The UK's chief vet has appealed to East Anglia's poultry keepers to do everything in their power to help halt the region's escalating bird flu epidemic.
Four more Norfolk cases of avian influenza were confirmed on Monday night - in commercial housed poultry near Holt, Mundford and Attleborough, and in a mixed flock of ornamental birds near Oxborough.
It prompted more mass culls of farm poultry, adding to the mounting toll of tens of thousands of chickens, turkeys, geese and ducks which have been slaughtered in recent weeks.
And it brought the county's total to 10 confirmed cases since the start of October, with more across the border in Suffolk - making East Anglia the epicentre of the UK's worst-ever bird flu outbreak.
As a result, a mandatory housing order will be enforced from today, requiring all captive birds across Norfolk, Suffolk and parts of Essex to be kept indoors, including free-range poultry and backyard hobby flocks.
But chief veterinary officer Christine Middlemiss said the lockdown was no cause for complacency, as the winter return of migrating birds is set to bring the potential for more outbreaks in the coming months.
And she said cleanliness and strict biosecurity were still the most critical factors in halting the spread of the disease.
"The four cases last night reiterate there is a very high risk level in your area at the moment and people need to take all level of precautions, including housing birds, making sure the housing is as effective as possible, not letting visitors in, and the whole 'cleaning your boots' thing every time you go into the birds, all the time, every day," she said.
"I am worried that people think we have housed the birds so that is all fine, they will all be protected. It is not. It really is all about that combination of housing and top-notch biosecurity which is most effective.
"Though housing helps reduce the direct contact between wild birds and your own birds, and therefore reduces the risk, biosecurity and cleanliness remain the number one factor.
"A teaspoon of infected bird droppings on the bottom of your welly can drop off and start an infection, which is why this 24/7 cleanliness message is so important."
In response to suggestions from some farmers that the regional housing lockdown should have been enforced sooner, Dr Middlemiss said it was based on monitoring the increasing risk level from wild birds - with preventative extra biosecurity measures installed first, on September 27, as they are proven to be more effective.
"Biosecurity and cleanliness have a 40-fold reduction in the risk of exposure, while housing has a two-fold reduction, " she said. "That is from a European study.
"Two-fold is still worth having, that is why we are doing it, but this is why the preventative measures are the most important, with housing following that.
"To make the housing as effective as it can be, remember to patch up holes in your shed, or your roof, make sure birds and rodents cannot get in, and that people are not walking it in - all these things are really important."
Dr Middlemiss said animal health teams have been "working flat out" to respond to the worrying rise in cases in Norfolk and Suffolk.
"It has been a really busy few days right across the weekend, and we are bringing in more vets to support the effort because of the number of cases, but there is also a lot of work around the investigations and licensing, so we are prioritising all our vet use across the department," she said.
She added that some "potential risk pathways" for direct or indirect wild bird contact had already been identified at the most recent Norfolk cases.
Although avian influenza can be devastating for birds, the UK Health Security Agency advise that the risk to public health is very low and the Food Standards Agency says it poses a very low food safety risk.
Poultry keepers and members of the public should report dead wild birds to the Defra helpline on 03459 33 55 77 and keepers should report suspicion of disease to APHA on 03000 200 301.
Free-range anxieties
As free-range farmers bring their birds indoors to comply with the avian influenza lockdown, one turkey producer fears the disease risk may force people out of the industry.
Robert Garner of Godwick Turkeys at Tittleshall, near Fakenham, brought his 4,000 birds indoors a week ago as a "practical and sensible precaution" after cases started to rise in the south of the county.
He said the annual anxiety over a potential bird flu outbreak might leave some farmers considering quitting.
"Without a shadow of a doubt," he said. "The risk factor of growing free-range Christmas turkeys is off the scale. Each year it gets harder.
"The risks and the financial implications are substantial. It is something a lot of producers will be thinking long and hard about.
"It is extremely worrying. Bird flu is a devastating disease in every way, it is horrific.
"Every year we are battling this problem as best we can, and hopefully we can get through to Christmas and keep these birds safe.
"Our biosecurity is as good as it can be, we have very clear and defined practices around the poultry sheds to try and ensure the birds' safety - but we can only do so much.
"When you go around every morning to check your birds you do it with a very nervous feeling in your stomach.
"All our birds are shut up now, and our buildings are bird-proof so no wild birds can get near our turkeys. But obviously they are not allowed out to range any more, which does cause some other issues, because they are used to going outside.
"We will hang things up in the houses to enrich their environment to keep them busy, but when they get bored it gets difficult. When you are in a high welfare system like ours you want to give them the best.
"The sheer number of cases this year is alarming but it is definitely the correct thing to house these birds and keep them away from this virus."
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