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Photo Courtesy of the Animal Welfare Institute

Last Thursday the World Health Organization declared the first flu pandemic in 41 years, after swine flu (H1N1) was found in 74 countries, infecting nearly 29,000 people so far. Even with the use of modern antiviral drugs where they are available, a severe flu pandemic could kill over 100 million people. The WHO statement said nothing about the current epidemic's underlying causes, which are undeniably complex. But what is clear is that the danger of such pandemics has been exacerbated by the industrialization of animal farming.

The first known victim of the current swine flu outbreak was a young boy in Vera Cruz, Mexico living near an industrial hog operation. The massive 56,000-sow facility is a subsidiary of Smithfield Foods, the US-based meat company. Local residents, who say they've suffered from rampant respiratory ailments for years, believe that the flu virus originated at the Smithfield facility, which continually ventilates its air to the community and stores hundreds of millions of gallons of liquefied pig manure. There has been no definitive evidence of that link, however, and pork trade associations vociferously assert that there is neither a connection to the Smithfield operation nor to hog production generally.

But whether or not a direct link to the Smithfield facility is ever established, this pandemic reminds us that the current method of raising farm animals is fraught with risks to human health. In 1998, a virus that combined strains of human, swine, and bird flu was discovered in pigs at industrial operations in North Carolina. It rapidly mutated, or "reassorted," as it moved from pig to pig and from herd to herd. Within months, the hybrid virus was showing up in hog operations throughout the United States.

Intensive farming systems make industrial poultry and swine operations into breeding grounds for a host of perilous diseases.

By early 1999, blood samples of pigs from 23 states showed that 20.5 percent had been exposed, according to Dr. Michael Greger, author of the book Bird Flu. "It is from this pool of viruses," Greger writes, "that the current swine flu threat derives three-quarters of its genetic material." Dr. Robert Webster, a leading flu expert and a director of the WHO Collaborating Center for Studies on the Ecology of Influenza in Animals and Birds, says that this "triple reassortment virus" is the likely precursor to the swine flu that is now sweeping the globe.

Pigs in the United States have become "an increasingly important reservoir of viruses with human pandemic potential," according to Dr. Richard Webby, also a director of the WHO Collaborating Center. One in five US pig workers now shows antibodies to H1N1, showing they have been exposed to the virus.

This is to be expected. My husband and I, as livestock ranchers ourselves and advocates of reform in industrial farming, have visited dozens of industrial animal operations. We've seen commercial swine operations with tens of thousands or even hundreds of thousands of pigs. And we've visited chicken operations with hundreds of thousands or millions of birds. These are typical operations. Extreme crowding and barren surroundings stress the animals, rendering them effective disease vehicles and making their environments conducive to the formation of new diseases. Lack of genetic diversity within flocks and herds renders them more susceptible to illnesses. Large populations of flies and insects aid in disease transmission.

"Industrial farm animal production facilities that house large numbers of animals in very close quarters can be a source of new or more infectious agents," the Pew Commission on Industrial Animal Production warned in April 2008. Ellen Silbergeld, professor at Johns Hopkins School of Public Health, says of industrial animal operations, "For many years, there's been a great deal of concern about their potential contribution to the evolution and spread of newly emerging diseases."

Dr. Silbergeld identifies three primary factors: crowding, ventilation systems that spread pathogens to the surrounding environment, and massive volumes of manure. It is "astounding," she says, that there are no requirements for any waste treatment applied to these huge animal operations--as, of course, there are for human sewage.

Additionally, global shipping of animals and travel of workers foster the rapid spread of diseases over large areas. An Alberta, Canada hog operation worker who vacationed in Mexico carried the current swine flu virus back with him, infecting pigs where he worked. The entire herd of 3,000 was killed as a result.

Like swine flu, avian flu (H5N1) lurks as a serious public health menace, and can likely also be traced to industrial animal-raising practices. As with swine production, the poultry industry was industrialized over the twentieth century and experienced a dramatic rise in disease problems. Until the 1920s, chickens were raised in small flocks numbering in the dozens, with birds that spent much of their time roaming outdoors. When farmers first began scaling up their flocks and putting their fowl in buildings in the 1920s, typical death losses quadrupled, jumping from 5 to 20 percent.

The poultry industry and even public health officials have often blamed the threat of avian flu on backyard poultry flocks and wild migratory fowl. But editors of the leading medical journal The Lancet wrote in 2006 that "despite extensive testing of wild birds for the disease, scientists have only rarely identified live birds carrying bird flu in a highly pathogenic form." The Lancet editorial went on to point out that rather than arising backyard flocks and wild fowl, the avian flu threat can primarily be traced to the growth of a large, highly concentrated poultry industry: "The geographic spread of the disease does not correlate to migratory [bird] routes and seasons. The pattern of outbreaks follows major road and rail routes, not flyways." A report entitled Fowl Play: The Poultry Industry's Central Role in the Bird Flu Crisis, likewise concluded, "The deadly H5N1 strain of bird flu is essentially a problem of industrial poultry practices." In Southeast Asia, where most bird flu outbreaks have occurred, poultry production has increased eightfold over the past three decades. Ironically, there is even evidence that the occasional wild birds that have contracted H5N1 flu got it from Asia's poultry confinement industry, which commonly dumps its manure into fish farms as feed.

In short, intensive farming systems--with crowded animals, ventilation systems, and huge collections of manure--make industrial poultry and swine operations into breeding grounds for a host of perilous diseases. For that reason, since 2003 the American Public Health Association has called for a moratorium on these facilities.

On our own farm in Marin County, California, we raise cattle, heritage breed turkeys, and goats. We believe that healthy living conditions lead to healthy animals. All of our animals spend most or all of their time (depending on the species) on pastures. All of them have plenty of room to roam and none of them are caged in cramped conditions. Their daily routines include breathing fresh air, exercising, and soaking in the sun's rays. There's little stress and plenty of opportunities for enjoyment. In the six years I've lived here, I can count on one hand the animals that have been sick enough to require medication.

Of course, flu epidemics and pandemics predate the era of industrial animal production. But given the potentially extreme danger posed by this or a future flu pandemic, efforts should be made to address all contributing factors--including industrial animal operations. As part of its efforts to mitigate the risk of a catastrophic flu pandemic, Congress should adopt a national moratorium on industrial animal operations. And it should simultaneously pursue policies that will support smaller-scale, regionalized food systems with healthy, uncrowded, pasture-based animal farming.