Wild Guess

INDIA’S action plan to contain bird flu appears focused on the risk of migratory birds coming from countries affected with the disease....

INDIA’S action plan to contain bird flu appears focused on the risk of migratory birds coming from countries affected with the disease. Experts in India, however, say wild birds pose ‘minimum’ risk.

‘‘There have been no cases reported where migratory birds have spread the highly pathogenic avian influenza viruses. The disease is so deadly that an ill bird can hardly migrate when affected with the virus,’’ says Gopi Sundar, research associate (India) for International Crane Foundation.

According to him, the bar-headed geese were seen as a threat after deaths due to the virus (H5N1) were reported in a lake in China. The potential of migratory birds as risk arises from the fact they leave their homes in a particular time and follow the same path to predictable destinations. They can carry viruses either in their blood or on the mites and ticks usually present on their feathers. In case of the bar-headed geese from China, India is their winter destination.

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‘‘The bar-headed geese die within 48 hours of contracting the virus. They cannot take a flight in such a condition,’’ says Sundar.

ACCORDING to WHO, the role of migratory birds in the spread of highly pathogenic avian influenza is not fully understood. While the wild waterfowl are considered the natural reservoir of all influenza A viruses, they have probably carried influenza viruses, with no apparent harm, for centuries. They are known to carry viruses of the H5 and H7 subtypes, but usually in the low pathogenic form. Considerable circumstantial evidence suggests that migratory birds can introduce low pathogenic H5 and H7 viruses to poultry flocks, which then mutate to the highly pathogenic form.

The WHO website further says that in the past, highly pathogenic viruses have been isolated from migratory birds on very rare occasions involving a few birds, usually found dead within the flight range of a poultry outbreak. This finding suggests that wild waterfowl are not agents for the transmission of these viruses.

Flying risks
• The current outbreak of highly pathogenic avian influenza, which began in south-east Asia in mid-2003, is the largest and most severe on record. Never before the disease has affected so many countries simultaneously.
• The causative agent, the H5N1 virus, has proved to be especially tenacious. Despite the death or destruction of an estimated 150 million birds, the virus is now considered endemic in many parts of Indonesia and Vietnam and in some parts of Cambodia, China, Thailand, and possibly also the Lao People’s Democratic Republic. According to WHO, Control of the disease in poultry is expected to take several years.

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Recent events however make it likely that some migratory birds are now directly spreading the H5N1 virus in its highly pathogenic form. ‘‘Recent evidence shows that wild ducks can carry the virus and keep on excreting it for nine days,’’ he added. The ducks are shoveller and pin tails. ‘‘Even these bird deaths were recorded in breeding ground,’’ Sundar added.

According to him only two instances of deaths in birds after migration were reported. ‘‘It was a mute swan in Croatia (Europe) and a mallard duck in Romania. But the disease was self contained as they died after the flights,’’ added Sundar.

Other experts agree with him. ‘‘No human has contracted the disease from migratory birds. It has mostly been contracted by those who are in touch with poultry for a long time. You have to actually hold the bird in your lap to get the disease,’’ says Dr C.M. Gulati, former WHO drug expert and editor of MIMS India. ‘‘The government has to make sure that the poultry and wild birds don’t mix,’’ said Dr Gulati.

Avian flu poses two major risks
According to WHO, there is risk of direct infection when the virus passes from poultry to humans, resulting in very severe disease.
Unlike normal influenza, where infection causes only mild respiratory symptoms, the disease caused by H5N1 follows an unusually aggressive clinical course, with rapid deterioration and high fatality. Primary viral pneumonia and multi-organ failure are common- more than half of those infected in the present outbreak died.
A second risk is that the virus ‘ if given enough opportunities ’ will change into a form that is highly infectious for humans and spreads easily from person to person. Such a change could mark the start of a global outbreak (a pandemic) which are likely to kill millions.

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Even the high security animal testing lab in Bhopal, which is the apex lab, has not found strain in any of the samples send from various parts of the country.

THE threat of bird flu is likely to revive a controversial project that late Prime Minister Indira Gandhi closed down 30 years ago because of the data’s potential for being misused in biological warfare (bw).

Between 1967 and 1973 the Bombay Natural History Society (BNHS) in Mumbai carried out a “bird ringing” project. It was funded by the US under a programme called “migratory animal pathological survey” or maps of the US Army.

Blood samples were collected from migratory birds arriving in India and the blood slides sent to Bangkok for analysis.

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‘‘Prevention is better than cure. We have to ensure that poultry is away from wetlands, besides of course increasing surveillance of wild birds,’’ says Sundar.