New restrictions have been declared across Great Britain to prevent the spread of “highly infectious” bird flu, the UK’s chief veterinary officer has said.

Christine Middlemiss said England, Scotland and Wales were now an Avian Influenza Prevention Zone (AIPZ), meaning bird keepers will have to legally follow strict new measures.

It comes after a new case of avian flu was discovered in captive birds at a chicken farm in Herefordshire on Wednesday.

Bird flu at Craigies Poultry Farm
More than 13,000 birds had to be culled at a farm in Cheshire (Andrew Milligan/PA)

Two separate, unrelated cases involving captive birds were confirmed in Kent and Cheshire last week, the Department for Environment, Food and Rural Affairs (Defra) said.

It resulted in 13,500 birds at the farm in Cheshire being culled.

A “very small” number of wild geese in Gloucestershire, swans in Devon and a wild goose in Dorset have also been found with avian influenza H5N8.

Public Health England said the risk to the public from the virus was “very low”.

Under the new measures, keepers with more than 500 birds will need to restrict access for non-essential people on their sites.

Workers will need to change clothing and footwear before entering bird enclosures and site vehicles will need to be cleaned and disinfected regularly.

So-called backyard owners with smaller numbers of poultry including chickens, ducks and geese are also urged to strengthen their biosecurity measures.

Ms Middlemiss said: “I have today declared a national Avian Influenza Prevention Zone (AIPZ) legislating for actions all bird keepers must take to help prevent the disease spreading to more poultry and other domestic birds.”

She added: “Whether you keep just a few birds or thousands, you are now legally required to meet enhanced biosecurity requirements and this is in your interests to do, to protect your birds from this highly infectious disease.”

The risk level for avian influenza incursion into wild birds in Great Britain was raised from “medium” to “high” last week.

The Food Standards Agency said that avian influenzas pose a “very low” food safety risk for UK consumers.

Properly cooked poultry and poultry products, including eggs, are safe to eat, Defra added.