Avian Influenza: Frequently Asked Questions
Avian Influenza: Frequently Asked Questions
|1.||What is High Pathenogenicity Avian Influenza H5N1?|
|2.||Why is there so much concern about this virus?|
|3.||How are wild birds linked to avian influenza?|
|3.1 Can wild birds catch H5N1?|
|3.2 What is the role of wild birds in spreading High Pathogenicity Avian Influenza H5N1?|
|3.3 Conservation implications for wild birds|
|3.4 What further research is needed?|
|3.5 Should wild birds be culled to stop the disease spreading?|
|3.6 Should wetlands be drained to deter waterbirds?|
|4.||Can I still go birdwatching?|
|5.||Should I stop feeidng wild birds in my garden?|
|6.||How is the virus spread?|
|7.||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 contaminated feed, litter or water.
The H5N1 virus currently circulating is a High Pathogenicity Avian Influenza (HPAI). This strain of the virus first appeared in Hong Kong in 1997. It evolved in poultry from Low Pathogenicity Avian Influenza (LPAI) viruses that were probably acquired from wild birds. The current series of outbreaks began in 2003 in South-east Asia.
2. Why is there so much concern about this virus?
The scale of the current outbreak of high pathogenicity avian influenza in poultry is unprecedented. H5N1 is causing huge economic damage. The virus can spread very quickly among domestic poultry, such as chickens, ducks and turkeys, and kills nearly all birds. Many more birds have to be killed to try and stamp out infections. This, with the necessary restrictions on movement and trade of birds, causes serious losses to farmers, businesses and national economies.
At present, H5N1 is not easily transmitted to humans. Many people have been exposed to infected birds in the present outbreak, but fewer than 200 have caught the disease. Nevertheless, more than half of the people who contracted H5N1 have died.
H5N1 is not easily transmitted from human to human. However, this may change since the virus is constantly evolving. A form of H5N1 that is transmitted easily between people could cause a global influenza pandemic. Such a virus could arise through ‘reassortment’ (when human and avian influenza viruses exchange genetic material, during co-infection of a human or a pig) or through a more gradual process of adaptive mutation. Continued outbreaks of H5N1 increase the chances of this happening.
3.1 Can wild birds catch H5N1?
Yes. The current strain has caused deaths in a number of wild bird species, mostly waterbirds. Most of these flock or nest in colonies on waterbodies or nearby farmland. Others are birds that feed and scavenge in polluted waterways near towns and farms. Yet others are scavenging species likely to forage around poultry farms, such as crows and magpies.
3.2 What is the role of wild birds in spreading High Pathogenicity Avian Influenza H5N1?
Recent outbreaks of H5N1 in 2006 among wild birds in Europe and the Middle East show that wild birds are capable of carrying the virus long distances after infection—at least during the disease’s incubation period, which may be several days.
One important, unanswered question is how easily infected wild birds can pass the disease on. Data from Croatia show that waterfowl sharing the same ponds as infected swans remained free of the disease; but a sick swan housed with chickens at an Austrian animal rescue centre did pass the infection on.
Earlier outbreaks show a very different pattern to recent incidents in Europe. They do not show the trails of dead birds following migration routes that we would expect if wild birds had been spreading the disease across continents. Numbers of dead wild swans have not been found in Asia, for example. Some countries on flight paths of birds from Asia remain flu-free, whilst their neighbours suffer repeated infections. There is no correlation between the pattern and timing of wild bird migrations and outbreaks in domestic birds.
Many migrant wild birds have been tested for H5N1, but the virus has been found in very few. Only six out of more than 13,000 wild birds tested in China were positive for the virus, whilst 3% had antibodies to H5N1. Elsewhere, no healthy migrant bird has been found to have the disease, out of more than 100,000 tests carried out worldwide. This includes 16,000 over the last decade in Hong Kong, a location so close to widespread infection in poultry in mainland China that it is remarkable that not a single infected live bird has been found. In currently uninfected areas, several thousand migratory waterbirds recently tested in New Zealand, Australia and Canada were all found to be negative for HPAI H5N1.
The European incidents show that wild birds can move the virus, and potentially spread it, over long distances. The previous spread of H5N1 shows that it is essential to consider other transmission routes as well (see below). These include the movements of untreated poultry and poultry products, the re-use of inadequately cleansed transportation crates, the use of infected poultry manure as fertiliser in agriculture and as feed in fish-farms and pig farms, and the trade in wild birds.
3.3 Conservation implications for wild birds:
The virus appears to kill most, perhaps all, of the wild birds it infects. Two globally threatened bird species may already have been affected. The virus was recently isolated from a Red-breasted Goose Branta ruficollis in Greece, and samples from a second individual are currently being tested. This is of concern as 90% of the world population of 88,000 is confined to just five roosts in Romania and Bulgaria, both affected countries. Several dead Dalmatian Pelicans Pelecanus crispus are currently being tested in Bulgaria. This species is vulnerable as it breeds in colonies in freshwater wetlands and coastal lagoons. The world population of 15,000 is confined largely to the Baltic and Black Sea regions, where many of the countries in which it breeds are already affected by H5N1.
It is also estimated that between 5% and 10% of the world population of the Bar-headed Goose Anser indicus (classified as a Least Concern species) perished in the outbreak at Lake Qinghai, in China in spring 2005.
Attempts to cull wild birds might compromise the status of some species. In some countries politicians have called on hunters to wipe out incoming migrant birds. Some governments have reportedly revived plans to drain wetlands, under the pretext of denying waterfowl landing and breeding places. Nests of birds, such as the Barn Swallow Hirundo rustica, which breed in close proximity with man have been destroyed, in the mistaken belief that this will reduce the risk of contracting bird ‘flu.
3.4 What further research is needed?
There are many significant gaps in our knowledge about H5N1 in wild birds. We need better information on how wild birds contract the infection, how long the incubation period is, when and for how long they shed the virus (and in what quantity), how ill it makes them (and how this varies among individuals, and affects their ability to migrate), and which species are affected.
We also need better systems of monitoring and surveillance for migrants – both for conservation purposes and to help predict and control the spread of H5N1 should migrant birds be found to carry it in the future.
Should wild birds be culled to stop the disease spreading?
This would be a highly misguided response. The World Health Organisation, Food and Agriculture Organisation and OIE (the World Organisation for Animal Health) agree that control of avian influenza in wild birds by culling is not feasible, and should not be attempted. Juan Lubroth, FAO senior officer responsible for infectious animal diseases, has commented: "[Culling] is unlikely to make any significant contribution to the protection of humans against avian influenza. There are other, much more important measures to be considered that deserve priority attention."
In the event that wild birds were found to be carrying HPAI H5N1, any attempts at culling would spread the virus more widely, as survivors dispersed to new places, and healthy birds became stressed and more prone to infection.
3.6 Should wetlands be drained to deter waterbirds?
Absolutely not. Apart from their extremely high conservation value, wetlands provide vital ecosystem services like flood control, water purification and nutrient recycling, and the livelihoods of many communities depend on them.
Draining wetlands is not only environmentally disastrous, but also likely to be counterproductive — for the same reasons that culling would be more likely to spread the Avian Influenza virus than control it. Birds would seek alternative staging places on their migration routes, and wildfowl forced to fly further and endure more crowded conditions along their migration route would become stressed and exhausted, and more prone to infection.
4. Can I still go birdwatching?
Yes. The risk of acquiring infection from wild birds is extremely low. Take sensible precautions and avoid touching birds, their droppings or water near them, and wash your hands before eating and after any contact with animals.
5. Should I stop feeidng wild birds in my garden?
The birds that visit feeders and bird tables are very unlikely to carry the H5N1 virus. Observe sensible hygiene precautions: wash hands after handling equipment that has been splashed with bird faeces.
Clean and disinfect feeders bird-tables and bird-baths regularly, using 10% disinfectant solution. Rinse out several times after treatment to ensure all the disinfectant has been removed. Water containers should be rinsed out daily during the warmer months.
Do not bring the feeders into the house to clean them, but do it outside, using separate utensils. Wear gloves when cleaning feeders and bird tables, and always wash your hands when finished.
Bird-tables and feeding areas should be swept clean regularly, and moved several times a year, to prevent build up of food particles or droppings. If food takes days to clear either from containers or the ground, reduce the amount of food offered.
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—both legal and illegal. The legal trade involves literally millions of hatching eggs and poultry being shipped to destinations worldwide. For example, prior to the outbreaks in Egypt, the country was reported to export 180 million day-old-chicks plus 500,000 mature fowl a year. Almost 12 million live chickens were officially imported into the Ukraine in 2004 and more than 16 million into Romania. In Turkey, one factory has the capacity to produce over 100 million hatching eggs per year, many of them exported to Eastern Europe and the Middle East. Recent outbreaks in India, Nigeria and Egypt originated within the poultry industry, and there is strong circumstantial evidence that movements of poultry and poultry products are responsible.
For obvious reasons, there is little information on the extent of the illegal poultry trade, but 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 November 2005 the UK authorities revealed that large quantities, possibly hundreds of tonnes, of chicken meat had been illegally imported from China, and fraudulently relabelled before being sold on to food manufacturers across the country. In February 2006, 20 kg of chicken tongues from China were found by customs in Rio de Janeiro, Brazil, and 21 tonnes of (mainly) poultry meat from China were confiscated in southern Spain. These indicate continuing lapses in border controls, despite the widely publicised risks. Illegal poultry movements are reported to be extensive in central Asia. In 2005, Ukraine’s State Department of Veterinary Medicine said there had been substantial illegal re-exportation of meat from Ukraine to Russia via third countries.
The widespread illegal trade in cage birds is known to have transported flu-infected birds over large distances. Customs in Taiwan recently intercepted two consignments of infected birds smuggled from mainland China. An outbreak of H5N1 at a bird quarantine station in the UK may also be attributable to smuggled birds ‘laundered’ into a legally imported consignment. The most likely source of infection in captive birds is at live animal ‘wet’ markets, where domestic and wild-caught birds are kept in close proximity, posing a high-risk of bird flu cross-contamination.
The use of untreated chicken, duck and other poultry manure as fertiliser and feed for pigs, fish and other livestock is widespread in Asia and Eastern Europe. Birds infected with the H5N1 virus excrete virus particles in their faeces: putting untreated faeces from infected birds into fish ponds provides a new source of infection. The manure may be transported for long distances before being used or sold, a dangerously effective way of spreading the virus. The United Nation’s Food and Agricultural Organisation recommends that "the feeding of poultry manure/poultry litter should be banned in countries affected by or at risk from avian influenza, even if correctly composted, ensiled or dried with heat treatment."
7. What should be done to prevent the spread of HPAI H5N1?
As H5N1 continues to spread, there is need for responses to be calm, balanced, prompt and effective. A broad range of measures is needed. The role of wild birds must be seen in the much larger context of the global poultry industry and the movements of huge quantities of poultry products around the world. Focusing attention on migrating wild birds alone is misplaced, and a potentially dangerous diversion of energy, effort and resources.
BirdLife believes that the measures needed include:
The best veterinary advice concerning issues such as confinement of free-ranging flocks and vaccination should be sought and followed. Vaccination may be effective—providing there is adequate antigen in the vaccine. Poor-quality vaccines stop the signs of the disease but allow the virus to continue replicating, spreading and evolving. There is continuing debate among virologists, veterinarians and politicians over the merits of vaccination.