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Muhsin MA, Wang X, Kabole FM, Zilabumba J, Yang K. The Indispensability of Snail Control for Accelerating Schistosomiasis Elimination: Evidence from Zanzibar. Trop Med Infect Dis 2022; 7:tropicalmed7110347. [PMID: 36355889 PMCID: PMC9699613 DOI: 10.3390/tropicalmed7110347] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Revised: 10/27/2022] [Accepted: 10/31/2022] [Indexed: 11/06/2022] Open
Abstract
Schistosomiasis is a serious and neglected global tropical disease, affecting upwards of 230 million people, with more than 95% of infections concentrated in Africa. For many years, the main schistosomiasis control strategy in Africa focused on mass drug administration (MDA). The aim of this study was to compare the difference between MDA alone and alongside another intervention, namely snail control, by exploring effective measures for eliminating schistosomiasis. Retrospective data of human prevalence on Schistosoma haematobium and major control measures were collected from the China-Zanzibar-WHO Cooperation Project for Schistosomiasis Elimination (CZW) and the Zanzibar Elimination of Schistosomiasis Transmission (ZEST) project since 2012. The optimal order polynomial regression fitting model and joinpoint regression model (JRM) were used to analyze trends in schistosomiasis prevalence and the consistency of change points with strengthening of the control measures. In Unguja Island, the main control measure was MDA, and prevalence decreased to a nadir in 2019, and then rebounded. The R2 value of the optimal fitting model was 0.6641. There was a single JRM changepoint in 2019, the annual percent change (APC) was −19.3% (p < 0.05) from 2012 to 2019, and the APC was 59.7% (p > 0.05) from 2019 to 2021. In Pemba Island, the main control measures until 2016 was MDA, while integrated measures of MDA and snail control were implemented from 2017, the prevalence continuously decreased, and the R2 value was 0.8673. There was also a single JRM changepoint in 2017, the APC was −22.2% (p < 0.05) from 2012 to 2017, and was maintained at −8.6% (p > 0.05) from 2017 to 2021. Our data indicate that, while it is challenging to eliminate schistosomiasis by MDA alone, integrated measures, including both MDA and snail control, can prevent reinfection and help to eliminate the diseases in Africa.
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Affiliation(s)
- Mtumweni Ali Muhsin
- School of Medicine, Jiangnan University, Wuxi 214122, China
- Neglected Tropical Disease Control Programme, Ministry of Health, Mnazi Mmoja, Zanzibar 16108, Tanzania
| | - Xinyao Wang
- Jiangsu Institute of Parasitic Diseases, Wuxi 214064, China
- Key Laboratory of National Health and Family Planning, Commission on Parasitic Disease Control and Prevention, Jiangsu Provincial Key Laboratory on Parasite and Vector Control Technology, Jiangsu Institute of Parasitic Diseases, Wuxi 214064, China
| | - Fatma Mohammed Kabole
- Neglected Tropical Disease Control Programme, Ministry of Health, Mnazi Mmoja, Zanzibar 16108, Tanzania
| | - January Zilabumba
- Neglected Tropical Disease Control Programme, Ministry of Health, Mnazi Mmoja, Zanzibar 16108, Tanzania
| | - Kun Yang
- School of Medicine, Jiangnan University, Wuxi 214122, China
- Jiangsu Institute of Parasitic Diseases, Wuxi 214064, China
- Key Laboratory of National Health and Family Planning, Commission on Parasitic Disease Control and Prevention, Jiangsu Provincial Key Laboratory on Parasite and Vector Control Technology, Jiangsu Institute of Parasitic Diseases, Wuxi 214064, China
- School of Public Health, Nanjing Medical University, Nanjing 211166, China
- Correspondence:
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Kengne Fokam AC, Sumo L, Bagayan M, Nana-Djeunga HC, Kuete T, Nganjou GSO, Tchami Mbagnia MC, Djune-Yemeli L, Wondji CS, Njiokou F. Exposition of Intermediate Hosts of Schistosomes to Niclosamide (Bayluscide WP 70) Revealed Significant Variations in Mortality Rates: Implications for Vector Control. Int J Environ Res Public Health 2022; 19:12873. [PMID: 36232172 PMCID: PMC9566429 DOI: 10.3390/ijerph191912873] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/21/2022] [Revised: 08/15/2022] [Accepted: 08/23/2022] [Indexed: 06/16/2023]
Abstract
(1) Background: Schistosomiasis remains a public health issue in Cameroon. Snail control using Niclosamide can prevent schistosome transmission. It is safe to determine lethal concentrations for the population. This study aimed at assessing the toxicity of Niclosamide on different developmental stages of snail populations; (2) Methods: Snails were collected, identified, and reared in the laboratory. Egg masses and adult snails were exposed to Niclosamide, at increasing concentrations (0.06, 0.125, 0.25, 0.5, 1 mg/L for egg embryos and 0.06, 0.08, 0.1, 0.12, 0.14, 0.16, 0.18, 0.2 mg/L for adults). After 24 h exposure, egg masses and snails were removed from Niclosamide solutions, washed with source water and observed; (3) Results: Snail susceptibility was species and population dependent. For egg embryos, Biomphalaria pfeifferi was the most susceptible (LC50: 0.1; LC95: 6.3 mg/L) and Bulinus truncatus the least susceptible (LC50: 4.035; LC95: 228.118 mg/L). However, for adults, B. truncatus was the most susceptible (mortality rate: 100%). The LC50 and LC95 for Bi. camerunensis eggs were 0.171 mg/L and 1.102 mg/L, respectively, and were higher than those obtained for adults (0.0357 mg/L and 0.9634 mg/L); (4) Conclusion: These findings will guide the design of vector control strategies targeting these snail species in Cameroon.
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Affiliation(s)
- Alvine Christelle Kengne Fokam
- Department of Animal Biology and Physiology, Faculty of Science, University of Yaoundé 1, Yaoundé P.O. Box 812, Cameroon
- Centre for Research in Infectious Diseases (CRID), Yaoundé P.O. Box 13591, Cameroon
| | - Laurentine Sumo
- Department of Biological Sciences, Faculty of Science, University of Bamenda, Bambili P.O. Box 39, Cameroon
| | - Mohamed Bagayan
- Animal Biology and Ecology Laboratory, University of Joseph Ki-Zerbo, Ouagadougou P.O. Box 7021, Burkina Faso
| | | | - Thomas Kuete
- Department of Biological Sciences, Faculty of Medicine and Pharmaceutical Sciences, University of Douala, Douala P.O. Box 24157, Cameroon
| | - Gabriella S. Ondoua Nganjou
- Department of Animal Biology and Physiology, Faculty of Science, University of Yaoundé 1, Yaoundé P.O. Box 812, Cameroon
- Centre for Research on Filariasis and Other Tropical Diseases (CRFilMT), Yaoundé P.O. Box 5797, Cameroon
| | - Murielle Carole Tchami Mbagnia
- Department of Animal Biology and Physiology, Faculty of Science, University of Yaoundé 1, Yaoundé P.O. Box 812, Cameroon
- Centre for Research in Infectious Diseases (CRID), Yaoundé P.O. Box 13591, Cameroon
| | - Linda Djune-Yemeli
- Centre for Research on Filariasis and Other Tropical Diseases (CRFilMT), Yaoundé P.O. Box 5797, Cameroon
| | - Charles Sinclair Wondji
- Centre for Research in Infectious Diseases (CRID), Yaoundé P.O. Box 13591, Cameroon
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L35QA, UK
| | - Flobert Njiokou
- Department of Animal Biology and Physiology, Faculty of Science, University of Yaoundé 1, Yaoundé P.O. Box 812, Cameroon
- Centre for Research in Infectious Diseases (CRID), Yaoundé P.O. Box 13591, Cameroon
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Nguyen KH, Boersch-Supan PH, Hartman RB, Mendiola SY, Harwood VJ, Civitello DJ, Rohr JR. Interventions can shift the thermal optimum for parasitic disease transmission. Proc Natl Acad Sci U S A 2021; 118:e2017537118. [PMID: 33836584 DOI: 10.1073/pnas.2017537118] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Temperature constrains the transmission of many pathogens. Interventions that target temperature-sensitive life stages, such as vector control measures that kill intermediate hosts, could shift the thermal optimum of transmission, thereby altering seasonal disease dynamics and rendering interventions less effective at certain times of the year and with global climate change. To test these hypotheses, we integrated an epidemiological model of schistosomiasis with empirically determined temperature-dependent traits of the human parasite Schistosoma mansoni and its intermediate snail host (Biomphalaria spp.). We show that transmission risk peaks at 21.7 °C (T opt ), and simulated interventions targeting snails and free-living parasite larvae increased T opt by up to 1.3 °C because intervention-related mortality overrode thermal constraints on transmission. This T opt shift suggests that snail control is more effective at lower temperatures, and global climate change will increase schistosomiasis risk in regions that move closer to T opt Considering regional transmission phenologies and timing of interventions when local conditions approach T opt will maximize human health outcomes.
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Wood CL, Sokolow SH, Jones IJ, Chamberlin AJ, Lafferty KD, Kuris AM, Jocque M, Hopkins S, Adams G, Buck JC, Lund AJ, Garcia-Vedrenne AE, Fiorenza E, Rohr JR, Allan F, Webster B, Rabone M, Webster JP, Bandagny L, Ndione R, Senghor S, Schacht AM, Jouanard N, Riveau G, De Leo GA. Precision mapping of snail habitat provides a powerful indicator of human schistosomiasis transmission. Proc Natl Acad Sci U S A 2019; 116:23182-23191. [PMID: 31659025 PMCID: PMC6859407 DOI: 10.1073/pnas.1903698116] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Recently, the World Health Organization recognized that efforts to interrupt schistosomiasis transmission through mass drug administration have been ineffective in some regions; one of their new recommended strategies for global schistosomiasis control emphasizes targeting the freshwater snails that transmit schistosome parasites. We sought to identify robust indicators that would enable precision targeting of these snails. At the site of the world's largest recorded schistosomiasis epidemic-the Lower Senegal River Basin in Senegal-intensive sampling revealed positive relationships between intermediate host snails (abundance, density, and prevalence) and human urogenital schistosomiasis reinfection (prevalence and intensity in schoolchildren after drug administration). However, we also found that snail distributions were so patchy in space and time that obtaining useful data required effort that exceeds what is feasible in standard monitoring and control campaigns. Instead, we identified several environmental proxies that were more effective than snail variables for predicting human infection: the area covered by suitable snail habitat (i.e., floating, nonemergent vegetation), the percent cover by suitable snail habitat, and size of the water contact area. Unlike snail surveys, which require hundreds of person-hours per site to conduct, habitat coverage and site area can be quickly estimated with drone or satellite imagery. This, in turn, makes possible large-scale, high-resolution estimation of human urogenital schistosomiasis risk to support targeting of both mass drug administration and snail control efforts.
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Affiliation(s)
- Chelsea L Wood
- School of Aquatic and Fishery Sciences, University of Washington, Seattle, WA 98195;
| | - Susanne H Sokolow
- Hopkins Marine Station, Stanford University, Pacific Grove, CA 93950
| | - Isabel J Jones
- Hopkins Marine Station, Stanford University, Pacific Grove, CA 93950
| | | | - Kevin D Lafferty
- Western Ecological Research Center, United States Geological Survey, Santa Barbara, CA 93106
- Marine Science Institute, University of California, Santa Barbara, CA 93106
| | - Armand M Kuris
- Marine Science Institute, University of California, Santa Barbara, CA 93106
| | - Merlijn Jocque
- Aquatic and Terrestrial Ecology, Royal Belgian Institute of Natural Sciences, 1000 Brussels, Belgium
| | - Skylar Hopkins
- Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24060
| | - Grant Adams
- School of Aquatic and Fishery Sciences, University of Washington, Seattle, WA 98195
| | - Julia C Buck
- Department of Biology and Marine Biology, University of North Carolina Wilmington, Wilmington, NC 28403
| | - Andrea J Lund
- Emmett Interdisciplinary Program in Environment and Resources, Stanford University, Stanford, CA 94305
| | - Ana E Garcia-Vedrenne
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA 90095
| | - Evan Fiorenza
- School of Aquatic and Fishery Sciences, University of Washington, Seattle, WA 98195
| | - Jason R Rohr
- Department of Biological Sciences, Environmental Change Initiative, Eck Institute of Global Health, University of Notre Dame, Notre Dame, IN 46556
| | - Fiona Allan
- Wolfson Wellcome Biomedical Laboratories, Department of Life Sciences, Natural History Museum, London SW7 5BD, United Kingdom
- London Centre for Neglected Tropical Disease Research, Imperial College London School of Public Health, London W2 1PG, United Kingdom
| | - Bonnie Webster
- Wolfson Wellcome Biomedical Laboratories, Department of Life Sciences, Natural History Museum, London SW7 5BD, United Kingdom
- London Centre for Neglected Tropical Disease Research, Imperial College London School of Public Health, London W2 1PG, United Kingdom
| | - Muriel Rabone
- Wolfson Wellcome Biomedical Laboratories, Department of Life Sciences, Natural History Museum, London SW7 5BD, United Kingdom
- London Centre for Neglected Tropical Disease Research, Imperial College London School of Public Health, London W2 1PG, United Kingdom
| | - Joanne P Webster
- London Centre for Neglected Tropical Disease Research, Imperial College London School of Public Health, London W2 1PG, United Kingdom
- Centre for Emerging, Endemic, and Exotic Diseases, Department of Pathology and Population Sciences, Royal Veterinary College, University of London, London NW1 0TU, United Kingdom
| | - Lydie Bandagny
- Biomedical Research Center Espoir Pour La Santé, BP 226 Saint-Louis, Senegal
| | - Raphaël Ndione
- Biomedical Research Center Espoir Pour La Santé, BP 226 Saint-Louis, Senegal
| | - Simon Senghor
- Biomedical Research Center Espoir Pour La Santé, BP 226 Saint-Louis, Senegal
| | - Anne-Marie Schacht
- Biomedical Research Center Espoir Pour La Santé, BP 226 Saint-Louis, Senegal
| | - Nicolas Jouanard
- Biomedical Research Center Espoir Pour La Santé, BP 226 Saint-Louis, Senegal
- Station d'Innovation Aquacole, BP 524 Saint-Louis, Senegal
| | - Gilles Riveau
- Biomedical Research Center Espoir Pour La Santé, BP 226 Saint-Louis, Senegal
| | - Giulio A De Leo
- Hopkins Marine Station, Stanford University, Pacific Grove, CA 93950
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Bergquist R, Gray DJ. Schistosomiasis Elimination: Beginning of the End or a Continued March on a Trodden Path. Trop Med Infect Dis 2019; 4:tropicalmed4020076. [PMID: 31060317 PMCID: PMC6630800 DOI: 10.3390/tropicalmed4020076] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Accepted: 04/15/2019] [Indexed: 12/21/2022] Open
Abstract
In spite of spectacular progress towards the goal of elimination of schistosomiasis, particularly in China but also in other areas, research gaps and outstanding issues remain. Although expectations of achieving elimination of this disease have never been greater, all constraints have not been swept aside. Indeed, there are some formidable obstacles, such as insufficient amounts of drugs to treat everybody and still limited use of high-sensitive diagnostic techniques, both for the definitive and the intermediate hosts, which indicate that prevalence is considerably underrated in well-controlled areas. Elimination will be difficult to achieve without a broad approach, including a stronger focus on transmission, better diagnostics and the establishment of a reliable survey system activating a rapid response when called for. Importantly, awareness of the crucial importance of transmission has been revived resulting in renewed interest in snail control together with more emphasis on health education and sanitation. The papers collected in this special issue entitled ‘Prospects for Schistosomiasis Elimination’ reflect these issues and we are particularly pleased to note that some also discuss the crucial question when to declare a country free of schistosomiasis and present techniques that together create an approach that can show unequivocally when interruption of transmission has been achieved.
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Affiliation(s)
| | - Darren J Gray
- Research School of Population Health, Australian National University, Canberra, ACT 2601, Australia.
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Hewitt R, Willingham AL. Status of Schistosomiasis Elimination in the Caribbean Region. Trop Med Infect Dis 2019; 4:E24. [PMID: 30708966 DOI: 10.3390/tropicalmed4010024] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 01/23/2019] [Accepted: 01/26/2019] [Indexed: 01/08/2023] Open
Abstract
Schistosomiasis elimination status in the Caribbean is reviewed with information on historical disease background, attempts to control it and current situation for each locality in the region where transmission has been eliminated (Sint Maarten, Saint Kitts, Vieques), eliminated but not yet verified (Puerto Rico, Dominican Republic, Antigua, Montserrat, Guadeloupe, Martinique) and still ongoing (Saint Lucia, Suriname). Integrated control initiatives based on selective and mass treatment and snail control using environmental, chemical and biological methods along with public service improvements (housing, safe water, sanitation) and changes in demography (urbanization) and economy (change from sugarcane and banana production to tourism) have resulted in reduction in the burden of schistosomiasis over the past century. Introduction of Biomphalaria-competitor snails into the region as a cost-effective, low maintenance control method appears to have had the most sustainable impact on transmission reduction. A regional inventory of B. glabrata, other Biomphalaria species and Biomphalaria-competitor snails as well as investigation of possible animal reservoir hosts in persisting endemic areas would be helpful for control. Elimination of schistosomiasis appears achievable in the Caribbean. However, a regional surveillance and monitoring program is needed to verify elimination in the various localities and identify and monitor areas still endemic or at risk.
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