Entamoeba histolytica: Difference between revisions

Latest revision as of 13:43, 7 October 2023

Background

Microbiology

Intestinal protozoan parasite within the genus Entamoeba
Microscopically distinguishable from the non-pathogenic E. dispar, E. moshkovskii, and E. bangladeshii

Epidemiology

Present worldwide, but most disease occurs in the developing world
Causes 34 to 50 million cases annually and up to 100,000 deaths

Clinical Manifestations

Amoebic Diarrhea and Dysentery

Amoebic diarrhea, with or without dysentery, is common
- About 15 to 30% of cases involve amoebic dysentery (with macroscopic or microscopic blood)
Typically a subacute onset over 3 to 4 weeks and abdominal pain
- However, can be up to months
Fever is rare, even in dysentery
In children, can lead to intussusception, perforation, and necrotizing colitis

Amoebic Liver Abscess

Amoebic liver abscess is far more common in men than women, and rare in children
Symptoms progress over 2 to 4 weeks, with fever (80%) and abdominal pain (80%)
- Right upper quadrant tenderness (75%), weight loss (40%), diarrhea (15-35%), cough (10%), and jaundice (10-15%)
- The pain is typically a dull ache in the right upper quadrant or epigastrium
More likely to present with abdominal pain and right upper quadrant tenderness than pyogenic liver abscess

Disseminated Amoebiasis

Metastatic infections are possible, most often from direct extension of a liver abscess
Most commonly spreads to chest, with empyema, bronchohepatic fistula, pericarditis
Cerebral disease is rare but can happen

Diagnosis

Microscopically indistinguishable from the non-pathogenic E. dispar, so needs molecular tests to confirm diagnosis
On aspiration, the fluid is classically odorless, thick, yellow-brown liquid, described as "anchovy paste"

Management

Diarrhea or Dysentery

Either
- Metronidazole 750 mg p.o. tid for 5 to 10 days
- Tinidazole 2 g PO daily for 3-5 days
Followed by a luminal agent, as below

Liver Abscess

Either
- Metronidazole 750 mg PO tid for 10 days, or
- Tinidazole 2 g PO daily for 5 days
Followed by a luminal agent:
- Paramomycin 500 mg p.o. tid for 7 days
- Iodoquinol 650 mg p.o. tid for 20 days
- Diloxanide furoate 500 mg p.o. tid for 10 days
May need surgery or aspiration if the lesion is large or medication has failed

Asymptomatic Carriage

Treat with a luminal agent, as above

Treatments in Canada

Metronidazole, iodoquinol, and paromomycin are all available in Canada

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+==Background==
-* Intestinal protozoan parasite
+===Microbiology===
-* Causes amebic dysentery
-* Microscopically distinguishable from the non-pathogenic ''E. dispar'', so needs molecular tests to confirm diagnosis
+*Intestinal protozoan parasite within the genus ''[[Entamoeba species|Entamoeba]]''
-{{DISPLAYTITLE:''Entamoeba histolytica''}}
+*Microscopically distinguishable from the non-pathogenic ''E. dispar'', ''E. moshkovskii'', and ''E. bangladeshii''
+===Epidemiology===
+*Present worldwide, but most disease occurs in the developing world
+*Causes 34 to 50 million cases annually and up to 100,000 deaths
+==Clinical Manifestations==
+===Amoebic Diarrhea and Dysentery===
+*[[Causes::Amoebic diarrhea]], with or without dysentery, is common
+**About 15 to 30% of cases involve [[Causes::amoebic dysentery]] (with macroscopic or microscopic blood)
+*Typically a subacute onset over 3 to 4 weeks and abdominal pain
+**However, can be up to months
+*Fever is rare, even in dysentery
+*In children, can lead to intussusception, perforation, and necrotizing colitis
+===Amoebic Liver Abscess===
+*[[Causes::Amoebic liver abscess]] is far more common in men than women, and rare in children
+*Symptoms progress over 2 to 4 weeks, with [[fever]] (80%) and [[abdominal pain]] (80%)
+**Right upper quadrant tenderness (75%), weight loss (40%), diarrhea (15-35%), cough (10%), and jaundice (10-15%)
+**The pain is typically a dull ache in the right upper quadrant or epigastrium
+*More likely to present with abdominal pain and right upper quadrant tenderness than [[pyogenic liver abscess]]
+===Disseminated Amoebiasis===
+*Metastatic infections are possible, most often from direct extension of a liver abscess
+*Most commonly spreads to chest, with empyema, bronchohepatic fistula, pericarditis
+*Cerebral disease is rare but can happen
+==Diagnosis==
+*Microscopically indistinguishable from the non-pathogenic ''E. dispar'', so needs molecular tests to confirm diagnosis
+*On aspiration, the fluid is classically odorless, thick, yellow-brown liquid, described as "anchovy paste"
+==Management==
+=== Diarrhea or Dysentery ===
+*Either
+**[[Is treated by::Metronidazole]] 750 mg p.o. tid for 5 to 10 days
+**[[Is treated by::Tinidazole]] 2 g PO daily for 3-5 days
+*Followed by a luminal agent, as below
+===Liver Abscess===
+*Either
+**[[Is treated with::Metronidazole]] 750 mg PO tid for 10 days, or
+**[[Is treated with::Tinidazole]] 2 g PO daily for 5 days
+*Followed by a luminal agent:
+**[[Is treated by::Paramomycin]] 500 mg p.o. tid for 7 days
+**[[Is treated by::Iodoquinol]] 650 mg p.o. tid for 20 days
+**[[Is treated by::Diloxanide furoate]] 500 mg p.o. tid for 10 days
+*May need surgery or aspiration if the lesion is large or medication has failed
+===Asymptomatic Carriage===
+*Treat with a luminal agent, as above
+=== Treatments in Canada ===
+* Metronidazole, iodoquinol, and paromomycin are all available in Canada
+== Further Reading ==
+* Adrienne J. Showler, Andrea K. Boggild. Entamoeba histolytica. <abbr>''CMAJ''</abbr> Sep 2013, 185 (12) 1064; '''DOI:''' [https://doi.org/10.1503/cmaj.121576 10.1503/cmaj.121576]{{DISPLAYTITLE:''Entamoeba histolytica''}}
 [[Category:Protozoa]]