The situation of nonhuman animals living on land farms makes them very susceptible to a number of diseases. In addition, the crowded conditions facilitate the spread of these diseases to the point they can become massive epidemics.
Furthermore, animals commonly suffer from a wide range of debilitating conditions, as the section on diseases in the wild explains. In the wild, this makes them more susceptible to being killed by other animals. Animals living in farms face the danger of being killed by humans for being sick or potentially sick, even sooner than they would have been killed if they had remained relatively healthy.
The following is a sampling of the major diseases mammals and birds raised in farms suffer. These diseases have not only caused great harm to the infected animals, but have also triggered mass slaughters of enormous numbers of animals in order for humans to avoid economic losses from their spread.
After sea animals, the animals who are exploited by humans in the highest numbers are chickens. Avian influenza has resulted in international pandemics affecting birds and other animals, including humans. Avian influenza, also called avian flu or bird flu, is a highly infectious disease caused by a flu virus. It is transmitted between birds and occasionally to other animals, including humans. It causes high levels of mortality among birds, who, after an incubation process of a couple of days, may die in a matter of three to five days. In humans, symptoms can be confused with those of a normal flu, although the most severe cases can cause respiratory problems and pneumonia.
There have been epidemics caused by different strains of this virus. The most feared is the H5N1 strain, which has been considered the most dangerous for human populations. Due to the fear of transmission of this disease to human beings, and in order to avoid financial cost to the poultry industry, massive bird killings have been carried out in several countries.
During the 2000s, millions of healthy birds were exterminated due to their potential for transmitting avian flu. Between 2003 and 2006 alone, more than 200 million chickens, geese and ducks were killed in Asia, Africa, Europe and the Middle East.1 Among other cases, the following deserve to be mentioned:
The most common methods of killing animals vary significantly depending on the country and the number of animals to be killed. Animals may be gassed, electrocuted, beaten and clubbed, burned alive (commonly by throwing them into large fires), buried alive (in plastic bags or under a layer of fire-fighting foam), or ground up alive in macerating machines or in wood chipping machines (in which they are thrown alive and fully conscious into machines designed for turning wood into chippings).4
All of these animals, whether they are actually sick, suspected of being sick, or susceptible to sickness, are considered by the industry to be hazardous waste. As such, it is deemed necessary to kill and dispose of them as soon as possible. Due to this, and also because the number of animals is typically substantial, the workers in charge of killing them will usually work as fast as possible and kill them by using the least expensive method, without taking into account the suffering they cause to animals. Nonhuman animals raised for food are considered commodities, and when these commodities stop being profitable to those who exploit them, they are often exterminated without their wellbeing being taken into account.
Bovine spongiform encephalopathy is a degenerative disease of bovine nervous systems that is caused by the presence of infectious proteins (prions). It mostly affects cows but can also be transmitted to human beings. It was first discovered in the UK in November 1986. The incubation period of this disease is a rather long one (about 4-5 years on average, but possibly much longer). This disease causes the progressive degeneration of the nervous system, with sufferers displaying, among other symptoms, a clumsy coordination of their movements. Eventually individuals who are infected with it die from it.5
Until 1994, 146,895 cases of animals with BSE were detected in the European Union, and from 1995 to 2007, 189,875 more cases were detected.
Several possible causes for the diseases were initially considered. The one most accepted by the scientific community is that it was caused by the consumption of food made out of powdered meat and bones of animals killed in various circumstances, including some who had been suffering from degenerative nerve diseases (for instance, sheeps with scrapie).
The eradication of the disease requires the elimination of animal proteins from the food given to herbivores. From December 2000 to June 2001, out of fear of an epidemic, the European Union temporarily banned the feeding of processed animal proteins to any animal destined to be killed for human consumption. This included a ban on powdered flesh, bones, hooves, horns, feathers, and any foodstuff made with products coming from blood and plasma, with some exceptions such as fish flour (powdered fishes) being fed to non-ruminant animals.
Another approved measure was that any animal either infected or suspected of being infected should be killed and their body incinerated immediately.
As a precautionary measure, in many farms all of the animals were killed, even if there was only one sick animal or there was just a mere suspicion that one of them was suffering from the disease. In Great Britain alone, 4.4 million bovine animals were killed for this reason during the peak of the so-called “mad cow disease” outbreak.6
Foot and mouth disease is a very contagious condition caused by a virus that affects pigs, cows, sheeps and goats. It does not usually affect humans except in some extraordinary cases where those infected have been in very close contact with the virus.
It causes high fever during the first two or three days, after which very painful blisters appear both in the mouth mucoses and in the feet of the animals. It causes many sufferers to experience a loss of appetite that can consequently cause them to lose weight and produce less milk. In most cases, this disease is not lethal and there are vaccines to protect against it.
During the last few years, several foot and mouth disease outbreaks have occurred, which have resulted in the deaths of millions of animals. The large number of deaths has occurred not because of the deadliness of the disease, but rather because of the precautionary measures implemented in different countries, which have included killing healthy animals. The reason for many of those deaths was not to prevent other animals from dying from the disease, but to stop the reduced productivity of the animals who could get infected. A few noteworthy cases are listed below.
In addition, more than 100,000 cows and bulls were slaughtered due to the same issue in Korea and Japan.10
Another disease that has affected significant numbers of animals, therefore causing them to be slaughtered, is Swine Vesicular Disease (SVD). This disease is caused by the Swine Vesicular Disease Virus and can cause those infected to suffer painful ulcers in several parts of their bodies, including in their mouths and on their feet.11
Other diseases animals regularly suffer from if they are living in farm situations include the following:
|Acariasis||Avian Mycoplasmosis||Blue Eye Disease|
|Bovine Viral Diarrhoea||Brucellosis||Campylobacteriosis|
|Cryptococcosis||Dermatophytosis||Epizootic Hematopoietic Necrosis|
|Epizootic Lymphangitis||Hemorrhagic Septicemia||Leptospirosis|
|Mastitis||Mycobacteriosis||Porcine Epidemic Diarrhea|
|Porcine Reproductive Respiratory Syndrome (PRRS)||Salmonella Screwworm Myiasis||Sheep and Goat Pox|
|Viral Hemorrhagic Fever (caused by Arenavirus and by Filovirus)||Viral Hemorrhagic Septicemia||West Nile Virus|
AVIS (2000) “OIE health disease cards”, fao.org [accessed on 25 March 2013].
Bengis, R. G.; Kock, R. A. & Fischer, J. (2002) “Infectious animal diseases: The wildlife/livestock interface”, Revue Scientifique et Technique, 21 (1), pp. 53-65.
The Center for Food Security and Public Health & Iowa State University of Science and Technology (2004-2013) “Animal disease information”, cfsph.iastate.edu [accessed on 20 March 2013].
Committee on Foreign Animal Diseases of the United States Animal Health Association (2008) Foreign animal diseases: The gray book, 7th ed., St. Joseph: United States Animal Health Association.
Craig, R. A. (1919) Common diseases of farm animals, Philadelphia & London: J. B. Lippincott.
Food and Agricultural Organization of the United Nations & Agriculture and Consumer Protection Department (2013) “Animal production and animal health”, fao.org [accessed on 23 March 2013].
Martinez-Salas, E.; Saiz, M. & Sobrino, F. (2008) “Foot-and-mouth disease virus”, in Mettenleiter, T. C. & Sobrino, F. (eds.) Animal viruses: Molecular biology, Norfolk: Caister Academic Press, pp. 1-38.
Miller, L. & Hurley, K. (2009) Infectious disease management in animal shelters, Ames: Wiley-Blackwell.
Rezac, D. J.; Thomson, D. U.; Siemens, M. G.; Prouty, F. L.; Reinhardt, C. D. & Bartle, S. J. (2014) “A survey of gross pathologic conditions in cull cows at slaughter in the Great Lakes region of the United States”, Journal of Dairy Science, 97 (7), pp. 4227-4235.
Tully, D. C. & Fares, M. A. (2008) “The tale of a modern animal plague: Tracing the evolutionary history and determining the time-scale for foot and mouth disease virus”, Virology, 382, pp. 250-256.
United States Department of Agriculture (2009) “National Agricultural Library”, agricola.nal.usda.gov [accessed on 13 March 2013].
Wildlife Data Integration Network (ca. 2012) “Wildlife disease: Domestic animal health”, wdin.org [accessed on 14 February 2013].
2 Tweed, S. A.; Skowronski, D. M.; David, S. T.; Larder, A.; Petric, M.; Lees, M.; Li, Y.; Katz, J.; Krajden, M.; Tellier, R.; Halpert, C.; Hirst, M.; Astell, C.; Lawrence, D. & Mak, A. (2004) “Human illness from avian influenza H7N3, British Columbia”, Emerging Infectious Diseases, 10, pp. 2196-2199 [accessed on 30 March 2013].
3 BBC News (2008) “The discovery of bird flu in turkeys at Redgrave Park Farm in Suffolk is the latest episode of the virus now affecting the UK”, BBC, 10 January [accessed on 5 April 2013].
4 Tenpenny, S. J. (2006) Fowl! Bird flu: It’s not what you think, Kampala: NMA Media Press.
5 The Merck Veterinary Manual for Veterinary Professionals (2011) “Overview of bovine spongiform encephalopathy”, merckmanuals.com [accessed on 29 March 2013]. The Center for Food Security and Public Health (2012) “Bovine spongiform encephalopathy: Mad cow disease, BSE”, cfsph.iastate.edu [accessed on 22 March 2013]. World Health Organization (2013) “Bovine spongiform encephalopathy (BSE)”, who.int [accessed on 29 March 2013].
6 Brown, D. (2000) “The ‘recipe for disaster’ that killed 80 and left a £5bn bill”, The Telegraph, 27 October [accessed on 2 April 2013]. Segarra, A. E.; Rawson, J. M. (2001) “Mad cow disease: Agriculture issues”, U. S. Department of State, March 2012 [accessed on 27 March 2013].
7 Foreign Agricultural Service, U. S. Department of Agriculture (1997) “Foot-and-mouth disease spreads chaos in pork markets”, FASonline, Livestock and Poultry: World Markets and Trade Circular Archives, October.
9 Wong, C. M. (2011) “South Korea reportedly buries 1.4 million pigs alive to combat foot and mouth disease”, The Huffington Post, 25 May [accessed on 5 April 2013].
10 UN News Centre (2010) “UN agency warns of increased foot-and-mouth threats after outbreaks in Asia”, UN News Centre, 28 April [accessed on 27 March 2013]. Muroga, N.; Hayama, Y.; Yamamoto, T.; Kurogi, A.; Tsuda, T. & Tsutsui, T. (2012) “The 2010 foot-and-mouth disease epidemic in Japan”, Journal of Veterinary Medical Science, 74, pp. 399-404.
11 Morilla, A.; Yoon, K.-J. & Zimmerman, J. J. (2002) Trends in emerging viral infections of swine, Ames: Iowa State Press.