INFECTIOUS DISEASES

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Amebiasis

Reporting Obligations

Amebiasis is designated as a disease of public health significance and is reportable under the Ontario Health Protection and Promotion Act. Report suspect and confirmed cases within one business day to the local Health Unit.

Epidemiology

Aetiologic Agent:

Amebiasis is an enteric infection caused by Entamoeba histolytica, a microscopic intestinal parasite excreted as cysts or trophozoites in stools of infected people.

Clinical Presentation:

Clinical syndromes associated with E. histolytica infection include non-invasive intestinal infection, intestinal amebiasis, ameboma and liver abscess. Most infections are asymptomatic.

Persons with non-invasive intestinal infection may be asymptomatic or may have non-specific intestinal tract complaints. Persons with intestinal amebiasis (amebic colitis) generally have 1 to 3 weeks of increasingly severe diarrhea progressing to grossly bloody dysenteric stools with lower abdominal pain and tenesmus. Weight loss and fever may

be present. Amebic granulomata (ameboma), sometimes mistaken for carcinoma, may occur in the wall of the large intestine in patients with intermittent dysentery or colitis of long duration. These usually resolve with therapy and do not require surgery. Dissemination via the bloodstream may occur and produce abscesses of the liver, less commonly of the lung or brain.

Modes of transmission:

Mainly through ingestion of fecally contaminated food or water containing amoebic cysts, which are relatively chlorine resistant. Cysts can survive in moist environmental conditions for weeks to months. Transmission may occur sexually by fecal-oral contact with a chronically ill or asymptomatic

cyst excreter, or direct rectal inoculation through colonic irrigation devices. During the acute phase of the illness, those infected tend to shed more trophozoites than cysts and

pose only limited danger to others because of the absence of cysts in dysenteric stools and the fragility of trophozoites. Incubation Period:

From a few days to several months or years; commonly 2-4 weeks.

Period of Communicability:

During the period that E. hystolytica cysts are passed, which

Risk Factors/Susceptibility

Sexual transmission via anal-oral contact
Close contact with case
Consumption of raw unwashed produce
Consumption of potentially contaminated water
Travel outside province/country
Poor hand hygiene

Diagnosis & Laboratory Testing

E. hystolytica is morphologically identical to non-pathogenic

E. dispar.

Ova and parasite (O&P) screening on stool samples preserved in Sodium acetate-acetic acid-formalin (SAF) fixative. If positive for E.histolytia/dispar by screen, then stool antigen detection using ELISA on unpreserved stool sample to distinguish between E. histolytica from E. Dispar.

Treatment & Case Management

Treatment is under the direction of the attending health care provider.

Provide information to patients on personal prevention measures (careful hand hygiene after defecation, sexual contact and before preparing or eating food) including advice to avoid public swimming pools when symptomatic. Household members should be assessed for symptoms.

Inform patients that symptomatic cases will be excluded from conducting activities in high-risk settings such as the food industry, healthcare, or daycare, for 24 hours after diarrhea resolves or for 48 hours after completion of antibiotic treatment.

Public Health will follow up as needed.