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- Gloria Heresi, MD*
- Thomas G. Cleary, MD†
- *Fellow, Pediatric Infectious Diseases.
- †Director, Pediatric Infectious Diseases, University of Texas-Houston Health Sciences Center, Houston, TX.
IMPORTANT POINTS
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Most patients who have Giardia lamblia infections are asymptomatic.
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In the majority of patients diagnosed with G lamblia infection, the medical history, physical examination, and stool studies are sufficient to make the diagnosis.
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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.
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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.
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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 …
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