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Entamoeba histolytica

Aka: Entamoeba histolytica, E. histolytica, Amebiasis, Amebic Dysentery, Ameboma, Amoeba Histolytica Dysentery

I. See Also

  1. Diarrhea
  2. Infectious Diarrhea

II. Epidemiology

  1. Prevalence: 10% worldwide
  2. Asymptomatic cyst carriage in 90% cases
  3. Symptomatic cases per year: 50 million worldwide
  4. Fatalities per year: 100,000

III. Risk factors

  1. Mental health institutions (High Prevalence)
  2. Crowded living conditions
  3. Poor sanitation
  4. Travel to endemic areas
    1. Asia
    2. Africa
    3. Latin America

IV. Pathophysiology

  1. Two forms
    1. Cyst (12 um diameter): Spheres with up to 4 nucleii
      1. Divides into trophozoites in Small Intestine
      2. Cysts can survive weeks in moist environment
    2. Trophozoite (25 um long)
      1. Contains 1 nucleus and ingested RBCs
      2. Moves via finger-like pseudopods toward colon
      3. Some trophozoites transform into cysts
  2. Results in enterocolitis
    1. Intraluminal disease
      1. Profuse Diarrhea with malabsorption
      2. Ulceration of colon and terminal ilium
      3. Intestinal bleeding
    2. Systemic dissemination
      1. Liver Abscess
      2. Lung Abscess
      3. Brain abscess
  3. Transmission via fecal-oral route
    1. See Waterborne Illness
    2. See Foodborne Illness
    3. Food preparation contaminated by poor hygiene
    4. Human waste used for crop fertilization
    5. Oral-anal sex

V. Symptoms

  1. Acute
    1. Fulminant onset
    2. Cramping, moderate to severe Abdominal Pain
    3. Bloody, profuse Diarrhea
    4. Mucus in stools
    5. Tenesmus
    6. Malaise
  2. Chronic
    1. Normal stools alternate with symptomatic phase

VI. Signs

  1. Acute
    1. Fever
    2. Diffuse abdominal tenderness
    3. Dehydration
    4. Weight loss
  2. Chronic
    1. Fever
    2. Tenderness and cramping of cecum and ascending colon
  3. Liver Abscess (within 5 months of onset)
    1. Fever (10-15 of cases)
    2. RUQ Abdominal Pain or liver tenderness
    3. Liver friction rub if Liver Abscess present
    4. Diarrhea (33% of cases)

VII. Differential Diagnosis

  1. See Waterborne Illness
  2. See Foodborne Illness
  3. Appendicitis
  4. Inflammatory Bowel Disease (especially Crohn's Disease)

VIII. Complications

  1. Ameboma growth into intestinal lumen
    1. Risk of Bowel Obstruction
    2. Risk of Intussusception
  2. Toxic Megacolon
  3. Pneumatosis coli
  4. Abscess formation
    1. Lung Abscess
    2. Brain abscess
    3. Liver Abscess
      1. See signs above
      2. Risk of rupture
      3. Risk factors for complication
        1. Multiple cysts or cysts >10 cm in size
        2. Superior right liver lobe involvement
        3. Left liver lobe involvement
      4. Course
        1. Spontaneous resolution by 6 months in 66%
        2. Persist >1 year in 10%

IX. Labs

  1. Entamoeba histolytica stool antigen testing (preferred)
    1. Test Sensitivity: 87%
    2. Test Specificity: >90%
  2. Ova and Parasite exam (3 samples required)
    1. Fresh Stool Exam with Microscopy and gross exam
    2. Motile or encysted organisms
    3. Watery stool with mucus or blood
  3. Other tests
    1. Fecal Leukocytes positive
    2. Occult blood positive
    3. Fecal Eosinophilia (Charcot-Leyden crystals present)

X. Diagnostic Testing

  1. Endoscopy
    1. Mimics Crohn's Disease
    2. Colonic ulcerations
      1. Discrete ulcers of variable depth in right colon
      2. Exudative hyperemic ulcers with small Hemorrhages
  2. Biopsy
    1. Intramural trophozoites at edge of ulceration

XI. Radiology

  1. Barium Enema may show Ameboma
    1. Irregular barium distribution in ascending colon
  2. Right Upper Quadrant Ultrasound
    1. Hepatic Abscess (oval hypoechoic cyst)

XII. Management: Asymptomatic cysts

  1. Preferred agents
    1. Paromomycin 25-35 mg/kg/day orally divided three times daily for 7 days or
    2. Iodoquinol (Yodoxin) 650 mg orally three times daily for 20 days
  2. Alternative agent
    1. Diloxanide furoate (Furamide) 500 mg orally three times daily for 10 days

XIII. Management: Diarrhea or mild dysentery

  1. Requires combined use of both tissue and luminal agent
  2. Tissue agents for trophozoites (choose one)
    1. Metronidazole (Flagyl) 500 to 750 mg orally three times daily for 7-10 days or
    2. Tindazole 2 g orally daily for 3 days
  3. Luminal agents for cysts (choose one)
    1. Paromomycin 25-35 mg/kg/day orally divided three times daily for 7 days or
    2. Iodoquinol (Yodoxin) 650 mg orally three times daily for 20 days

XIV. Management: Severe disease (e.g. Liver Abscess)

  1. Requires combined use of both tissue and luminal agent
  2. Tissue agents for trophozoites (choose one)
    1. Metronidazole (Flagyl) 750 mg IV three times daily for 10 days or
    2. Tindazole 2 g orally daily for 5 days
  3. Luminal agents for cysts (choose one)
    1. Paromomycin 25-35 mg/kg/day orally divided three times daily for 7 days or
    2. Iodoquinol (Yodoxin) 650 mg orally three times daily for 20 days

XV. References

  1. Gilbert (2013) Sanford Guide
  2. Kucik (2004) Am Fam Physician 69(5):1161-8 [PubMed]
  3. Petri (1999) Clin Infect Dis 29:1117-25 [PubMed]

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Ontology: Amebiasis (C0002438)

Definition (MSHCZE) Infekce (nákaza) některým z rozli�ných amébních mikroorganismů. U většiny jednotlivců se jedná o asymptomatický stav nositelů (hostitelů) infekce, ale onemocnění se může vyskytnout v různém rozsahu od chronického mírného průjmu až po fulminantní (náhlou) úplavici.
Definition (NCI) A parasitic infectious disorder caused by amoebas. The parasite may cause colitis which is manifested with bloody diarrheas, abdominal pain, nausea and fever. In rare cases it may spread to the liver, brain and lungs.
Definition (MSH) Infection with any of various amebae. It is an asymptomatic carrier state in most individuals, but diseases ranging from chronic, mild diarrhea to fulminant dysentery may occur.
Definition (CSP) infection with any of various amebae; an asymptomatic carrier state in most individuals, but diseases ranging from chronic, mild diarrhea to fulminant dysentery may occur.
Concepts Disease or Syndrome (T047)
MSH D000562
ICD9 006.9, 006
ICD10 A06 , A06.9
SnomedCT 387754006, 186122001, 111909004, 154274000, 282008000, 187278004, 111910009, 388759003, 105637008
English Amebiases, Amoebiases, Amoebiasis, Amebiasis NOS, Amebiasis, unspecified, Amoebiasis NOS, Amoebiasis, unspecified, [X]Amebiasis, unspecified, [X]Amoebiasis, unspecified, amebiasis (diagnosis), amebiasis, infection due to Entamoeba histolytica, Amebiasis [Disease/Finding], amebiases, Amoebic infections, Amoebiasis (disorder), Amebiasis (disorder), Amoebic infection (disorder), [X]Amebiasis, unspecified (disorder), Amebiasis NOS (disorder), Amebic infection, Amoebic infection, Disease due to Endamoebidae (disorder), Disease due to Endamoebidae, Infection due to Entamoeba histolytica (disorder), Infection due to Entamoeba histolytica, Amebic infection (disorder), Amebiasis, Infection due to Entamoeba histolytica, SAI, Infection due to Entameba histolytica, SAI, Infection due to Entameba histolytica, Amebic infections, amoebiasis
Italian Infezioni amebiche, Amebiasi, non specificata, Amebiasi NAS, Amebiasi non specificata, Amoebiasi, Amebiasi
Dutch amoebiasis niet-gespecificeerd, amoebiasis NAO, Amoebiasis, niet gespecificeerd, amoebeninfecties, amoebiasis, Amoebiasis
French Amibiase, non précisée, Amibiase SAI, Infections amibiennes, Amibiase
German Amoebiasis, unspezifisch, Amoebiasis NNB, Amoebiase NNB, Amoebiasis, nicht naeher bezeichnet, Amoebiasis, Infektionen durch Amoeben, Amöbiase, Amöbiasis
Portuguese Amebíase NE, Amibiase, Infecções por amibas, Amebíase, Amoebíase
Spanish Amebiasis no especificada, Amebiasis NEOM, [X]amebiasis, no especificada, amebiasis, SAI (trastorno), amebiasis, SAI, [X]amebiasis, no especificada (trastorno), amebiasis (trastorno), amebiasis, enfermedad causada por Endamoebidae (trastorno), enfermedad causada por Endamoebidae, infección amebiana (trastorno), infección amebiana, infección amebiásica (trastorno), infección amebiásica, infección amébica, infección por Entamoeba histolytica (trastorno), infección por Entamoeba histolytica, Infecciones por amebas, Amebiasis, Amoebiasis
Japanese アメー�症�詳細�明, アメー�感染, アメー�症ＮＯＳ, ｱﾒｰﾊﾞｶ�ｾ�, ｱﾒｰﾊﾞｼｮｳNOS, ｱﾒｰﾊﾞｼｮｳ, ｱﾒｰﾊﾞｼｮｳｼｮｳｻｲﾌﾒｲ, アメー�肉芽腫, アメー�症, 肉芽腫-アメー�, ヨードアメー�症
Swedish Amöbainfektion
Czech amébiáza, Amébóza, Amébóza, blíže neur�ená, Amébové infekce, Amébóza NOS, amébóza
Finnish Amebiaasi
Russian AMEBIAZ, ABSTSESS AMEBNYI, �БСЦЕСС �МЕБ�ЫЙ, �МЕБИ�З
Korean 아메바�, �세불명� 아메바�
Croatian AMEBIJAZA
Polish Amebioza, Amebiaza, Pełzakowica
Hungarian Amoebiasis, nem meghatározott, amoebiasis k.m.n., Amőba fertőzések, amoebiasis, Amoebiasis, amoebiasis, nem meghatározott, Amoebiasis k.m.n.
Norwegian Amøbeinfeksjoner
Derived from the NIH UMLS (Unified Medical Language System)

Ontology: Ameboma (C0002445)

Concepts Disease or Syndrome (T047)
MSH D000562
ICD10 A06.3
SnomedCT 20958005
English Amebomas, ameboma, ameboma (diagnosis), Ameboma NOS, Amebic granuloma, Amoeboma, Amoebic granuloma, Ameboma (disorder), Ameboma
Portuguese Ameboma
Spanish Ameboma, ameboma (trastorno), ameboma, granuloma amebiano, granuloma amébico
German Amöbom
Italian Ameboma
French Amoebome, Amébome
Dutch Amoeboom
Derived from the NIH UMLS (Unified Medical Language System)

Ontology: Entamoeba histolytica (C0014323)

Definition (MSHCZE) Améba vyvolávající tzv. amébovou úplavici (dysenterii). U �lověka se vyskytuje ve dvou formách. Forma minuta – trofozoit o velikosti 10–20 μm, tvoří �tyřjaderné cysty, které slouží jako zdroj infekce. Forma dysenterica (magna) – patogenní forma, trofozoit o velikosti 20–40 μm, který vniká do střevní sliznice, destruuje buňky. Netvoří cysty. Hematogenním rozsevem vniká do dalších orgánů (játra, plíce, mozek aj.). Přenáší se alimentárně, výskyt je kosmopolitní; E. h. je velmi rozšířena. Klinicky manifestní onemocnění vzniká jen u �ásti osob a má různou klinickou závažnost. (cit. Velký lékařský slovník online, 2013 http://lekarske.slovniky.cz/ )
Definition (MSH) A species of parasitic protozoa causing ENTAMOEBIASIS and amebic dysentery (DYSENTERY, AMEBIC). Characteristics include a single nucleus containing a small central karyosome and peripheral chromatin that is finely and regularly beaded.
Definition (CSP) species of parasitic protozoa causing entamoebiasis and amebic dysentery; characteristics include a single nucleus containing a small central karyosome and peripheral chromatin that is finely and regularly beaded.
Concepts Eukaryote (T204)
MSH D004748
SnomedCT 4716008
LNC LP16698-0, MTHU004659
English Endamoeba histolytica, Entamoeba histolytica, Eh - Entameba histolytica, Endamoeba histolyticas, histolytica, Endamoeba, histolytica, Entamoeba, histolyticas, Entamoeba, histolyticas, Endamoeba, Entamoeba histolyticas, entamoeba histolytica, entameba histolytica, histolytica entamoeba, ENTAMOEBA HISTOLYTICA, Eh - Entamoeba histolytica, Entamoeba histolytica (organism), Entameba histolytica
Swedish Entamoeba histolytica
Czech Entamoeba histolytica
Spanish Entamoeba histolytica, Entameba histolytica, Entamoeba histolytica (organismo), Endamoeba histolytica
Finnish Entamoeba histolytica
Russian AMEBA DIZENTERIINAIA, KISHECHNAIA AMEBA, ENTAMOEBA HISTOLITICA, �МЕБ� ДИЗЕ�ТЕРИЙ��Я, КИШЕЧ��Я �МЕБ�
Japanese 赤痢アメー�
Polish Pełzak czerwonki
Norwegian Endamoeba histolytica, Entamoeba histolytica
French Entamoeba dysenteriae, Entamoeba histolytica
German Entamoeba dysenterica, Entamoeba histolytica
Italian Entamoeba histolytica
Dutch Dysenterieamoebe, Endamoeba histolytica, Entamoeba histolytica, Ingewandsamoebe
Portuguese Endamoeba histolytica, Entamoeba histolytica
Derived from the NIH UMLS (Unified Medical Language System)

Ontology: Amoeba histolytica dysentery (C0857976)

Concepts Disease or Syndrome (T047)
Dutch Amoeba histolytica-dysenterie
French Dysenterie à Amoeba histolytica
German Ruhr infolge von Amoeba histolytica
Italian Dissenteria da ameba istolitica
Spanish Disentería por Amoeba histolytica
Japanese 赤痢アメー�性赤痢, ｾｷﾘｱﾒｰﾊﾞｾｲｾｷﾘ
Czech Dyzenterie způsobená Entamoeba histolytica
English Amoeba histolytica dysentery, Ameba histolytica dysentery
Hungarian Amoeba histolytica dysenteria
Portuguese Disenteria por ameba histolítica
Derived from the NIH UMLS (Unified Medical Language System)

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