Food Poisoning, Diarrhoea and Gastroenteritis

Dan Freeman

Introduction

• Food poisoning or foodborne disease is any illness resulting from the consumption of contaminated food or water, typically resulting in gastroenteritis.

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• Diarrhea is loose, watery and possibly more-frequent bowel movements. It is a very common condition and usually resolves without intervention.�

Introduction

• Contamination may be due to pathogenic bacteria, viruses, parasites and fungi, as well as chemical or natural toxins such as poisonous mushrooms.�
• Gastroenteritis in older children and adults may occur sporadically or in epidemics, and is often associated with food poisoning.�

Causes�Bacteria�The most common bacterial pathogens are:�Campylobacter jejuni�Clostridium perfringens – “cafeteria germ”�Salmonella spp. especially S. typhimurium�Escherichia coli O157:H7��Other common bacterial food poisoning pathogens are Bacillus cereus, Escherichia coli – EIEC, EPEC, ETEC, EAggEC; Listeria monocytogenes, Shigella spp., Staphylococcus aureus, Streptococcus, Vibrio cholerae, Vibrio parahaemolyticus.

Exotoxins�Food poisoning is sometimes caused by bacterial exotoxins. Symptoms typically appear after 24 hours depending on the amount of toxin ingested. ��Pathogens producing exotoxins include Clostridium botulinum, Clostridium perfringens, Staphylococcus aureus, Bacillus cereus, Vibrio cholera.��Botulism can result when C botulinum grows in improperly canned low-acid foods, producing botulin - a powerful paralytic toxin.��Mycotoxins causing food poisoning include Aflatoxins, Altertoxins, Citrinin, Citreovirid, Cytochalasins, Ergot.�

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Viruses

• Viral causes of food poisoning include Enterovirus, Hepatitis A, Hepatitis E, Norovirus, and Rotavirus.

Parasites

• Most foodborne parasites are zoonoses.
• Platyhelminthes: Diphyllobothrium sp., Taenia saginata, Taenia solium
• Nematode: Ascaris lumbricoides, Trichinella spiralis, Trichuris trichiura
• Protozoa: Acanthamoeba and other free-living amoebae, Cryptosporidium parvum, Entamoeba histolytica, Giardia lamblia, Toxoplasma gondii

Natural Toxins�Several foods can naturally contain toxins, many of which are not produced by bacteria or fungi. Certain plants may be toxic, but naturally poisonous animals are rare.��Natural Toxins include: Alkaloids, Ciguatera poison, Grayanotoxin (honey intoxication), Mushroom toxins, Phyto-haemagglutinin (red kidney bean poisoning; destroyed by boiling), Shellfish toxin, Scombrotoxin e.t.c.

Pathogenesis & Clinical Findings��Incubation periods range from hours to days, depending on the agent and the infective dose. Early onset of symptoms (1-6hrs), suggest that it is caused by a bacterial toxin or a chemical rather than live bacteria.��Nausea, vomiting, abdominal pain, diarrhea and fever are the major clinical findings in gastrointestinal infections. The predominant symptoms are dependent on the etiologic agent and whether it is toxigenic or invasive or both.� �S. aureus and B. cereus produce preformed toxins in food; nausea and vomiting - and less diarrhea - occur a few hours following ingestion of the food. �

Pathogenesis & Clinical Findings (Contd)��Organisms that produce enterotoxins affect the proximal small bowel and tend to cause watery diarrhea (eg ETEC, V. cholerae). Agents such as rotaviruses, Norwalk virus and G. lamblia cause watery diarrhea via mucosal irritation or destruction. ��Invasive or cytotoxin-producing bacteria infect the colon and cause abdominal pain, frequent diarrhea, often with blood and mucus, fever, and dehydration. Such organisms include salmonellae, shigellae, C. jejuni, EIEC, C. difficile, and E. histolytica.

Diagnosis�In only a small percentage of cases are the aetiologic agents demonstrated by means of stool culture or immunoassay. ��Finding of WBCs on faecal wet mount is highly suggestive of infection.��Management�Maintenance of adequate hydration is the most important feature of treatment, especially in infants and children. ��Antimicrobial therapy is necessary in treatment of enteric fever; also shortens the duration of symptoms in shigella, V cholerae and campylobacter infections.

Epidemiology�Gastrointestinal infections are very common, especially in developing countries, accounting for high mortality rates in infants and young children. ��Food poisoning usually arises from improper food handling, preparation or storage. They occur as individual or sporadic cases. Most outbreaks originate from commercial food facilities.

Prevention�Public health measures through fostering good hygiene (regular hand-washing), providing clean water and food supplies, proper storage and refrigeration of food is of utmost importance. ��The definition of strict rules of hygiene and veterinary surveillance of animal products in the food chain industry should be emphasized.