In the current era of intensified and integrated control targeting schistosomiasis and other neglected tropical diseases, it must be emphasized that tools and strategies with proven track records are available to fight schistosomiasis. However, we need to constantly adapt and fine-tune intervention packages as control programs progress, and carefully monitor whether they have the desired impact. Innovation, validation and application of new tools and strategies, and thinking outside the box, must be seen as integral parts. As highlighted in this review, numerous research gaps remain, and there is a need to show flexibility in the approaches taken, particularly now that we are escalating from schistosomiasis control to interruption of transmission and finally elimination.
To further our understanding of the burden and impact of schistosomiasis, there is a need to conduct additional high-quality, confounder-controlled studies to measure and quantify acute and chronic morbidity in SAC and PSAC. Additionally, physical fitness, cognition and nutritional disorders should be measured in Schistosoma-infected and non-infected children and it should be determined whether these indicators improve over the course of praziquantel treatment. Moreover, the effect, mediating pathways and impact of schistosomiasis on co-infections such as malaria need further scientific inquiry, particularly in PSAC who are at greatest risk of developing severe malaria. The effect of intensified schistosomiasis control/elimination efforts on the susceptibility toward other infectious and noncommunicable diseases, on vaccine responses and on the clinical management of concomitant infections needs to be carefully assessed. With regard to treatment of schistosomiasis, we have praziquantel, a safe, inexpensive and efficacious drug against all human schistosome species. However, praziquantel lacks activity against the young developing stages of the parasite. The artemisinins and mefloquine are active against juvenile worms, and hence present interesting candidates for combination chemotherapy with a drug that is active against the adult schistosome stages (i.e., praziquantel). It must be noted, however, that the artemisinins or mefloquine should always be used in combination with an antimalarial partner drug (e.g., lumefantrine) to avoid selection for resistance development in malaria parasites. At present, there is no praziquantel formulation that is convenient for the uptake by infants and PSAC, which is of considerable concern as new research showed that schistosomiasis already affects children at very young age. Studies on drug disposition in young children and the development of a child-friendly formulation of praziquantel are thus of great importance. The growing pressure of praziquantel raises the risk of parasites developing resistance to this drug. Because the antischistosomal drug development pipeline is empty, the risk of praziquantel resistance cannot be overemphasized. Drugs that have been used before (e.g., oxamniquine) could again be utilized, but new drugs – and also vaccines – must be developed.
Large-scale control programs will only effectively reduce schistosomiasis transmission if preventive chemotherapy is complemented by measures to reduce the number of infected intermediate hosts (e.g., snail control) and reservoir hosts (e.g., chemotherapy targeting water buffaloes or fencing of these animals), to improve sanitation and access to clean water, and to educate at-risk populations in a way that they take action in preventing infection and transmission. To achieve the highest level of success in the control/elimination of schistosomiasis, governments and international donors must be highly committed and provide the necessary financial, technical and human resources. Moreover, integrated control packages can only be successfully implemented, if the health sector builds bridges with the agricultural, education, financial and water and sanitation sectors.[12,120,122,224] The voice and proposals of the affected communities must be considered. Indeed, developing and implementing interventions together with communities will render them more accepted and effective. If people's concerns and suggestions are considered, higher drug intake coverage might be achieved in mass treatment programs, water supply and latrines might be constructed at appropriate places and be used and maintained by children and the community, and contact with open water bodies be reduced or avoided if there are alternative water sources and play options for children. More research is needed to determine and evaluate the impact of different control approaches, particularly of sanitation, snail control and behavior change interventions. Qualitative research to deepen the understanding of community perceptions about schistosomiasis prevention and the use and acceptance of an improved sanitary infrastructure in different social–ecological settings are crucial for getting interventions right. The development and evaluation of alternatives to toxic molluscicides for snail control constitutes another important research need.
The implementation of control measures over multiple years will reduce infection intensities in targeted settings. To avoid an underestimation of the number of infected people, particularly those with low-intensity infections, highly sensitive diagnostic tools are needed. Although the widely used urine filtration and Kato–Katz techniques are suitable for assessing prevalence and infection intensity in high-endemicity settings, those two assays are less suitable in low-intensity settings. Hence, more sensitive methods such as POC-CCA, CAA-UCP and PCR must be considered. The reliability of these diagnostic approaches needs, however, further validation in low-endemicity areas, and standard protocols for high throughput are needed. A drawback of the more sensitive methods is their higher cost and the need for sophisticated laboratory equipment. The development of highly sensitive and specific RDT formats for monitoring and surveillance of schistosomiasis would therefore be an important achievement.
Expert Rev Anti Infect Ther. 2013;11(11):1237-1258. © 2013 Expert Reviews Ltd.