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Chapter 13: Infectious Diseases (ID)
Parasitic Infections
ID: Amebiasis
LTC Wortmann, MC, USAIntroduction: Third leading parasitic cause of death in developing nations. Caused by Entamoeba histolytica.
Transmitted through contaminated food or water. Incubation: 2-4 weeks.
Subjective: Symptoms
Gradual onset of bloody diarrhea with associated abdominal pain and tenderness.
Focused History Questions: Do you have bloody diarrhea and abdominal pain? (Abdominal pain and bloody
stools suggests amebiasis or bacterial colitis.) Do you have a fever? (1/3 of patients)
Objective: Signs
Using Basic Tools: Vital Signs: Temperature over 101°F
Inspection: Bloody, loose, mucus-containing stools
Palpation: The liver may be enlarged and tender.
Using Advanced Tools: Lab: Heme positive (Guaiac test) stool. O & P: Multiple examinations (minimum of
3) of stool to demonstrate E. histolytica trophozoites.
Assessment:
Differential Diagnosis
Diarrhea - giardiasis, viral gastroenteritis, bacterial gastroenteritis, cryptosporidiosis, isosporiasis, E. coli
0157:H7, shigellosis and inflammatory bowel disease.
Plan:
Treatment: Metronidazole 750 mg tid x 10 days followed by paromomycin 30 mg/kg/d in 3 divided doses
x 10 days. Maintain oral fluids.
Patient Education
General: Maintain adequate oral intake of fluids to avoid volume depletion.
Activity: As tolerated.
Diet: As tolerated.
Medications: Metronidazole should not be used in the first trimester of pregnancy. Avoid alcohol to avoid an
Antabuse-like effect (anxiety, vomiting, headache, etc.).
Prevention and Hygiene: Filters with pores < 1 micron or boiling for 1 min. can make water safe. Good
hand washing and safe food preparation.
Follow-up Actions
Return evaluation: If diarrhea continues, consider other etiologies. Stool should be examined after
successful treatment, as continued E. histolytica mandates re-treatment.
Consultation Criteria: Failure to improve after initiation of antibiotics.