New chicken virus created by vaccines
Two new strains of a poultry disease that have been plaguing chickens in Australia since 2008 have been revealed as hybrids of viruses from live vaccines - the first time such recombination has been seen between vaccine viruses in the wild.
In 2007, chicken farmers in Australia were using two commercial, live vaccines for infectious laryngotracheitis (ILT) made from Australian strains of virus. However, after they started using a third live vaccine containing a European strain, outbreaks of two new ILT strains began. The hybrids have proved just as deadly as wild ILT, killing 18% of affected flocks.
Glenn Browning and a team from the University of Melbourne in Parkville, Australia, have sequenced the new viruses and found that in each case they arose when the European vaccine strain acquired genes from the Australian vaccine viruses.
He commented: "We were quite surprised. The newer strain is half European, half Australian, and has outcompeted the original strain - it now dominates outbreaks in Australia."
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