LONDON – The Dept. for Environment, Food and Rural Affairs (DEFRA) in the United Kingdom is keeping a close eye on an outbreak of highly pathogenic H7N7 avian influenza in Italy.

In a preliminary outbreak assessment, DEFRA reported the outbreak occurred in commercial chicken layers in the Ferrara region of Italy. In accordance with European Union rules, 17,000 birds were culled and restriction zones have been implemented. This outbreak comes after low-pathogenic H2N2 was discovered in poultry breeders in the Pordenone region, and a finding of low-pathogenic H7N7 in “ornamental birds” in the Ferrara region, DEFRA reported. Low-pathogenic viruses can mutate into highly pathogenic viruses over time.

DEFRA noted it is unclear if the HP H7N7 virus was introduced to the commercial chicken flock, or was the result of a previously undetected low-pathogenic virus mutating into a highly pathogenic virus. However, the agency said the most likely scenario is that an undetected incursion of the low-pathogenic virus mutated as it spread through the flock.

“If this is a wild bird strain of H7N7 which causes HPAI infection in poultry, as opposed to a mutation from an LPAI strain to an HPAI strain in poultry, then this would be concerning and novel,” DEFRA said. “It is possible there is an as yet undetected H7N7 HPAI virus circulating in poultry or captive birds elsewhere which has not caused clinical signs, in which case this reinforces the difficulties experienced with using passive surveillance only for some of these viruses and the need to enhance such systems through early reporting where signs are not suggestive of AI, therefore utilizing the Testing to Exclude (TTE) scheme.”