Entamoeba histolytica

Life Cyle
  • Infection with Entamoeba occurs following ingestion of the organism in its environmentally-resistant cyst form which is shed in the feces of infected individuals. Once inside the small intestine motile amoeboid trophozoites are released from cysts and begin feeding and reproducing within the alimentary tract. Some trophozoites transform back into cysts and are shed in the feces to continue the cycle of replication. Given this life cycle, transmission of entameoba occurs through fecal-oral transmission by ingestion of contaminated foods or water.
Pathogenesis
  • Amoeboid trophozoites attach to the GI mucosa and feed on the intestinal contents and intestinal bacteria. More virulent organisms can cause ulcerations of the GI mucosa which elicits erythrocytes that the trophozoites then ingest and consume. Occaionally, the amoeba can disseminate throughout the body and cause abscesses in multiple organs. Dissemination first occurs through the portal circulation and the liver is usually the initial organ colonized, resulting in liver abscess.
Clinical Consequences
  • Infections with entamoeba are often subclinical and go unnoticed, allowing chronic shedding of cysts. When clinical consequences do arise most individuals suffer from abdominal pain and weight loss along with a mild bloody or mucoid infectious diarrhea. Naturally, severe intestinal infections can result in a much more intense diarrheal syndrome. Liver abscess is the most common but infrequent complication of this disease.
Treatment