الله بسمالرحیم الرحمن

AmebiasisAmebiasis

(Amebic Dysentery)(Amebic Dysentery)

Dr. M.H.ANVARIDr. M.H.ANVARI

AmebiasisAmebiasis(Amebic Dysentery)(Amebic Dysentery)

Causal agentCausal agent: : Entamoeba histolyticaEntamoeba histolytica is well recognized is well recognized as a pathogenic amoeba.as a pathogenic amoeba.

Geographic DistributionGeographic Distribution: Worldwide, with higher : Worldwide, with higher incidence of amebiasis in developing countries. incidence of amebiasis in developing countries. 

In industrialized countries, risk groups include male In industrialized countries, risk groups include male homosexuals, travelers and recent immigrants, and homosexuals, travelers and recent immigrants, and institutionalized populations.institutionalized populations.

History: Loosh was first described in 1875

MorphologyMorphology Different form of E. histolytica; Different form of E. histolytica;

1- trophozoite 1- trophozoite

2- precyst2- precyst

3- cyst(1, 2, 4 nuclei)3- cyst(1, 2, 4 nuclei)

Trophozoite chractereTrophozoite chractere

SizeSize: : 12-6012-60μμm m in diameter in diameter; ;

Non-invasive form ( minuta) / E. dispareNon-invasive form ( minuta) / E. dispare Invasive form (magna) contain RBC, E. histolyticaInvasive form (magna) contain RBC, E. histolytica PseudopodiaPseudopodia: :

MotilityMotility: :

EctoplasmEctoplasm::

EndoplasmEndoplasm: : may be contain ingested may be contain ingested RBCRBC NucleoplasmNucleoplasm::

Non-invasive forminvasive form

Different form of E.histolytica cystDifferent form of E.histolytica cyst

Life cycleLife cycle

Life cycle

EpidemiologyEpidemiology PrevalencePrevalence of amebic infection varies with level of sanitation of amebic infection varies with level of sanitation

and generally higher in tropics and subtropics than in and generally higher in tropics and subtropics than in tempearate climates. tempearate climates.

*Worldwide prevalence is about 10% to 50%*Worldwide prevalence is about 10% to 50% **Cyst passersCyst passers are important source of infection are important source of infection

The true estimated prevalence of E. histolytica is close to 1% The true estimated prevalence of E. histolytica is close to 1% worldwide.worldwide.

Entamoeba histolyticaEntamoeba histolytica is the second leading cause of is the second leading cause of mortality due to parasitic disease in humans. (The first being mortality due to parasitic disease in humans. (The first being malaria). Amebiasis is the cause of an estimated malaria). Amebiasis is the cause of an estimated 50,000-50,000-100,000100,000 deaths each year. deaths each year.

TransmissionTransmission

1-driect contact of person to person( fecal-oral)1-driect contact of person to person( fecal-oral) 2- Veneral transmission among homosexual 2- Veneral transmission among homosexual

males( oral-analmales( oral-anal 3- Food or drink contaminated with feces containing 3- Food or drink contaminated with feces containing

the E.his. cystthe E.his. cyst 4- Use of human feces (night soil) for soil fertilizer4- Use of human feces (night soil) for soil fertilizer 5- contamination of foodstuffs by flies, and possibly 5- contamination of foodstuffs by flies, and possibly

cockroachescockroaches

PathogenesisPathogenesis

Effective factores:Effective factores: 1- strain virulence1- strain virulence: : - classic strain - classic strain - non-classic strain; Laredo , Huff, ….- non-classic strain; Laredo , Huff, …. - pathogen zymodemes- pathogen zymodemes

2- susceptibility of the host; nutrition status, immune-sys.2- susceptibility of the host; nutrition status, immune-sys. 3- breakdown of immunologic barrier (tissue invasion)3- breakdown of immunologic barrier (tissue invasion)

Pathogenicity mechanismsPathogenicity mechanisms 1- secreting proteolytic enzymes( histolysine ) 1- secreting proteolytic enzymes( histolysine )

and cytotoxic substances. and cytotoxic substances. 2 - contact-dependent cell killing2 - contact-dependent cell killing 3 – cytophagocytosis3 – cytophagocytosis

Amebic killing target cell: Amebic killing target cell:

1- receptore-mediated adherence of amebae to target cell ( adherence 1- receptore-mediated adherence of amebae to target cell ( adherence lectin)lectin)

2- amebic cytolysis of target cell 2- amebic cytolysis of target cell 3- amebic phagocytosis of killed target cell3- amebic phagocytosis of killed target cell

Clinical symptomsClinical symptoms Asymptomatic infection Symptomatic infectionAsymptomatic infection Symptomatic infection

Intestinal Amebiasis Extraintestinal AmebiasisIntestinal Amebiasis Extraintestinal Amebiasis

Dysenteric Non-Dysenteric colitisDysenteric Non-Dysenteric colitis Hepatic Pulmonary The extra Hepatic Pulmonary The extra focifoci

Liver abscces Acut nonsupprativeLiver abscces Acut nonsupprative

Intestinal Amebiasis symptoms: Intestinal Amebiasis symptoms: Diarrhea or dysentery, abdominal pain, cramping , anorexia, Diarrhea or dysentery, abdominal pain, cramping , anorexia, weight loss, chronic fatigueweight loss, chronic fatigue

Pathology of AmebiasisPathology of Amebiasis

Flask-like UlcerFlask-like Ulcer

Extra-ntestinalAmebiasisExtra-ntestinalAmebiasis

Pyogenic- Liver AbscessPyogenic- Liver Abscess

Liver abscessLiver abscess

This is an amebic abscess of liver. Abscesses may arise in liver when there is seeding of infection from the bowel, because the infectious agents are carried to the liver from the portal venous circulation.

DiagnosisDiagnosis

Paraclinical Diagnosis:Paraclinical Diagnosis: Sigmoidoscopic examination:Sigmoidoscopic examination:

precence of a grossly normal mucosa between the ulcers serves to precence of a grossly normal mucosa between the ulcers serves to differentiate amebic from bacillary dysentery,( the entire mucosa being differentiate amebic from bacillary dysentery,( the entire mucosa being involvoed in bacillary dysentery).involvoed in bacillary dysentery).

HepatomegallyHepatomegally C.B.C. : C.B.C. : leukocytosis in Amebic dys. rises above 12000 per leukocytosis in Amebic dys. rises above 12000 per

microliter, but counts may reach 16000 to 20000 per microliter.microliter, but counts may reach 16000 to 20000 per microliter.

Laboratory DiagnosisLaboratory Diagnosis Entamoeba histolyticaEntamoeba histolytica must be differentiated from other intestinal must be differentiated from other intestinal

protozoa including: E. coli, E. hartmanni, E. dispare,……protozoa including: E. coli, E. hartmanni, E. dispare,……

Differentiation is possibleDifferentiation is possible, , but not always easy, based on morphologic but not always easy, based on morphologic characteristics of the cysts and trophozoites.characteristics of the cysts and trophozoites.

   The nonpathogenicThe nonpathogenic Entamoeba disparEntamoeba dispar, , however, is morphologically however, is morphologically

identical toidentical to E. histolyticaE. histolytica, , and differentiation must be based onand differentiation must be based on isoenzymaticisoenzymatic or or immunologic analysisimmunologic analysis. . 

Molecular methods are also useful in distinguishing between Molecular methods are also useful in distinguishing between E. E. histolyticahistolytica and and E. disparE. dispar and can also be used to identify and can also be used to identify E. E. poleckipolecki. .

MicroscopyMicroscopy

Microscopic identification Microscopic identification

This can be accomplished using:This can be accomplished using:

Fresh stool: wet mounts and permanently stained preparations Fresh stool: wet mounts and permanently stained preparations (e.g., trichrome). (e.g., trichrome).

Concentrates from fresh stool: wet mounts, with or without Concentrates from fresh stool: wet mounts, with or without iodine stain, and permanently stained preparations (e.g., iodine stain, and permanently stained preparations (e.g., trichrome). trichrome). 

Trophozoites ofTrophozoites of Entamoeba histolytica Entamoeba histolytica //EE. . dispar dispar (( trichrome staintrichrome stain ))

   

Microscopy

 AB

 

In the absence of erythrophagocytosis, the pathogenic E. histolytica is morphologically indistinguishable from the nonpathogenic E. dispar!

  Each trophozoite has a single nucleus, which has a centrally placed karyosome and uniformly distributed peripheral chromatin.

Trophozoites ofTrophozoites of Entamoeba histolyticaEntamoeba histolytica with ingested with ingested

erythrocytes erythrocytes ((trichrome staintrichrome stain))

The ingested erythrocytes appear as dark inclusions.  Erythrophagocytosis is the only morphologic characteristic that can be

used to differentiate E. histolytica from the nonpathogenic E. dispar.

             

          

                                      

    EF

Cysts ofCysts of Entamoeba histolytica Entamoeba histolytica //EE. . dispardispar

GHIGHI

                                                       

     

                                                       

     

                                                         

     GHI

Cysts of Entamoeba histolytica/E. dispar, permanent preparations stained with trichrome.

 

ImmunodiagnosisImmunodiagnosis(Antibody Detection)(Antibody Detection)

1- Antibody detection

2- Antigen detection may be useful as an adjunct to microscopic diagnosis

The indirect hemagglutination The indirect hemagglutination ((IHAIHA))

The EIA test detects antibody specific for The EIA test detects antibody specific for E. histolyticaE. histolytica in in approximately 95% of patients with extraintestinal amebiasis, approximately 95% of patients with extraintestinal amebiasis, 70% of patients with active intestinal infection, and 10% of 70% of patients with active intestinal infection, and 10% of asymptomatic persons who are passing cysts of asymptomatic persons who are passing cysts of E. histolyticaE. histolytica.  . 

Antigen DetectionAntigen Detection

Antigen detection may be useful as an adjunct to microscopic Antigen detection may be useful as an adjunct to microscopic diagnosis in detecting parasites and to distinguish between diagnosis in detecting parasites and to distinguish between pathogenic and nonpathogenic infectionspathogenic and nonpathogenic infections..  

Recent studies indicate improved sensitivity and specificity of Recent studies indicate improved sensitivity and specificity of fecal antigen assays with the use of monoclonal antibodies fecal antigen assays with the use of monoclonal antibodies which can distinguish betweenwhich can distinguish between EE. . histolyticahistolytica andand EE. . dispardispar infectionsinfections. .

Molecular diagnosisMolecular diagnosis

In reference diagnosis laboratories, PCR is the In reference diagnosis laboratories, PCR is the method of choice for discriminating between method of choice for discriminating between the pathogenic speciesthe pathogenic species ((EE. . histolytica)histolytica) from the from the (nonpathogenic species(nonpathogenic species ( (EE. . dispardispar..

TreatmentTreatment Intestinal Amebiasis:Intestinal Amebiasis: **Asymptomatic amebiasis(cyst passer)Asymptomatic amebiasis(cyst passer): : Diloxanide furoate Diloxanide furoate

( furamide)( furamide) 500 mg 3 times daily / 10 days500 mg 3 times daily / 10 days

**Symptomatic amebiasis ( troph. & cyst):Symptomatic amebiasis ( troph. & cyst): - Iodoquinol , 650 mg 3 - Iodoquinol , 650 mg 3 times daily/ 20 days or Metronidazole (Flagyl) , 750 mg 3 times daily/ 10 times daily/ 20 days or Metronidazole (Flagyl) , 750 mg 3 times daily/ 10 daysdays

*Amebic *Amebic colitis: Chloroquine, 250 mg 2 times daily colitis: Chloroquine, 250 mg 2 times daily

* Acute amebic dysentery: Emetine hydrochloride, 1mg/kg daily IM or SC* Acute amebic dysentery: Emetine hydrochloride, 1mg/kg daily IM or SC

TreatmentTreatment

Extraintestinal AmebiasisExtraintestinal Amebiasis::

**Amebic liver abscess, ameboma:Amebic liver abscess, ameboma:

Metronidazole, as above plus dehydroemetine / 10 days or Metronidazole, as above plus dehydroemetine / 10 days or Metronidazole or dehydroemetine as above plus Chloroquine , Metronidazole or dehydroemetine as above plus Chloroquine , 500 mg 2 times daily / 2 days,…..500 mg 2 times daily / 2 days,…..