AMEBIASIS

DEFINITION

Amebiasis is infection with intestinal

pathogen Entameba histolytica (tissue lysing

ameba)

Most Infection are asymptomatic

disease ranging from Dysentry to

extaintestinal infectons like liver absess

Most of asymptomatic infection is due to

E.dispar Endemic area Mexico,India & tropical regions

of Africa,South and Central America

LIFE CYCLE AND TRANSMISSION

E. histolytica exists in two stages

multinucleate cyst Motile Trophozoite

TRANSMISSION

E. histolytica are most common in areas where poor sanitation and crowding compromise the barrier to contamination of food and drinking water with human feces

Infection is acquired by ingestion of cysts in faecally contaminated water or food

Cysts are resistant to the acid in the stomach

LIFE CYCLE

PATHOGENESIS AND PATHOLOGY

E.histolytica trophozoites invade through the

submucosal layer, creating the classic flask

shaped ulcers that appear on pathologic

examination as narrow-necked lesions

broadening in the submucosal region Ulcers tend to stop at the muscularis layer,

and full-thickness lesions and colonic perforation are unusual

FLASK SHAPED ULCER

PATHOGENESIS AND PATHOLOGY

In some individuals, trophozoites invade the portal venous system and reach the liver, where they cause amebic liver abscesses

characteristic appearance on pathologic examination: the roughly circular abscesses contain a large necrotic center resembling anchovy paste

CLINICAL MANIFESTATIONS

Two types- Intestinal and Extra Intestinal Amebic colitis generally appear 2-6 weeks

after ingestion of the cyst of parasite diarrhea and lower abdominal pain are the

most common complaints Fever is present in 40% cases Severe dysentry with 10-12 small volume,

blood and mucus containing stools may develop

CLINICAL MANIFESTATIONS

Fulminant amebic colitis – profuse diarrhea, severe abdominal pain, fever,and pronounced leukocytosis

It affects young children, pregnant women, individuals treated with steroids and in diabetes and alcoholism

Intestinal perforation occus in >75% of pts.with fulminant disease

Complications includes Toxic Megacolon in .5% with severe bowel

dilatation and intraluminal air Ameboma-presents as abd. mass

AMEBIC LIVER ABSCESS

Most common extraintestinal complication Most individuals do not have concurrent

signs or symptoms of colitis The classical presentation of ALA are right

upper quadrant pain, fever and liver tenderness

Its acute in nature lasting < 10 days Jaundice is uncommon most common laboratory findings are

leukocytosis (without eosinophilia), an elevated alkaline phosphatase level, mild anemia, and an elevated ESR

OTHER MANIFESTATIONS AND COMPLICATIONS

Rt-sided pleural effusion - common in cases of ALA

In 10% rupture of abscess through diaphragm may cause pleuro-pulmonary amebiasis

Sudden onset cough, pleuritic chest pain and shortness of breath

Hepatobronchial fistula is dramatic complication in which pt has complaint of cough with content of liver abscess

Liver abscess may rupture into pericardial cavity and can cause pericarditis with 30% mortality due to cardiac temponade

DIAGNOSTIC TESTS

Demonstration of E.histolytica trophozoite or cyst in the stool or colonic mucosa of pts with diarrhea

presence of amebic trophozoites containing red blood cells in a diarrheal stool is highly suggestive of E. histolytica infection

Antigen detection based ELISAs that can specifically identify E.histolytica in the stool

colonoscopy with examination of brushings or mucosal biopsies for E. histolytica trophozoites

Amebic serology

DIAGNOSTIC TESTS

Diagnosis of amebic liver abscess is based on the detection of one or more space occupying lesions in the liver by Ultrasound and CT scan and a positive serology

classically described as single, large and located in right lobe of liver

When a pt. with space ahs a occupying lesion in the liver, a positive serology is highly sensitive(>94% ) and highly specific(>95%) for the diagnosis of the liver abscess

CT SCAN LIVER WITH ALA IN RT LOBE

TREATMENT

The nitroimidazole compounds tinidazole and metronidazole are the drug of choice

Tinidazole appears to be better tolerated and more effective

Whenever possible fulminant amebic colitis should be managed conservatively

TREATMENT

Aspiration of liver abscess reserved for pyogenic abscess or a bacterial superinfection is

suspected, for pts failing to respond to tinidazole or

metronidazole ( those who have persistent fever or abdominal pain after 4 days of treatment),

for individuals with large liver abscesses in the left lobe

large abscess with risk of imminent rupture Pleuropulmonary amebiasis Amebic pericarditis

TREATMENT

luminal agents (Paramomycin or iodoquinol) to ensure eradication of infection

Paramomycin is preferred agent Asymptomatic individuals with documented

E. histolytica infection should be treated because of the risks of developing amebic colitis or amebic liver abscess in the future and of transmitting the infection to others

TREATMENT

Drug Dosage Duration

Amebic Colitis Or ALA

Tinidazole 2g/day with food 3

Metronidazole 750mg tid PO or IV 5-10

Luminal Infection

Paramomycin 30mg/kg qd PO in 3 divided dose

5-10

Iodoquinol 650 mg PO tid 20