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Section 3. Summaries of Infectious Diseases
Amebiasis
Clinical Manifestations
Etiology
Epidemiology
Diagnostic Tests
Treatment
Isolation of the Hospitalized Patient
Control Measures
CLINICAL MANIFESTATIONS: Clinical syndromes associated with
Entamoeba histolytica infection include noninvasive intestinal
infection, intestinal amebiasis, ameboma, and liver abscess.
Disease is more severe in the very young, the elderly, and pregnant
women. Patients with noninvasive intestinal infection may be
asymptomatic or may have nonspecific intestinal tract complaints.
People with intestinal amebiasis (amebic colitis) generally
have 1 to 3 weeks of increasingly severe diarrhea progressing
to grossly bloody dysenteric stools with lower abdominal pain
and tenesmus. Weight loss is common, and fever occurs in one
third of patients. Symptoms may be chronic and may mimic inflammatory
bowel disease. Progressive involvement of the colon may produce
toxic megacolon, fulminant colitis, ulceration of the colon
and perianal area, and rarely, perforation. Progression may
occur in patients inappropriately treated with corticosteroids
or antimotility drugs. An ameboma may occur as an annular lesion
of the cecum or ascending colon that may be mistaken for colonic
carcinoma or as a tender extrahepatic mass mimicking a pyogenic
abscess. Amebomas usually resolve with antiamebic therapy and
do not require surgery.
In a small proportion of patients, extraintestinal disease may occur. Although the liver is the most common extraintestinal site, the lungs, pleural space, pericardium, brain, skin, and genitourinary tract also may be involved. Liver abscess may be acute with fever, abdominal pain, tachypnea, liver tenderness, and hepatomegaly or chronic with weight loss, vague abdominal symptoms, and irritability. Rupture of abscesses into the abdomen or chest may lead to death. Evidence of recent intestinal infection usually is absent.
ETIOLOGY: Entamoeba histolytica is classified into 2 species
that are morphologically identical but genetically distinct
protozoa. The pathogenic
E histolytica and the nonpathogenic
Entamoeba dispar are excreted as cysts or
. . . [Go to Full Text]
Related text in Red Book:
- Drugs for Parasitic Infections
Red Book
2006: 790-820.
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