A 55-year-old business man presents with a 15 day history of watery, non-bloody diarrhoea associated with anorexia and abdominal bloating. His symptoms started 4 days after returning from a trip to Pakistan. On examination he is apyrexial with dry mucous membranes but normal skin turgor. What is the most likely causative organism?
Salmonella
Giardia lamblia
Shigella
Escherichia coli
Norovirus
Although Escherichia coli is the most common cause of travellers’ diarrhoea, in this particular case the length of illness and nature of symptoms (bloating, watery diarrhoea) points to a diagnosis of Giardiasis.
Giardiasis
Giardiasis is caused by the flagellate protozoan Giardia lamblia. It is spread by the faeco-oral route
Features
often asymptomatic
lethargy, bloating, abdominal pain
non-bloody diarrhoea
chronic diarrhoea, malabsorption and lactose intolerance can occur
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