AMEBIASIS

Two morphologically identical but genetically distinct species of Entamoeba commonly infect humans.

1-Entamoeba dispar, the more prevalent species

2-E. histolytica, the pathogenic species can become invasive

Infection is established by ingestion of parasite cysts.

ETIOLOGY

Cysts are resistant to environmental conditions such as low temperature and the concentrations of chlorine commonly used

can be killed by heating to 55°C cyst, which is resistant to gastric acidity and

digestive enzymes→excysts in the small intestine to form 8

trophozoites→colonize the lumen of the large intestine and

may invade the mucosal lining.

Food or drink contaminated with Entamoeba cysts and direct fecal-oral contact are the most common means of infection

Untreated water and human feces used as fertilizer are important sources of infection.

EPIDEMIOLOGY

range from asymptomatic cyst passage to amebic colitis, amebic dysentery, ameboma, and extraintestinal disease.

. E. histolytica infection is asymptomatic in about 90% of persons, but it has the potential to become invasive and should be treated

Severe disease is more common in young children, pregnant women, malnourished

Extraintestinal disease usually involves only the liver, but rare extraintestinal manifestations include amebic brain abscess, pleuropulmonary disease, ulcerative skin, and genitourinary lesions.

CLINICAL MANIFESTATIONS

occur within 2 wk of infection or be delayed for months

colicky abdominal pains Diarrhea Stools are blood stained and contain a fair

amount of mucus with few leukocytes fever documented in only ⅓ of patients incidence is strikingly high in children 1–5

yr of age amebic dysentery is associated with sudden

onset of fever, chills, and severe diarrhea

Amebic Colitis

is uncommon in children. Amebic liver abscess may occur months to

years after exposure. In children, fever is the hallmark and is

frequently associated with abdominal pain, distention, and enlargement and tenderness of the liver.

Amebic Liver Abscess

unremarkable in uncomplicated amebic colitis in amebic liver abscess :leukocytosis,

moderate anemia, high erythrocyte sedimentation rate, and elevations of hepatic enzyme (particularly alkaline phosphatase) levels.

Stool examination negative results in >50% of patients with documented amebic liver abscess.

Ultrasonography, CT, or MRI can localize and delineate the size of the abscess cavity

LABORATORY FINDINGS

amebic colitis :detection of antigens in stool by ELISA

examination of stool samples microscopy cannot differentiate between E.

histolytica and E. dispar unless phagocytosed erythrocytes, which are specific for E. histolytica, are seen.

DIAGNOSIS

Invasive amebiasis is treated with metronidazole (35–50 mg/kg/day in 3 divided doses for 7–10 days)or tinidazole (50 mg/kg/day once daily for 3 days)

followed by treatment with a luminal amebicide : paromomycin(7 days), iodoquinol(20 days) OR Diloxanide furoate (7 days)

Asymptomatic intestinal infection with E. histolytica should be treated with paromomycin, which is preferred, or iodoquinol or diloxanide furoate.

TREATMENT.