AmebiasisAmebiasis

AMEBIASIS AMEBIASIS IncidenceIncidence

Possibly 10 % of world's population infectedPossibly 10 % of world's population infectedPrevalence in tropical countries : 30 %Prevalence in tropical countries : 30 %Prevalence in U.S.A. : 1 to 5 %Prevalence in U.S.A. : 1 to 5 %Man is primary reservoirMan is primary reservoirPrevalence in U.S. homosexual population : Prevalence in U.S. homosexual population : 25 %25 %

Reported epidemic in Grand Junction Reported epidemic in Grand Junction Colorado from chiropractic "colonic therapy" Colorado from chiropractic "colonic therapy" irrigationirrigation

AMEBIASIS AMEBIASIS PathophysiologyPathophysiology

Two life cycle forms (as for Giardia) :Two life cycle forms (as for Giardia) :–Trophozoite : causes illnessTrophozoite : causes illness–Cysts : passed in stool, are infectiousCysts : passed in stool, are infectious

Transmission by fecal-oral routeTransmission by fecal-oral routeMost infections are asymptomaticMost infections are asymptomaticAttack rates 5 to 30 %Attack rates 5 to 30 %Cysts can remain viable for months in Cysts can remain viable for months in moist environmentmoist environment

Cysts sensitive to chlorination, dessication, Cysts sensitive to chlorination, dessication, boilingboiling

Iodine stain of Entamoeba histolytica trophozoite in stool

Entamoeba histolytica tropohozoites in stained stool

Life cycle of Entamoeba histolytica

AMEBIASIS AMEBIASIS PathologyPathology

Main pathology is in colonMain pathology is in colon–Initial mucosal inflammationInitial mucosal inflammation–Then mucosal erosions, then ulcersThen mucosal erosions, then ulcers

Extraintestinal spread is hematogenousExtraintestinal spread is hematogenousLarge abscesses can develop in :Large abscesses can develop in :–LiverLiver–LungLung–BrainBrain–Other tissuesOther tissues

Amebic liver abscess

Amebic pleuro-pericardial abscess

AMEBIASIS AMEBIASIS Symptoms Symptoms

Incubation period variable, but often 5 to 10 Incubation period variable, but often 5 to 10 daysdays

Crampy abdominal painCrampy abdominal painDysenteryDysentery+/- weight loss+/- weight loss+/- anorexia, nausea+/- anorexia, nauseaFocal symptoms if complications developFocal symptoms if complications develop

AMEBIASIS AMEBIASIS ComplicationsComplicationsFatality rate for amebic dysentery is 2 %Fatality rate for amebic dysentery is 2 %Overall complication rate is 3 to 4 %Overall complication rate is 3 to 4 %–Colon perforation Colon perforation –Toxic megacolonToxic megacolon–Ameboma (abd. mass, bowel obstruction)Ameboma (abd. mass, bowel obstruction)–Liver abscess - may rupture into pleural or Liver abscess - may rupture into pleural or pericardial spacepericardial space–Brain abscessBrain abscess

May cause 40,000 to 75,000 deaths May cause 40,000 to 75,000 deaths annually annually (2nd or 3rd parasitic cause of death in the world after (2nd or 3rd parasitic cause of death in the world after malaria +/- leishmaniasis )malaria +/- leishmaniasis )

Sigmoid colon perforation from amebiasis

Externally ruptured amebic groin abscess

AMEBIASIS AMEBIASIS DiagnosisDiagnosis

Fresh stool or colon mucus shows cysts or Fresh stool or colon mucus shows cysts or trophozoitestrophozoites

Often 3 or more stool exams requiredOften 3 or more stool exams requiredSerologic tests important to distinguish Serologic tests important to distinguish amebiasis from ulcerative colitisamebiasis from ulcerative colitis

Sigmoidoscopy useful to inspect ulcers Sigmoidoscopy useful to inspect ulcers and obtain stool or mucus for culture & and obtain stool or mucus for culture & stainstain

Abd. CT needed if liver abscess suspectedAbd. CT needed if liver abscess suspected

Computed tomography scan showing amebic liver abscess

Aspirating “anchovy paste” pus from amebic liver abscess

AMEBIASIS AMEBIASIS TreatmentTreatment

Two general classes of meds used:Two general classes of meds used:–Tissue amebacides : combat invasive Tissue amebacides : combat invasive amebiasis in bowel & liveramebiasis in bowel & liverMetronidazoleMetronidazoleEmetine, dehydroemetineEmetine, dehydroemetineChloroquineChloroquine

–Lumenal drugs : kill amebas within colonLumenal drugs : kill amebas within colonIodoquinolIodoquinolParamomycinParamomycinDiloxanideDiloxanide

AMEBIASIS AMEBIASIS Treatment of Asymptomatic CarriersTreatment of Asymptomatic Carriers

Recommended for:Recommended for:–Food handlers (always)Food handlers (always)–All cases in low incidence regions ( U.S.A., All cases in low incidence regions ( U.S.A., Europe)Europe)–Not always recommended for asymptomatic Not always recommended for asymptomatic cases in high incidence tropical countriescases in high incidence tropical countries

AMEBIASIS : Treatment Regimens for AMEBIASIS : Treatment Regimens for Asymptomatic CarriersAsymptomatic Carriers

IodoquinolIodoquinol–650 mg tid x 10 days (40 mg / kg / day )650 mg tid x 10 days (40 mg / kg / day )–Side effects mild : nausea, emesis, rashSide effects mild : nausea, emesis, rash

ParamomycinParamomycin–500 mg tid x 7 to 10 days (30 mg / kg / day)500 mg tid x 7 to 10 days (30 mg / kg / day)–OK in pregnancyOK in pregnancy

Diloxanide furoate (Furamide)Diloxanide furoate (Furamide)–500 mg tid x 10 days (20 mg / kg / day)500 mg tid x 10 days (20 mg / kg / day)–Only available in U.S.A. by calling CDC in Only available in U.S.A. by calling CDC in AtlantaAtlanta

AMEBIASIS : Treatment of Invasive DiseaseAMEBIASIS : Treatment of Invasive Disease

Metronidazole 750 mg tid x 10 days, followed Metronidazole 750 mg tid x 10 days, followed by iodoquinol 650 mg tid x 20 days (or by iodoquinol 650 mg tid x 20 days (or paramomycin 25 to 30 mg / kg / day in 3 paramomycin 25 to 30 mg / kg / day in 3 divided doses x 7 days)divided doses x 7 days)

Dehydroemetine one to 1.5 mg / kg / day Dehydroemetine one to 1.5 mg / kg / day (max. 90 mg / day) IM up to 5 days following (max. 90 mg / day) IM up to 5 days following iodoquinoliodoquinol

Tetracycline 500 mg qid x 10 days (indirect Tetracycline 500 mg qid x 10 days (indirect amoebacidal action)amoebacidal action)

Chloroquine phosphate : 2nd line agent for extralumenal infection ; Chloroquine phosphate : 2nd line agent for extralumenal infection ; 1gram / day, then 500 mg / day x 2 to 3 weeks1gram / day, then 500 mg / day x 2 to 3 weeks