Scientists at Megan Health Inc., a St. Louis company that will produce the vaccine, are awaiting approval from the Department of Agriculture to conduct larger field trials, involving thousands of birds.

If those studies are successful, the USDA could license the vaccine next year.