Infection with the parasite Guardia Lamblia frequently occurs in epidemics though it can account for isolated cases of persistent diarrhoea. Any diarrhoea that persists beyond five days warrants examination of the stool for evidence of parasites of which Guardia is one. It is easily treated with antibiotics and is also transferable within families. It may not necessarily be associated with weight loss or failure to thrive so any persistent warrants investigation.