Human schistosomiasis in the post mass drug administration era

Abstract

Profound changes are occurring in the epidemiology of schistosomiasis, a neglected tropical disease caused by a chronic infection with parasitic helminths of the genus Schistosoma. Schistosomiasis affects 240 million people worldwide, mostly in subSaharan Africa. The advent and proliferation of mass drug administration (MDA) programs using the drug praziquantel (PZQ) is resulting in substantial increases in the number of people, mainly school-aged children, being effectively treated, approaching the point where the majority of people in endemic areas will receive one or more treatments during their lifetimes. PZQ treatment not only cures infection but also frees the host from the powerful immunomodulatory action of the parasites and simultaneously enhances exposure to key parasite antigens, accelerating the development of protective acquired immunity, which takes many years to develop naturally. At a population level these changes constitute a substantial alteration to schistosome ecology in that the parasites are more likely to be exposed not only to PZQ directly but also to hosts with altered immune phenotypes. Here, we consider the consequences of this for schistosome biology and immuno-epidemiology and for public health. We anticipate that there could be significant impacts on chronic pathology, natural immunity, vaccine development strategies, immune disorders and drug efficacy. This makes for a complex picture that only will become apparent over timescales of decades. We recommend careful monitoring and evaluation to accompany the roll-out of MDA programs in order to ensure that the considerable health benefits to populations are achieved and sustained. antigens, accelerating the development of protective acquired immunity, which takes many years to develop naturally. At a population level these changes constitute a substantial alteration to schistosome ecology in that the parasites are more likely to be exposed not only to PZQ directly but also to hosts with altered immune phenotypes. Here, we consider the consequences of this for schistosome biology and immuno-epidemiology and for public health. We anticipate that there could be *Manuscript with revisions highlighted significant impacts on chronic pathology, natural immunity, vaccine development strategies, immune disorders and drug efficacy. This makes for a complex picture that only will become apparent over timescales of decades. We recommend careful monitoring and evaluation to accompany the roll-out of MDA programs in order to ensure that the considerable health benefits to populations are achieved and sustained. Human Schistosomiasis in the post

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“…The infection is prevalent in tropical and subtropical areas, in poor communities without potable water and adequate sanitation. Schistosoma mansoni, which causes intestinal schistosomiasis, accounts for around 80 million infections in Africa, the Near East, and South America (1). The disease is caused primarily by parasite eggs in the tissues.…”

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“…1 H NMR or 13 C NMR experiments were obtained on the Bruker AVANCE-300 or Bruker AVANCE-500 spectrometers. 1 H and 13 C spectra were calibrated using residual chloroform or DMSO as an internal reference (CHCl 3 Chemical shifts for 13 C NMR are reported in terms of chemical shift (d ppm). Purity of assayed compounds was determined by elemental analysis recorded on Heraeus CHN-O-rapid analyser performed by the analytical department at CAI (UCM) and values were within ±0.4% of the theoretical values for all compounds.…”

“…Treatment and control of all forms of schistosomiasis fully rely on mass drug administration with the only available antischistosomal drug praziquantel (PZQ) 3 . Even considering it is safe, effective, operationally convenient and low-cost, there is an increasing concern among the scientific community to anticipate PZQ therapeutic failure 4 .…”

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“…To date, many potential factors have been suggested to explain this variation, such as pre‐treatment infection intensity, level of schistosome endemicity, age, sex and co‐infection with human immunodeficiency virus (HIV) . This is important for understanding the consequences of the epidemiological transition occurring in populations subject to national schistosome control programs through mass drug administration both for the host and the parasite . However, there has not been a systematic review of published studies investigating the potential determinants of the heterogeneity in post‐treatment immune responses.…”