Giardiasis: a common, sexually transmissible parasitic diarrhea with pitfalls in diagnosis.

Giardia lamblia is the number one intestinal parasite in the United States. Symptoms of giardiasis include upper abdominal pain and distress, flatulence, nervousness, and diarrhea. Multiple stool specimens examined for ova and parasites by nonexpert parasitologists will frequently not provide the diagnosis, and special studies must then be done. Antibiotics, antidiarrheals, certain enema preparations, and oily laxatives can cause a temporary disappearance of parasites from the stool. Treatment of choice is a five-day course of quinacrine hydrochloride. Recently, attention has been brought to the fact that oral sex may be responsible for transmission in a significant number of cases of giardiasis.