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The first UK H5N1-type bird flu case in sheep has been confirmed in Yorkshire as authorities intensify efforts to avoid the mass outbreaks of the disease seen in US livestock.
The infection was identified after “routine surveillance of co-located livestock on a premises where avian influenza had been confirmed in captive birds”, the Department for Environment, Food and Rural Affairs said on Monday.
UK officials played down the risks to livestock and people, but authorities and scientists have urged precautions to avoid a repeat of the widespread transmission seen in US poultry and cattle.
“Strict biosecurity measures have been implemented to prevent the further spread of disease,” said Christine Middlemiss, UK chief veterinary officer.
“While the risk to livestock remains low, I urge all animal owners to ensure scrupulous cleanliness is in place and to report any signs of infection to the Animal and Plant Health Agency immediately,” she added.
The US bird flu outbreak has led to culls of chickens and fears the virus might, at some point, mix genetic material with another pathogen and become more transmissible between humans. Dozens of cases have been reported in people in the US, including a fatality in January.
The UK case added to evidence from the US and other countries that mammals could be infected with bird flu, said Meera Chand, emerging infection lead at the UK Health Security Agency.
“However, current evidence suggests that the avian influenza viruses we’re seeing circulating around the world do not spread easily to people — and the risk of avian flu to the general public remains very low,” added Chand.
Since the latest strain of avian flu was discovered in November last year, 49 cases have been confirmed across the UK. Defra says 2.3mn captive and wild birds have since been culled.
Officials say the culls represent only a small proportion of the UK poultry industry’s weekly 20mn bird production, while both cooked chicken and eggs remain safe to eat.
In the US, the administrations of both former president Joe Biden and his successor Donald Trump have faced criticism for allowing the outbreak to spread since a year ago and to persist nationwide.
The UK spillover case from birds to a mammal was “not unexpected” and underscored the importance of good farm hygiene and separating species, said Professor Ian Brown, leader of the avian virology group at the Pirbright Institute, which studies viral livestock diseases.
While it was too early to know whether such a virus was capable of onward spread within sheep, there were reasons to hope a US-style mass animal outbreak could be avoided, he added.
“The pathways of spread of these viruses in the USA [have] been shown to be by [the] movement of dairy cattle in commercial milking herds, which appears not applicable in this single case of one animal becoming infected,” he said.
The livestock industry has also sought to reassure consumers that the outbreak is not a threat to food safety.
“This is not a threat to [the] food safety of consumers and it’s very important to make that clear,” said Phil Stocker, chief executive of the National Sheep Association.
“What this shows though is the importance of biosecurity . . . in this instance sheep and poultry have mixed on the same farm, resulting in the transmission of avian influenza,” he added.