P1: SBT
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Amebiasis 107to show it. Less sensitive than Ag tests, cannot distinguish E. histolyt-
ica from E. dispar.
E. histolytica-specific antigen tests (fecal or serum) – ELISA, IF, or
radioimmunoassay – very useful in diagnosis.
Serology – Abs to E. histolytica (not formed to E. dispar) usually in
1 week of acute infection and can last years; therefore less useful in
patients from endemic areas
■Systemic disease: Ultrasound or CT scan locates abscess. Serology,
done as IHA or CIE, is positive in 95% of cases of liver abscess. For
cutaneous disease, use biopsy. Stool O&P exam positive in about 50%
of cases.
■Other tests: Intestinal disease: serology, done as IHA, positive in 85%.
PCR not widely available. Barium enema can suggest ulcerative dis-
ease, and will locate amebomas (which can resemble carcinoma).
Sigmoidoscopy or colonoscopy with biopsy of ulcer (which is typi-
cally well demarcated with undermined edges) shows amebae.
➣Systemic disease: Chest X-ray can show elevated right diaphragm
and fluid in right chest.differential diagnosis
■Intestinal disease: Entamoeba dispar, which looks identical to E
histolytica but is non-pathogen. Ulcerative colitis, Crohn’s disease,
infectious diarrheas, carcinoma of colon.
■Systemic disease: Pyogenic liver abscess (main distinguishing fea-
ture is positive IHA test), tumors. Skin ulcers resemble pyoderma,
tuberculosis, fungal disease.management
What to Do First
■All forms: assess severity, correct fluid and electrolyte problems,
transfuse if needed.
General Measures
■Investigate others who may have shared contaminated items.specific therapy
Indications
■All infected persons, even asymptomatic since they can spread the
infection. When E. histolytica and E. dispar cannot be distinguished,
probably best to treat as histolytica.