01/01/2010
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Bird flu: beyond the hysteria

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Wetland by Steve Young
Wetland by Steve Young

The term “Intercontinental Ballistic Missiles” is probably not one that has been applied to migratory birds before, but a lot of unusual language has been used by governments and media across the world since bird flu, or more precisely the H5N1 strain of Avian Influenza Type A, has come to prominence in the past few months. Other editorials have compared migratory birds to warheads, and called for the mass destruction of flocks of birds, as well as swathes of wetland habitat.

It is fair to say that wild birds have received a fairly raw deal in terms of media coverage, with many poorly informed writers accusing migratory species of being a huge threat in terms of their ability to transmit the virus around the globe. In fact, evidence is coming to light that the potential of wild birds as a vector is tiny in comparison to that posed by humans and their questionable animal husbandry practices.

Bird flu: the history

There were four flu pandemics in the 20th century, all of which are thought to have derived from bird flu. They include the notorious outbreak at the end of the First World War that is thought to have killed between 20-40 million people around the world in 1918-19 – more than the total casualties of the war itself. Bird flu, which is distinct from human flu, has 15 sub-types and nearly 150 different strains. Most lead to mild illness in birds but some can be fatal, particularly the H5 and H7 sub-types. It wasn’t realised that bird flu could be contracted by humans until a case was identified in Hong Kong in 1997. In humans the virus causes acute inflammation of the lung tissue, leading to life-threatening respiratory problems. Its affects on other parts of the body are unclear at present.

The deadly strain that is causing concern at the moment, known as H5N1, first appeared in South-East Asia in 2003. Poultry flocks in the region are often kept in crowded conditions and in close contact with people, making transmission to humans more likely. The virus is spread through contact with the saliva or faeces of an infected bird. Even dried infected faeces can transmit the virus. It is considered that there is no danger from eating chicken, assuming that the meat is properly cooked.

In the region the birds are frequently slaughtered in and around homes, putting a lot more people at risk than in countries where most poultry is killed at centralized slaughterhouses. In many parts of South-East Asia, huge flocks of domestic ducks are a common sight in paddyfields, where they are free to mingle with wild birds during the day, and then penned up with other poultry at night, while birds from different areas are brought to poultry markets, where the disease can be easily transmitted. So far all cases in the region have been traced to movements of poultry. As of 25 November 2005 there had been 132 cases the H5N1 strain of bird flu in humans and 68 deaths, including 42 in Vietnam, with the remainder in Cambodia, China, Indonesia and Thailand.

At present, there have been two cases of the virus possibly being transmitted from human to human – in Thailand and Vietnam – although this wasn’t in a form that could spark a pandemic. However, flu viruses are notorious for mutating. It might take something as simple as a person contracting H5N1 and a conventional human flu virus at the same time for the necessary mutation to occur that would allow the virus to adapt itself to easy human-to-human transmission. It is possible that the killer strains that caused the 20th century pandemics may have come together and mutated in pigs. As H5N1 spreads across the globe, the chances of a mutation that could lead to a pandemic are increasing all the time. There is currently no vaccine to protect specifically against H5N1, although existing drugs such as Tamiflu may help to treat the symptoms.

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The spread of H5N1

During 2005 global interest in H5N1 suddenly heightened when the virus made a huge jump across the world, appearing in Turkey, Romania and Croatia (and also in Britain in a quarantined consignment of birds which was imported from Taiwan). This led to proclamations that the virus must have been brought to the region by migratory birds. Some of the more ill informed and scaremongering headlines in the media included “Ducks of Death” in British newspaper The Sun, while a report on Middle Eastern Birdnet quoted from an article from the United Arab Emirates entitled: “No bird flu on our poultry farms." This feature in the Khaleej Times on Wednesday 26 October apparently stated: “A large number of people living along the Emirate’s seashore have called on the authorities to help them get rid of the migratory birds in the area,” referring to birds which gather on the Ras Al Khaimah (RAK) shores each winter. “UAE national Ahmed Rashid Al Mansowir called on the RAK Police Air Wing to extend help to rid the shores of the birds.”

Initially, there was panic in governments and the media about how the disease could have transferred halfway across the globe. The knee-jerk reaction was to blame wild migratory birds for the transmission.

A more likely cause

However, thinking logically for a moment, the flyway from Vietnam to the Black Sea is not a well-travelled one. The occasional wader or duck could conceivably make such a journey, but if they were infected with such a deadly virus it seems unlikely that they would be able to travel far or survive for long. Surely some other factor had to be at work?

The BirdLife International website states that “Within South-East Asia, movements of poultry and poultry products are known to have been involved in the virus’s spread among flocks and between countries. Outbreaks in China, Kazakhstan and southern Russia are connected by major road and rail routes. The outbreaks in Kazakhstan, Mongolia and Russia occurred in summer, when most wild birds would be moulting and not undertaking long migrations. The involvement of wild birds in these outbreaks thus seems highly unlikely. The source of recent outbreaks in Europe is not known, but movements of poultry and poultry products provide as plausible an explanation as transmission by wild birds.” An article by Nial Moores on the Birds Korea website goes so far as to rename the disease ‘poultry flu’ in an effort to disassociate wild birds from accusations that they could be a serious vector in the transmission of the virus.

There have been recorded cases of H5N1 affecting wild birds, with the most notable example being the death of a large number of Bar-headed Geese at Lake Qinghai in China, while closer to home Mute Swans in Croatia were found to have become infected.

In a scenario that sounds frighteningly familiar after the BSE crisis, it has emerged that dubious animal husbandry practices may once again have played a role and unwittingly helped to spread the disease. It transpires that fish farm procedures frequently involve feeding chicken faeces and other waste to fish. This resulted in the contamination of a river system with avian flu in Vietnam. The practice is also apparently widespread in Eastern Europe and this seems a much more likely cause of the infection of Mute Swans in Croatia with H5N1, rather than the virus being passed on by migratory birds. The same may be true with regard to the mass mortality of Bar-headed Geese in China.

What can be done?

Birders can help to play an important role, firstly through spreading the word that migratory birds are not the major factor in transmitting the disease – rather it is a virus that is spread primarily through poultry and suspect practices with regard to the human treatment of livestock. In addition, birders can remain vigilant while out in the field, in case of any suspicious mass deaths of birds.

Culling flocks of wild birds or draining wetlands to keep birds away are both measures that have been considered to deal with the spread on H5N1, and BirdLife International believes that neither would be effective at stopping the spread of the disease. On the contrary, if bird flu were present in wild bird populations, such measures would have the effect of stressing the birds and making them gather in larger concentrations – both of which would make them more prone to infection and spreading the disease. The World Health Organisation agrees that control of the disease in wild birds through culling is not feasible, and should not be attempted.

Organisations such as BirdLife International and the RSPCA recommend improving security measures for the transport and keeping of domestic livestock as an essential move, and stress that there is an urgent need for preventive measures against the disease, especially in places where poultry, wild birds and humans gather. The RSPCA commented: “One of the key lessons to be learned from the Foot and Mouth Disease crisis was the need for strict biosecurity measures on all premises with animals at risk from infection. This greatly reduces the risk of disease being spread. ”Another recommendation is for a ban on the import of domestic poultry and wild birds.

Can any good come from bird flu?

If there is one small silver lining to emerge from the bird flu episode, perhaps it will be an ending to the import and export of wild birds which helps sustain the cagebird trade. The EU has already put in place a temporary ban, which will stay in force until 31 January 2006 at least. However, David Bowles, the RSPCA’s Head of External Affairs, said: “Grounds for a permanent ban on the import of wild birds are now stronger than ever. The EU is the largest importer of wild-caught birds in the world, responsible for over 90 per cent of imports of threatened and endangered species. There is a very real threat of introducing bird flu into the EU through this trade.”

If the groups are successful in securing a ban on the trade in wild birds, it could be scant consolation if indeed the “Ducks of Death” come home to roost in the form of a major flu epidemic. If that is the case, you can rest assured that humans and poultry are much more likely to have made a significant contribution to the disaster than flocks of wild birds.

Further Information:

www.birdlife.org
www.birdskorea.org
www.defra.gov.uk
www.rspb.org.uk
www.rspca.org.uk