Factory farming implicated in emerging human diseases

October 22, 2007


Chickens raised for meat are crammed by the tens of thousands inside giant warehouses.

In August 2007, the World Health Organization (WHO) released its annual World Health Report. In the introduction, WHO Director-General Margaret Chan noted that when the WHO was founded around 60 years ago, the infectious disease situation was relatively stable, and new diseases were considered rare.

“Since then,” she writes, “profound changes have occurred in the way humanity inhabits the planet.” Now, the disease situation is “anything but stable.” In part because of “intensive farming practices, environmental degradation, and the misuse of antimicrobials,” she notes that new infectious diseases are now emerging at a rate unprecedented in the history of medicine—nearly 40 new diseases since the 1970s, approximately one new disease every year. During the last five years, the WHO has verified more than 1,100 epidemic events worldwide.(1)

The Price of Industrial Agribusiness


At the launch of the WHO report, Chan specifically singled out poultry production. “The intensity of poultry farming is such that we really need to look at how the human-animal interface is managed. It should not come as a surprise that we are seeing more and more disease outbreaks coming from the animal sector.”(2) Similarly, a research report released this summer by the Food and Agriculture Organization (FAO) of the United Nations suggests that the industrialization of animal agriculture in recent decades is increasing public health risks on a global scale.

Considered the greatest threat to global public heath is the possibility of an influenza pandemic triggered by a bird flu virus such as H5N1, the strain that has killed approximately 200 people and 200 million birds since its emergence a decade ago.

Breeding Grounds for Disease

In 1980, nearly all chickens in China were raised outdoors in small, traditional backyard flocks.(3) By 1997, though, the year H5N1 arose in Hong Kong, approximately half of the now 10 billion chickens(4) in China were intensively confined(5) in more than 60,000 industrial facilities, a few of which raised more than 10 million chickens at a time.(6) An article published by scientists in Vietnam and Thailand in the Annals of the New York Academy of Sciences explains why such facilities may be particularly risky:

The large concentration of animals farmed in overcrowded conditions in industrial batteries (several hundreds or even several thousands of individuals in a confined space), provides an extremely infectious context through contact with numerous pathogens, as opposed to natural extensive or semi-extensive breeding conditions….The numbers and density in which animals are bred result in overcrowded conditions, which, among other things, stress the animals, modify their metabolic performances, weaken their immune system, and above all maintain a high risk of hyperinfection by massive infectious loads….Where a small infectious dose would naturally be controlled by a normal immune system, there is no chance, even for an efficient immune system, of controlling huge infectious doses which “saturate” defense effector mechanisms and “overflow” the animals’ immune mechanisms….(7)

The scientists offer a potential solution:

Possible alternatives that would reduce the risks of contact could for instance include replacing large industrial units with several smaller-scale production units containing lower densities of animals. In other words, this means favoring product quality over industrial yield. There are many advantages to this: animals would be less stressed and thus more resistant to infectious aggressions; contact between individuals would be less intense, which would reduce infection rates since infectious doses would be lower.(8)

Stark Connections

An editorial in the September 2007 issue of the American Journal of Public Health goes a step further and questions the necessity of eating so many chickens in the first place. Noting the level of human suffering that “probably could have been avoided had humans treated animals better” caused by diseases that originated from animals such as AIDS, SARS, and mad cow disease, the editorial states:

It is curious, therefore, that changing the way humans treat animals—most basically, ceasing to eat them or, at the very least, radically limiting the quantity of them that are eaten—is largely off the radar as a significant preventive measure. Such a change, if sufficiently adopted or imposed, could still reduce the chances of the much-feared influenza epidemic. It would be even more likely to prevent unknown future diseases that, in the absence of this change, may result from farming animals intensively and from killing them for food. Yet humanity does not consider this option. Insofar as the focus is not on cures for the resultant diseases, attention is only given to lesser preventive measures.

The American Journal of Public Health editorial concludes:

Humans have suffered a great deal as a result of the mistreatment of animals…In any event, those humans who suffer are not just the ones responsible for animal mistreatment. Innocents are often adversely affected. When the (infected) chickens come home to roost, it may be another person, possibly from the next generation, who suffers or dies from avian influenza. Those who consume animals not only harm those animals and endanger themselves, but they also threaten the well-being of other humans who currently or will later inhabit the planet. To switch avian images, it is time for humans to remove their heads from the sand and recognize the risk to themselves that can arise from their maltreatment of other species.

The American Journal of Public Health is the official publication of the American Public Health Association (APHA)—the oldest, largest, and most diverse organization of public health professionals in the world. In 2003 the APHA passed a “Precautionary Moratorium on New Concentrated Animal Feed Operations” in which it urged all federal, state, and local authorities to impose an immediate moratorium on the building of new factory farms out of concern for the health of local communities given the land, air, and water pollution associated with these industrial facilities.(9) The dangers posed by these operations are greatly enhanced by the threat of the emergence of new human infectious diseases when animals are kept under such intensive conditions.

Further Reading

The FAO report “Industrial Livestock Production and Global Health Risks” is available at http://www.fao.org/ag/AGAinfo/projects/en/pplpi/docarc/rep-hpai_industrialisationrisks.pdf, and an earlier paper published this year that echoes much of this growing awareness, “The Potential Role of Concentrated Animal Feeding Operations in Infectious Disease Epidemics and Antibiotic Resistance,” can be downloaded at http://www.ehponline.org/members/2006/8837/8837.pdf.


1. World Health Organization. 2007. The World Health Report 2007. A Safer Future: Global Public Health Security in the 21st Century (Geneva: WHO). http://www.who.int/entity/whr/2007/whr07_en.pdf. Accessed August 31.

2. Deutsche Presse-Agentur. 2007. Poultry farming must be re-examined: WHO. http://www.eux.tv/article.aspx?articleId=13235. Accessed August 31.

3. Bingsheng K. 1998. Industrial livestock production, concentrate feed demand and natural resource requirements in China. (Beijing, China: China Agricultural University).

4. Food and Agriculture Organization of the United Nations. 2007. FAOSTAT. Rome, Italy.

5. Bingsheng K. 1998. Industrial livestock production, concentrate feed demand and natural resource requirements in China. (Beijing, China: China Agricultural University).

6. Simpson JR, Shi Y, Li O, Chen W, and Liu S. 1999. Pig, broiler and laying hen farm structure in China, 1996. Proposal to International Agro-Hydrology Research and Training Centre (IARTC) International Symposium, June 25-26.

7. Maillard J-C and Gonzalez J-P. 2006. Biodiversity and emerging diseases. Annals of the New York Academy of Sciences 1081(1):1-16.

8. Maillard J-C and Gonzalez J-P. 2006. Biodiversity and emerging diseases. Annals of the New York Academy of Sciences 1081(1):1-16.

9. American Public Health Association. 2003. Precautionary moratorium on new concentrated animal feed operations. Association News: 2003 Policy Statements. http://www.apha.org/advocacy/policy/policysearch/default.htm?id=1243. Accessed September 5, 2007.

Source: Humane Society US/September 17, 2007

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