Frequency distribution of Entamoeba histolytica zymodemes in a rural South African population.

To determine the prevalence of Entamoeba histolytica and its zymodeme distribution pattern, isoenzyme electrophoresis was performed on isolates of the parasite from 1381 individuals of the population of a semirural endemic area south of Durban. About 10% of the population was found to harbour E histolytica. The zymodeme distribution was similar to that described in other surveys but two new zymodemes were observed, a non-pathogenic zymodeme XIX and a pathogenic zymodeme XX. Non-pathogenic zymodemes were more frequent in females than in males. In apparently healthy individuals there was a 1% prevalence of pathogenic E histolytica; the distribution was the same in males and females even though invasive amoebiasis was far more common in males. Symptoms of amoebic colitis subsequently developed in only 2 of the 14 symptomless individuals from whom pathogenic zymodemes of E histolytica were isolated.