Around 170,000 chickens at the affected U.K farm at Goosnargh near Preston in the county of Lancashire have died after contracting avian influenza or been humanely euthanased, according to Stephen Lister, a partner at Crowshall Veterinary Services LLP, based in Attleborough, Norfolk.

The farm comprises a total of 10 layer flocks aged 67 weeks, with around 120,000 hens in enriched cages and 50,000 on free range. Not all of the flocks have showed signs of the disease but all have been scheduled for destruction, using mobile gas containers outside the buildings.

Lister said that the first signs of disease were a drop in egg production and some respiratory symptoms. Over the next few days, the mortalities increased -- to reach a total of around 36,000 -- and the U.K. government’s Department of Agriculture, Food and Rural Affairs (DEFRA) was informed.

The suspicion of avian influenza led to a government order to euthanize all the birds on the farm, a process that started on July 13 and has now been completed. Subsequent tests confirmed the presence of a highly pathogenic H7N7 strain of the virus.

Advertisement

Based on current information, Lister said, he thought that the most likely source of infection would be wild birds. It is possible for low-pathogenic forms to exist silently in wild birds and mutate to become highly pathogenic following entry into a poultry flock.

The area around the affected farm remains subject to controls on movements and testing of poultry within a 10-kilometer surveillance zone and an inner 3-kilometer protection zone.

Lister added that there has been a call for free-range poultry farmers in the area of the affected farm to keep their hens housed for a period of time as a precaution against further spread of the avian flu virus and yet maintain their “free-range” designation. The request is understood to be under consideration.