Pathogenic effects of Entamoeba histolytica is very significant for human health. Although about 10% of human population is infected, yet most of them are carriers and no harm is caused by Entamoeba histolytica. According to Hoarse (1962), E. histolytica is characteristically a great commensal and, only in a few cases symptoms of disease are seen.
- Amoebic dysentery: The trophozoites penetrate the mucosa and submucosa of intestine (colon) and causes its necrosis and form small wounds or abscesses which later become flash-shaped bleeding ulcers. The cavity of ulcers is generally filled with mucous, bacteria, amoeae and cell-debris. The abscesses pour their contents into the lumen of intestine. In amoebic dysentery, the stools are acidic and contain pure blood and mucous in which swarms of amoebae and blood corpuscles, are usually present. The patient is largely discomforted owing to intense gripping pains with the passing of blood and mucous with stools after every few minutes.
- Abscesses in liver, lungs and brain: Sometimes, Entamoeba histolytica passes into the portal circulation and then to liver where the parasites settle and form abscesses in the liver by attacking the liver tissue. The patient has pain in liver and fever may develop. Lung abscesses may also occur. The trophozoites through blood circulation may also enter spleen, gonads and brain where they also destroy the tissue causing specific abscesses. Abscesses elsewhere are rare. In acute cases, they might prove to be fatal.