The control of schistosomiasis: epidemiological aspects of reinfection

Abstract

Current strategies for schistosomiasis control rely heavily on drug treatment intended to reduce morbidity and disease to an insignificant level of public health importance. This approach reduces but rarely, if ever, eliminates transmission. Indeed, snail infection rates may be little altered by such chemotherapy. Reinfection is inevitable. The mean human community prevalence usually returns rapidly to precontrol levels but the mean intensity of infection takes much longer, distorting the general relationship between the two. Because of the focality of schistosomiasis transmission, retreatment based on mean population prevalence is often too late to protect people living near active transmission sites. However, if suitable methods can be developed to examine man after treatment, they should simplify the detection of the main transmission sites, allowing the employment of alternative, focal control measures to consolidate the beneficial effects of mass chemotherapy.

Association between socio economic status and schistosomiasis infection in Jinja District, Uganda

“…Whereas previous studies have mainly suggested that the influence of social economic conditions on the prevalence and intensity of schistosomiasis infection is mainly mediated through low social economic class being more likely to result in contact with infectious water at an increasing intensity (Useh & Ejezie 1999;van der Werf et al 2003;King et al 2005), and due to limited access to mass treatment (Sturrock 1989;Savioli et al 2004;Kabatereine et al 2007), this study suggests that when access to treatment and water contact is controlled for wealth index does remain an independent predictor of schistosomiasis infection and intensity. A possible explanation for this is that infection of schistosomiasis within a home is a cause as well as a consequence of poverty (Hotez et al 2007;WHO 2007).…”

“…The main strategy for the control of S. mansoni in Uganda and most low income countries of sub-Saharan Africa is mass treatment with praziquantel (Kabatereine et al 2007;WHO 2007). Whereas it may reduce morbidity and risk of transmission, it rarely if ever eliminates infection, and prevalence usually returns rapidly to precontrol levels (Sturrock 1989;Savioli et al 2004;Utzinger et al 2005). Thus long term control of schistosomiasis will have to include other measures, such as improvement in social economic status of the population.…”

Micro-Geographical Heterogeneity in Schistosoma mansoni and S. haematobium Infection and Morbidity in a Co-Endemic Community in Northern Senegal

“…A more targeted approach will be even more relevant in view of resolution WHA65.21 on the elimination of schistosomiasis, recently adopted by the WHO [77]. It is expected that MDA alone cannot break the Schistosoma life cycle and that complementary interventions will have to be put in place [79]. Micro-geographical studies will help to get much needed insights into local transmission dynamics of S. mansoni and S. haematobium and hence to develop sustainable control and elimination strategies [80].…”

Should nutrition be considered as a supplementary measure in schistosomiasis control?

“…The effectiveness of the Brazilian programme, for example, did not come up to the expectations of public-health workers in terms of maintaining the initial, positive gains (Coutinho and Domingues, 1991). Although mass-therapy campaigns usually produce rapid decreases in the prevalence of infection, these decreases tend to be shortlived (Sturrock, 1989;Barbosa and Silva, 1992).…”