By Emily Gilbert
According to the United Nations Food and Agriculture Organization (FAO), there are alarming signs that a new mutant strain of the avian flu, or H5N1 Highly Pathogenic Avian Influenza, is spreading in Asia and beyond. H5N1 Highly Pathogenic Avian Influenza (HPAI) is a potentially devastating virus, associated with a high mortality rate and high economic losses. HPAI viruses can jump species barriers and infect humans, becoming a potential source of a future pandemic.
A chicken being vaccinated against the H5N1 virus (Photo credit: CRDF)
Although wild birds and small-scale poultry production have been blamed for the spread of avian flu, recent research conducted by Tour du Valat, a Mediterranean wetland conservation research center, has found that when the avian flu virus infects poultry, not wild bird species, it mutates into the highly pathogenic strains of the flu . These findings are supported by separate research on outbreaks in Nigeria and Thailand, which found that human agricultural activity and industrial poultry production, or factory farming, are major sources of the global spread of the avian flu.
After a 2002 bird flu outbreak in Chile, a study published in Emerging Infectious Diseases identified poultry as the primary species in which the more highly pathogenic strains evolved. A separate study produced in part by the Joint Influenza Research Centre at Hong Kong University found that, “transmission within poultry is the major mechanism for sustaining H5N1 virus endemicity in this region.” Interestingly, in the Southeast Asian countries where most of the bird flu outbreaks are concentrated, including Thailand, Laos, and Vietnam, poultry production grew eightfold over the last three decades, from around 300,000 metric tonnes of meat produced in 1971 to 2,440,000 metric tonnes in 2001. In China where the H5N1 virus has also spread, poultry production tripled during the 1990s, with 15 billion ducks, geese and chickens raised in 2004.
In the crowded conditions of factory farms, the low pathogenic influenza virus typically found in wild bird species, can evolve into a more pathogenic and highly transmissible form of the virus, capable of spreading to other species.
The research conducted by the Tour du Valat research center also found that outbreaks tend to be clustered around densely populated commercial hubs, rather than solely dependent on wild bird migratory routes, making the chances of human transmission greater. “When plotted, the pattern of outbreaks follows major road and rail routes, not flyways. And the absence of outbreaks in Africa, South and Southeast Asia and Australasia this autumn is hard to explain, if wild birds are the primary carriers,” says BirdLife‘ s Dr. Richard Thomas in 2006. This close proximity of large numbers of poultry in factory farms to congested urban centers has been the primary result of unregulated zoning and subsidies that encourage livestock production. According to Barcelona-based agriculture organization, GRAIN, of the 45 outbreaks that occurred in Laos in 2004, 42 of them occurred on factory farms, and 38 of them in the country’s capital.
While the H5N1 virus has been eradicated from the majority of infected countries, it has remained endemic in six nations, including China, Indonesia, India, and Thailand. But since 2008, the number of outbreaks has risen progressively, with almost 800 cases of H5N1 recorded in 2010-2011, twice as many as the year before, and confirmed cases appearing in previously unaffected countries such as Israel.
Finding ways to prevent the impacts of factory farming in the transmission of the avian flu will be especially important as urbanization and meat consumption increase across the developing world. In order to protect the global human and animal health, policy-makers will need to develop better, more holistic approaches, such increased international monitoring of both domestic and wild bird species and improved public awareness.
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Emily Gilbert is a research intern with the Nourishing the Planet project.