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For further information, see CMDT Part 35-10: Giardiasis
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Essentials of Diagnosis
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Acute diarrhea; may be profuse and watery
Chronic diarrhea with greasy, malodorous stools
Abdominal cramps, distention, and flatulence
Cysts or trophozoites in stools
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General Considerations
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This upper small intestine infection is caused by the flagellate Giardia lamblia (also called G intestinalis and G duodenalis)
The organism occurs in feces as a flagellated trophozoite and as a cyst
Reservoirs for infection
Under moist, cool conditions, cysts can survive in the environment for weeks to months
Transmission occurs as a result of
Infectious dose is low, requiring as few as 10 cysts
Hypogammaglobulinemia, low secretory IgA levels in the gut, achlorhydria, and malnutrition favor development of infection
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The parasite occurs worldwide, especially in areas with poor sanitation
In the United States and Europe, the infection is the most common intestinal protozoal pathogen
US estimate is 100,000 to 2.5 million new infections leading to 5000 hospital admissions yearly
Groups at special risk include
Travelers to endemic areas
Persons who swallow contaminated water during recreation or wilderness travel
Men who have sex with men
Persons with impaired immunity
Multiple cases are common in households, children's day care centers, and residential facilities
Outbreaks occur from contamination of water supplies
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About 50% of infected persons have no discernable infection and about 10% become asymptomatic cyst passers
Acute diarrheal syndrome develops in 25–50% of persons
Incubation period is usually 1–3 weeks but may be longer
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May resolve spontaneously but is commonly followed by chronic diarrhea
May begin gradually or suddenly
May last days or weeks and is usually self-limited
The initial illness may include profuse watery diarrhea
Hospitalization may be required due to dehydration, particularly in young children
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Abdominal cramps, bloating, flatulence, nausea, malaise, and anorexia are typical
Malabsorption may also be present
Fever and vomiting are uncommon
Diarrhea
Stools are greasy or frothy and foul smelling, without blood, pus, or mucus
Weight loss is frequent
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Differential Diagnosis
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Viral or bacterial gastroenteritis
Amebiasis
Lactase deficiency
Irritable bowel syndrome
Malabsorption due to other causes, eg, celiac sprue
Laxative abuse
Crohn disease
Cryptosporidiosis
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