26
views
0
recommends
+1 Recommend
0 collections
    0
    shares
      • Record: found
      • Abstract: found
      • Article: found
      Is Open Access

      Impact and cost-effectiveness of snail control to achieve disease control targets for schistosomiasis

      research-article

      Read this article at

      Bookmark
          There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

          Significance

          Schistosomiasis is an infectious disease that affects over 240 million people living in low- and middle-income countries, and is caused by parasitic worms that require snail hosts to complete its lifecycle. To improve public health control of this disease, there is growing interest in using chemical-based snail control that kills snail populations in environmental water sources, which will reduce infection rate in people. We modeled transmission of schistosomiasis and cost-effectiveness of various strategies with data from low- and high-prevalence rural Kenyan communities. Adding snail control alongside conventional mass treatment programs (instead of mass treatment programs alone) was found to be cost-effective, especially in settings with high disease burden and nonparticipation in mass treatment programs.

          Abstract

          Schistosomiasis is a parasitic disease that affects over 240 million people globally. To improve population-level disease control, there is growing interest in adding chemical-based snail control interventions to interrupt the lifecycle of Schistosoma in its snail host to reduce parasite transmission. However, this approach is not widely implemented, and given environmental concerns, the optimal conditions for when snail control is appropriate are unclear. We assessed the potential impact and cost-effectiveness of various snail control strategies. We extended previously published dynamic, age-structured transmission and cost-effectiveness models to simulate mass drug administration (MDA) and focal snail control interventions against Schistosoma haematobium across a range of low-prevalence (5–20%) and high-prevalence (25–50%) rural Kenyan communities. We simulated strategies over a 10-year period of MDA targeting school children or entire communities, snail control, and combined strategies. We measured incremental cost-effectiveness in 2016 US dollars per disability-adjusted life year and defined a strategy as optimally cost-effective when maximizing health gains (averted disability-adjusted life years) with an incremental cost-effectiveness below a Kenya-specific economic threshold. In both low- and high-prevalence settings, community-wide MDA with additional snail control reduced total disability by an additional 40% compared with school-based MDA alone. The optimally cost-effective scenario included the addition of snail control to MDA in over 95% of simulations. These results support inclusion of snail control in global guidelines and national schistosomiasis control strategies for optimal disease control, especially in settings with high prevalence, “hot spots” of transmission, and noncompliance to MDA.

          Related collections

          Most cited references47

          • Record: found
          • Abstract: found
          • Article: not found

          Schistosomiasis and water resources development: systematic review, meta-analysis, and estimates of people at risk.

          An estimated 779 million people are at risk of schistosomiasis, of whom 106 million (13.6%) live in irrigation schemes or in close proximity to large dam reservoirs. We identified 58 studies that examined the relation between water resources development projects and schistosomiasis, primarily in African settings. We present a systematic literature review and meta-analysis with the following objectives: (1) to update at-risk populations of schistosomiasis and number of people infected in endemic countries, and (2) to quantify the risk of water resources development and management on schistosomiasis. Using 35 datasets from 24 African studies, our meta-analysis showed pooled random risk ratios of 2.4 and 2.6 for urinary and intestinal schistosomiasis, respectively, among people living adjacent to dam reservoirs. The risk ratio estimate for studies evaluating the effect of irrigation on urinary schistosomiasis was in the range 0.02-7.3 (summary estimate 1.1) and that on intestinal schistosomiasis in the range 0.49-23.0 (summary estimate 4.7). Geographic stratification showed important spatial differences, idiosyncratic to the type of water resources development. We conclude that the development and management of water resources is an important risk factor for schistosomiasis, and hence strategies to mitigate negative effects should become integral parts in the planning, implementation, and operation of future water projects.
            Bookmark
            • Record: found
            • Abstract: found
            • Article: not found

            Reassessment of the cost of chronic helmintic infection: a meta-analysis of disability-related outcomes in endemic schistosomiasis.

            Schistosomiasis is one of the world's most prevalent infections, yet its effect on the global burden of disease is controversial. Published disability-adjusted life-year (DALY) estimates suggest that the average effect of schistosome infection is quite small, although this is disputed. To develop an evidenced-based reassessment of schistosomiasis-related disability, we did a systematic review of data on disability-associated outcomes for all forms of schistosomiasis. We did structured searches using EMBASE, PUBMED, and Cochrane electronic databases. Published bibliographies were manually searched, and unpublished studies were obtained by contacting research groups. Reports were reviewed and abstracted independently by two trained readers. All randomised and observational studies of schistosomiasis morbidity were eligible for inclusion. We calculated pooled estimates of reported disability-related effects using weighted odds ratios for categorical outcomes and standardised mean differences for continuous data. 482 published or unpublished reports (March, 1921, to July, 2002) were screened. Of 135 selected for inclusion, 51 provided data for performance-related symptoms, whereas 109 reported observed measures of disability-linked morbidities. Schistosomiasis was significantly associated with anaemia, chronic pain, diarrhoea, exercise intolerance, and undernutrition. By contrast with WHO estimates of 0.5% disability weight assigned to schistosomiasis, 2-15% disability seems evident in different functional domains of a person with schistosomiasis. This raised estimate, if confirmed in formal patient-preference studies, indicates a need to reassess our priorities for treating this silent pandemic of schistosomiasis.
              Bookmark
              • Record: found
              • Abstract: found
              • Article: not found

              Conquering schistosomiasis in China: the long march.

              The last half-century of schistosomiasis control activities in China have brought down the overall prevalence of human infection with Schistosoma japonicum to less than 10% of the level initially documented in the mid 1950s. Importantly, this reduction is not only, or even mainly, due to the advent of praziquantel in the 1970s and its subsequent dramatic fall in price. Instead, it is the result of a sustained, multifaceted national strategy, adapted to different eco-epidemiological settings, which has been versatile enough to permit subtle adjustments over time as the nature of the challenge changed. Consequently, prevalence has been falling relatively smoothly over the whole period rather than suddenly dropping when mass chemotherapy became feasible. Thus, early recognition of the huge public health and economic significance of the disease, and the corresponding political will to do something about it,underpinned this success. In addition, intersectoral collaboration and community participation played important roles in forming a sustained commitment to a working control strategy based on local resources. The unfolding story is presented from the early years' strong focus on snail control, by means of environmental management, to the last period of praziquantel-based morbidity control carried out under the 10-year World Bank Loan Project (WBLP). An important legacy of the WBLP is the understanding that a research component would sustain control measures and enable future progress. We are now witnessing the payoffs of this forward thinking in the form of a new promising class of drugs, improved diagnostics, and budding vaccine development in addition to novel ways of disease risk prediction and transmission control using satellite-based remote sensing. Different aspects of social and economic approaches are also covered and the importance of health promotion and education is emphasized. Issuing from the review is a set of recommendations, which might further consolidate current control activities, with the ultimate aim to eliminate schistosomiasis from the Chinese mainland.
                Bookmark

                Author and article information

                Journal
                Proc Natl Acad Sci U S A
                Proc. Natl. Acad. Sci. U.S.A
                pnas
                pnas
                PNAS
                Proceedings of the National Academy of Sciences of the United States of America
                National Academy of Sciences
                0027-8424
                1091-6490
                23 January 2018
                4 January 2018
                4 January 2018
                : 115
                : 4
                : E584-E591
                Affiliations
                [1] aDivision of Infectious Diseases and Geographic Medicine, Stanford University School of Medicine , Stanford, CA 94305;
                [2] bDivision of Epidemiology, Stanford University School of Medicine , Stanford, CA 94305;
                [3] cDepartment of Mathematics, Applied Mathematics and Statistics, Case Western Reserve University , Cleveland, OH 44106;
                [4] dCenter for Global Health and Diseases, School of Medicine, Case Western Reserve University , Cleveland, OH 44106;
                [5] eUnité de Formation et de Recherche Biosciences, Université Félix Houphouët-Boigny , Abidjan 01, Côte d’Ivoire;
                [6] fCentre Suisse de Recherches Scientifiques en Côte d’Ivoire , Abidjan 01, Côte d’Ivoire;
                [7] gSwiss Tropical and Public Health Institute , 4051 Basel, Switzerland;
                [8] hEpidemiology and Public Health, Swiss Tropical and Public Health Institute, University of Basel , 4001 Basel, Switzerland;
                [9] iPrimary Care and Population Health, Stanford University , Stanford, CA 94305;
                [10] jCenter for Health Policy and the Center for Primary Care and Outcomes Research, Stanford University , Stanford, CA 94305;
                [11] kSchistosomiasis Consortium for Operational Research and Evaluation, University of Georgia , Athens, GA 30602;
                [12] lWHO Collaborating Centre for Research and Training for Schistosomiasis Elimination , Cleveland, OH 44106
                Author notes
                1To whom correspondence should be addressed. Email: nathan.lo@ 123456stanford.edu .

                Edited by Andrea Rinaldo, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland, and approved November 7, 2017 (received for review May 25, 2017)

                Author contributions: N.C.L., D.G., J.T.C., and C.H.K. designed research; N.C.L., D.G., and N.Y. performed research; N.C.L. and D.G. contributed new reagents/analytic tools; N.C.L., D.G., J.T.C., E.B., J.R.A., and C.H.K. analyzed data; and N.C.L., D.G., J.T.C., E.B., J.R.A., and C.H.K. wrote the paper.

                Author information
                http://orcid.org/0000-0002-5407-2005
                http://orcid.org/0000-0002-5314-7888
                Article
                201708729
                10.1073/pnas.1708729114
                5789907
                29301964
                27dfb0a7-eab8-4836-8225-9b15ca160574
                Copyright © 2018 the Author(s). Published by PNAS.

                This open access article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND).

                History
                Page count
                Pages: 8
                Categories
                PNAS Plus
                Social Sciences
                Economic Sciences
                Biological Sciences
                Population Biology
                PNAS Plus

                mathematical modeling,parasitology,cost-effectiveness,epidemiology,environmental control

                Comments

                Comment on this article