A virosome vaccine
against Newcastle disease is administered to a baby chick by Darrell
Kapczynski. Click the image for additional information about
New Approach to Fighting Exotic Newcastle
Disease By Sharon Durham
October 29, 2003
ATHENS, Ga., Oct. 29--A new approach to experimental
vaccines that combat exotic Newcastle disease (END) in poultry flocks has been
developed by U.S. Department of Agriculture
scientists. END is a contagious and fatal viral disease that affects most
species of birds and kills almost all unvaccinated birds within days.
Microbiologist Darrell Kapczynski and colleagues developed the
experimental vaccine at the Agricultural Research Service's
Southeast Poultry Research Laboratory
in Athens, Ga. ARS is USDA's chief in-house scientific research agency. The
vaccine will not be available in the near future, and USDA's
Animal and Plant Health Inspection
Service would have to approve the new technology before it could be used by
"Many scientists are working on diagnostic tools, as well as
preventative vaccines, to prevent a devastating END outbreak in U.S. commercial
poultry flocks," said Edward B. Knipling, acting ARS administrator. "These
tools to protect against Newcastle disease are essential to commercial poultry
producers as well as those with backyard poultry flocks."
California recently was hit hard by a severe outbreak of END. In
all, some 3.5 million commercial and backyard poultry--such as geese, chickens,
turkeys, pigeons and peacocks--were euthanized to stop the virus from spreading
to other states. More than $104.5 million was spent by the federal-state task
force working to contain and eradicate END.
Current vaccines rely on either attenuated (weakened) live virus
or killed virus to stimulate an immune response that induces protection in the
bird against subsequent exposure to the virus. While these vaccines are
effective, some birds' adverse reactions to the vaccines result in production
losses. To overcome this problem, Kapczynski said he essentially took the virus
apart, removed its replicating genetic material and then put it back together.
"This experimental vaccine, called a virosome vaccine, induces
protective immunity but doesn't allow the virus to replicate--copy itself--or
pass from bird to bird," said Kapczynski. The experimental vaccine causes a
protective immune response in the birds and makes it possible to differentiate
between vaccinated and virus-infected birds.
In one study, day-old chicks were divided into three groups: a
control group that received a saline solution, a group that received live-virus
vaccine, and a group that received the virosome vaccine. After being exposed to
END, all of the birds were monitored daily for clinical signs of disease and
mortality. Birds in the control group did not survive, while birds that
received either vaccine were 100 percent protected.
The new approach holds promise that in the future, better
vaccines can be produced through biotechnology.