BirdLife Position StatementThe numerous strains of avian influenza [At least 135 strains are recognised, based on the combination of different H and N subtypes] can be divided into two classes, according to their pathogenicity (disease-causing ability) to domestic poultry. Low pathogenic strains circulate in wild birds, especially waterbirds, usually at low levels. These cause no, or only mild, illness. However, strains of the H5 and H7 subtypes can occasionally become highly pathogenic following a specific mutation. These highly pathogenic viruses can cause great mortality in domestic poultry flocks but are very rare in wild birds, with only one recorded instance prior to 1997 when the current strain of concern, H5N1 appeared.
Poultry flu, H5N1, is highly pathogenic. Genetic evidence clearly points to it originating in domestic birds through mutation of low pathogenic sub-types of avian flu. Subsequently, H5N1 has been passed from poultry to wild birds on several occasions, and as the disease spreads, these instances are likely to become more frequent.
Transmission is promoted in domestic flocks due to the density of birds and the consequent close contact with faecal and other secretions that contain the virus. Husbandry methods like those in SE Asia, where domestic flocks are often allowed to mix freely with wild birds, especially waterfowl, make the transmission to migratory waterbirds easier.The H5N1 virus is spreading, with recent outbreaks in China, Kazakhstan, Mongolia and several regions of Russia, on top of the spread through SE Asia since the end of 2003. It is not yet clear how the disease is spreading: movement of domestic birds is likely to have a significant role, and migrating waterbirds may also be involved. Evidence suggests the outbreak in China had its origins in domestic birds. However, there is a recent instance, in Kovsgol Province, Mongolia, where poultry flu has been detected in wild migratory birds that had no apparent contact with domestic poultry. There, as in other outbreaks in wild birds, the disease was quickly self-limiting. Around 100 out of 6,500 waterfowl at the lake died, and tests on 139 live birds at this and a nearby site all proved negative for the virus. [ see: http:// www.mydna.com/resources/news/200508/news_20050819_birsam.html ]The points below are based on the best information available on 25 August 2005:
1 There have been no recorded instances of transmission of the disease between infected wild birds and humans. The H5N1 virus strain is not currently contagious between humans and most human cases to date have been associated with close contact with infected domestic poultry. The risk of a human contracting the disease from a wild bird is remote, unless there was excessive close contact with infected birds and their excreta.
2 Wildlife and health experts (including the World Health Organization, Food and Agriculture Organization of the United Nations, and World Organisation for Animal Health) are agreed that culls of wild birds are highly unlikely to stop the spread of the disease. Indeed, they are certain to be counterproductive in encouraging birds to disperse widely. Moreover, culls would divert resources away from important disease control measures. [The World Heath Organization (WHO), The Office International des Epizooties (OIE) and the Food and Agriculture Organization (FAO) all concur that "the control of avian influenza infection in wild bird populations is not feasible and should not be attempted."] 3 The most efficient control techniques involve improved biosecurity, primarily of the poultry industry, to reduce the likelihood of contact between domestic stock and wild birds or infected water sources. This needs to be coupled with swift and complete culls of infected poultry flocks in the event of an outbreak. Further measures that should be considered include strengthening surveillance for the disease, and stricter controls on wild bird markets and movements of domestic poultry. Such measures should be introduced worldwide. Countries currently free of the disease should consider a ban on imports of domestic poultry, wild birds for the pet trade and untreated bird products (feathers, fresh meat etc) from affected regions. Preventing public access to infected sites is also clearly a sensible precaution.
4 We fully recognise the potential for a human pandemic should the current viral strain increase its transmissibility through mutation or reassortment, thus facilitating human to human transfer of the disease. We also recognise the impact the current strain is having on local economies forced into culls of domestic flocks. The considerations highlight the need for the limited resources available to be focused on the places and activities where people, livestock and wildlife come into close contact.
5 In addition to the impact of the disease on economics and livelihoods, and the potential impacts for human health, there are potential implications for conservation. For instance, it is estimated that somewhere between 5% and 10% of the world population of the Bar-headed Goose Anser indicus perished in the recent outbreak in China.
4th July 2014