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Defining Foodborne Diseases
Foodborne pathogens are infectious agents, commonly bacteria, which affect the safety of the food you eat. Foodborne diseases are a widespread public health problem all over the world, putting people of all ages at risk.1 Foodborne pathogens are often found in foods of animal origin, such as beef, poultry, milk and eggs, but all foods, including vegetables, may become contaminated. Help defend yourself from foodborne illness by knowing more about the food you eat, including learning about possible symptoms and controls for foodborne illnesses.
Common Types of Foodborne Disease-causing Bacteria
Some of the most frequently reported foodborne illnesses causing human hospitalization in the United States stem from Salmonella and Escherichia coli (E. coli) bacteria.
Salmonella sp. are Gram negative, facultative anaerobic, enteric microbes that can cause significant disease. These bacteria are often transmissible to humans.
The species of Salmonella that can cause disease in cattle and humans is called Salmonella enterica (S. enterica), of which there are more than 2,500 serovars or serotypes. Of these bacteria, two serotypes account for half of all foodborne infections in the United States: Salmonella serotype Enteritidis and Salmonella serotype Typhimurium. These bacteria live in the intestinal tracts of infected animals and humans.2
Escherichia coli (E. coli) are a large and diverse group of Gram negative, rod-shaped, facultative anaerobic bacteria. Most strains are harmless and actually benefit their hosts by aiding in food digestion, producing vitamins and helping prevent the establishment of harmful bacteria within the intestine. However, certain types of E. coli can cause disease and illness by producing what is known as a Shiga toxin, most commonly identified in North America as E. coli O157. 3
The Centers for Disease Control and Prevention (CDC) estimates that E. coli O157 causes nearly 63,000 human illnesses in the United States each year. However, many illnesses go unreported. 4
Consuming food or beverages contaminated by E. coli O157 or Salmonella can result in foodborne disease. Other disease-causing pathogens can also contaminate foods and cause foodborne infection. In addition, other poisonous chemicals or other harmful substances can cause foodborne illnesses if they are present in food.5
As reported by the Centers for Disease Control and Prevention (CDC), more than 250 foodborne diseases are caused by a variety of bacteria, viruses and parasites. Symptoms of foodborne illness also can be a result of eating food that is unsafe for human consumption, for example, poisonous mushrooms. Microbes are spread in various ways, so it is not always easy to know if symptoms are a result of an actual foodborne disease.5. It is important to report possible foodborne illnesses to public health officials to help stop any possible further spread of infection.
A century ago, typhoid fever, tuberculosis and cholera were common foodborne diseases.5 Improvements in food safety, such as milk pasteurization, safe canning and disinfection of water supplies, have helped conquer diseases that previously posed serious threats to our society.5 It is possible for foodborne pathogens to exist in animals and cause no clinical symptoms, yet the same pathogens can make people sick. Bacteria, such as E. coli and Salmonella, can be transmitted to humans by consuming meat that is raw or undercooked. Other sources include foods that may have become contaminated, such as vegetables, drinking contaminated water or working in close contact with animal feces. Pathogens also can be spread from person to person. Detection in the food prior to consumption is nearly impossible as it may not affect the taste, smell or even the appearance of food.5
Symptoms and Risks of Foodborne Illness
Once the pathogen is ingested, there is an incubation period, ranging from hours to days, before onset of symptoms of foodborne illness. Prior to the incubation period, it is most common for the microbe to enter the body orally into the gastrointestinal tract and cause the first symptoms there. Nausea, vomiting, abdominal cramps and diarrhea are common symptoms in many foodborne diseases.5
The symptoms produced from foodborne illness depend greatly on the type of pathogen. Numerous microorganisms, such as E. coli, and Salmonella, can cause similar symptoms, especially diarrhea, abdominal cramps and nausea. There is so much overlap between foodborne diseases that it is often not possible to determine which microbe is likely to be causing a given illness unless laboratory tests are done to identify the pathogen, or unless the illness is part of a recognized outbreak.5
A physician should be consulted when a foodborne disease is suspected.
Salmonella can cause significant disease in calves and adult cattle as well as many other animals and humans. Healthy-appearing carrier animals as well as sick, infected animals; rodents; and environmental contamination can help spread Salmonella to cattle and into the production environment. As a result, Salmonella infection sources are difficult to eliminate and illness within a herd may be prolonged due to continuing exposure.
The disease caused by Salmonella bacteria in cattle, other animals and humans is called salmonellosis. According to the Centers for Disease Control and Prevention (CDC), human salmonellosis causes more than 1 million cases of foodborne illness, 19,336 hospitalizations and 378 deaths annually in the United States.6
E. coli O157 in cattle does not cause disease in cattle themselves. Ingestion of any foods contaminated with E. coli O157 can pose a threat to human health. Cattle, swine and deer can be hosts of E. coli O157.
1World Health Organization. Food safety and foodborne illness fact sheet. March 2007. Available at:www.who.int/mediacentre/factsheets/fs237/en/. Accessed February 8, 2012.
2U.S. Food Safety and Inspection Service. Salmonella Questions and Answers. September 20, 2006. Available at: www.fsis.usda.gov/factsheets/salmonella_questions_&_answers/index.asp. Accessed February 8, 2012.
3Centers for Disease Control and Prevention. Escherichia coli O157:H7. Updated July 21, 2010. Available at: www.cdc.gov/nczved/divisions/dfbmd/diseases/ecoli_o157h7/index.html#what. Accessed February 8, 2012.
4Scallan E, Hoekstra RM, Angulo FJ, et al. Foodborne illness acquired in the United States — major pathogens. January 2011. Available at: http://wwwnc.cdc.gov/eid/article/17/1/p1-1101_article.htm. Accessed February 8, 2012.
5Centers for Disease Control and Prevention. Foodborne Illness. January 10, 2005. Available at: www.cdc.gov/ncidod/dbmd/diseaseinfo/files/foodborne_illness_FAQ.pdf. Accessed February 8, 2012.
6Centers for Disease Control and Prevention. CDC 2011 Estimates: Findings. February 7, 2012. Available at: www.cdc.gov/foodborneburden/2011-foodborne-estimates.html. Accessed February 8, 2012.
7Centers for Disease Control and Prevention. Salmonella: Diagnosis and Treatment. September 27, 2010. Available at: www.cdc.gov/salmonella/general/diagnosis.html. Accessed February 8, 2012.
8Salmonella and Campylobacter on U.S. Dairy Operations, 1996-2007. National Animal Health Monitoring Service, U.S. Department of Agriculture. Available at: www.aphis.usda.gov/animal_health/nahms/dairy/downloads/dairy07/Dairy07_is_SalCampy.pdf. Accessed February 8, 2012.
9Cummings KJ, Warnick LD, Alexander KA, et al. The duration of fecal Salmonella shedding following clinical disease among dairy cattle in the northeastern USA. Prev Vet Med 2009; 92:134-139.
10U.S. Department of Health and Human Services. 2012. Inspections and compliance. Available at: http://foodsafety.gov/compliance/index.html. Accessed February 8, 2012.
11Plant Familiarization: Characteristics and Manufacturing Processes – Livestock Slaughter 2008. Available at: www.fsis.usda.gov/PDF/LSIT_PlantFamiliarization.pdf. Accessed February 8, 2012.
12U.S. Department of Health and Human Services. October 2010. The basics: Clean, separate, cook and chill. Available at: www.foodsafety.gov/keep/basics/index.html. Accessed February 12, 2012.
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