Preventing avian flu: Bigger isn’t always better

But several NGOs, including the Humane Society of the United States and GRAIN, have disputed this claim, claiming that the filthy and extremely crowded conditions of factory farms--some poultry farms house more than 300,000 birds--provide the perfect environment for the spread of disease among birds and humans. And now the UN Food and Agriculture Organization (FAO) has issued a report pointing to “evidence that bioexclusion measures of (at least some) large-scale industrial poultry operations are not impenetrable by influenza A viruses.” In other words, bigger doesn’t necessarily mean better protection from the spread of disease.

Although most poultry CAFOs (Confined Animal Feeding Operations) implement biosecurity measures, such as requiring employees to wear masks, walk through chemical baths, and shower before handling birds, these are not always effective at preventing disease. For one thing, according to the report, “the design and operational requirements of large-scale poultry and swine houses...result in compromises of biosecurity.” These facilities, for example, are typically ventilated with high-volume fans “that result in considerable movement of materials into the external environment, and dust emissions...can be substantial.” The FAO also reports that aerosol emissions from a broiler (chicken meat) operation revealed “a millionfold elevated concentration of aerosolized invisible dust near a poultry barn fan as compared to outdoor air in a semi-rural area.” These particles, according to the study, “have the potential to remain suspended in the air for up to several days, and, depending on prevailing winds, poultry barn dust could be found several kilometers from its source.”

The high numbers of insects present at many factory farms can also spread disease. A study in Denmark found that as many as 30,000 flies can enter a broiler farm during just one flock rotation in the summer. And research in Kyoto, Japan, in 2004 found that flies caught near broiler operations where an avian flu outbreak took place “carried the same strains of H5N1 influenza virus as found in chickens of an infected poultry farm."

A third pathway for spreading disease is the transport of live birds and poultry products from place to place in trucks and shipping containers or on boots or clothing. Just one gram of infected bird feces can contain 10 billion infectious virus particles. Meanwhile, the huge concentration of CAFOs and CAFO workers in certain areas creates further opportunities for the disease to spread. According to the FAO report, when CAFO workers make up more than 15 percent of a community, they may act as avian flu amplifiers for the community as a whole.

Small and medium-sized farms, on the other hand, can often prevent diseases among poultry and other animals more efficiently. Such farms usually have more genetically diverse flocks and herds that are less stressed and better adapted to climate and disease.