How to Diagnose Amebiasis

Amebiasis, an infection by a pathogenic amoeba, usually Entamoeba histolytica, causes almost 100,000 deaths per year. Entamoeba histolytica has two forms: a motile form called the trophozoite and a cyst form. The trophozoite inhabits the large intestine and causes lesions but can change to the hardier cystic form in the presence of an adverse environment. The following steps will show how to diagnose amebiasis.

Difficulty:

Challenging

Instructions

1. Perform an antigen test to distinguish between the pathogenic Entamoeba histolytica and Entamoeba dispar, which does not cause disease or antibody production.

2. Run an enzyme immunoassay (EIA). This is the best test for making a clinical diagnosis of amebiasis. Techlab of Virginia offers this type of EIA commercially.

3. Detect antibodies using an indirect hemagglutination antibody (IHA) test when an extraintestinal amebiasis such as amebic liver abscess is suspected. An antibody titer that is greater than 1:256 can be expected in 95 percent of these cases, but the stool samples are frequently negative.

4. Take an ultrasonography when an amebic liver abscess is suspected and look for a single lesion on the posterosuperior aspect of the right lobe of the liver. This procedure has the advantage of a lack of adverse effects, low cost and speed.

5. Use a colonoscopy and rectosigmoidoscopy to obtain diagnostic information on intestinal amebiasis. Endoscopy should be considered when the stool examination is negative and a high suspicion of amebiasis exists. Look for small mucosal ulcers with yellowish exudates.