Amebiasis (Entamoeba Histolytica)

Amebiasis is a gastrointestinal infection caused by the parasite Entamoeba histolytica characterized by diarrhea that can be bloody and sometimes accompanied with fever. However its manifestation can range from no symptoms to life threatening perforation of the colon to even abscesses of the liver, lung etc.

Where does it occur?

I t occurs worldwide but is more common is developing countries. It is most common in Asia, Africa, Central and South America.

How is it transmitted?

It is transmitted primarily by ingesting fecally contaminated food and water. The infective cysts can survive inadequate chlorination and exists in moist environments for months. Many outbreaks in travelers have been traced to the use of ice. It can also be sexually transmitted through oral – anal contact.

Is it contagious from person to person?

It can be contagious from person to person through sexual practices involving oral-anal contact. The person with diarrhea is not felt to be directly contagious with casual contact, but strict hand washing should be practiced.

What is the risk for travelers?

Generally the risk is low, but increased in travelers to developing nations who eat adventurously.

How soon after exposure will one develop symptoms?

Symptoms generally develop 2-4 weeks after ingestion, but can range from few days to years.

What are the signs and symptoms?

Symptoms start with gradual onset of loose stools with abdominal pain and cramps. Initially these may alternate with periods of normal stools or constipation. Alternately it can present with sudden onset of diarrhea, with blood or pus and fever. Occasionally one can see severe colonic involvement with perforation.

If the parasite spreads through the blood stream it can cause abscesses in the liver and can manifest with abdominal pain localized to the upper right side along with nausea and vomiting. Occasionally the abscess in the liver can rupture resulting in spread of the infection to lung, pericardium or abdominal cavity resulting in chest and severe abdominal pain with high fevers, rapid heart rate and even shock.

Are there any lab tests to diagnose the illness?

Diarrheal illness can be diagnosed by examining the stool for parasites, or with EIA (enzyme immunoassay) tests. Abscesses of the liver, lung etc can be aspirated and examined under the microscope. Blood antibody (IgM/IgG) test are useful in cases of abscesses. Stool tests may be negative in these situations.

Is there any treatment?

Antibiotics like metronidazole and tinidazole are used followed with treatment of cysts with paromomycin or iodoquinol.

What preventive measures can be taken?

Practice strict hand washing and eat only in places that have a modicum of sanitation. Follow food safety and water safety precautions.

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