Overview
Giardiasis is the infection of the small intestine by the protozoan Giardia lamblia. It is spread by the faecal-oral route (e.g. through contaminated food) and person-to-person contact. Upon entry, trophozoites colonise and reproduce in the small bowel.
Giardiasis is the most common cause of prolonged diarrhoea in returning travellers.
Risk Factors
- Consuming contaminated food/water
- Swimming in contaminated water
- Sexual transmission – higher risk in men who have sex with men
- Foreign travel – particularly to South Asia
Presentation
Overview
Often people are asymptomatic. Features of symptomatic infection include:
- Non-bloody diarrhoea:
- These are usually watery initially but can lead to steatorrhoea over time
- Abdominal cramps, bloating, flatulence
- Malabsorption, weight loss, and lactose intolerance can occur:
- In children, this may present with faltering growth
- Less commonly, vomiting and fever can occur
Giardiasis should be considered in someone with chronic diarrhoea associated with malabsorption and weight loss.
Investigations
Overview
Some investigations include:
- Stool microscopy – may identify trophozoites and cysts
- Stool antigen assay – done using immunofluorescence or ELISA (enzyme-linked immunosorbent assay) may identify antigens associated with Giardia lamblia
Management
Overview
Treatment involves metronidazole.
