Abstract
BackgroundIn the developing world co-infections and polyparasitism within humans appear to be the rule rather than the exception, be it any combination of inter-specific and/or inter- and intra-Genera mixed infections. Mixed infections might generate synergistic or antagonistic interactions and thereby clinically affect individuals and/or impact parasite epidemiology.MethodsThe current study uniquely assesses both Schistosoma mansoni- and Schistosoma haematobium-related morbidity of the liver and the bladder as assessed by ultrasound as well as spleen and liver morbidity through clinical exams. The impact of praziquantel (PZQ) treatment on such potential inter-specific schistosome interactions and resulting morbidity using uniquely detailed longitudinal data (pre- and one year post-PZQ treatment) arising from the National Schistosomiasis Control Program in three areas of Mali: Ségou, Koulikoro and Bamako, is also evaluated. At baseline, data were collected from up to 2196 children (aged 7-14 years), 844 of which were infected with S. haematobium only, 124 with S. mansoni only and 477 with both. Follow-up data were collected from up to 1265 children.ResultsResults suggested lower liver morbidity in mixed compared to single S. mansoni infections and higher bladder morbidity in mixed compared to single S. haematobium infections. Single S. haematobium or S. mansoni infections were also associated with liver and spleen morbidity whilst only single S. haematobium infections were associated with bladder morbidity in these children (light S. haematobium infection OR: 4.3, p < 0.001 and heavy S. haematobium infection OR: 19, p < 0.001). PZQ treatment contributed to the regression of some of the forms of such morbidities.ConclusionsWhilst the precise biological mechanisms for these observations remain to be ascertained, the results illustrate the importance of considering mixed species infections in any analyses of parasite-induced morbidity, including that for the proposed Disability Adjusted Life Years (DALYs) revised estimates of schistosomiasis morbidity.
Highlights
In the developing world co-infections and polyparasitism within humans appear to be the rule rather than the exception, be it any combination of inter-specific and/or inter- and intra-Genera mixed infections
The mean ages were: for the uninfected children 10.13 years old; for the children with single S. haematobium infection 10.52 years old; for the children with single S. mansoni infection 10.96 years old; for those children who were co-infected with both schistosomes species the mean age was 10.64 years old
Our study has indicated through univariate analysis that at baseline significantly more children with S. haematobium only, compared to uninfected children, had liver morbidity or spleen morbidity as assessed by clinical examination; baseline results from multivariate analysis yielded significant increased risks of hepatomegaly as assessed by positive PSL scores for children with single S. haematobium infections compared to uninfected children (ORs for Estimates from multinomial model with dependent variable indicating the change of liver image patterns during the 2 time points of the study (Adjusted odds ratios (ORs) for gender and age, 95% CIs & p-values)
Summary
In the developing world co-infections and polyparasitism within humans appear to be the rule rather than the exception, be it any combination of inter-specific and/or inter- and intra-Genera mixed infections. Mixed infections might generate synergistic or antagonistic interactions and thereby clinically affect individuals and/or impact parasite epidemiology. In the developing world co-infections and polyparasitism within humans appear to be the rule rather than the exception. Synergistic or antagonistic interactions resulting from such co-infections may be predicted to clinically affect individuals and/or impact parasite epidemiology [2]. Schistosomiasis is a chronic and debilitating disease which affects millions of people, the rural poor in the developing world. The clinical manifestations of schistosomiasis are classically associated with the species-specific ovipositioning (egg-laying) sites; the mesenteric venous systems for Schistosoma mansoni (prevalent in sub-Saharan Africa and South America) leading to chronic hepatic and intestinal fibrosis and the vesical venous plexus of the urogenital system for Schistosoma haematobium (prevalent in sub-Saharan Africa) associated with ureteral and bladder fibrosis, calcification of the urinary tract and bladder cancer [4]
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