Module 7: Case Studies: Health and Environmental Impacts of Specific Foods

Antimicrobial Resistance

The World Health Organization (WHO) defines antimicrobial resistance (AMR) as the “resistance of a microorganism to an antimicrobial medicine to which it was previously sensitive.”(1) Because the microorganism is resistant to antibiotics, infections caused by AMR bacteria often lead to prolonged illness and greater risk of death. Antimicrobial resistance makes it more difficult and more expensive to treat illnesses that were previously treated with antibiotics. Inappropriate use, or excessive use, of antimicrobial medicines (antibiotics) leads to the emergence of AMR bacterial strains.

Antibiotics are used in agriculture to treat diseases of food-producing animals. In fact, about half of all antibiotics in Europe are prescribed for animals. In the United States, about 70% of all antibiotics are used in the agricultural industry.(2) The amount of antibiotics used for agricultural purposes, such as for cattle, poultry farming, hog farming, fish farming, and honeybee hives is much greater than the amount of antibiotics used to treat human illness. As with humans, the excessive use of antibiotics in agriculture has led to  AMR in animals. Farm animals are often given antibiotics for growth promotion or to increase feed efficiency. This long-term exposure to low dose antibiotics may lead to the survival and growth of resistant bacteria.(3) To make matters worse, resistant bacteria in animals are being transferred to humans through infected feces, both during the slaughtering process and when spread on crops. Scientists estimate that in the Netherlands, one third to one half of human AMR stems from AMR in livestock.(4)

The risk of AMR is particularly high in nations where national policies on AMR are inadequate or poorly enforced and so global health organizations have stepped in to deal with AMR issues. Broadly, WHO policies on AMR include the following government actions:

      1. Strengthen the knowledge and evidence base through research and surveillance, including developing national surveillance systems.
      2. Strengthen surveillance and laboratory capacity to allow for rapid detection and solutions to infections.
      3. Guarantee uninterrupted access to essential, quality medicines, including antimicrobials.
      4. Ensure rational use of antimicrobials through the promotion of national guidelines for treatment.
      5. Research new tools to combat AMR (and improve current diagnostic tests and antimicrobials) and incentivize industries to do the same.(5)

For example, the Food and Agriculture Organization of the United Nations (FAO) and the WHO collaborated with the Kenya Medical Research Institute (KEMRI), to strengthen Kenyan national policies, systems for detection, and regulation of AMR risks in the poultry, beef, and pig sectors. The central task of this project was to identify the critical stages at which preventative or corrective actions can be implemented most effectively. Similarly, the WHO and FAO worked on another project in Cambodia to assess and manage the public health risks associated with salmonella and campylobacter. The overall goal of this project was to facilitate the sharing of information among organizations, so that they can use a more integrated approach to address AMR risks at all stages.

Climate Change and Food Safety

Scientists generally agree that climate change is associated with increased global temperatures, trends toward stronger storm systems, increased frequency of heavy precipitation events and droughts, and rising sea levels. Therefore, climate change affects both food yields and food safety. Although climate change is generally due to the behavior of developed nations (and their high demand for energy and food), climate change is expected to cause the greatest harm to the developing world.(6)

Seasonality and temperature affect the prevalence of some diseases. For example, weeks of elevated temperatures increase the prevalence of salmonellosis and campylobacteriosis. Furthermore, higher temperatures and humidity increase the susceptibility of animals to disease, which can then be transmitted to humans. Excessive temperatures and humidity predispose cattle to bacterial syndromes, one of which is mastitis. Aquatic animals also become vulnerable, as the metabolic processes of fish are influenced by temperature, salinity, and oxygen levels.(7) Climate change may also change the incidence of foodborne zoonoses, which are diseases that can be transmitted from animals to humans, thereby increasing the use of veterinary drugs, which could lead to AMR.

Climate change also affects the mycotoxin contamination of crops. For example, in Italy, since 2003, frequent hot and dry summers have increased the occurrence of A. flavus, leading to a serious outbreak of aflatoxin contamination.(8) Maize is also heavily affected by droughts, as the crop requires relatively high levels of water. Species of the fungus genus Fusarium often live in close association with maize, and during a drought, Fusarium symbionts and A. flavus both produce more of their respective mycotoxins.(9) This phenomenon spreads up the food chain, to a point where humans are at a greater risk of mycotoxin contamination.

Climate change also leads to more harmful algal blooms (HABs) in many marine and coastal regions. These algae can produce toxins that are harmful to humans, when contaminated seafood is ingested. Resulting illnesses include amnesic shellfish poisoning (ASP), diarrheic shellfish poisoning (DSP), neurotoxic shellfish poisoning (NSP), azaspiracid shellfish poisoning (AZP), paralytic shellfish poisoning (PSP), and ciguatera fish poisoning. The toxins cause a variety of illnesses in humans, including respiratory and digestive problems, memory loss, seizures, lesions, and skin irritations.(10)


The term “bushmeat” refers to all wildlife species that are killed for meat, including elephants, gorillas, chimpanzees, forest antelopes, crocodiles, porcupines, bush pigs, cane rats, pangolins, monitor lizards, and guinea fowl. Bushmeat is often an essential part of the diet in remote rural areas, particularly in low resource settings. In more urban areas, bushmeat is considered a luxury item and is often consumed by the rich. For example, 98% of the animal protein consumed in parts of Cameroon consists of bushmeat. In the Congo basin, 4.5 to 5 million tons of bushmeat are consumed annually. The trading of bushmeat in the global market is valued at several billion dollars annually.(11)

Bushmeat is a global health concern, because consuming bushmeat has unique food safety risks. In addition to the microbiological hazards associated with other meat, bushmeat may contain emerging or re-emerging pathogens, such as bacillus anthrax, tubercle bacillus, and trichinella.(12) Many diseases can jump between non-human primates and humans, because of the similar genetic backgrounds. Therefore, consumption of bushmeat increases the risk of contracting zoonotic diseases. For example, simian immunodeficiency virus (SIV) has infected over 26 different species of African nonhuman primates, many of which are killed and consumed as bushmeat. Two of these SIVs, SIVcpz from chimpanzees, and SIVsm from sooty mangabeys, are the original causes of HIV in humans. SIVcpz and SIVsm have together been directly transmitted from the nonhuman primates to humans on multiple occasions.(13) Evidence also shows that HIV recombinants are appearing in regions where bushmeat hunting is greater.

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(1) WHO. "Antimicrobial Resistance." Accessed on 19 September 2018.

(2) Levitt, T. "Overuse of Drugs in Animal Farming Linked to Growing Antibiotic-resistance in Humans." (May 23, 2011) The Ecologist. Accessed on 19 September 2018.

(3) CDC National Antimicrobial Resistance Monitoring System  for Enteric Bactera (NARMS). “Antibiotic Resistance.” (January 26, 2018) Accessed on 19 September 2018.

(4) Levitt, T. "Overuse of Drugs in Animal Farming Linked to Growing Antibiotic-resistance in Humans." (May 23, 2011) The Ecologist. Accessed on 19 September 2018.

(5) WHO. “Global Action Plan on Antimicrobial Resistance.” (2015) Accessed on 19 September 2018.

(6) FAO. “Climate Change: Implications for Food Safety.” (2008) Accessed on 19 September 2018.

(7) Ibid.

(8) Ibid.

(9) Ibid.

(10) Ibid.

(11) Brashares, J., Golden, C., Weinbaum, K., Barrett, C., & Okello, G. (2011) “Economic and geographic drivers of wildlife consumption in rural Africa.” Proceedings of the National Academy of Sciences, 201011526.

(12) Poirson, J-M. "Wild Meat/Bushmeat - Food Safety Implications." FAO Animal Protection and Health Division. UN Food and Agriculture Organization. Accessed on 19 September 2018.

(13) Heeney, J., Rutjens, E., Verschoor, E., Niphuis, H., ten Haaft, P., Rouse, S., … Murthy, K. (2006). “Transmission of Simian Immunodeficiency Virus SIVcpz and the Evolution of Infection in the Presence and Absence of Concurrent Human Immunodeficiency Virus Type 1 Infection in Chimpanzees.” Journal of Virology, 80(14), 7208–7218.

(14) Rambaut, A., Posada, D., Crandall, K. A., & Holmes, E. C. (2004). “The causes and consequences of HIV evolution.” Nature Reviews: Genetics, 5(1), 52.