Amebiasis

Amebiasis is an infection of the large intestines, sometimes affecting other organs, that is caused by the amoeba parasite Entamoeba histolytica.

The condition is relatively common in locations where sanitation is poor, such as areas of Africa, India and Latin America.

Causes

E. histolytica can exist in two forms: as an active parasite (trophozoite) or dormant, as a cyst. Infection occurs when the cysts are swallowed.

Cysts can be spread directly through person-to-person contact, or through food and water. Fruits and vegetables can be contaminated if grown in soil containing human faeces; washed in contaminated water; or prepared by an infected person.

Disease pathway

When ingested, the cysts hatch and trophozoites are released. The amoebae multiply and form ulcers, causing damage to the gastrointestinal tract.

Sometimes, the amoebae will spread to the liver and to other parts of the body, resulting in wider-spread damage.

Symptoms and diagnosis

Many patients with amebiasis will have little to no symptoms. If symptoms are present, they may include:

·         Increased gas (flatulence);

·         Intermittent diarrhea;

·         Constipation; and

·         Abdominal cramps.

To diagnose amebiasis, a doctor will analyse stool samples, testing it for a type of protein released by the amoeba. Seeking the amoebae themselves tends to be inconclusive, as they are indistinguishable from other, harmless amoeba.

Treatment

An amebicide is administered to target the trophozoites. This will not necessarily eliminate the cysts that remain in the large intestine, however, and so a second drug is given to kill the cysts and prevent a relapse.