Animal Diseases and their Threat to Food and Food Security

Posted: February 21, 2018 at 10:25 am, Last Updated: February 21, 2018 at 10:26 am

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Garrett Milne, Carleton University

Animal diseases threaten the lives of millions of livestock on a daily basis. These animals are relied upon in the food supply, meaning massive losses can lead to widespread food shortages. This March, 73,500 chickens were culled on a farm in Tennessee after higher than usual numbers of birds started dying–the killer, a virus known as H7N9, a strain of bird flu.[1]

The farm in Tennessee, along with approximately 30 other poultry farms within a 10 km radius of the original site, were put under quarantine in order to quell the spread of the virus. Efforts to quarantine the farm turned out to be insufficient as two weeks later, bird flu was discovered on a farm that was in the quarantine zone less than 3.2 km away. An additional 55,000 birds were culled in an attempt to contain the virus’ spread.

Avian influenza outbreaks are becoming more and more common. In 2004, an outbreak of Highly Pathogenic Avian Influenza (HPAI) began on a poultry farm in British Columbia’s Fraser Valley. In total, 42 commercial farms and 11 backyard flocks became infected. Nearly 17 million birds were slaughtered as a result, representing almost 90 percent of the poultry population in the area.[2] A total of $380 million in gross economic costs were incurred before the outbreak was eventually suppressed.

Bird flu is not isolated to North America; the World Health Organization has stated that more than 1,000 outbreaks among poultry have been reported to the WHO ranging from Europe, to the Middle East, Africa, and Asia since June 2016.[3]

Influenza is not the only disease threatening livestock numbers and the nutrition they provide. The massive 2001 outbreak of foot-and-mouth disease (FMD) in Great Britain was responsible for losses estimated at approximately £3.1 billion GBP. This clearly demonstrates the threat to livestock production and food security from transboundary animal diseases.[4]

When it comes to food supply issues resulting from animals diseases, the developing world is especially susceptible. FMD has debilitating effects on the food supply in countries where food production is already difficult. It is estimated that FMD circulates in 77 percent of the global livestock population.[5] In poorer countries, FMD impacts the overall herd fertility, and leads to direct losses because of limited livestock productivity. This causes food security issues and leads to malnutrition.[6] Rift Valley Fever, which disrupts the food supply in developing countries in a similar way to FMD, has seen outbreaks in 2006 and 2007 in Tanzania and 2008 and 2010 in South Africa.[7]

Another transmissible and fatal disease, Bovine Spongiform Encephalopathy (BSE)–more commonly referred to as Mad Cow Disease–affects the central nervous system of adult cattle. BSE is an infectious agent called a prion that is currently not well understood. These prions are thought to be caused by a protein that has adopted an abnormal form, causing neurodegenerative diseases.

Mad Cow was first detected in England in the mid-1980s, where it killed over 180,000 cattle. Between the time cows were first reported dying from BSE, and the time the disease was identified as BSE, almost 1 million cows made it into the food supply of Europeans. After BSE was identified, almost five million head of cattle were slaughtered in order to stop the BSE from spreading.[8] Despite these measures BSE spread to Europe where the disease still kills 2-3 cattle each day.[9]

To understand the effect animal diseases have on the food supply, it’s important to understand just how much animal protein is consumed and relied upon for daily caloric intake. According to the Organization for Economic Co-operation and Development, the average American adult consumed 90 kilograms of meat in 2014. The global average during that same year was 34 kilograms.[10]

This means that the average diet consists of almost 25% meat and animal by-product. According to studies, the average individual in the United States, European Union, and developed world total meat intake averaged 128 g/day.[11] In the developing world, subsistence and agriculture based communities are highly dependent upon livestock for milk and meat.  Livestock kept by impoverished peoples can produce a regular supply of protein; a critical supplement and diversity to plant-based diets. This is particularly true for milk and eggs, which can help mitigate the effects of often large seasonal fluctuations in grain availability.[12]

This reliance leads to vulnerabilities. Whether it be the virus itself, or the disease management, hundreds of thousands or potentially millions of animals are killed each year because of pathogenic outbreaks among herds. This is most alarming in the developing world, where over 700 million people keep farm animals and up to 40 percent of household income depends on them.

In this situation, where access to protein is already limited, animal diseases reduce the availability of a critical source of protein.[13]  Because of the diverse uses of livestock in poorer countries with less established veterinary services, livestock diseases have broader, more nuanced effects on markets, poverty, livelihoods, and the food supply[14]

The 2015 outbreak of influenza in the United States affected more than 48 million birds and caused a drastic shortage of eggs.[15] Egg suppliers estimated that the egg shortage would last between 18 and 24 months. A consensus of economists who study food shortages and pricing is that for every million birds lost, there is about a 1.6 percent price increase.[16]

In 2004 alone the global impact of Avian Influenza outbreaks led to a more than 30 percent increase in international poultry prices. This shows how vulnerable the food supply is to a disease outbreak among livestock. Similar effects are seen with beef, but the effects are longer lasting because of the long reproduction and growth cycles of cattle. Following the 2004 North American BSE outbreak, beef farmers in the region experienced a ban on North American beef world-wide, which led to a 20 percent increase in international beef prices.[17]

It is not easy to protect livestock from influenzas and other animal diseases for a number of reasons. One of the most important things to know when trying to understand the danger of animal diseases is a concept known as ‘reservoir hosts’. Of the diseases discussed so far, this concept applies specifically to Influenza. A reservoir host is a situation wherein the virus and the host can survive in equilibrium. The host is not sickened or killed by the virus and can live without issue for a long period of time.

This presents a challenge in that it means infectious diseases cannot be eradicated unless the reservoir host is found and destroyed. When influenza outbreaks subside, it does not mean that the virus has vanished, it means that the virus is ‘hiding’ in its reservoir host, waiting for an opportunity to enter and spread among other hosts.[18] This also means that diseases can be reoccurring, an alarming situation for farmers with short life-cycle livestock.

Something else to consider which applies to all animal diseases more broadly, and is apparent with H7N9, is the ability for the virus to spread to different parts of the globe affecting multiple livestock populations simultaneously.

Locomotion of animal diseases on an international scale can be achieved in a number of ways. International trade is one vector that can have a serious impact.

Worldwide, poultry exports have increased by 520 percent, from 2.2 million tonnes a year in the late 1980s, to 13.6 million tonnes a year in the late 2000s.[19] This means millions of potentially infectious birds traverse international borders at rapid rates, leaving ample opportunity for infectious diseases to ‘hitch a ride’ from one location to another. At both the local and national levels, trade across borders creates a new, very direct dissemination of infection and a new challenge for public health.

What makes livestock, and in turn the food supply, especially susceptible to animal diseases all over the world is the increasing use of industrialized farming. These farms continue to grow in size and crowdedness. In the past livestock was spread out among thousands of small family run farms; this is no longer the case.

More than half of the world’s pigs and chickens are raised on industrialized farms, and more than 40 percent of the world’s beef is produced in feedlots where hundreds of thousands of animals are raised in close quarters.[20] Large, cramped populations allow for more virulent viruses to continue to thrive.

In smaller populations, virulent viruses have a tendency to kill the organism quickly before it can find a new host, thereby ending that virus’s life cycle. In larger populations that are crowded together, a virus has the ability and opportunity to remain virulent and highly transmissible.[21] In this way, massive livestock populations crammed into a small vicinity allow highly virulent diseases to remain prevalent and deadly.

Infectious disease outbreaks can have a negative impact on the perception of consumers as well. A study from 2010 showed that after Bovine Spongiform Encephalopathy was discovered in a cow in the United States, a pronounced and significant reduction in beef sales occurred.[22] A study conducted by the Food and Agriculture Organization of the United Nations supported this claim in stating, “Consumer reactions play an important role in determining the size of market losses associated with animal diseases, with non-disease infected exporters significantly and adversely affected.[23]

While this does not necessarily cause a shortage of animal protein for consumption, consumers choose to switch to other sources, which can be limiting. Findings show that consumer demand falls drastically after an outbreak in livestock, causing market oversupply. This situation occurred when BSE was discovered in a Canadian cows.

An international ban was placed on Canadian beef. Bans forced Canadian farmers to deal with a massive numbers of cattle that could not be exported–750,000 to 1,000,000 head of live cattle in total.  Prior to the BSE discovery these cattle were forecast to be exported to the United States.[24] This means more cattle remained on farms and as previously discussed, overcrowded farms can make infectious diseases much worse.

In order to help prevent mass animal disease outbreaks among livestock, a number of policies and mitigation strategies must be put in place. The frequency of these outbreaks among livestock presents potentially catastrophic outcomes for the world’s food supply. There must be combative policies and strategies in place to monitor livestock populations.

This is this reason bio surveillance of livestock, as well as rapid response plans from all levels of government involved should be created and maintained. The impact of not implementing these measures could be large food shortages such as the egg shortage in the United States in 2015.

One of the most important aspects of controlling disease outbreaks in livestock is informing the industry and the public about biosafety information in order to keep them informed and up to date.

National and local governments must also have strict biosafety guidelines in place as preventative measures against outbreaks. This must be coupled with evidence and risk-based interventions and containment strategies, preventing unnecessary economic loss or food shortages when an outbreak does occur.

Another sobering thought, is the fact that these diseases and infectious agents all have the potential to ‘spillover’ into humans, presenting larger issues than simple food shortages.

Garrett Milne is currently completing the Master in Infrastructure Protection and International Security program at Carleton University in Ottawa, Ontario. His academic interests are threats to Canada’s agricultural sector stemming from infectious diseases. Included in this area of interest are the policy responses and the regulatory frameworks that attempt to deal with these types of pathogens. Garrett is also interested in how pandemics threaten Canada’s healthcare system and global public health more broadly.


[1] Jo Winterbottom, “Bird flu found in Tennessee chicken flock on Tyson-contracted farm,” Reuters, March 6, 2017, accessed March 31, 2017,

[2]Tini Garske et al., “The Transmissibility of Highly Pathogenic Avian Influenza in Commercial Poultry in Industrialised Countries,” PLoS ONE, 2(4): e349, 2007, accessed April 2, 2017,

[3] Meera Senthilingam, “Bird flu cases surged this season, but human risk remains low, WHO says,” CNN, March 2, 2017, accessed March 31, 2017,

[4]Jens F. Sundström, Albihn, A., Boqvist, S. et al. “Future threats to agricultural food production posed by environmental degradation, climate change, and animal and plant diseases – a risk analysis in three economic and climate settings,” Food Security,  6: 201, 2014, accessed April 4, 2017, doi 10.1007/s12571-014-0331-y.

[5]Jonathan Rushton, “The impact of foot and mouth disease,” Preventative Veterinary Medicine, 2013, 1;112(3-4):161-73. doi: 10.1016/j.prevetmed.2013.07.013.

[6] Ibid.

[7] José M. Fafetine et al., “Rift Valley Fever Outbreak in Livestock, Mozambique, 2014,” Emerging Infectious Diseases, 2016, 22(12): 2165–2167, accessed April 5, 2016, doi:  10.3201/eid2212.160310.

[8] “Quick facts about mad cow disease,” CBC, Jan 20, 2012, accessed April 1, 2017,

[9] “Mad Cow Disease,” Centre for Food Safety, accessed April 2, 2017,

[10] “Meat consumption,” The Organisation for Economic Co-operation and Development (OECD), accessed April 5, 2017,

[11] Carrie R. Daniel et al., “Trends in meat consumption in the United States,” Public Health Nutrition, 2011; 14(4): 575–583, doi: 10.1017/S1368980010002077.

[12] T. F. Randolph et al., “Role of livestock in human nutrition and health for poverty reduction in developing countries,” Journal of Animal Science, 2007; 85:2788–2800, doi:10.2527/jas.2007-0467.

[13] Paul Karaimu, “Livestock boom risks aggravating animal ‘plagues,’ poses growing threat to food security and health of world’s poor,” The International Livestock Research Institute, February 10, 2011, accessed April 3, 2017,

[14] “The economic and poverty impacts of animal diseases in developing countries: new roles, new demands for economics and epidemiology,” Preventive Veterinary Medicine, 2011, 101(3-4):133-47. doi: 10.1016/j.prevetmed.2010.08.002.

[15] Hayley Fitzpatrick, “Fast-food chains are taking eggs off the menu,” Business Insider, July 16, 2015, accessed April 2, 2017,

[16] Brad Tuttle, “How the Bird Flu Outbreak Is Affecting Your Grocery Bill,” Money, May 13, 2015, accessed April 3, 2017,

[17] N. Morgan & A. Prakash, “International livestock markets and the impact of animal disease,” Revue scientifique et technique (International Office of Epizootics), 2006, 25 (2), 517-528, accessed April 3, 2017.

[18] David Quammen, Spillover: Animal Infections and the Next Human Pandemic, (New York: Norton, 2012), 23.

[19] J. Slingenbergh et al., “World Livestock 2013: Changing disease landscapes,” Food and Agriculture Organization of the United Nations, 2013, accessed April 6, 2017,

[20] Sonia Shah, Pandemic: Tracking Contagions, from Cholera, to Ebola and Beyond, (New York: Picador, New York), 85.

[21] Ibid., 86.

[22] Wolfram Schlenker and Sofia B. Villas-Boas, “Consumer and Market Responses to Mad-Cow Disease,” Department of Agricultural & Resource Economics, University of California, Berkley, 2006, accessed April 2, 2017,

[23] “Impacts of Animal Disease Outbreaks on Livestock Markets,” Food and Agriculture Organization of the United Nations, 2006, accessed March 30, 2017,

[24] Marta Norton, “Factors affecting beef and cattle producer prices movements,” Monthly Labor Review, 2005, April 1, 2017,

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