It is estimated that 2 million people (both adults and children) die each year from contaminated food (WHO, 2015). In the past year alone, over 300 disease outbreaks occurred as a result of contaminated food (IDSP, Ministry of Health & Family Welfare, Govt. of India). There has been some progress in surveying for food-borne diseases. For example, surveillance for food-borne diseases have been in progress for the past two years in the states of Gujarat and Tamil Nadu (NCDC, MoHFW, Govt. of India).
The contamination of food may occur at any stage in the supply chain, from food production to consumption. Food-borne diseases primarily exhibit gastrointestinal symptoms, although other symptoms involving various other systems of the body can also occur. The onset of symptoms for food-borne diseases is variable. Diseases caused by food-borne pathogens can lead to serious complications, including permanent disability and even death.
The major food-borne pathogens include bacteria, parasites and viruses. In exceptional cases, prions can also cause disease.
The most common bacteria responsible for food-borne diseases include Escherichia coli, Salmonella and Campylobacter, which can cause serious complications, including death. Most of the symptoms are gastrointestinal, such as diarrhea and vomiting, but other symptoms like fever can also occur. Examples of foods involved in outbreaks caused by bacteria include undercooked poultry, eggs, raw milk, contaminated drinking water etc.
Listeria monocytogenes is another food-borne pathogen that can cause reproductive complications in pregnant women or death of babies. Although the prevalence of disease is quite low, serious outbreaks have been known to occur with great severity. This bacterium is found in unpasteurized dairy products and also in pre-cooked foods. The bacterium is particularly dangerous because of the fact that unlike most other bacteria, it can survive even in refrigerators.
Vibrio cholerae causes cholera and infects people through contaminated water or food. The predominant symptom is profuse watery diarrhea (rice water stool) leading to severe dehydration and death in the absence of prompt treatment. Cholera nowadays predominantly occurs in Africa and Asia.
There are a number of parasites that are spread through contaminated food and water. These include fish-borne trematodes, Echinococcus spp., Ascaris, Cryptosporidium, Entamoeba histolytica and Giardia. In most of these infections, the predominant feature is again gastrointestinal in nature.
The common food-borne viruses are Norovirus and Hepatitis A virus. Norovirus is found in shelled seafood such as oysters etc. The virus can cause profuse vomiting, watery diarrhea and severe abdominal pain, which as all gastrointestinal in nature. Hepatitis A virus can cause chronic liver disease and can be spread through raw or undercooked seafood or contaminated raw produce.
Other food-borne pathogens include a number of bacteria, like Shigella spp., Yersinia enterocolitica, Clostridium botulinum, Clostridium perfringens etc., the single-celled parasite Toxoplasma gondii, and fungi such as yeasts and molds.
In extremely rare instances, infectious agents composed solely of protein – called prions – contaminate brain tissue and cause neurodegenerative diseases. In cows, prions causes a disease of the brain called bovine spongiform encephalopathy (BSE) popularly called “mad cow disease”. In humans, prion diseases as usually associated with cannibalism. Creutzfeldt-Jakob Disease (CJD) is a prion disease in humans that occurs from eating contaminated human brain tissue.