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 poultry producers.

“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 outbreak

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.