H5N1 definition updated, as avian flu identified in sheep
A new definition for H5N1 now applies to lactating animals.
The Department for Environment, Food and Rural Affairs (Defra) has published an updated definition of avian influenza H5N1 for veterinary surgeons.
It follows a confirmed case of influenza of avian origin (H5N1) in a single sheep in Yorkshire. This is the first time that the virus has been confirmed in a sheep.
The discovery was made during routine surveillance of livestock on a farm which had previously confirmed cases of avian influenza in its captive birds. Repeat positive milk testing revealed that the sheep was infected with H5N1 avian influenza.
The infected sheep was humanely culled to enable further testing. The Animal and Plant Health Agency also performed further testing on the remaining flock of sheep at its reference laboratory in Weybridge.
No further infection was detected in the remaining flock of sheep and there is no evidence that it poses a risk to other livestock in the UK.
This case has now been reported to the World Organisation for Animal Health (WOAH) and the World Health Organisation (WHO). The UK Health Security Agency has committed to working with Defra, APHA and other organisations to monitor the situation.
Although this is the first time that avian influenza has been detected in a sheep, it is not the first time that it has been detected in livestock. Veterinary surgeons have reported outbreaks of avian influenza among herds of dairy cows in the USA, which has prompted Defra to introduce livestock surveillance in the UK.
Defra has also now published new information about the disease, now applying to lactating animals, which includes a suspect case definition as well as diagnostic testing criteria.
Livestock keepers are urged to closely monitor their animals for any of the clinical signs of avian influenza. Biosecurity is considered essential to protect the wealth of animals and prevent the spread of disease in the event of outbreak.
Christine Middlemiss, UK chief veterinary officer, said: “We have confirmed the detection of influenza of avian origin (H5N1) in a single sheep on a farm in Yorkshire. Strict biosecurity measures have been implemented to prevent the further spread of disease.
“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 Plant Health Agency immediately.”
Livestock keepers are legally required to report any suspicion of H5N1 avian influenza to APHA by calling 03000 200 301 in England, 0300 303 8268 in Wales or contacting your local Field Services Office in Scotland.
The new definition of avian influenza H5N1 can be found here.
Image © Shutterstock
BSAVA is to partner with BVA Live (11-12 June 2026) to champion clinical research.
