Giardiasis is caused by the flagellate protozoan Giardia lamblia. It is spread by the faecal-oral route.

Risk factors

• foreign travel
• swimming/drinking water from a river or lake
• male-male sexual contact

Features

• often asymptomatic
• non-bloody diarrhoea
  • steatorrhoea
• bloating, abdominal pain
• lethargy
• flatulence
• weight loss
• malabsorption and lactose intolerance can occur

Investigations

• stool microscopy for trophozoite and cysts: sensitivity of around 65%
• stool antigen detection assay: greater sensitivity and faster turn-around time than conventional stool microscopy methods
• PCR assays are also being developed

Treatment is with metronidazole.