Giardia lamblia is a flagellated protozoan parasite infecting the small intestine and biliary tree

-it is endemic around the world 

-risk factors: drinking contaminated water, hypochlorhydria, immunocompromise, unprotected sex, exposure to infected day care centers, camping sites, swimming areas

-After ingestion, cysts excyst in the small intestine and release flagellated trophozoites in the proximal small intestine. Both cysts and trophozoites are excreted in feces.  

-Chlorination does not destroy cysts; they can be eradicated from water by either boiling or filtration 

-In the United States and Europe, Giardiasis is the most common intestinal protozoan pathogen

Symptoms & Signs 

-the manifestations of infection range from asymptomatic carriage (most common) to chronic diarrhea and malabsorption 

Acute giardiasis: nausea, vomiting, abdominal pain, bloating, belching, flatus, diarrhea; The stool is greasy in appearance, foul-smelling, and floats. It is usually devoid of blood or mucus. 

Chronic giardiasis: can be episodic or continual; diarrhea, increased flatulence, sulfurous belching, weight loss, malabsorption,vitamin deficiencies,  growth retardation, dehydration; stools are foul smelling, greasy or frothy, without blood, pus or mucus. 


-It can be diagnosed by detection of parasite antigens in the feces, by identification of cysts or trophozoites in the feces or by nucleic acid amplification tests 

-Cysts are oval and contain four nuclei; Trophozoites are pear-shaped and contain 

two nuclei and four pairs (8) of flagella; they have ventral sucking disks 


Effective agents: Metronidazole, tinidazole, quinacrine, furazolidone, nitazoxanide and paromomycin 

-Unlike metronidazole, tinidazole, furazolidone is safe in pregnancy 

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