Animal Agriculture and Human Health

The new laboratories for deadly viruses

Book Chapter In:  Castle S, Goodman A-L (eds). Rethink Food 2014.

Chapter 4. Foul Farms: The State of Animal Agriculture

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.’

Chapter 5. Animal Agriculture: Our Health and Our Environment

Even if we could, no matter how unlikely, contain the pathogens running amok among factory farms, we are still faced with a much larger problem. This is because there are just too many animals being produced for food: animals grown for meat and dairy products account for 20 per cent of the world’s terrestrial animal biomass. To sustain this massive production requires unprecedented quantities of water, energy, land, pesticides and feed crops (crops fed to farmed animals). In exchange for all these depleted resources, we get polluted water, air and land, and perhaps one of the most significant climate transformations in human history.

In September 1999, Hurricane Floyd hit the eastern part of North Carolina, acting as a catalyst for the environmental disaster that followed. As many as 50 animal waste lagoons, some of them several acres in size, filled with floodwaters and overflowed. This manure flowed into the surrounding wetlands and groundwater aquifers, resulting in massive contamination and pollution of drinking water. In addition to multi-antibiotic-resistant fecal bacteria and antibiotics, excess levels of nitrogen nutrients were discovered in the groundwater near some of the farms following the flooding. North Carolina is the second largest pig producer in the USA; pig production in that state alone exploded in the 1990s, growing from 2.6 million pigs in 1988 to almost 10 million today, most of them confined to factory farms. The aftermath of Hurricane Floyd highlighted the disturbing environmental implications of industrial animal agriculture.

In the USA, animal agriculture is responsible for 32 and 33 per cent, respectively, of the nitrogen and phosphorus loads found in freshwater sources. The problem with these nutrients is that, like manure, there are too much of them. The application of manure to cropland and leakage from manure lagoons cause nitrogen, phosphorus and other nutrients to run off agricultural land and into waterways. Excess nutrient loading of waterways causes eutrophication, or overfertilization, leading to loss of oxygen, algal blooms and massive die-offs of fish and other animal populations. Most marine algae are harmless. However, the growth of several toxic species of algae is boosted by nutrient supersaturation. These species produce potent neurotoxins that can be transferred through the food web, where they adversely affect and kill fish, birds, marine mammals and humans that either directly come in contact with or consume them.

One harmful species, Pfiesteria, is believed to be the cause of massive fish kills along the eastern shore of the USA. It produces a potent neurotoxin and an epidermal toxin that have been linked to significant neurological illness and skin lesions in humans. Additionally, nitrogen in manure and liquid waste can contaminate drinking water. These nitrates, which are associated with human health risks, have been identified by the US Environmental Protection Agency (EPA) as the most widespread agricultural contaminant in drinking water wells. Elevated nitrate levels in water can cause severe methemoglobinemia (‘blue baby syndrome’), particularly in infants. This is a frequently fatal condition in which the blood has a reduced capacity to carry oxygen.

Excess nitrates and eutrophication render water unfit for drinking. Compounding the eutrophication of our waterways, animal agriculture also consumes 70 per cent of the freshwater supply and is among the most damaging industries to the earth’s increasingly scarce water resources, contributing significantly to water pollution. According to the EPA, agriculture, is ‘the leading contributor to identified water quality impairments in the nation’s rivers and streams, lakes, ponds, and reservoirs’. In excess of 129,000 miles of streams and rivers and more than 3.2 million acres of lakes have been impaired as a result of agriculture, a significant part due to animal waste and factory farms. The primary pollutants associated with animal waste are nutrients (particularly nitrogen and phosphorus), organic matter, solids and odorous/volatile compounds.

Animal waste also contains pesticides, hormones and, of course, pathogens and antibacterials. Pollutants in animal waste can impact water supplies through several possible pathways, including surface runoff, erosion, spills, direct discharge to surface waters and leaching into soil and groundwater. Atmospheric transport is another major pathway by which nitrogen and other pollutants are deposited back to the land and waterways. More than 80 per cent of ammonia emissions in Europe are generated by animal agriculture. Factory farm waste emits a number of pollutants of concern to human health, including heavy metals, volatile gases, methane, nitrous oxide and hydrogen sulphide.

Why our health depends on treating animals better

An international group of scientists recently ended a year-long moratorium on controversial research on potentially deadly strains of the H5N1 avian flu virus. The purpose of the research was to engineer strains of H5N1 in order to understand how it might gain the ability to spread easily among people.

Regardless of whether or not this research continues, you can bet one thing: Our risk for a deadly form of the “bird flu” virus and other pathogens remain high as long as we don’t improve our treatment of animals.

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How protecting animals benefits us, too

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However, not only is this notion that we must either protect animals or humans not true, in fact, the opposite is true. The human plight is inextricably tied with that of other animals.

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We are not safe from bird flu as long as factory farms exist

CNN reports that Cambodia is seeing a spike in the number of deaths due to the H5N1 strain of bird flu. In a related case, Mexico recently slaughtered more than 1 million chickens infected with the H7N3 strain of bird flu. Despite the increase in bird flu in Cambodia, H5N1 is currently not very contagious among humans (most people who contracted the virus were in direct contact with sick farmed animals), and H7N3 is not known to cause harm to humans.
In spite of our current low risk, it is just a matter of time before H5N1, H7N3 or another influenza strain evolves into a dangerous form that results in a pandemic. And the events in Mexico and Cambodia beg the question: Are we ever going to be safe from bird flu?

As long as we continue to treat animals raised for food poorly, the answer is a definite “no.”

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