Yorkshire sheep infected with avian influenza

A sheep in Yorkshire has tested positive for H5N1 avian influenza on a property that also held captive birds, making it the first sheep in the UK to test positive for the virus.

The sheep was humanely culled to enable extensive testing. Additional tests by the Animal and Plant Health Agency (Apha) Weybridge laboratory confirmed no further infection in the remaining sheep flock.

See also: Thumbs down for vaccination as a bird flu control measure

The infected sheep had shown mastitis symptoms, but the avian influenza infection was identified via routine surveillance on the infected farm – a measure in place since the US started to report cases of infected dairy cows.

The current total for birds culled this avian influenza season stands at just over 2 million.

The latest case was recorded in a backyard flock near Inverness on 18 March, and so far 57,000 turkeys have been culled in North Yorkshire and Herefordshire this month.

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Vigilance

While Defra says there is no evidence to suggest an increased risk to the nation’s livestock population, the UK’s chief veterinary officer, Christine Middlemiss, is urging all livestock keepers to remain vigilant.  

In line with the UK’s international reporting requirements, this case will now be reported to both the World Organisation for Animal Health and the World Health Organisation.

 “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,” Dr Middlemiss said.

No food safety risk

The National Sheep Association (NSA) highlights that, while this latest case in sheep reinforces the need for stringent bio-security measures, especially during lambing time, it doesn’t pose any risk to consumers.

“This is not a threat to food safety,” said NSA chief executive Phil Stocker. “It’s very important to make that clear.

“What this shows, though, is the importance of biosecurity and an understanding of what biosecurity means.”

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Interspecies transmission

While this is the first time this virus has been reported in a sheep, it is not the first time bird flu has been detected in livestock in other countries, or in non-avian wildlife in the UK.

Defra figures reveal that, so far this year, 15 grey seals and one fox have tested positive for avian influenza.

In the US there have been numerous cases of dairy cattle infected with avian influenza, which causes mastitis in lactating cows.

The US strains are said to be distinctive and have not been seen in Europe. It is believed the virus has spread from cow to cow via milking equipment.

H5N1 infections have also been reported in cats, from consuming infected milk or bird meat.

While humans cases of infection have been reported in some parts of the world, there have been no reports of human-to-human transmission, and no significant human adaptations of the virus have been seen so far.

There is also very limited evidence of mammal-to-mammal transmission in the wild, and the available genomic surveillance data reported by Apha in the UK does not suggest widespread adaption of the virus in mammals. 

Dr Meera Chand, emerging infection lead at the UK health security agency, said: “Globally, we continue to see that mammals can be infected with avian influenza.

“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.”