Entamoeba Histolytica or the Intestinal Amoeba | Parasitology

In this article we will discuss about:- 1. Discovery of Entamoeba Histolytica 2. Systematic Position of Entamoeba Histolytica 3. Habits and Habitat 4. Types.

Discovery of Entamoeba Histolytica:

Apart from free-living forms, certain amoe­bae lead a commensal or parasitic life in the intestine of man and other animals. Entamoeba histolytica was first discovered by Lambl in 1859 and its pathological nature was proved by a Russian Zoologist, Friedrick Losch in 1875, while Schaudinn (1903) differentiated pathogenic and non-pathogenic types of amoebae.

Entamoeba histolytica is the cause of amoebiasis, amoebic dysentery of man. It has also been found in many species of monkey and in the dog, cat, rat and pig. Experimentally, the rat, rabbit, mouse and Guinea-pig can be infected. It is estimated that 10% of world population is suffering from amoe­biasis.

Systematic Position of Entamoeba Histolytica:

Subphylum – Sarcomastigophora

Superclass – Sarcodina

Class – Rhizopodea

Geographical Distribution of Entamoeba Histolytica:

Geographically it is world-wide (cosmopolitan) in distribution occur­ring in countries with temperate, sub-tropical or tropical climates. It is, however, more prevalent in the tropics and sub-tropics than in cooler climates, though surveys in countries such as Great Britain and the United States have shown a substantial level of infection. It has been reported that inci­dence of infection is high in Mexico, China, India etc.

It has also been found that the incidence is considerably higher in rural and densely populated urban areas. The prevalence in various countries is detailed by Hoare (1950) and the results of various other surveys are quoted by Levine (1961).

Habits and Habitat of Entamoeba Histolytica:

Entamoeba histolytica is a microscopic endoparasite of man. It inhabits the mucous and sub-mucous layers of the large intestine of man. It may also occur in the liver and lung and rarely invades brain, spleen etc. producing ulcers.

Entamoeba sp. causes amoebic dysentery or amoebiasis. If a person suffering from this disease, the intestinal wall exhibits minute ulcers which are formed as a result of the dissolution and destruction of the mucous lining of intestine.

Types of Entamoeba sp Found in Man:

The Entamoeba infecting man may be classi­fied according to their pathogenicity and habitat as follows:

(a) Pathogenic amoeba:

E. histolytica is a pathogenic parasite found in the colon and variety of other organs and tissues causing amoebic dysentery, amoebic abscess of liver, kidney, spleen etc., which are collectively called amoebiasis.

(b) Non-pathogenic (harmless commen­sals) amoeba:

i. E. gangivialis is observed in tarter on teeth and in gum. Though largely fee­ding on bacteria, it has been seen to aggravate the diseases of teeth and gum like pyrrhoea etc.

ii. E. coli, E. nana etc. are found in colon. They feed exclusively on bacteria, food-debris and are considered harm less commensals.