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Can Vietnam stave off bird flu?

N. Gopal Raj

The question is whether Vietnam's strategy of vaccinating all poultry can stop the virus from establishing itself again within the country. Besides, vaccination is not without its risks.

NGUYEN VAN Tich and his wife Hanh are proud of their small farm. Living in a village about 30 km from Hanoi, the capital of Vietnam, they keep a few hundred chicken and ducks as well as some pigs. Since shifting from rice cultivation to animal husbandry some four years back, they have seen their income grow considerably.

Neighbouring countries are battling the deadly form of bird flu known as H5N1 and Mr. Tich and his wife, like many others in Vietnam, worry that the virus could reappear in their country too. After all, from 2003 to 2005, theirs was a country badly affected by bird flu.

During 2004 alone, more than 44 million birds had to be destroyed, according to reports provided by the Vietnamese Government to the World Organisation for Animal Health (OIE). In a country where half of all families, in towns as well as villages, keep a few chicken in their backyard, it was doubtless a grievous loss that touched countless families, many of them poor and dependent on their birds for much-needed income and food.

The widespread outbreaks among poultry also resulted in the virus occasionally infecting humans. Till this year, Vietnam had more human cases of bird flu than any other country; over 90 Vietnamese caught the disease and nearly half of them died of it.

Last year, the Vietnamese government decided to vaccinate all poultry. So far this year there have been no outbreaks of bird flu in the country's flocks and, consequently, no human cases either. But although vaccination increases the resistance birds have to the disease, it cannot guarantee that birds will not become infected.

No one has forgotten the virus or the havoc it can wreak. Mr. Tich and his wife have so far lost none of their birds to bird flu. But other families in Viet Doan commune, which covers four other villages and a small town, were not so fortunate. Several thousand chicken and ducks in the commune died or had to be slaughtered when the disease struck in 2003. "People are worried about bird flu returning," said Trinh The Mua, vice-chairman of the People's Committee for the commune.

It is a concern that goes to the highest levels of Government. The disease might re-emerge in Vietnam during the coming winter, the country's Vice-Minister of Health, Trinh Quan Huan, admitted to visiting foreign journalists. Neighbouring countries, such as China, Cambodia, Laos, and especially Indonesia, have been seeing bird flu outbreaks among their poultry, he pointed out.

Vietnam has temporarily banned poultry imports from countries reporting bird flu. But that may not suffice to keep the virus out as there appears to be a thriving illicit trade in chicken being brought over the border from China where the birds are available at much lower prices.

According to the Minister, some 70 tonnes of illegally imported birds were seized during the first six months of this year. But it was difficult to be sure of the extent of smuggling that was going on, he added. A few months back, however, The Washington Post reported that smuggling rings had established large-scale operations along Vietnam's border with China.

The question is whether Vietnam's strategy of vaccinating all poultry will prove capable of stopping the virus from establishing itself again within the country. Vietnam has about 220 million birds in its poultry flocks and more than half of those birds are the backyard variety, according to FAO estimates. Vaccinating millions of birds is in itself a herculean task, and backyard poultry adds to the difficulties of carrying it out properly. Moreover, this mammoth exercise has to be done not once but repeatedly each year in order to keep the protective shield in place.

Culling was generally the first line of defence recommended when highly virulent H5N1 outbreaks were detected in poultry flocks, according to Robyn Alders, technical adviser for avian influenza at the Food and Agriculture Organisation's Regional Office for Asia and the Pacific in Bangkok. Vaccination was suggested only when culling and other control activities had failed and the disease had become widespread in the country, she told this correspondent.

The purpose of culling is to stop the highly contagious virus from spreading to birds and flocks elsewhere. That requires killing not just the sick birds but also healthy-looking ones that might have become infected. India was fortunate that the slaughter of a few lakh chicken stopped the bird flu outbreaks that occurred in Maharashtra and neighbouring areas during the early part of this year.

But that was not the case in Vietnam where repeated culling failed to curb the disease. Hoang Van Nam, deputy director at the Department of Animal Health, has been quoted as saying: "If outbreaks are occurring literally everywhere, eradication is not an option. So as the disease came in waves, we geared up at the end of the second wave and began vaccinating poultry before the arrival of the third wave."

Vaccinating backyard poultry poses particular problems and Vietnam has had to train thousands of staff to carry out the task properly. Village poultry flocks are likely to have birds of different ages and all these birds must be vaccinated, points out Dr. Alders. Vaccinators must be able to confidently deal with even small or less plump birds without harming them.

At least 70 per cent to 80 per cent of the birds in village flocks must be properly vaccinated in order to prevent outbreaks of bird flu from occurring. Besides, the vaccination campaigns need to be repeated every three or four months to ensure that newly introduced or newly hatched birds are immunised, she added.

All those who kept chicken and ducks were required to have their birds vaccinated, Bui Quang Anh, Director-General of Vietnam's Department of Animal Health, told the visiting journalists. Vaccination teams went to every commune and village in the country. People could bring their birds to one place and have them vaccinated. Or else the teams went door to door, injecting birds.

The Government had worked hard to educate people about the importance of vaccination, said Dr. Anh. Village meetings had been called to tell people why it was necessary that every bird be vaccinated. Local organisations like the women's union were roped in to carry the message to every home.

In 2005, 80 per cent of the poultry had been vaccinated, according to Dr. Anh. But since there had been no outbreaks of bird flu this year, the campaign carried out earlier this year had been less successful and only about 65 per cent to 70 per cent of the birds could be vaccinated. There would be "strong measures" to make sure that this year's second campaign matched the success achieved in 2005, he added.

Grass-roots support

There appears to be strong grass-roots support for the vaccination campaign. "If people get their poultry vaccinated, then the birds will not catch bird flu," said Mr. Tich. After vaccination started, the disease had vanished, he pointed out.

Thousands of bird samples analysed as part of the post-vaccination surveillance showed the virus was not circulating in Vietnamese poultry, Dr. Anh said. The absence of any outbreaks of bird flu in the country this year was a measure of the success of the vaccination programme, he added.

Carrying out such massive vaccination campaigns is not cheap. Dr. Anh put the cost of two years of poultry vaccinations at $10 million. But then the loss due to bird flu in just one province of Vietnam during 2004 was estimated to be about $12 million.

Vaccination is also not without its risks. On the one hand, vaccinated poultry become less susceptible to the disease. When birds do become infected, they shed less viruses in their faeces and nasal secretions, thus reducing the chances of the disease spreading.

On the other hand, vaccinated birds that get infected may show no signs of ill health and outbreaks within a flock become more difficult to detect. So, while vaccinating birds against the H5N1 virus reduced the risk of outbreaks within a flock, it also increased the possibility for a "silent spread" of the virus to other flocks, according to research carried out by Nicholas Savill at the Centre for Infectious Diseases of the University of Edinburgh in Britain and other scientists.

For their paper that was published recently in the journal Nature, Dr. Savill and his colleagues had used mathematical models to study how the virus might spread among caged birds. But, theoretically, the results would hold for backyard flocks as well, he told this correspondent in an email. "Vaccination will make it harder to detect bird flu thus increasing the chance of silent spread. However, this has to be weighed against the smaller chance of bird flu getting into a vaccinated population [of birds]," he observed.

"So far vaccination in Vietnam appears to be working," he added.

Now, the challenge for Vietnam is to keep its guard up for as long as bird flu swirls about in its neighbourhood.

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