Schistosomiasis is more prevalent than previously thought:what does it mean for public health goals,policies,strategies,guidelines and intervention programs?

Mapping and diagnosis of infections by the three major schistosome species(Schistosoma haematobium,S.mansoni and S.japonicum)has been done with assays that are known to be specific but increasingly insensitive as prevalence declines or in areas with already low prevalence of infection.This becomes a true challenge to achieving the goal of elimination of schistosomiasis because the multiplicative portion of the life-cycle of schistosomes,in the snail vector,favors continued transmission as long as even a few people maintain low numbers of worms that pass eggs in their excreta.New mapping tools based on detection of worm antigens(circulating cathodic antigen-CCA;circulating anodic antigen-CAA)in urine of those infected are highly sensitive and the CAA assay is reported to be highly specific.Using these tools in areas of low prevalence of all three of these species of schistosomes has demonstrated that more people harbor adult worms than are regularly excreting eggs at a level detectable by the usual stool assay(Kato-Katz)or by urine filtration.In very low prevalence areas this is sometimes 6-to10-fold more.Faced with what appears to be a sizable population of“egg-negative/worm-positive schistosomiasis”especially in areas of very low prevalence,national NTD programs are confounded about what guidelines and strategies they should enact if they are to proceed toward a goal of elimination.There is a critical need for continued evaluation of the assays involved and to understand the contribution of this“egg-negative/worm-positive schistosomiasis”condition to both individual morbidity and community transmission.There is also a critical need for new guidelines based on the use of these more sensitive assays for those national NTD programs that wish to move forward to strategies designed for elimination.

Building a global schistosomiasis alliance:an opportunity to join forces to fight inequality and rural poverty

Schistosomiasis,one of the 17 neglected tropical diseases listed by the World Health Organization,presents a substantial public health and economic burden.Of the 261 million people requiring preventive chemotherapy for schistosomiasis in 2013,92%of them lived in sub-Saharan Africa and only 12.7%received preventive chemotherapy.Moreover,in 2010,the WHO reported that schistosomiasis mortality could be as high as 280000 per year in Africa alone.In May 2012 delegates to the sixty-fifth World Health Assembly adopted resolution WHA65.21 that called for the elimination of schistosomiasis,and foresees the regular treatment of at least 75%of school age children in at-risk areas.The resolution urged member states to intensify schistosomiasis control programmes and to initiate elimination campaigns where possible.Despite this,in June 2015,schistosomiasis was indicated to have the lowest level of preventive chemotherapy implementation in the spectrum of neglected tropical diseases.It was also highlighted as the disease most lacking in progress.This is perhaps unsurprising,given that it was also the only NTD with access to drug donations but without a coalition of stakeholders that collaborates to boost commitment and implementation.As a consequence,and to ensure that the WHO NTDs Roadmap Targets of 2012 and World Health Assembly Resolution WHA65.21 are met,the Global Schistosomiasis Alliance(GSA)has been set up.Diverse and representative,the GSA aims to be a partnership of endemic countries,academic and research institutions,international development agencies and foundations,international organizations,non-governmental development organizations,private sector companies and advocacy and resource mobilisation partners.Ultimately,the GSA calls for a partnership to work for the benefit of endemic countries by addressing health inequity and rural poverty.

Molluscicidal effectiveness of Luo-Wei,a novel plant-derived molluscicide,against Oncomelania hupensis,Biomphalaria alexandrina and Bulinus truncatus

Background:Control of snail intermediate hosts has been proved to be a fast and efficient approach for interrupting the transmission of schistosomiasis.Some plant extracts have shown obvious molluscicidal activity,and a new compound Luo-Wei,also named tea-seed distilled saponin(TDS),was developed based on the saponins extracted from Camellia oleifera seeds.We aimed to test the molluscicidal activity of 4%TDS against the intermediate host snails in China and Egypt,and evaluate its environmental safety to non-target organisms.Methods:In the laboratory,Oncomelania hupensis,Biomphalaria alexandrina and Bulinus truncatus were exposed to 4%TDS,and the median lethal concentration(LC5o)was estimated at 24,48 and 72 h.In the field,snail mortalities were assessed 1,2,3 and 7 d post-immersion with 2.5 g/m34%TDS and 1,3,7 and 15 d post-spraying with 5 g/m24%TDS.in addition,the acute toxicity of 4%TDS to Japanese quail(Coturnixjaponica),zebrafish(Brachydanio rerio)and freshwater shrimp(Macrobrachium nipponense)was assessed by estimations of LC5o or median lethal dose(LD5o).Results:In the laboratory,the LC5o values of 4%TDS for O.hupensis were 0.701,0.371 and 0.33 mg/L at 24,48 and 72 h,respectively,and 4%TDS showed a 0.33 mg/L 24 h LC5o against B.alexandrina,and a 1.396 mg/L 24 h LCs0 against B.truncatus.Across all study regions,the pooled mortalities of O.hupensis were 72,86,94 and 98%at 1,2,3 and 7 d,following field immersion of 4%TDS at a dose of 2.5 g/m3,and were 69,77,85 and 88%at 1,3,7 and 15 d,following field spraying at 5 g/m2,respectively.4%TDS had moderate toxicity to Japanese quail(7 d LD5o>60 mg/kg)and to shrimp(96 h LCs0=6.28 mg/L;95%CI:3.53-11.2 mg/L),whereas its toxicity to zebrafish was high(96 h LCso--0.15 mg/L;95%CI:0.14-0.17 mg/L).Conclusions:4%TDS is active against O.hupensis,B.alexandrina and B.truncatus under laboratory and field conditions,and it may be a candidate molluscicide of plant origin.