Major Food Borne Diseases and Causes

Manisha Parmar¹, Paviter Kaur² and JS Bedi³

1,2: Department of Veterinary Microbiology, GADVASU, Ludhiana
3: Centre for One health, GADVASU, Ludhiana

Food-borne disease is any sickness or infectionthat iscaused by the consumption of contaminated food, water or beverage which is infected with a variety of harmful bacteria, viruses, parasites and chemicals.

Symptoms of food borne diseases:

Food borne diseases can affect any person who consumes contaminated food; however, certain populations (infants, pregnant women, the elderly, and people on some type of medications) are less resistant to the disease with a greater severity of illness and symptoms may vary with the causal agents. Fig.1 shows general symptoms of food borne diseases.

Generally food borne diseases are classified into two categories: food borne infections and food borne intoxications (Fig.1)

1. Food borne infections: These are caused by the pathogenic bacteria, viruses, parasites and prions. The food borne infections have a propensity of longer incubation periods (period between the consumption of contaminated food and the first appearance of symptoms) and are generally characterized by fever.During the incubation period, microbes pass through the stomach and enter into the small intestine. They attach to cells lining the intestinal walls and start to multiply. Some microbes may produce toxins while others directly invade deeper body tissues.

1. Bacteria: Raw foods, eggs, unpasteurized milk, dairy products and even fresh produce can carry bacteria that can cause the infections of gastrointestinal tract. Most common bacterial food-borne pathogens are:

• Salmonellaspp.: Salmonellaare a group of bacteria that comprises of over 2000 different serotypes and these organisms are found in many foods (raw and undercooked meat, poultry, egg shells, dairy products and seafood). Salmonella causes two types of diseases: 1) Enteric fever, which includes typhoid and paratyphoid fever caused by Salmonella typhi and Salmonella paratyphi A, B and C, respectively. Enteric fever is usually characterized by high fever, diarrhea and aches, and2) Salmonellosis, which generally shows symptoms like fever, nausea, vomiting, diarrhea and cramps, lasting for few days and diminishing within a week.The mode of transmission can be either directly from slaughter animals to food or from human excreta to food.
• Shigella: Shigella causes inflammation of the colon also called Shigellosis or Bacillary dysentery. The various species involved in causing Shigellosis are Shigella dysenteriae, Shigella flexneri, Shigella boydii and Shigella sonei. The incubation period ranges from 1-7 days and major symptoms of this disease are watery diarrhea, which is composed of pus, mucus threads and blood, abdominal pain, dehydration and constant tenesmus. The mode of transmission of this disease is by fecal-oral route and person-to-person transmission is common.
• Vibrio cholera: V. cholera causes an acute diarrheal disease called Cholera, which is marked by the sudden outset ofvomiting, excessive watery diarrhea, abdominal pain and cramps. Itcan even lead to death in 12 to 24 hrs ascribed to dehydration and electrolyte imbalance. Cholera is usually transmitted through contaminated water or food and human is the only natural host of the disease.
• EnteropathogenicEscherichia coli: E. coli can enter the body via contaminated food or water and oftentimes isassociatedwithserious food-borne outbreaks around the world.  Feces and untreated water are the prime source of bacteria in the environment and its presence in foods is the indication of faecal contamination. Symptoms generally appear within 12-72 hours and include fever, abdominal pain, vomiting and diarrhea.

2. Viruses: Viruses are the leading cause of gastroenteritis globally. These are common food borne pathogens which are transmitted through contaminated food. Viruses emerge from the human intestine and are excreted in high numbers in the faeces. 

• Hepatitis A virus:Hepatitis A is a liver infection which spreads from person to person and fecal-oral route is the primary course of transmission.It is excreted in faeces of the person infected with the virus produces clinical disease when an individual ingests contaminated water or foods. It has longer incubation period of 15-50 days and symptoms include sudden fever, nausea, abdominal pain, headache and several days of jaundice.
• Norovirus:Norovirus causes Norwalk gastroenteritis withsymptoms generally starts within 2 days of consuming the contaminated food. The incubation period is of 3 days and emesisappears as the first visible symptom, along with diarrhea and cramps. Headache, mild fever, and muscle aches may also occur.The primary route of transmission is from person-to-person through faecal−oral and vomit-oral routes and indirectly through food, water and environment.

3. Parasites:

• Giardiasis: Giardiasis is a diarrheal illness caused by Giardia intestinalis (also known as Giardia lamblia).Recently, Giardia has become one of the most common causes of waterborne illness in humans.Giardia spreads easily and can spread from person to person or through contaminated water, food, surfaces, or objects. The most common way people get sick is by swallowing contaminated drinking water or recreational water. Symptoms generally begin 1 to 3 weeks after exposure and last about 2 to 6 weeks in healthy persons and common symptoms include diarrhea, greasy stools, stomach cramps, loss of appetite and fever.
• Toxoplasmosis: Toxoplasmosis is an infection caused by Toxoplasma gondii.It is generally transmitted by eating or handling raw or undercooked pork, lamb, eating unwashed fruits and vegetables grown in soil contaminated with feces and drinking contaminated water.Pregnant women and people with weakened immune systems are more likely to have serious illness due to toxoplasmosis. Pregnant women can pass the infection to their unborn baby if they become infected for the first time during or just before pregnancy. Symptoms usually begin within 1 to 3 weeks after exposure and symptoms includeswollen glands, muscle aches and pain and tiredness.
• Cryptosporidiosis: Cryptosporidiosis is a diarrheal disease caused by the protozoan parasite Cryptosporidium spp.Cryptosporidium is passed in the stool of an infected person or animal. Common ways b which Cryptosporidium is transmitted includes drinking raw or unpasteurized milk and apple cider, eating foods contaminated with the parasiteand having contact with animals, especially calves and goats, and their environment. Symptoms generally begin a week after exposure but can begin as short as 2 days or as long as 2 weeks after exposure to the parasite and generally include watery diarrhea, stomach cramps, loss of appetite, weight loss, slight fever and vomiting.

2. Food borne intoxications: These are caused by the consumption of toxins that are eitherpresent in the tissues of some animals (biotoxicants), or are produced by microorganisms in food (metabolic products), or are added to the food during production, transportation and storage. The food borne intoxications tend to have shorter incubation period and no fever.

1. Chemical contaminants:This is a type of food borne intoxication caused by the consumption of food containing poisonous chemicals, intentionally or unintentionally added to the food during production, processing, transportation or storage. Accidental contamination by heavy metals, pesticides, and radionuclide, intentional addition of preservatives such as nitrite and sodium nicotinate for color preservation and fungicides used as dressing during storage, leaching from containers e.g. zinc galvanized containers by acid foods, lead pipes and asbestos roofs are the few examples of chemical contaminants. Chemical food borne intoxication exhibit a very short incubation period, usually a few minutes to a few hours, with an average of one hour. Symptoms are mainly due to effect on gastrointestinal tract and central nervous system and include nausea, headache, convulsions, gastrointestinal irritation, abdominal cramps, vomiting and diarrhea, pallor, cyanosis, blurred vision, sweating, and collapse.
2. Natural toxins:These are naturally present in plants and animals. Most of the natural toxins, particularly those occurring in plant-derived foods, induce adverse effects only after chronic ingestion or by allergic reactions.

• Mushroom poisoning: Wild mushrooms contain several toxins, such as muscimol and muscarine, which can cause vomiting, diarrhoea, confusion, visual disturbances, salivation, and hallucinations. Onset of symptoms occurs 6–24 hours or more after ingestion of mushrooms. Fatal poisoning is usually associated with delayed onset of symptoms which are very severe, with toxic effect on the liver, kidney and nervous systems.
• Neuro-Lathyrism: Lathyrism, one of the oldest neurotoxic diseases known to man, results from excessive consumption of flour made from the drought-resistant chickling pea, Lathyrus sativus, and certain related species. Lathyrism is a form of irreversible, non-progressive spastic paraparesis associated with poorly understood degenerative changes in spinal cord. Domestic animals, notably the horse, also develop hindlimb paralysis after prolonged feeding on lathyrus fodder.

3. Bacterial toxins:

• Staphylococcal poisoning: It is a major type of food borne intoxication which is caused by the ingestion of food contaminated with enterotoxins produced byStaphylococcus aureus. The organism produces five serologically different enterotoxins and individual strains of S. aureuscan produce one or more than one kind of enterotoxin. The toxin appears to act as neurotoxins that stimulate vomiting and typical symptoms include salvation, nausea, abdominal cramps, diarrhea with prostration. The incubation period is 1-6 hrs after the consumption of contaminated food.
• Botulism: Botulism is caused by the consumption of foodcontaminated with botulinum toxinproduced by Clostridium botulinum. It is a neurotoxin that can resist the action of the gastric and intestinal juices. The incubation period is 12-72 hrs and symptoms of botulism include fatigue, nausea, blurred vision, constipation, difficulty in swallowing and speaking, nerve paralysis, muscle weakness, respiratory failure and death. Infant botulism is the most common form which occurs in infants less than 1 year of age. The infant becomes constipated, listless, generally weak, and eats poorly.
• Bacillus cereus poisoning:It is caused by the toxins produced byBacillus cereus that causestwo types of gastrointestinal illness: the emetic syndrome and the diarrheal syndrome. The emetic toxin is produced in the food and the syndrome is characterized by vomiting and abdominal cramps occurring after 1-6 hrs of ingestion of contaminated food. The diarrheal syndrome occurs when enterotoxins are produced in the small intestine and symptoms appear after 8 to 24 hours of consumption of contaminated food. The symptoms of diarrheal syndrome aretenesmus, watery stools, nausea, vomiting and cramp like pains.

4. Fungal toxins: Mycotoxins are secondary toxic metabolites synthesized by a variety of fungie.g., Aspergilli, Penicilli, Rhizopus, Fusarium spp. etc. The illness that results from the ingestion of foods containing fungal toxins is called ‘mycotoxicosis’. Mycotoxins can cause a variety of adverse health effects and pose a serious health threat to both humans and livestock.The adverse health effects of mycotoxins range from acute poisoning to long-term effects such as immune deficiency and cancer.

• Ergotism: It is caused by the ingestion of grasses and cereals, particularly rye, infected with the fungal species of the genus Clavicepspurpurea.Symptoms in humans vary greatly and are generally classified as convulsive (Confusion, hallucinations, formication and death), gangrenous (Vasoconstriction, hot and cold feelings in the extremities, cold skin, spontaneous abortion, agalactia, and gangrene) and gastrointestinal or enteric (Nausea, vomiting, and giddiness.). Cattle are particularly susceptible to both gangrenous and hyperthermic ergotism (Fever, diarrhea, clear nasal discharge, open-mouthed labored breathing, increased metabolic rate, excessive salivation, and low levels of prolactin).
• Aflatoxin food poisoning:Aflatoxins are a group of structurally related, toxic, secondary metabolites produced mainly by Aspergillus flavus and A. parasiticus,and is the most importantmycotoxins in the world for human food and animal feed. Aflatoxin B₁, the most toxic, is a potent carcinogen and has been directly correlated to adverse health effects, such as liver cancer, in many animal species. Aflatoxins specifically target the liver organ and early symptoms of hepatotoxicity comprises of fever, malaise and anorexia followed with abdominal pain, vomiting, and hepatitis.