Researchers Allegedly Link New Poultry Viruses to Live-Attenuated Vaccines

University of Melbourne researchers have reportedly demonstrated that
viruses from two live-attenuated poultry vaccines have combined in the
field to produce new infectious viruses “responsible for widespread disease
in Australian commercial poultry flocks.” Sang-Won Lee, et al., “Attenuated
Vaccines Can Recombine to Form Virulent Field Viruses,” Science, July 2012.
According to a July 13, 2012, press release, two vaccines used simultaneously
in chickens to control laryngotracheitis (ILT), an acute respiratory disease, apparently produced two new recombinant viruses that scientists then
identified using whole-genome sequencing. Previous studies had apparently
suggested that such recombination could happen under laboratory conditions
but was unlikely in field settings.

“We alerted the Australian Pesticide and Veterinary Medicines Authority
(APVMA) to our findings and they are now working closely with our research
team, vaccine registrants and the poultry industry to determine both short
and long term regulatory actions,” a study co-author was quoted as saying.
“Short-term measures include risk assessment of all live virus vaccines
currently registered by the APVMA in regard to the risk of recombination and
could include changes to product labels, which may result in restrictions on
the use of two vaccines of different origins in the one animal population.”