Experts are calling for all birds within 50km of the bird flu outbreak to be kept housed to prevent the spread of the disease.

One hundred and seventy thousand hens at a farm producing eggs have been culled after an outbreak of bird flu.

Officials threw a six mile surveillance zone and a 1.8 mile protection zone around the farm in Coppul near Preston after the outbreak was confirmed.

But The British Free Range Egg Producers’ Association (Bfrepa) has called for the chief vet to initiate a housing order for all birds in the region.

Policy director Robert Gooch said: “We would like all birds within a 50km zone at least to be housed.

“That would probably cover the whole of the North West. We would urge all producers to look carefully at their biosecurity.”

The strain of avian flu found is H7N7, which can infect people and is highly pathogenic, which means it is contagious in flocks, where it can be fatal for birds.

However, it is not the H5N1 strain, which has led to hundreds of deaths in people worldwide and Public Health England has said the risk to public health from this strain is very low.

The Food Standards Agency has confirmed there is no food safety risk for consumers.

The farm, owned by family business Staveley’s Eggs, produces and packages free range and colony cage eggs and owners state on their website they strictly ‘maintain best practice’ when it comes to poultry health and infection.

Staveley’s has a 120,000 colony of cage laying eggs and 50,000 free-range laying hens.

On their website the company say: “We continue to produce birds in excellent health and condition, and maintain best practice through adhering to the best codes of practice and industry information.”

Nick Phin, deputy director of Public Health England’s national Infections service, said: “We know that in 2003 a flu of this type in the Netherlands was a contributing factor to the death of a vet working on controlling the disease.

“We have learned from this incident and are confident of the precautions we have put in place, including the on-going monitoring of handlers and workers.”

The animal exclusion zone rules hit exhibitors at Sunday’s Goosnargh and Longridge show, where 400 birds were due to be shown, with exhibitors travelling from Cheshire, Yorkshire, Lincolnshire and Wales.

Chief veterinary officer Nigel Gibbens said: “Final tests results have confirmed a case of avian flu at a farm in Lancashire.

“Restrictions put in place last week will continue and the humane culling of all birds at the site is progressing.

“These actions are part of our tried and tested approach to dealing with previous outbreaks.

“Public Health England has confirmed that the risk to public health from this strain is very low. The Food Standards Agency has said there is no food safety risk for consumers.

“Bird keepers should remain alert for any signs of disease, report suspect disease to their nearest Animal and Plant Health Agency office immediately and ensure they are maintaining good biosecurity on their premises.”

Poultry farmers within the six mile zone around the infected premises are not allowed to move poultry, captive birds or other mammals except under licence.

In February, a low-severity H7N7 strain of bird flu was confirmed in chickens at a farm in Hampshire.

The last highly pathogenic case of avian flu was an outbreak of H5N8 flu in Yorkshire last November, following outbreaks of the same strain in Europe.

Most types of bird flu are harmless to humans but two types – H5N1 and H7N9 – have caused serious concerns.

Other bird flu strains, including H7N7, have infected people, but these have been very rare or have only rarely caused severe illness.