ABSTRACT
This is the commonest gastrointestinal protozoal infection, found throughout the tropics and temperate regions. It is particularly prevalent in the developing world, where it is a common cause of morbidity and mortality in young children. It is transmitted by contaminated food or water, and may cause water-borne epidemics in the West. Person-to-person spread may occur in institutions. Giardiasis is now a recognized sexually transmitted disease, especially if there is oro-anal contact.
