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H5N1 Bird Flu Surveillance Shortfalls in Great Britain
April 12, 2006
The weekly magazine said its suspicions were raised because samples of droppings from more than 3,000 wild birds taken for DEFRA last December by the conservation group The Wildfowl and Wetlands Trust (WWT) showed only 0.06 percent had the ordinary flu that ducks and geese normally carry.
Crommie said DEFRA told the WWT samplers to take fecal samples on a sterile moistened swab and to put them in dry plastic tubes before freezing. But the independent experts said the samples would need to be immersed in a saline or preservative solution before being frozen.
"If you left a swab in the refrigerator in its sheath like that, it could dry out and your would lose all your virus," said Bjorn Olsen, of the University of Kalmar in Sweden, who tests 10,000 birds each year for avian flu.
The above comments describe one way to generate false negatives, but there are countless other ways, and the low percentage of samples that are positive for bird flu indicates the testing procedure in Great Britain is flawed.
The flawed testing in Europe has been described previously. Last fall Canada reported H5 in as many as 24% of the birds tested in British Columbia. H5 has detected in all reporting areas and the number of bird flu positives was higher than the H5 numbers. Last fall most European countries were reporting negative results, although a handful of countries had detected H5N1 in wild bird populations and the H5N1 detected was the predicted H5N1 strain.
Although European countries have yet to detect H5N1 in live wild birds, most have now detected H5N1 in dead wild birds, especially swans. Russia detected H5N1 in about two dozen species of wild birds as described in the OIE Mission Report and conceded that their numbers were an underestimate because many sparsely populated regions were not tested. The Russian data from last summer would suggest that by now H5N1 would be widespread in Europe, the Middle East, Africa, and south central Asia because major flyways in those areas intersect in southern Siberia where H5N1 was concentrated and those birds would spread H5N1 during fall and winter migrations. Thus, the affected countries, like England, that continue to deny widespread H5N1 infections are simply admitting that their surveillance system is flawed.
In Europe, evidence suggest that H5N1 arrived in the fall, and was most often detected in the winter in resident birds like the mute swan at a time when most migratory birds had flown through the Middle East into Africa. Those birds are now beginning to return, but most of the H5N1 detected in Europe in the past several months are from H5N1 that arrived in the fall.
England would not be exempt from birds migrating in from Russia last fall and the failure to detect H5N1 in over 3000 samples reflects testing flaws. Testing methodologies in countries in Europe, the Middle East, and Africa which still maintain an H5N1 free status should be investigated.