UK's bird tests may be missing flu virus

http://www.newscientist.com/article/mg19025473.600-uks-bird-tests-may-be-missing-flu-virus.html

a.. 12 April 2006
b.. From New Scientist Print Edition
c.. 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 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.


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