License vaccine that kills Salmonella in chicken eggs.

Hens lay eggs that can harbor S. enteritidis, which can lead to salmonellosis, a disease characterized by nausea, vomiting and severe diarrhea, symptoms we would all rather avoid. USDA-ARS immunologists, veterinarians and immunochemists have been working on vaccination strategies in poultry to reduce the potential for S. enteritidis entering the egg in the first place.

S. enteritidis infection is a major problem for the egg industry and consumers, since unbroken table eggs from infected flocks can be contaminated. Reducing the prevalence of S. enteritidis in poultry would likely reduce human infection from poultry and egg consumption. Toward this end, investigators developed an oil emulsion vaccine of inactivated S. enteritidis that provides substantial protection to hens exposed to the bacteria.

Birds were given the vaccine subcutaneously in two doses four to six weeks apart. The hens were then exposed to S. enteritidis. The experimental emulsion vaccine differs from commercial preparations in that it was formulated to increase levels of specific antibodies that get into the intestinal tract and which can reduce the amount of S. enteritidis present. This decreases the chance of the bacterium invading internal organs and being shed in feces. Shedding involves excretion of an organism by an infected animal. S. enteritidis would be excreted primarily in the feces.

The researchers found that the new vaccine reduced S. enteritidis shedding up to 40% more effectively than the three commercial vaccines used by the U.S. poultry industry. A U.S. patent application for the vaccine has been filed (March 21, 2002, SN 10/101,943), and the technology is available for licensing.

A vaccine that reduces Salmonella shedding would be helpful to the poultry industry, since this is the primary means by which Salmonella infection spreads through a flock. A vaccine that can eliminate shedding would be a boon for poultry exporters since poultry-breeding stock sold to overseas markets must be Salmonella-free. Vaccinating poultry flocks is an important way to reduce S. enteritidis problems in flocks in today's marketplace. About 25 million doses of S. enteritidis vaccine are used annually in U.S. poultry, while 50 million to 75 million doses are administered worldwide.

Further information. Peter Holt, USDA-ARS Poultry Disease Research Unit, Southeast Poultry Research Laboratory, 934 College Station Rd., Athens, GA; phone: [phone]; fax: [phone]; email: [e-mail].