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Farmers should prepare for another challenging AI winter

An avian influenza outbreak

POULTRY farmers should assume that the infection pressure from avian influenza will be maintained over the next winter season, and prepare accordingly.

With wild birds continuing to be found with the virus both here and across Europe and the virus having spread further and faster than in previous years, high levels of biosecurity remain critical.

See also: Learn more about the latest threat of avian influenza at Poultry.Network Live on 8 September

“We cannot drop our guard,” Ian Brown, head of the virology department at the APHA says.

“Prospects for the immediate future control are not great, I’m afraid,” he told a recent conference organised by the Poultry Health and Welfare Group.

Prof Brown detailed how the first sign of problems in the UK was a Great Skua testing positive for HPAI H5 in the summer of 2021.

‘Major Change’

That turned out to be a “very close cousin” of the strains of H5 HPAI that caused devastation across the UK and wider Europe over the 2021/2022 winter, he explained. Seeing the virus in the summer represented a “major change”.

Fast-forward to the winter, and there were 125 cases across the UK. “It was off the scale,” when compared with previous outbreaks, said Prof Brown. There was a correlation between where wild birds spend the winter and where commercial cases were found in the UK.

The virus was found in wild birds across the UK – in previous years, Scotland has been relatively unaffected, but this year birds were affected GB-wide and in Northern Ireland, to a lesser extent.

Case spread

It was a similar story in Europe, with cases detected as far south as the Iberian Peninsula, another first.

“We’ve not had more wild birds coming into the UK – the population is quite static – it’s that the ones that have come here, more of them have been carrying the virus.”

Prof Brown described the characteristics of the strain that hit the UK, saying it spreads between wild birds very easily, and only a tiny amount getting into a poultry shed can rapidly cause mass die-offs.

The primary cause of spread is thought to be in liquid droplets brought into sheds either by people, wild birds defecating or contaminated bedding.

Persistant

The virus appears to be persisting in some wild bird populations across the coast of the UK.

North America, a country experiencing a considerable outbreak at present, has been hit by related strains of the virus.

“We have proven this virus has travelled from Northern Europe, across the Arctic Circle and down into Newfoundland in Canada, and that is the first time that this has happened.

‘Game changer’

“That’s a game-changer,” said Prof Brown, “Because not only is the virus being maintained in the flyways in Asia, it’s being maintained in the American flyways.

“And we know that some of those birds that wind up in Greenland and Iceland will come back to the UK next winter – so we’ve potentially got a threat from that direction too.”

Looking to the winter ahead, Prof Brown said it was impossible to predict with any great precision whether disease pressure would be more or less severe.

“But we can look at all the evidence. Nothing at the moment says we have tipped the balance [in our favour]. So we’ve got to be preparing for the worst.”