Live vaccines prompt Newcastle disease fears

The use of live vaccines to protect poultry against Newcastle disease may lead to unpredictable and dangerous outbreaks of the disease in the future, researchers in the USA have warned.

Biologists working at Pennsylvania State University have discovered attenuated live vaccines forNewcastle disease seem to be mixing with wild strains of the virus creating new strains and possibly leading to more widespread and damaging outbreaks of disease.

“Our findings indicate that birds can be simultaneously infected with the live virus vaccine and several other strains of this avian virus,” professor of biology, veterinary and biomedical sciences Mary Poss said in the latest issue of Informa Agra’s Animal Pharm magazine.

“This raises concerns that modified live virus vaccines, though effective, may combined with circulating viruses to create unpredictable new strains.”

Prof Poss said farmers mixing vaccines into a flocks’ drinking water or dispersing via aerosols can accidentally lead to wild birds becoming infected with the vaccine virus. This then combines with wild strains in these birds creating new varieties of the virus which birds have no immunity to.

Vaccine developers are advised by the research team to use killed or inactivated viruses in vaccines to avoid the possibility of further evolution of the virus in the wild.

This would present challenges for large scale producers as inactivated vaccines can only be administered to birds by direct inoculation.

The last outbreak of Newcastle disease in the UK was in East Lothian in 2006.