UK's Birs Tests May Be Missing Bird Flu Virus

New Scientist ^ | 4-12-2006 | Debora MacKenzie

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UK's bird tests may be missing flu virus

12 April 2006
From New Scientist Print Edition
Debora MacKenzie

WHEN France reported its first case of H5N1 bird flu in February, the UK's response was adamant: samples had been taken from more than 3500 wild birds, and those tested so far showed the disease was not yet in the UK. Additional precautions, such as moving poultry indoors, were unnecessary, said the authorities.

Last week, scientists found H5N1 bird flu for the first time in the UK, in a dead swan in Fife, Scotland. The UK's environment ministry DEFRA again stated that all wild birds tested so far were negative for flu, so it was unlikely to be widespread. Now an investigation by New Scientist suggests that all those tests were flawed, meaning no one really knows just how widespread infection among British wild birds might be.

Suspicions have been raised because DEFRA's tests revealed none of the ordinary flu that ducks and geese normally carry. Of the 3343 faecal samples from wild birds taken for DEFRA by the conservation group the Wildfowl and Wetlands Trust (WWT) in December, only two were shown to contain low-pathogenicity bird flu - 0.06 per cent. In a parallel study for DEFRA conducted by hunters, bird flu was found in only three of 423 freshly shot ducks, or 0.7 per cent. "We thought there was an unusually low level," says Ruth Crommie of the WWT, "but perhaps that happens in some bird populations."

Flu experts contacted by New Scientist disagree. "There's something wrong with those numbers," says Björn Olsen of the University of Kalmar in Sweden, who tests up to 10,000 wild birds per year in Europe's biggest monitoring programme for avian flu. Normally, he says, around 10 per cent of dabbling ducks and 1 per cent of geese should be carrying low-pathogenicity bird flu in Europe in December.

Richard Slemmons of Ohio State University in Columbus has tested 2000 to 3000 water birds per year for 20 years. His chief technician, Jacqueline Nolting, told New Scientist that "at least 6 or 7 per cent should be positive" at any time.

The problem may have been DEFRA's method of collecting samples. Crommie says DEFRA told WWT samplers to moisten a sterile swab on a stick with saline, take a faecal sample from the bird, then put the swab back in its dry plastic tube. The tubes were then kept at refrigerator temperature and taken to the testing laboratories the next day.

Both Nolting and Olsen are adamant that swabs must be immediately immersed in a saline or preservative solution, and also frozen quickly. "If you left a swab in the refrigerator in its sheath like that, it would dry out and you'd lose all your virus," says Olsen. He says whoever planned the tests "should have talked to us". DEFRA has not done large-scale flu surveys before.

“If you left a swab in the refrigerator in its sheath like that, it would dry out and you'd lose all your virus”"If you just want to identify the viruses present you could put it in a nutrient solution or in ethanol, but you need a transport medium," says Nolting. "We never take dry swabs." Both groups also quickly freeze samples.

DEFRA declined to comment on whether its sampling method would deliver intact virus to the testing labs. It says different results in previous surveys "did not invalidate the present survey".

Meanwhile, Olsen says H5N1 was most likely carried to the UK by migratory ducks, which could have spread the virus to wintering grounds all over the country. DEFRA's tests would probably not have picked it up.

Free-range poultry have been brought indoors in the region where the Scottish swan was found, but as New Scientist went to press poultry elsewhere were still outside - where, as far as anyone knows, they may remain at risk.

From issue 2547 of New Scientist magazine, 12 April 2006, page 12