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Giardiasis is a diarrhoeal illness caused by the protozoan Giardia lamblia. It is a one-celled, microscopic parasite that lives in the intestine of people and animals. Person to person transmission occurs by hand to mouth transfer of cysts from the faeces of an infected individual, especially in institutions and day care centres. Period of communicability, entire period of infection. 

Mostly man

Incubation period
1-2 weeks after being infected

Signs and Symptoms
  • Diarrhoea (loose or water stool)
  • Stomach cramps
  • Nausea
  • Vomiting
  • Weight loss
  • Dehydration
  • Some people have no symptoms.

Identification of cysts/trophozoites in faeces - repeat 3 stools specimens before considering result negative since it can be difficult to diagnose.

Metronidazole (Flagyl) is the treatment of choice (prescribed by medical doctor).

Control and Prevention
  • Educate families, inmates of institutions, especially adult personnel of day centres in personal hygiene, and the need for hand washing before eating and after toilet use.
  • Filter public water supplies that are exposed to human or animal faecal contamination
  • Protect public water supplies against contamination with human and animal faeces.
  • Boil emergency water supplies.
  • Microscopic examination of faeces of household members and susceptible contacts, especially those that are symptomatic, is required.