Gastroenteritis: causes

Gastroenteritis may either occur whilst at home or whilst travelling abroad (travellers' diarrhoea)

Travellers' diarrhoea may be defined as at least 3 loose to watery stools in 24 hours with or without one of more of abdominal cramps, fever, nausea, vomiting or blood in the stool. The most common cause is Escherichia coli.

Another pattern of illness is 'acute food poisoning'. This describes the sudden onset of nausea, vomiting and diarrhoea after the ingestion of a toxin. Acute food poisoning is typically caused by Staphylococcus aureus, Bacillus cereus or Clostridium perfringens.

Stereotypical histories

Infection _ Typical presentation| Escherichia coli_ Common amongst travellers Watery stools Abdominal cramps and nausea| Giardiasis _ Prolonged, non-bloody diarrhoea| Cholera _ Profuse, watery diarrhoea Severe dehydration resulting in weight loss Not common amongst travellers| Shigella _ Bloody diarrhoea Vomiting and abdominal pain| Staphylococcus aureus _ Severe vomiting Short incubation period| Campylobacter _ A flu-like prodrome is usually followed by crampy abdominal pains, fever and diarrhoea which may be bloody May mimic appendicitis Complications include Guillain-Barre syndrome| Bacillus cereus _ Two types of illness are seen

• vomiting within 6 hours, stereotypically due to rice
• diarrhoeal illness occurring after 6 hours|

Yersinia enterocolitica _ Associated with ndercooked porku Fever, abdominal pain and diarrhoea, which may be bloody Terminal ileitis and mesenteric lymphadenitis may mimic appendicitis| Amoebiasis _ Gradual onset bloody diarrhoea, abdominal pain and tenderness which may last for several weeks| Incubation period

• 1-6 hrs: Staphylococcus aureus, Bacillus cereus*
• 12-48 hrs: Salmonella, Escherichia coli
• 48-72 hrs: Shigella, Campylobacter
• > 7 days: Giardiasis, Amoebiasis

*vomiting subtype, the diarrhoeal illness has an incubation period of 6-14 hours