Bird flu (avian influenza) factsheet
What is bird flu?
Bird flu is an infectious disease of birds caused by type A strains of the influenza virus. It was first discovered in Italy more than 100 years ago and there are now at least 144 different strains recognised worldwide (1). The disease can take two forms:
1) Low Pathogenic Avian Influenza (LPAI). Many LPAI strains circulate in wild birds at low levels, especially in waterfowl and gulls, but cause little or no illness (2).
2) Highly Pathogenic Avian Influenza (HPAI). Highly infectious strains cause many deaths in domestic poultry flocks but are very rare in wild birds (2).
(Pathogenic means disease forming.)
Once introduced to domestic poultry flocks, some low pathogenic forms (H5 and H7 strains) can mutate or change rapidly (within a few months) into highly pathogenic forms that are likely to cause disease (3). This is how the current highly pathogenic virus, H5N1, originated (3). In other words, a relatively harmless virus in wild birds infected farmed poultry and changed itself into a more deadly bug. This bug – H5N1 – was then transmitted back to wild birds and is highly deadly in them too (2). Without farmed poultry, H5N1 would most likely not exist.
Why does the virus mutate so rapidly in domestic poultry?
Farmed birds have been selectively bred for increased meat and egg production. This vastly increased physical demand weakens their immune system and increases their susceptibility to disease. The dramatic growth of farmed poultry production in recent decades has also led to increased density of flocks and subsequent close contact with faeces, allowing viruses to spread and mutate rapidly (2, 4).
How is bird flu spread?
The virus is both airborne and transmitted through infected faecal, nasal and eye discharges (4). The deadly (highly pathogenic) strains, such as H5N1, can survive for long periods in the environment, especially in low temperatures, eg over 30 days at 0°C (1). Disease can therefore spread locally from flock to flock through live poultry markets as well as contaminated farm equipment such as vehicles, cages, feed and clothing (4). Spread from region to region occurs through the international trade in live poultry and through infected migratory birds (2). H5N1 has so far been found in wild or domestic birds in Hong Kong, Japan, Vietnam, South Korea, China, Thailand, Laos, Taiwan, Burma, Cambodia, Malaysia, Indonesia, Mongolia, Russia, Kazakhstan, Croatia, Romania, Ukraine, Poland, Slovakia, Slovenia, Serbia, Bulgaria, Denmark, Sweden, Austria, Germany, Switzerland, France, Italy, Greece, Cyprus, Turkey, Israel, Jordon, Iraq, Iran, Afghanistan, Pakistan, India, Egypt, Niger, Nigeria, Burkina Faso and the UK (6).
Despite Defra and the poultry industry trying to blame the February
2007 outbreak of the deadliest H5N1 strain (at an intensive Bernard
Matthews turkey unit in Suffolk) on migratory wild birds, the
migratory season did not start for another couple of months. The
likely cause of the outbreak is from elsewhere.
Many of the SE Asian countries affected by H5N1 are major poultry exporters, with China and Thailand accounting for 15 per cent of global poultry shipments (4). In 2002 the EU imported 175,000 tonnes of poultry from these two countries (4). The UK continues to import up to 200 million chickens a year from many ‘approved’ countries, despite the onward march of the H5N1 virus (13).
So birds raised in intensive sheds are safe from the disease?
No. Dr Perry Kendall, chief medical officer for British Columbia, Canada, said that the province's H7N3 bird flu outbreak in 2004 showed the chickens kept indoors were more vulnerable than those kept outside: “The intensely farmed birds tend to be very genetically similar. The methods of farming result in them being actually more frail and more vulnerable to diseases, particularly since there are so many of them in such a small volume of space (11).” He added, “Penning chickens indoors won't necessarily shelter them from avian flu viruses. Farm staff can tramp virus-laced bird droppings into a chicken house on their boots. Tractors can move viruses from farm to farm. Indoor poultry operations only keep birds safe from disease if stringent biosecurity standards are maintained (12).”
Experience has shown that stringent biosecurity measures are in fact rarely taken on most UK poultry farms so the risk of indoor birds becoming infected is the same as outdoor birds, but once an intensive flock is infected the disease will spread more quickly and kill a much higher proportion.
What is the risk to human health?
The first documented infection of humans with bird flu occurred in Hong Kong in 1997, when H5N1 caused severe respiratory disease in 18 people, killing six of them. Studies showed that those infected had close contact with live infected poultry and that the virus had jumped directly from the birds to humans (1). Rapid destruction, within three days, of Hong Kong’s entire poultry population stemmed the spread of the outbreak (1).
In January 2004 the second human outbreak of the disease occurred, with 11 people in Vietnam and Thailand infected – eight fatally. A total of 161 human cases have now been recorded, with 80 fatalities, in six countries: Cambodia; China; Indonesia, Thailand; Vietnam and Turkey (6). It is believed that all of these cases were caused through contact with infected domestic poultry or contaminated farm equipment. There have been no recorded transmissions of the disease from infected wild birds to humans (2).
Is it safe to eat poultry meat and eggs?
The bird flu virus can survive for long periods in body tissue and can also be found inside and on the surface of eggs laid by infected birds (5). Consumption of any raw poultry products, including meat, blood and eggs, from infected birds are therefore a potential risk (1). As the virus is heat sensitive, being inactivated by a temperature of 60°C in 30 minutes, well-cooked poultry meat and eggs should theoretically be free of the virus (1). However, millions of people in the UK fall ill every year from Salmonella and Campylobacter poisoning caused by undercooked poultry, demonstrating how often people do not ensure that meat is thoroughly cooked. Blood and body juices from raw infected poultry can also cross-contaminate other foods via chopping boards, knives and kitchen surfaces (1).
While imports of poultry products from all countries known to be infected with the H5N1 virus are currently suspended, the EU may still be importing poultry products from countries where the disease is present in bird flocks but has not yet been detected because there have been no human infections so far. The safest option is simply to avoid all poultry products, including eggs.
An animal welfare catastrophe
Since 2003, over 150 million birds have been killed in the fight to contain bird flu outbreaks in domestic flocks (6). While all of these animals were destined to be killed for meat (as even chickens kept for eggs are eventually killed for ‘low grade’ meat), the panic sparked by human deaths from catching the disease meant that many of these birds endured a more painful and prolonged death than they would have met in the slaughterhouse. Indeed, disturbing images of birds being violently handled by untrained or inexperienced people and buried or bagged alive have been broadcast from every region where outbreaks of H5N1 have occurred.
These practices contravene the World Organisation for Animal Health (OIE)’s guidelines on Humane Killing for Disease Control which require humane methods of killing to protect the animals from pain and distress. Animals should be killed instantly or stunned prior to being killed and remain unconscious until death. Professional veterinarians are required to oversee animal welfare aspects of the disease management plans and all staff must be trained and competent in humane slaughter, with appropriate equipment available (7).
Viva! is disgusted by the callous treatment of these sentient
creatures and calls on all governments to provide sufficient resources
and skilled personnel to ensure that avian influenza outbreaks are
managed swiftly, efficiently and humanely.
Another major animal welfare concern is the potential incarceration of free-range poultry flocks in Britain and other European countries. Britain’s Chief Vet, Debbie Reynolds, warned that if a case of H5N1 was found in Britain, all poultry keepers would be required to move their birds indoors (9).
In the February 2007 outbreak, all free-range birds were ordered
indoors within a 3km-10km restriction zone. These birds, who are used to relatively pleasant and natural life outdoors,
are forced to endure the overcrowded, stinking and unnatural conditions of a typical intensive poultry unit. There is
even a chance that farmers will still be able to market these birds as free-range, a devious move intended to mislead compassionate consumers (9).
Bird flu is just the latest in a long line of diseases caused by animal farming, including BSE, swine fever and foot and mouth disease. In addition to these high profile diseases, over 5 million people in the UK suffer from food poisoning every year, and many are killed, with over 95 per cent of cases caused by meat, dairy products and eggs (10). Of course animal products have also been conclusively linked to Britain’s three major killers – heart disease, stroke and many forms of cancer. It’s time we stopped this insanity and put an end to the animal, human and environmental damage caused by our meat addiction – It’s time to go veggie!!
- (2004) World Health Organisation. Factsheet: Avian influenza (“bird flu”) and the significance of its transmission to humans. Available from: www.who.int/mediacentre/factsheets/avian_influenza/en
- (2005) Royal Society for the Protection of Birds. Avian influenza factsheet. Available from:
- (2005) World Health Organisation. Avian influenza frequently asked questions. Available from: www.who.int/csr/disease/avian_influenza/avian_faqs/en
- (2005) United Nations Food and Agriculture Organisation. Avian influenza questions and answers. Available from www.fao.org/ag/againfo/subject/en/health/diseases-card/avian_qa.html
- (2004) McMullin, P. A Pocket Guide to Poultry Health and Disease. 5M Enterprises Ltd, Sheffield.
- (2006) BBC News On-line. Global impact of bird flu. Available from: www.news.bbc.co.uk/1/hi/health/4531500.stm
- (2005) Compassion In World Farming. Factsheet: Avian ‘flu concerns’. Available from: http://www.ciwf.org/campaigns/hot_topics/AvFlufactsheet.pdf
- (2005) DEFRA. Agriculture in the UK 2004. The Stationary Office.
- (2005) Allison, R. ‘Be ready to move birds indoors’. Poultry World, December 2005.
- (2000) Food Standards Agency. Press release: Food Standards Agency welcomes Consumer
Association campaign to cut food poisoning, 6th September 2000.
- (2005) Canadian Press, 24th August 2005.
- (2005) Emerging Infections Network (EINet). Available from: http://depts.washington.edu/einet/?a=printArticle&print=748
- (2006) Factory farms in Asia blamed for pandemic. The Independent, April 8th 2006.