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What is perceived as one of the greatest potential threats to human health has spurred the World Health Organisation (WHO) and health services everywhere into action, stockpiling vaccines that may not work and preparing for mass sickness and death on a devastating scale. Bird flu – avian influenza – is the reason. This threat, either real or imagined, joins other existing and future novel diseases which will inevitably develop and infect humans. It is another gift from intensive livestock production.
Bird flu is an infectious disease of birds caused by type A strains of the influenza virus. Discovered more than 100 years ago, there are now at least 144 different strains worldwide. Some circulate in wild birds and cause little or no illness while others are highly infectious, causing many deaths in domestic poultry but are rare in wild birds (WHO, 2004).
Once introduced to domestic poultry flocks, some low pathogenic (disease causing) forms (H5 and H7 strains) can mutate or change within a few months into highly pathogenic forms and this is how the current H5N1 virus originated (WHOa, 2005). 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 (RSPB, 2005). Without farmed poultry, H5N1 would most likely not exist.
Farmed birds have been selectively bred for increased meat and egg production at the expense of weakened immune systems and an increased susceptibility to disease. The dramatic growth of farmed poultry over recent years has inevitably led to intensive production worldwide, allowing viruses to spread and mutate rapidly.
The virus is both airborne and transmitted through infected fecal, nasal and eye discharges (UN FAOc, 2005). The deadly H5N1 strain can survive for long periods in the environment, especially in low temperatures - 30 days at 0°C (WHO, 2004). This allows the disease to spread from flock to flock through live poultry markets and contaminated farm equipment and from region to region through the international trade in live poultry and through infected migratory birds (RSPB, 2005).
The 2007 outbreak of bird flu at a Bernard Matthews’ turkey farm in Suffolk following a similar outbreak at Bernard Matthews’s plant in Hungary, seems to illustrate this. The fact that the government chose not to make this connection caused incredulity and is another indication of its special relationship with livestock farmers.
H5N1 has so far been found in wild or domestic birds in a large number of countries, many of which are major poultry exporters (BBC News, 2006), with China and Thailand accounting for 15 per cent of global poultry shipments. In 2002, the EU imported 175,000 tonnes of poultry from these two countries (UN FAOc, 2005) and the UK continues to import up to 200 million chickens a year, despite the onward march of the H5N1 virus (Independent, 2006).
Dr Perry Kendall, chief medical officer for British Columbia, Canada, said that the province's bird flu outbreak in 2004 showed that 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.” 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 (Canadian Press, 2005). Tractors can move viruses from farm to farm. Indoor poultry operations only keep birds safe from disease if stringent biosecurity standards are maintained.” Experience has shown that stringent biosecurity measures are rarely taken on poultry farms (EINet, 2005).
The current situation is that humans have caught H5N1 bird flu directly from poultry but there has been no proved transmission from human to human. That will require a further mutation of the virus, which most scientists believe is only a question of time. It follows that the more frequently people are subjected to the existing virus, the greater its opportunities to mutate.
Bird flu virus can survive for long periods in body tissue and inside and on the surface of eggs laid by infected birds (McMullin, 2004). Consumption of any raw poultry products, including meat, blood and eggs, from infected birds are therefore a potential risk. 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 (WHO, 2004). However, the same applies to Salmonella and Campylobacter food poisoning bacteria and yet millions of people in the UK are infected by them every year from handling and eating poultry.
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