Government vets gave warning last night that the deadly H5N1 strain of bird flu may already be endemic in the British wild bird population as an outbreak was confirmed on a Suffolk turkey farm.

An urgent inquiry was under way last night to identify the source of the latest outbreak as culling began of the 5,000 turkeys, 1,000 ducks and 500 geese at Redgrave Park Farm, near Diss. Poultry on another two farms feared to have been in contact with the infected farm may be culled in the next few days.

The arrival of the virus comes at the worst time for the poultry industry as it prepares for Christmas. East Anglia produces about a third of Britain’s turkeys and there are fears that if the virus takes hold the £400 million market for Christmas birds will be lost. There are three million birds alone in the 10km (six-mile) surveillance zone around Redgrave Park Farm.

Protection and surveillance zones of 3km and 10km were put in place around the infected farm, owned by the poultry producer Guy Topham, based in Wood-bridge, Suffolk.

There is particular concern that the infected free-range turkeys had been allowed to mingle with wild birds that gather at an ornamental lake which is part of the infected farm premises, and that a reservoir of virus may have built up in the bird population on the farm.

The Department for Environment, Food and Rural Affairs announced further restrictions throughout the whole of Suffolk and most of Norfolk.

Birds on farms in these areas were locked indoors as farmers and hobby keepers wait to find out whether the virus is circulating in the wild bird population. The arrival of the deadly bird flu, which tests have shown to be an identical strain to that found in outbreaks in the Czech Republic and southern Germany this autumn, came as another hammer blow for a rural economy already struggling to recover from the summer outbreaks of foot- and-mouth and bluetongue diseases.

The impact on the poultry industry will boost already soaring food prices, at a time when these are combining with the surging cost of petrol to inflict serious strains on the finances of households across the country.

Britain is facing an increasingly bleak winter as the nation confronts sharp rises in the cost of living before Christmas, while fears grow that a looming slump in the housing market will deepen the expected downturn across the economy.

Fred Landeg, the Government’s acting chief veterinary officer, appealed for calm last night and emphasised that avian flu was essentially a disease for birds and not humans, and that it was very difficult for people to contract the virus. Experience in the Far East has shown humans need close contact with birds to do so. Poultry products and eggs are safe to eat because H5N1 is sensitive to heat and normal cooking procedures will kill it.

However, some GPs were reporting an increase in requests for the winter flu inoculation.

Since the H5N1 strain spread from Asia to Europe and Africa in 2003 a total of 300 people have become infected though more than half have died.

Five poultry workers who had day- to-day contact with the infected turkeys have already been treated with the antiviral drug Tamiflu.All state veterinary surgeons, animal health officers, slaughtermen and anyone else involved in the cull are also being offered the treatment.

It also emerged yesterday that the Prime Minister has ordered a review of UK food security.Gordon Brown has asked the Cabinet Office strategy unit to study how food supplies can be protected and the role farming can play to combat the effects of climate change— such as greater use of land for flood plains.

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