HOW IS THE VIRUS SPREAD, IF NOT BY WILD BIRDS?
There are at least three likely transmission routes: • Movements of untreated poultry and poultry products, and the global trade in poultry • The trade in wild birds • Use of infected poultry manure as fertiliser in agriculture and agriculture, and as feed in fish-farms and pig farms Most outbreaks in south-east Asia can be linked to movements of poultry and poultry products (or infected material from poultry farms, such as mud on vehicles, or peoples’ shoes). Live animal or ‘wet’ markets have played a major part in spreading the virus in south-east Asia: they were identified as the source of the H5N1 infection in chicken farms in Hong Kong in 1997 when approximately 20% of the chickens in live poultry markets were found to be infected. There is also a huge international trade in poultry—legal, unregulated or illegal. Recently it was revealed that poultry meat is being illegally imported from Asia into the USA; in October 2005 3,000 chickens were intercepted by Italian customs after be
There are several ways that the virus can be spread. Globally the most important has been the unrestricted movement of poultry and poultry products. This is how the disease spread in south-east Asia, how it is likely to have reached Nigeria, and how it found its way into Russia. In addition the illegal trade in wild birds has been shown to have transported avian influenza over large distances. An outbreak of bird flu in a quarantine centre in the UK was likely to have been caused by smuggled birds that were ‘laundered’ into a legally imported consignment. The use of untreated chicken, duck and other poultry manure as fertilizer and feed for pigs, fish and other livestock is widespread in Asia and Eastern Europe. Birds affected with the H5N1 virus excrete virus particles in their faeces. Placing this untreated faeces onto fields or into fish ponds provides a new source of infection. Manure may be transported over large distances before being used and is a highly effective way to spread
6. What should be done to prevent the spread of HPAI H5N1? 1. WHAT IS HIGH PATHOGENICITY AVIAN INFLUENZA H5N1? There are numerous different strains of avian influenza, but only a very few of these are a serious health concern for animals or people. Most strains circulate in wild birds, especially waterbirds, at low levels, and at worst cause only mild disease. These ‘Low Pathogenicity Avian Influenza’ (LPAI) viruses also have only mild effects on poultry. In contrast, some variants of the H5 and H7 ‘subtypes’ can cause massive mortality in poultry. These are designated ‘High Pathogenicity Avian Influenza’ (HPAI). HPAI viruses do not normally occur in wild birds. They arise in poultry, where intensive rearing and crowded conditions allow the virus to evolve to a highly pathogenic form. Hence HPAI is also called ‘poultry flu’. Wild birds can also be infected with, and killed by, HPAI viruses. They appear to acquire the virus through contact with infected poultry or with facilities used b
• Movements of untreated poultry and poultry products, and the global trade in poultry • The trade in wild birds • Use of infected poultry manure as fertiliser in agriculture and agriculture, and as feed in fish farms and pig farms Most outbreaks in south-east Asia can be linked to movements of poultry and poultry products (or infected material from poultry farms, such as mud on vehicles, or peoples’ shoes). Live animal or ‘wet’ markets have played a major part in spreading the virus in south-east Asia: they were identified as the source of the H5N1 infection in chicken farms in Hong Kong in 1997 when approximately 20% of the chickens in live poultry markets were found to be infected. There is also a huge international trade in poultry—legal, unregulated or illegal. Recently it was revealed that poultry meat is being illegally imported from Asia into the USA; in October 2005 3,000 chickens were intercepted by Italian customs after being smuggled into the country from China; and in Nove
