Selective primary health care: strategies for control of disease in the developing world. XIX. Giardiasis.

Giardia lamblia infects millions of individuals throughout the world. In developed countries it appears primarily in waterborne epidemics of diarrhea. In developing countries, it is endemic, but only a small proportion of those infected appear ill. This flagellate parasite infects the small intestine of its host and may cause malabsorption and malnutrition, particularly among infants and young children. Little is known about the extent of illness caused by this parasite because few epidemiologic studies have been done; diagnosis is difficult and Giardia carriers frequently are simultaneously infected with other pathogens. Control measures include intermittent treatment of those infected and improved water supply and sanitation. Efforts to control individual infection can only be successful on a temporary basis. The greatest progress in control should derive from efforts to develop an effective vaccine.