Early warning call for H5N1 may have wrong indicator species
Speculation remains over which wild waterfowl species are most likely to harbour and spread highly pathogenic avian influenza in the environment and into commercial poultry flocks.
Bernard Matthews, the United Kingdom's (UK) top turkey-producing company, has more interest than most in pin-pointing and assessing wild bird risk. It was Bernard Matthews that suffered the UK's first outbreak of H5N1 HPAI in February 2007, losing 169,000 turkeys and a lot of public goodwill in the process.
Ironically, most of the fall out occurred when the incident inadvertently revealed how Bernard Matthews was importing a considerable amount of turkey meat into the UK. UK consumers had always been led to believe, through company advertising, that Bernard Matthews' turkey was exclusively home grown.
The Department for Environment, Food and Rural Affairs (Defra) claimed the most plausible source of the H5N1 outbreak in Bernard Matthews' turkey-growing sheds at Holton in the Country of Suffolk was from partly processed turkey meat imported into the UK from Hungary. A Bernard Matthews turkey processing plant was on the same site as the infected turkey farm, although the source, route of entry, and spread of the virus was never proven beyond absolute doubt. The virus had already been carried into Eastern Europe (including Hungary) on wild birds.
Concern over risk and role of wild birds
Bernard Matthews' concern over risk and role of infected wild birds spreading threatening to poultry is clearly heightened by perceived increased vulnerability related to a major overall in the company’s production systems. This was provoked by the H5N1 disaster and the subsequent controversy surrounding imports which led to Bernard Matthews brand sales halving at one point last year.
Bernard Matthews has promised to source all turkey from farms around its home base in East Anglia in the UK and to focus on free range production, which clearly raises the risk of H5N1 passing from wild birds into poultry. Together, with Defra's analysis that turkeys are almost 40 times more susceptible than chickens to H5N1 HPAI, it is easy to see why Bernard Matthews is very concerned.
Earlier this year, the 2008 Temperton Fellow called on the UK government and the poultry industry to work together to establish an early-warning system for migratory birds that can carry H5N1 avian flu. Armed with this knowledge, free-range turkey producers would be able to take measures to avoid contact between wild birds and poultry, such as temporarily housing flocks during the high-risk period, he said.
Delivering his Temperton Fellowship Report, Bernard Matthews Foods technical director Jeremy Hall highlighted the trend towards free-range Christmas turkeys. "TV chefs are encouraging consumers to go free range, which has led to a 15 percent growth in Christmas turkey volume. But outdoor farming brings risk and the sector needs to find how to manage this during the higher-risk autumn migration season. So the challenge is to rear turkeys through the highest risk months without any outbreaks,” Hall said.
One big limitation highlighted by Hall that undermines the industry's preparedness is the lack of information on movement of the virus. He claimed there was good European Union (EU) information on routine wild-bird testing but that the approach taken was disjointed. "The EC's [European Commission] way of reporting the previous quarter's results means that data is available only when it is about five months out of date. However, the European picture on virus movement is critical and we need a faster web-based reporting system," he said.
Hall went on to recount how he had meetings with the British Trust for Ornithology (BTO) and was amazed by the sophistication of its records and mapping. "Using those data with satellite tracking, we could track bird movement and know precisely when birds start their journey back to the UK," Hall said. "But the [UK] government needs to put more support into wild-bird testing and monitoring. At the moment, we are depending on the goodwill of the RSPB [Royal Society for the Protection of Birds] and BTO for bird spotting. Defra is inadequately supporting this and we need to halt the decline in bird collections for avian flu testing."
Defra's UK wild bird surveillance programme has previously come in for criticism from experts in continental Europe and North America. The extremely low detection rate of avian influenza viruses of any subtype suggest (36 out of 11,441 birds tested since 2006), and lower than continental Europe by a factor of around 30, indicates there could be a failure at some point in the sampling and/or sample storage/transportation procedure, they say.
Pochards, mallards potential long distance vectors
The pochard (Aythya farina) is the most likely candidate for carrying and harbouring the H5N1 avian flu virus in Europe, claimed Hall. "Looking at wild birds testing positive, there were mainly swans and pochards. But as swans either migrate short distances or don’t migrate at all, they are picking up infection from other species." In contrast, he said, the pochard travels huge distances to its breeding grounds in eastern Russia and China, and spends the summer in contact with wildfowl in areas known to have a high presence of infection. And about 84,000 of these return to the UK each autumn.
These views are not completely in tune with research carried out by a team of scientists at the Erasmus Medical Centre in Rotterdam, Netherlands, which includes acknowledged world expert Professor Albert Osterhaus. They acknowledge how wild birds are implicated in expansion of H5N1 HPAI outbreaks across Asia, the Middle East, Europe, and Africa (in addition to traditional transmission by infected poultry, contaminated equipment, and people).
Such a role, they say, requires wild birds to excrete virus in the absence of debilitating disease. By experimentally infecting wild ducks, they found that tufted ducks (Aythya fuligula), Eurasian pochards (Aythya farina), and mallards (Anas platyrhynchos) excreted significantly more virus than common teals (Anas crecca), Eurasian wigeons (Anas penelope), and gadwalls (Anas strepera). Only tufted ducks and, to a lesser degree, pochards became ill or died. They singled out mallards as the biggest potential long distance vectors of H5N1 HPAI while other species, like tufted ducks, were more likely to act as sentinels.