Giardiasis. Taming this pervasive parasitic infection.

Parasitic infection due to Giardia lamblia can produce severe, disabling gastrointestinal symptoms. Outbreaks have been linked to contaminated municipal water supplies and situations involving person-to-person contact. Immunocompromised patients are especially at risk. Because microscopic examination of stool detects the parasite in only about half of infected patients, use of enzyme-linked immunosorbent assay to detect Giardia-specific antigen is becoming increasingly popular. In most patients, therapy with quinacrine (Atabrine) hydrochloride, metronidazole (Flagyl, Protostat), or a combination of the two is effective.