A Possible New Vaccine To KO Salmonella in Chicken Eggs
Immunologist Peter Holt
(foreground) and veterinarian
Lara Vaughn collect and label
eggs that will be tested for
Food poisoning is a misnomer. One is not poisoned by the
food, but rather by the microbes growing in or on the food. Hens lay
eggs that can harbor microbes (microscopic organisms) called Salmonella
enteritidis, which can lead to salmonellosis, a disease characterized
by nausea, vomiting, and severe diarrhea, symptoms we would all rather
Service immunologist Peter Holt, veterinarian Henry Stone (retired),
and immunochemist Cam Greene, in Athens, Georgia, have been working
on vaccination strategies in poultry to reduce the possibility of S.
enteritidis getting into the egg in the first place. Salmonella
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 cause
a reduction in human infection from poultry and egg consumption,"
Under Holt's direction, the group from the Southeast Poultry
Research Laboratory developed an oil emulsion vaccine of inactivated
S. enteritidis that provided substantial protection to hens exposed
to the bacteria.
Birds were given the vaccine subcutaneously in two doses
4 to 6 weeks apart. The hens were then exposed to S. enteritidis.
To ensure that no other pathogens are present in the hens
before and during the vaccination and study phases, testing was conducted
under very stringent conditions.
The experimental oil emulsion vaccine differs from the
commercial preparations in that it was formulated to increase levels
of specific antibodies that get into the intestinal tract, thereby reducing
the amount of S. enteritidis present. This decreases the chance
of the bacterium invading internal organs and being shed in feces.
"We found that the new vaccine reduced S. enteritidis
shedding 10 to 40 percent more effectively than the three commercial
vaccines used by the U.S. poultry industry," says Holt. A patent
for the vaccine has been filed (March 21, 2002, SN 10/101,943), and
it is available for licensing.
A vaccine that reduces Salmonella shedding would
be helpful to the poultry industry, since this is the primary method
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 is required to be Salmonella
Vaccinating poultry flocks is an important method 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 to 75 million doses are used worldwide.By
Agricultural Research Service Information Staff.
This research is part of Food Safety (Animal and Plant
Products), an ARS National Program (#108) described on the World Wide
Web at www.nps.ars.usda.gov.
"A Possible New Vaccine To KO Salmonella in Chicken Eggs" was published in the May 2003 issue of Agricultural Research magazine.