Impact of Concurrent Schistosoma Mansoni and S. Haematobium Infections on Schistosomiasis Demographics and Pathology in an Endemic Community in Ghana

Abstract

Schistosomiasis remains endemic in Ghana, with Schistosoma mansoni and S. haematobium being the two dominant species of the schistosome parasites. In some parts of Africa, previous works indicated the occurrence of pairings between these two species, resulting in the production of non-viable eggs (parthenogenesis). In Ghana, although both species occur in sympatry, it is yet to be shown whether this can lead to hetero-specific pairing within the definitive host leading to consequent effects on disease outcome. In this study, the effects of concurrent S. mansoni and S. haematobium infections on the outcome of schistosomiasis is determined. Pupils from Peace International School, aged between 0 – 26 years were recruited for the study. Urine and stool samples were collected and screened for schistosome eggs, and snail vectors sampled for cercarial shedding. Laboratory bred snail vectors were infected with miracidia and induced to shed cercariae. Experimental mice were subsequently singly and concurrently infected with cercariae to determine the pathological effect. Questionnaires were also administered to assess the knowledge base of the people on the disease and determine water contact activities that predispose pupils to infections. The overall prevalence of urogenital and intestinal schistosomiasis observed were 66.8% (135/202) and 90.1% (163/181) respectively. It was revealed that both single and concurrent infections occurred among pupils, with the latter being more prevalent (50 and 131 respectively). Of the 131 individuals with concurrent infections, 50 presented with both S. mansoni in urine and S. haematobium in stool (type A), with the remaining 81 presenting with both parasites in urine and/or stool (type B). Whereas 65 individuals had heavy infection intensities in their urine, only 2 had heavy infections recorded in their stool. Biomphalaria pfeifferi and Bulinus truncatus snails were the vectors found hosting human infective cercarie, as well as two other morphologically distinct cercariae unknown in the community. The presence of unknown cercariae types suggest possible bovine or avian schistosomiasis and the likelihood for zoonotic transmission of the disease in the community. Apparently, the high prevalence recorded for S. mansoni could be indicative of rapid spreading and colonizing of new areas that were earlier reported to be S. haematobium endemic. Also the high loads of S. mansoni eggs observed in urine samples relative to S. haematobium eggs in stool may suggest greater inter-specific mating ability by S. haematobium males than S. mansoni males. Concurrent infections in mice resulted in more granuloma formation compared to single infections. Studies of concurrent schistosome infections should be expanded to other endemic parts of the country while assessing its pathological impact in humans to facilitate disease control and eventual elimination.