Giardia

IMPORTANT POINTS

1. Most patients who have Giardia lamblia infections are asymptomatic.

2. In the majority of patients diagnosed with G lamblia infection, the medical history, physical examination, and stool studies are sufficient to make the diagnosis.

3. Giardiasis in the United States is frequent in child care centers, facilities for the mentally retarded, family members of an index case, campers, and children in swimming classes.

4. Empiric treatment of giardiasis is advised in children who present with chronic diarrhea and malabsorption symptoms and negative stool studies before a more aggressive diagnostic approach is initiated.

5. Improvement in level of hygiene is the best way to interrupt transmission of infections in institutions.

Giardia lamblia is a protozoan parasite that has a worldwide distribution; in the United States and most other highly industrialized countries, it is the intestinal parasite identified most commonly. G lamblia was identified in 1681 by Von Leewenhock in his stools, and for centuries it was thought to represent a nonpathogenic organism. In the past 20 years, however, data have accumulated demonstrating that, at times, G lamblia can be a pathogen, causing disease in both sporadic and epidemic forms. Nevertheless, the majority of human infections are asymptomatic.

Etiology

G lamblia is a flagellated protozoa that has two life cycle stages: trophozoite and cyst. The trophozoite usually is seen in preparations of duodenal mucosa or fresh diarrheic stools. It is pear-shaped and dorsally convex with a spiral organelle, the sucking disk, on the ventral surface, which is its mode of attachment to the mucosal surface. The trophozoite is 10 to 21 mcm in length and 5 to 15 mcm in width, with two symmetric nuclei and four pairs of flagella. It resembles a human face on stained preparations. The cyst, the most common form seen in stool, is oval, measures 8 to 12 mcm long and 5 …