AMEBIASIS

Infection caused by Entamoeba hystolytica

90 % cases are asymptomaticFirst described by LÖsch (1875) from

a patient in Leningrad and discovered a trophozoit form

Quinche & Roos (1893) discovered a cyst form

Walker & Sellards proved that E, hystolytica caused amebic colitis

ETIOLOGY

Entamoeba hystolytica (pathogen ) & Entamoeba dispar (apathogen)E. hystolytica :Trophozoit : hystolytica & minuta

20-40 um (12-50 um), round nucleus, endoplasma (food vacuoles

RBC, phagocytized elements), clear ectoplasmaCyst : 10-20 um, oval or round, 1 – 4

nuclei

Entamoeba hystolyticaLIFE CYCLE …..(1)

Infective cyst is ingested the wall is digested in small intestines released of 4 quadrinucleat ameba.Passed into large intestine to grow and divide by binary fision to form trophozoitesTrophozoites live in the lumen and mucosal crypt of the large bowel (caecum, descending colon, recto-sigmoid)

Entamoeba hystolyticaLIFE CYCLE …..(2)

Invasion of mucosa and passage via bloodstream may occur colitis, liver abscessIn the absent of diarrhea, trophozoites round up and encyst in the lumen of large intestines (never in the tissue) passed in the faecesWithin few hours cysts are infected

EPIDEMIOLOGY

Worldwide , tropical regionInfect 10 % of world populationThird cause of death among parasitic diseases (schistosomiasis, malaria)Relevent factors in transmission : fecal disposal, water-borne infections, food handlers, personal hygiene, arthropodes as mechanical vectors.Humans are the principal reservoir

PATHOGENESIS

Trophozoites in the intestinal lumenDepletion of intestinal mucus, diffuse inflammation, disruption of the epithelial barrierAttach to the interglandular epithelMicroulceration of the mucosa (cecum sigmoid colon, rectum)Submucosal extension of ulceration flask shaped ulcer

CLINICAL MANIFESTATION ….. (1)

Asymptomatic cyst passage intestinal amebiasis fulminant disease

Asymptomatic cyst passage

most common type

persistent state

symptomatic form

CLINICAL MANIFESTATION ……(2)

Symptomatic amebic colitisdevelops 2-6 weeks after ingestion of infected cystlower abdominal pain, mild diarrhea malaise, weight loss full blown dysentriaestool : little fecal material, blood, mucus

CLINICAL MANIFESTATION ….(3)

Toxic megacolonfulminant intestinal infectionhigh fever, profused diarrhea, severe

abdominal pain, severe bowel dilatation with intramural airchildren, geriatric, steroidChronic amebic colitisuncommon, mimic IBS

CLINICAL MANIFESTATION ….(4)

Ameboma (amebic granuloma)excessive production of granulation tissuececum, rectosigmoidpresent as an irregular tumorpain, palpable mass, obstructive

symptoms, haemorrhage

CLINICAL MANIFESTATION ….(5)

Amebic liver abscesspreceded by intestinal colonizationtrophozoites invade vein through portal systemsliver parenchyma is replaced by necrotic materials anchovy paste) surrounded by a thin rim of congested liver tissueameba may be found near the capsule of the abscess

CLINICAL MANIFESTATION …..(6)

Amebic liver abscessfebrile, right upper quadrant abdominal

pain radiate to the shoulder, hepato- megaly, weight losselevated right dome of diaphragm on

chest X raycomplication : rupture amebic empyema, peritonitis, pericarditis, cardiac tamponade

CLINICAL MANIFESTATION …..(7)

Other form of extraintestinal amebiasis

- Cutaneus and genital amebiasis

- Pleuropulmonary amebiasis- Brain abscess

DIAGNOSIS ……(1)

AnamnesisPhysical diagnosisLaboratory- Stool : E. hystolytica) (trophozoite)- Culture- Serology : counterimmunodiffusion, agar gel diffusion, ELISA (6-12 mo neg), IHA (up to 10 yrs)

DIAGNOSIS …….(2)

Amebic liver abscess:Chest X-ray, liver scan, ultrasono-graphy, MRIRadiographic barium harmful in acute amebic colitis.Endoscopy + biopsy in ameboma

DIFFERENTIAL DIAGNOSIS

Bacterial diarrhoea caused by Campylobacter, enteroinvasive Esche-

richia coli, Shigella sp, Salmonella sp, Vibrio sp.Pyogenic liver abscess : older patient, underlying bowel disease, surgery

TREATMENT …..(1)

Luminal amebicides- Poorly absorbed- High concentration in the bowel- Limited to cyst & trophozoites close to mucosa- Iodoquinol, Diloxanide furoate,

Paromomycin

TREATMENT …..(2)Tissue amebicides- High concentration in blood and tissue - Metronidazole, Tinidazole, Ornida- zoleAspiration of liver abscess- Diagnostic- Failure to respond clinically in 3-5 days.- To threat of imminent rupture- To prevent left lobe liver abscess rupture

PREVENTION

Adequate sanitationEradication of cyst carriageDisinfection by iodination (tetragly-cine hydroperiodide)No effective chemoprophylaxis