Red herring
For almost two years, between 2003-2005, the avian flu was restricted mostly to China and southeast Asia. Several flu outbreaks were reported in poultry, domestic ducks and geese in Cambodia, Indonesia, Thailand, Vietnam and other countries, resulting in culling of over 140 million birds. Then, in May 2005, over 6,000 birds reportedly died at Qinghai Lake, in northwest China as the virus spread into Mongolia, Russia, Croatia, Romania and Kazakhstan. This set alarm bells ringing all over the world.
The reasons for the spread of the flu are still being hotly debated. Though poultry trade and illegal wild bird trade are seen as possible conduits, the migratory birds are portrayed as the primary carriers of the flu virus. There are two flyways (pre-determined paths, in specific seasons) that the birds use to migrate between south and southeast Asia, Western Siberia and Eastern Europe. It is inferred that these are the regions getting affected.
International conservation organisations, like Wetlands International and Birdlife International, are aghast at the charge against migratory birds. The spring migration occurs during April-May, while the first sign of an outbreak, outside China, was seen at the end of July. "The migratory patterns of the (supposed) carriers and the seasons do not match up with the outbreak time-table. Moreover, the infected ducks die within two days and would not be able to fly over long distances,' explains Gopi Sundar, a researcher with the International Crane Foundation's Delhi centre. "Even the outbreaks in Croatia and Romania in migratory birds have been self limiting, which means that the infected birds died quickly, without spreading the disease,' he adds.
Moreover, some scientists ask, with the virus doing the rounds of southeast Asia since 1997, why has it struck the migratory birds now?
Evidence against migratory birds being the primary carriers of the virus also comes from the World Organisation for Animal Health (oie), based in Paris. Its study on the avian influenza outbreak in Russia concluded the strain was different from that found in Qinghai Lake, rubbishing the theory of wild birds carrying the virus to Russia. Says Sundar, "Till now, there has been no confirmed record of transfer of the virus from migratory birds to poultry. Rather, it is the other way round.'
The oie report also determined that migratory species contracted the virus from waterfowl in lakes located close to the affected premises. The report suggested that if the h5n1 virus behaved as a low pathogenic strain in wild ducks, it could have persisted at a low endemic level in the breeding population. The local concentration of birds during July for annual moulting and the presence of juveniles might have amplified and spread the virus.
Meanwhile, the flu scare has prompted several countries to impose restrictions on poultry imports. The us , the biggest exporter (2.47 million tonnes in 2004), is suffering as Russia, the biggest poultry importer, along with China and South Korea have put a ban on poultry imports. Critics of the migratory bird-viral flu theory claim it is being used as a red herring to take attention away from the more imminent threat from poultry trade
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