As disturbing as the wildlife trade is in fostering the development of new infectious diseases, recent events suggest that the biggest and most imminent threat may lie much closer to home. Between 2007 and 2008, farmers in the Philippines noticed that pigs were falling sick and dying by the hundreds for unknown reasons. A subsequent investigation confirmed the presence of porcine reproductive and respiratory disease syndrome, a serious illness among pigs. But, much to the surprise of the investigators, a subtype of Ebola virus, Ebola Reston, was also discovered circulating in a sample of the pigs. This was the first time Ebola of any strain had been found in these animals. ‘We never thought that pigs could be infected’, says Pierre Rollin, an Ebola expert at the Centers for Disease Control and Prevention (CDC).Rollin believes that Ebola Reston is to blame for the pigs’ deaths because tissue studies revealed that the virus had pervaded the spleen, similar to its mode of attack in monkeys.
Ebola Reston is named after the strain that was discovered in monkeys shipped to laboratories in the USA from the Philippines on several occasions between 1989 and 1996. The first shipment of Ebola virus was discovered after hundreds of monkeys became severely ill or died in a quarantine facility owned by Hazleton Laboratories (now Covance, Inc.) in Reston, Virginia. Because this was the first confirmed instance of Ebola entering the USA, a panic swept across American health agencies. All remaining monkeys at the facility were euthanized and the building was eventually demolished. Although evidence revealed that humans were also infected, Ebola Reston proved to cause at worst only a mild flu-like illness in humans, unlike all other known strains of the virus. Thus, Ebola Reston, although deadly in monkeys, was deemed only a minor threat to us. However, new fears are rising since Ebola Reston was discovered in pigs.
The industrialization and mass production of animals for food is now among the biggest contributing factors to emerging infectious diseases over the past few decades. Pigs and other animals raised for food are critical sources of zoonotic pathogens that threaten human health and have been directly implicated in the emergence of the H5Nl avian influenza virus, the 2009 H1N1 ‘swine flu’ pandemic virus, the rise in foodborne infectious diseases, and other significant infectious pathogens and diseases. To understand how and why animal agriculture fosters the emergence of new pathogens, it helps to get a glimpse of the experiences of animals raised on modern ‘farms.’
Humans are consuming more animals than ever before. Once viewed as a luxury, meat is now becoming a dietary staple for many due to a worldwide growth in urbanized populations and affluence. Today, more than 64 billion animals are raised and killed for food worldwide annually. That means that more than nine farmed animals exist for every human at any one time. China and the USA are among the largest farmed animal producers in the world. In the USA alone, an excess of 9 billion land animals are slaughtered annually for food, approximately 1 million per hour. On average, each American eats the equivalent of 21,000 animals in his/her lifetime. And, global meat production is expected to double by 2020. Consequently, over the last half-century, a dramatic shift has taken place in the animal agriculture industry that may represent the most profound change in the relationship between humans and animals since animals were first domesticated.
In the name of efficiency, the industry has chosen to sacrifice the space and well-being of animals. Traditional farming practices in which animals were permitted to roam outdoors prior to slaughter have largely been replaced by immense, intensive animal operations. These concentrated animal-feeding operations (CAFOs) or factory farms changed the status of animals like nothing had before. The industrialized methods of raising animals for food have spread throughout much of the world. The result is that traditional farms in developing nations are being replaced at a rate of more than 4 per cent a year. The independent family farm is rapidly becoming a thing of the past. Today, most animals raised for food are produced by a few immense agribusiness corporations that intensively confine animals by the hundreds or thousands in consolidated operations. This demand-driven transformation of animal agriculture is so dramatic that it has been dubbed the ‘Livestock Revolution.’