Giardiasis

Giardiasis is the most common intestinal protozoa infection in children in the United States and in most of the world. More than 20,000 new cases of giardiasis are reported every year in the United States. It is caused by Giardia lamblia.

Giardia lamblia is a flagellated protozoan of the small intestine. Giardia lamblia is a cosmopolitan parasite of worldwide distribution and is an important cause if traveler’s diarrhea. Endemic worldwide, the infection is classically associated with drinking contaminated water, either in rural areas or in areas with faulty purification systems. But even ostensibly clean urban area water supplies can be contaminated intermittently.

Initially, the organisms were believed to damage the intestinal mucosa either through direct invasion or the elaboration of some toxin. Persons have acquired the infection in swimming pools. Fecal oral contamination allows person-to-person spread. Day care centers have been recognized as major sources of infection, with an incidence of up to 50% reported in some centers.

No symptoms occur in 25% of infected persons, facilitating spread to household contacts. Food-borne outbreaks also occur. Although infection is rare in neonates, giardiasis may occur at any age.

Giardiasis seldom fatal, it can be unpleasant. The acute symptoms of giardiasis mimic those of amoebic dysentery, bacillary dysentery, bacterial food poisoning and travelers diarrhea.
Giardiasis