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

• 2-4 weeks incubation
• Symptoms last several weeks

PC

• often asymptomatic
• lethargy, bloating, abdominal pain
• flatulence
• non-bloody watery diarrhoea
• chronic diarrhoea, malabsorption and lactose intolerance can occur

Investigations

• stool microscopy for trophozoite and cysts are classically negative, therefore duodenal fluid aspirates or 'string tests' (fluid absorbed onto swallowed string) are sometimes needed

Treatment is with metronidazole.