Infection of the gastrointestinal tract by Giardia lamblia a flagellate protozoa.
Giardia is found worldwide especially in the tropics and is an important cause of traveller’s diarrhoea, it is also found in the United Kingdom.
The organism is excreted in the faeces of infected patients as cysts. These are ingested, usually in contaminated drinking water. The organism then develops into a trophozoite, which colonises and multiplies in the small intestine. Diarrhoea results from inflammation of the epithelium.
Patients may be asymptomatic carriers or may present 1–2 weeks after ingestion of cysts with diarrhoea, nausea, anorexia, abdominal discomfort and distension. There may be steatorrhoea, and if the condition is prolonged there may be weight loss.
Stool specimen: Identification of trophozoites or cysts.
Aspirates from the duodenum or jejunal biopsy can be used for identification.
Serological responses can be measured.
A 3-day course of metronidazole or a single oral dose of tinidazole are highly effective treatments for giardiasis. Prevention is by improved sanitation and precautions with drinking water.