Giardia Lamblia Infection in Man

Leeuwenhoek in 1675, in examining his own stool, saw and described the protozoan now known as Giardia lamblia.1In 1859 Lambl described it under the name Cercomonas intestinalis. Stiles in 1915 placed it in the genus Giardia, calling it Giardia lamblia. The incidence of infection with Giardia lamblia varies markedly with the geographic location. It is much more frequently encountered in tropical and subtropical climates than in the temperate zone. Incidence in the United States has been found by Hegner, Root, Augustine and Huff2to average 12 per cent. In examinations of the stools of 1,539 selected patients and food handlers in the University of Chicago Clinics, this parasite was found in twenty-three instances (1.5 per cent). This incidence is considerably lower than that usually found in the North Temperate Zone. A probable explanation of this finding may be found in the fact that a higher income level