Introduction

To eradicate the virus altogether from poultry, national authorities would have to destroy all poultry farms and small-holdings, which would cause economic disaster. Authorities have already culled millions of chickens in an attempt to control outbreaks on farms, but even this has failed to halt the spread of the disease. In February 2004, the Food and Agriculture Organization of the United Nations (FAO) recommended the use of vaccination of targeted poultry flocks in an attempt to stem the spread of H5N1. However, experts are divided over its usefulness, because there is the risk that vaccinated chickens might still harbour and shed the virus, while appearing to be healthy.

Even if H5N1 could be eradicated from domestic birds, it might still persist in wild birds. It remains unclear how many wild birds are likely to be infected with H5N1 or how easily it can spread between them. Where deaths have occurred among the wild population due to H5N1 infection, only a minority of birds appear to have been affected. Experts therefore advise against any mass culling of wild birds or destruction of their habitats, as there is no evidence that this would prevent the spread of H5N1. In British Columbia, there was strong opposition to the idea of culling wild birds because of the threat to biodiversity. Instead, the WHO, the FAO and the World Organization for Animal Health (OIE) recommend measures such as close monitoring of wild bird populations, surveillance and testing of poultry, and strict controls over the movement and trade of poultry, poultry products and captured wild birds. Vaccination of poultry to protect against infection might be effective if the quality of the vaccine is sufficient to produce strong immunity. Otherwise, vaccination might mask the presence of the virus in a flock if it persists and spreads between birds but does not cause detectable signs of disease.