FREQUENCY DISTRIBUTION OF ENTAMOEBA HISTOLYTICA ZYMODEMES IN A RURAL SOUTH AFRICAN POPULATION

doi:10.1016/S0140-6736(85)91263-2

The Lancet

Volume 325, Issue 8431, 30 March 1985, Pages 719-721

https://doi.org/10.1016/S0140-6736(85)91263-2 Get rights and content

Abstract

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.

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Considerable progress has been made in understanding the epidemiology of amoebiasis, caused by E. histolytica, which occurs most commonly in tropical and subtropical regions. This condition typically presents as a dysenteric illness or a liver abscess and produces significant morbidity and mortality when treatment is delayed. In the interim, our efforts should first be aimed at preventing amoebiasis by health promotion and public health measures to prevent fecal contamination of food and water. Despite the widespread syndromic use of antimicrobials for dysentery, the diagnosis of amoebiasis should be established by available confirmatory tests. This will ensure prompt directed treatment with metronidazole and the prevention of life-threatening complications. Studies to map the genome of E. histolytica are under way and may help efforts to develop an effective vaccine.
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E histolytica infections have also been linked to childhood morbidities, growth stunting, and delayed cognitive development.4–6 E dispar, a nonpathogenic commensal species, is perhaps 10 times more common than E histolytica worldwide,7 but local prevalences may vary significantly. Evidence is now building that a second member of the Entamoeba genus, E moshkovskii, is also associated with human disease.8,9
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Amebiasis is defined as infection with Entamoeba histolytica, regardless of associated symptomatology. In resource-rich nations, this parasitic protozoan is seen primarily in travelers to and emigrants from endemic areas. Infections range from asymptomatic colonization to amebic colitis and life-threatening abscesses. Importantly, disease may occur months to years after exposure. Although E histolytica was previously thought to infect 10% of the world's population, 2 morphologically identical but genetically distinct and apparently nonpathogenic Entamoeba species are now recognized as causing most asymptomatic cases. To avoid unnecessary and possibly harmful therapies, clinicians should follow the diagnostic and treatment guidelines of the World Health Organization.

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FREQUENCY DISTRIBUTION OF ENTAMOEBA HISTOLYTICA ZYMODEMES IN A RURAL SOUTH AFRICAN POPULATION

Abstract

Lancet

Trans Roy Soc Trop Med Hyg

Trans Roy Soc Trop Med Hyg

Trans Roy Soc Trop Med Hyg

Trans Roy Soc Trop Med Hyg