BirdLife Statement on Avian Influenza
April 12, 2006
There are several ways in which H5N1 can be spread within and between countries. Three major potential routes are the movements of infected poultry (and poultry products), movements of caged wild birds in trade, and movements of wild birds. Effective responses need to focus on all of these possible means of spread.
Outbreaks among wild birds in Europe and Iran during 2006 show that wild birds are capable of carrying the virus to new sites after infection, possibly in a “leap-frog” fashion by travelling for a short time and passing on infection to another group of birds before dying. Many questions remain concerning the effects of the virus on wild birds and how efficiently they can spread it to other wild birds or to domestic poultry. (See section “The role of wild birds”.)
By contrast, recent outbreaks in Cameroon, Egypt, India, Israel, Jordan, Niger, Nigeria and Pakistan originated within the poultry industry. Here, as in most other H5N1 outbreaks, there is strong circumstantial evidence that movements of poultry and poultry products are responsible. The timing and location of these outbreaks do not match the movements of migratory birds. Moreover in many of these countries poultry outbreaks occurred almost simultaneously in multiple large-scale poultry operations, indicating that migratory birds were an unlikely agent of the transmission.
For south-east Asia, recent comprehensive analysis of viral lineages concludes that poultry movements were responsible for multiple reintroductions, both within and between countries, and that “transmission within poultry is the major mechanism for sustaining H5N1 endemicity in the region”.
As H5N1 continues to spread, there is need for responses to be calm, balanced, prompt and effective. In particular, BirdLife urges:
In some parts of the world, authorities have proposed attempting to control the spread of H5N1 by culling wild birds, or destroying their habitats, or displacing them from breeding and roosting grounds. These approaches are unlikely to prevent the transmission of the disease and may in fact spread it to non-infected areas by forcing already-infected birds to disperse. They are at best ineffective, probably counterproductive, and distract from more suitable interventions. They could also add to the stresses already imposed on some species through habitat loss.
The risk of humans contracting H5N1 remains very low. Practically all human cases have resulted from frequent and intimate contact with poultry, but in relation to the number of humans, especially in Asia, who have this degree of contact, the number of known human infections is tiny.
BirdLife believes that greater collaboration between veterinarians, the poultry industry and food, agriculture, health and environment bodies is needed to tackle the threat of avian ‘flu effectively. BirdLife participates actively in a task force on avian influenza comprising scientists and conservationists from nine different international organizations, including four UN bodies, convened by the UNEP Convention on Migratory Species (CMS).
The role of wild birds
Outbreaks among wild birds in Europe during 2006 show that wild birds are capable of carrying the virus to new sites after infection — at least during the early stages of infection. It is possible the birds spread the disease in a “leap-frog” fashion by travelling for a short time and passing on infection to another group of birds before dying. It is also possible that the initial outbreaks in Europe in February related to movements of birds away from the Black and Caspian Sea regions in response to unusually cold weather. These areas are known to have widespread H5N1 infection in poultry, and limited biosecurity measures in place.
In contrast to the recent European incidents, the movement of wild birds are not to date the main cause of the spread of H5N1 in Asia over the decade since the virus was first discovered there. Prior to April 2005, wild birds found dead or dying with H5N1 in Asia were largely sedentary species that scavenge near poultry, live markets or captive bird populations.
In May to July of 2005 there were significant die-offs of migratory wild birds in Qinghai Lake (1,500–6,300 birds) and Mongolia (126 birds). The majority of the birds affected in May of 2005 in Qinghai Lake were Bar-headed Geese Anser indicus. Deaths from H5N1 in the geese occurred weeks after their arrival from wintering grounds in India, suggesting that the source of the H5N1 infection was local to Lake Qinghai. Furthermore no Bar-headed Geese or other wild birds were found dead in other wetlands near to Qinghai Lake.
In Mongolia, at Lake Erhel, the main species found dead or dying with H5N1 in July 2005 were Bar-headed Geese and Whooper Swans Cygnus cygnus. Both species would have arrived to breed in Mongolia several months earlier, and during the outbreak the birds would have been near to completing their annual feather moult, during which they are sedentary. Bird surveys carried out during the same period at eight wetlands in Mongolia found no other birds with H5N1. These facts point to the source of H5N1 infection being local to Lake Erhel and that the infected wild birds did not spread the disease to new locations.
It is possible that in some Asian and Australasian countries where little or no surveillance work has been done, infected wild birds have gone undetected . However, in Japan, Korea, New Zealand and Australia, where there has been extensive surveillance, there have been no infected wild birds identified. Countries such as the Philippines, on a major migration route from south-east Asia, remain free of H5N1. Japan and South Korea have both remained free of the disease after early outbreaks confined to poultry were brought under control by closing borders to poultry imports.
Wild birds have tested positive to H5N1 in Asia. Six out of more than 13,000 wild birds tested in China were positive, and 3% of this total had antibodies to H5N1. However, out of 16,000 wild birds tested over the last decade in Hong Kong, not a single live bird infected with H5N1 has been found. This finding is particularly striking since Hong Kong is so close to centres of infection in poultry in mainland China.
The lack of a trail of H5N1 infections along migratory pathways from infected breeding habitats in Mongolia, China and Russia to southern wintering areas in Asia suggests that migratory wild birds are not spreading the disease long distances between continents. With few exceptions, there is limited correlation between the pattern and timing of spread among domestic birds and wild bird migrations.
Nevertheless some authorities argue that the timing and location of outbreaks in the Black Sea and Caspian Sea in the autumn of 2005 did follow the southern migration routes of birds. These outbreaks occurred after H5N1 was detected in poultry in Russia and wildfowl in south west Russia in the summer of 2005. However, there appeared to be no trails of death along this migration route; wild bird deaths were localised and at least in some instances were restricted to a few individuals from larger flocks. Equally plausible explanations for the spread of avian influenza westwards during the latter half of 2005 are the movements of poultry and poultry products (See section “Movements of poultry and poultry products”).
BirdLife believes that it is unlikely that migratory wild birds carried H5N1 to Africa. There is strong circumstantial evidence that movements of poultry and poultry products are responsible. The timing and location of these outbreaks do not match the movements of migratory birds. Moreover in countries such as Nigeria and Egypt poultry outbreaks occurred almost simultaneously in multiple large-scale poultry operations, indicating that migratory birds were an unlikely agent of the transmission. If H5N1 was carried by wild birds, outbreaks should have occurred in key wetlands for migratory birds, especially in East Africa where there has been surveillance of wild birds in place over the past six months.
Understanding of the epidemiology of H5N1 in wild birds, and the behaviour of the virus in the wider environment, remain very inadequate. Most of the research on H5N1 has been on domestic animals in laboratory environments. How easily infected wild birds can pass the disease on to other wildfowl or poultry remains an important, unanswered question. The limited evidence that exists suggests tremendous variability in transmission rates and virulence between different host species and different strains of the virus.
Better quality data collection and reporting is crucial to understanding general patterns in outbreaks, possible routes of transmission, and the potential impacts on migratory bird populations. This information can be used to focus contingency efforts, to predict future outbreaks, and to guide effective policy to reduce the economic and conservation impacts of avian influenza.
In the interests of all those attempting to control the spread of HPAI H5N1, BirdLife believes that all surveillance and test data, whether positive or negative, should be published and made freely available to researchers.
There are several ways in which H5N1 can be spread within and between countries. It is therefore essential to monitor and control those activities which are known or strongly suspected to spread H5N1. These include the movements of untreated poultry and poultry products, the re-use of inadequately cleansed transportation crates, and the trade in wild birds. Further investigation is also needed of the use of potentially infected poultry manure as fertiliser in agriculture and as feed in fish-farms and pig farms, described by the UN Food and Agriculture organisation as a high-risk activity.
Movements of poultry and poultry products
Most outbreaks in south-east Asia can be linked to movements of poultry and poultry products (or accidental transfer of infected material from poultry farms, such as water, straw or soil on vehicles, clothes and shoes). Globally, the most important route of spread remains unrestricted poultry movements. A recent paper (Chen et al., “Establishment of multiple sublineages of H5N1 influenza virus in Asia: Implications for pandemic control”, Proceedings of the National Academy of Sciences, 21 February 2006) analyses the viral lineages and concludes that poultry movements were responsible for multiple reintroductions in south-east Asia, both within and between countries.
Live animal or ‘wet’ markets may have played a major part in spreading the virus in south-east Asia, according to the UN Food and Agriculture Organisation (FAO), World Organisation for Animal Health (OIE) and World Health Organisation (WHO): “In 1992, live poultry markets in the USA were considered the ‘missing link in the epidemiology of influenza’. 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. The same situation was seen in Viet Nam, where the circulation of H5N1 in geese in live bird markets in Hanoi had been documented three years before the 2004 outbreaks in chicken farms.” (FAO/OIE/WHO Consultation on avian influenza and human health: Risk reduction measures in producing, marketing, and living with animals in Asia, Kuala Lumpur, Malaysia, July 2005).
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 world-wide. 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, little information is available on the extent of the unregulated and illegal poultry trade. However, 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 from third countries.
Illegal trade in cage birds
Faeces as fertiliser and livestock feed
Initial investigations reveal that Russian fish farms have recently started using chicken faeces as fertiliser, and this practice is followed in Eastern Europe where poultry faeces are also spread onto agricultural land and discharge inevitably runs off into waterways. The collection and transport of untreated poultry manure could be a highly effective way of spreading the virus. The FAO 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.”
For more information see BirdLife's March 2006 report, Fish farming and the risk of spread of avian influenza (PDF, 200 KB).
Prevention and control
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.
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 on wild birds alone is misplaced and a potentially dangerous diversion of energy, effort and resources. Attempts to cull migratory wild birds or destroy their habitat are highly misguided—experience shows that this approach is completely ineffective, and indeed is likely to make matters worse.
Risks to people
In the last 100 years there have been at least three major pandemics of human influenza A, which killed many people around the world. The origins of these deadly virus strains remain uncertain, but at least two are thought to have arisen when bird flu and human influenza viruses came together, possibly in pigs, and reassorted their genetic material. Continued outbreaks of H5N1 increase the chances of this happening again, especially as the current strain of H5N1 is exceptional in that it can pass directly from poultry to humans, without the intervention of an intermediate host.
There are a few anecdotal reports of humans contracting the virus directly from wild birds, but none confirmed as yet. Almost always, human infections have occurred in people who have been closely associated with poultry. Given the substantial number and distribution of outbreaks in domestic poultry and waterfowl, there have been relatively few cases in people, indicating that the transmission of the virus from poultry to man remains inefficient.
Activities such as bird watching and feeding garden birds are completely safe, if simple common sense precautions are followed. These include avoid touching carcasses of wild birds, and washing hands with soap and water after filling or cleaning bird feeders. Both measures are advisable as birds can carry other potentially dangerous pathogens. Terrestrial sites of known H5N1 outbreaks should be avoided, for at least six weeks after the last recorded case. However, as avian influenza viruses can survive a very long time in water (up to 100 days depending on PH, salinity or temperature) it is recommended that people avoid swimming in infected water bodies for much longer.
In countries where H5N1 outbreaks have occurred, people working with poultry or other captive birds need to take stricter precautions, to minimise the risk of carrying infection to the birds they work with. They should avoid direct contact with wild birds and should also avoid contact with water from ponds and other sources which are used by wild birds as much as possible.
Conservation implications for wild birds
There have been reports in the media of wild birds being demonised. In some countries politicians have called on hunters to wipe out or frighten away 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 Barn Swallow Hirundo rustica and House Martin Delichon urbica, which breed in close proximity with man have been destroyed in the mistaken belief that this measure will lessen the risk of contracting bird ‘flu. None of these measures will control the spread of avian influenza, instead putting wild birds and other biodiversity in jeopardy
The virus is generally highly pathogenic (causes a high level of mortality) to wild birds. However, the total number of wild birds affected has so far been small: very many more birds die of other, commoner avian diseases each year. Nevertheless, H5N1 could be damaging to species that are already threatened, and/or congregate in just a few localities. One globally threatened bird species may already have been affected. In February 2006, the virus was isolated from a Red-breasted Goose Branta ruficollis in Greece. 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. It is also estimated that between 5% and 10% of the world population of the Bar-headed Goose Anser indicus perished in the outbreak at Lake Qinghai, in China in spring 2005.
BirdLife International is a member of a task force on avian influenza comprising scientists and conservationists from nine different international organizations including four UN bodies, convened by the UNEP Convention on Migratory Species (CMS). The task force seeks much better data and information on the cause of the spread of the disease. It is convening a meeting in early April 2006 to assemble some of the top scientists to examine the latest information on avian influenza.