{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,9]],"date-time":"2026-09-09T12:19:12Z","timestamp":1788956352619,"version":"build-2803163510"},"update-to":[{"DOI":"10.1371\/journal.pntd.0009011","type":"new_version","label":"New version","source":"publisher","updated":{"date-parts":[[2021,5,24]],"date-time":"2021-05-24T00:00:00Z","timestamp":1621814400000}}],"reference-count":24,"publisher":"Public Library of Science (PLoS)","issue":"5","license":[{"start":{"date-parts":[[2021,5,12]],"date-time":"2021-05-12T00:00:00Z","timestamp":1620777600000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100000865","name":"Bill & Melinda Gates Foundation","doi-asserted-by":"publisher","award":["INV-010104"],"award-info":[{"award-number":["INV-010104"]}],"id":[{"id":"10.13039\/100000865","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000865","name":"Bill & Melinda Gates Foundation","doi-asserted-by":"crossref","award":["INV-010104"],"award-info":[{"award-number":["INV-010104"]}],"id":[{"id":"10.13039\/100000865","id-type":"DOI","asserted-by":"crossref"}]},{"DOI":"10.13039\/100000865","name":"Bill & Melinda Gates Foundation","doi-asserted-by":"crossref","award":["INV-010104"],"award-info":[{"award-number":["INV-010104"]}],"id":[{"id":"10.13039\/100000865","id-type":"DOI","asserted-by":"crossref"}]},{"DOI":"10.13039\/100000865","name":"Bill & Melinda Gates Foundation","doi-asserted-by":"crossref","award":["INV-010104"],"award-info":[{"award-number":["INV-010104"]}],"id":[{"id":"10.13039\/100000865","id-type":"DOI","asserted-by":"crossref"}]},{"DOI":"10.13039\/501100003246","name":"Dutch Research Council","doi-asserted-by":"crossref","award":["016.Veni.178.023"],"award-info":[{"award-number":["016.Veni.178.023"]}],"id":[{"id":"10.13039\/501100003246","id-type":"DOI","asserted-by":"crossref"}]}],"content-domain":{"domain":["www.plosntds.org"],"crossmark-restriction":false},"short-container-title":["PLoS Negl Trop Dis"],"abstract":"<jats:sec id=\"sec001\">\n<jats:title>Background<\/jats:title>\n<jats:p>The existence of locations with low but stable onchocerciasis prevalence is not well understood. An often suggested yet poorly investigated explanation is that the infection spills over from neighbouring locations with higher infection densities.<\/jats:p>\n<\/jats:sec>\n<jats:sec id=\"sec002\">\n<jats:title>Methodology<\/jats:title>\n<jats:p>We adapted the stochastic individual based model ONCHOSIM to enable the simulation of multiple villages, with separate blackfly (intermediate host) and human populations, which are connected through the regular movement of the villagers and\/or the flies. With this model we explore the impact of the type, direction and degree of connectedness, and of the impact of localized or full-area mass drug administration (MDA) over a range of connected village settings.<\/jats:p>\n<\/jats:sec>\n<jats:sec id=\"sec003\">\n<jats:title>Principal findings<\/jats:title>\n<jats:p>In settings with annual fly biting rates (ABR) below the threshold needed for stable local transmission, persistence of onchocerciasis prevalence can well be explained by regular human traffic and\/or fly movement from locations with higher ABR. Elimination of onchocerciasis will then theoretically be reached by only implementing MDA in the higher prevalence area, although lingering infection in the low prevalence location can trigger resurgence of transmission in the total region when MDA is stopped too soon. Expanding MDA implementation to the lower ABR location can therefore shorten the duration of MDA needed. For example, when prevalence spill-over is due to human traffic, and both locations have about equal populations, then the MDA duration can be shortened by up to three years. If the lower ABR location has twice as many inhabitants, the reduction can even be up to six years, but if spill-over is due to fly movement, the expected reduction is less than a year.<\/jats:p>\n<\/jats:sec>\n<jats:sec id=\"sec004\">\n<jats:title>Conclusions\/Significance<\/jats:title>\n<jats:p>Although MDA implementation might not always be necessary in locations with stable low onchocerciasis prevalence, in many circumstances it is recommended to accelerate achieving elimination in the wider area.<\/jats:p>\n<\/jats:sec>","DOI":"10.1371\/journal.pntd.0009011","type":"journal-article","created":{"date-parts":[[2021,5,12]],"date-time":"2021-05-12T17:54:58Z","timestamp":1620842098000},"page":"e0009011","update-policy":"https:\/\/doi.org\/10.1371\/journal.pntd.corrections_policy","source":"Crossref","is-referenced-by-count":17,"title":["The impact of mass drug administration expansion to low onchocerciasis prevalence settings in case of connected villages"],"prefix":"10.1371","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-4754-0026","authenticated-orcid":true,"given":"Anneke S.","family":"de Vos","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9509-1328","authenticated-orcid":true,"given":"Wilma A.","family":"Stolk","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4425-2264","authenticated-orcid":true,"given":"Luc E.","family":"Coffeng","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1830-5668","authenticated-orcid":true,"given":"Sake J.","family":"de Vlas","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"340","published-online":{"date-parts":[[2021,5,12]]},"reference":[{"key":"pntd.0009011.ref001","article-title":"Togetherness among Schistosomes: its effects on the dynamics of the infection","author":"RM May","year":"1977","journal-title":"Math Biosci"},{"key":"pntd.0009011.ref002","article-title":"Consequences of helminth aggregation for the dynamics of schistosomiasis","author":"DJ Bradley","year":"1978","journal-title":"Trans R Soc Trop Med Hyg"},{"key":"pntd.0009011.ref003","doi-asserted-by":"crossref","first-page":"581","DOI":"10.1016\/j.ijpara.2010.12.009","article-title":"Control of onchocerciasis in Africa: Threshold shifts, breakpoints and rules for elimination","volume":"41","author":"HP Duerr","year":"2011","journal-title":"Int J Parasitol"},{"key":"pntd.0009011.ref004","doi-asserted-by":"crossref","first-page":"43","DOI":"10.1016\/0169-2607(90)90030-D","article-title":"ONCHOSIM: a model and computer simulation program for the transmission and control of onchocerciasis","volume":"31","author":"AP Plaisier","year":"1990","journal-title":"Comput Methods Programs Biomed"},{"key":"pntd.0009011.ref005","article-title":"Elimination of African onchocerciasis: Modeling the impact of increasing the frequency of ivermectin mass treatment","author":"LE Coffeng","year":"2014","journal-title":"PLoS One"},{"key":"pntd.0009011.ref006","article-title":"Required duration of mass ivermectin treatment for onchocerciasis elimination in Africa: a comparative modelling analysis","author":"WA Stolk","year":"2015","journal-title":"Parasit Vectors"},{"key":"pntd.0009011.ref007","article-title":"How can onchocerciasis elimination in Africa be accelerated? Modeling the impact of increased ivermectin treatment frequency and complementary vector control","author":"S Verver","year":"2018","journal-title":"Clin Infect Dis"},{"key":"pntd.0009011.ref008","doi-asserted-by":"crossref","first-page":"1545","DOI":"10.12688\/gatesopenres.13067.1","article-title":"The World Health Organization 2030 goals for onchocerciasis: Insights and perspectives from mathematical modelling","volume":"3","author":"NTD Modelling Consortium Onchocerciasis Group","year":"2019","journal-title":"Gates Open Res"},{"key":"pntd.0009011.ref009","article-title":"The effect of assortative mixing on stability of low helminth transmission levels and on the impact of mass drug administration: Model explorations for onchocerciasis","author":"AS de Vos","year":"2018","journal-title":"PLoS Negl Trop Dis"},{"key":"pntd.0009011.ref010","article-title":"The geographic distribution of onchocerciasis in the 20 participating countries of the African Programme for Onchocerciasis Control: (2) pre-control endemicity levels and estimated number infected.","volume":"7.","author":"HGM Zour\u00e9","year":"2014","journal-title":"Parasit Vectors."},{"key":"pntd.0009011.ref011","article-title":"Model-Based Geostatistical Mapping of the Prevalence of Onchocerca volvulus in West Africa","author":"SJ O\u2019Hanlon","year":"2016","journal-title":"PLoS Negl Trop Dis"},{"key":"pntd.0009011.ref012","unstructured":"African Programme for Onchocerciasis Control. Report of the consultative meetings on strategic options and alternative treatment strategies for accelerating onchocerciasis elimination in Africa. 2015. Available: https:\/\/www.who.int\/apoc\/ATS_Report_2015.12.pdf"},{"key":"pntd.0009011.ref013","doi-asserted-by":"crossref","DOI":"10.1186\/s40249-016-0160-7","article-title":"Progress towards onchocerciasis elimination in the participating countries of the African Programme for Onchocerciasis Control: Epidemiological evaluation results","volume":"5","author":"AH Tekle","year":"2016","journal-title":"Infect Dis Poverty"},{"key":"pntd.0009011.ref014","article-title":"Reaching the last mile: Main challenges relating to and recommendations to accelerate onchocerciasis elimination in Africa","author":"G Gebrezgabiher","year":"2019","journal-title":"Infect Dis Poverty"},{"key":"pntd.0009011.ref015","unstructured":"World Health Organization & African Programme for Onchocerciasis control. Informal consultation on elimination of onchocerciasis transmission with current tools: \u201cshrinking the map.\u201d 2009. Available: https:\/\/apps.who.int\/iris\/bitstream\/handle\/10665\/275793\/WHO-APOC-MG-09.1-eng.pdf?sequence=1&isAllowed=y"},{"key":"pntd.0009011.ref016","unstructured":"Team R. R Development Core Team. R A Lang Environ Stat Comput. 2013."},{"key":"pntd.0009011.ref017","article-title":"Studies on the dynamics of transmission of onchocerciasis in a Sudan-savanna area of North Cameroon I. Prevailing Simulium vectors, their biting rates and age-composition at different distances from their breeding sites","author":"A Renz","year":"1987","journal-title":"Ann Trop Med Parasitol"},{"key":"pntd.0009011.ref018","unstructured":"African Programme for Onchocerciasis Control. Conceptual and Operational Framework of Onchocerciasis Elimination with Ivermectin Treatment. 2010. 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Available: https:\/\/apps.who.int\/iris\/bitstream\/handle\/10665\/273705\/WHO-CDS-NTD-PCT-2018.05-eng.pdf?ua=1"},{"key":"pntd.0009011.ref020","article-title":"Modelling exposure heterogeneity and density dependence in onchocerciasis using a novel individual-based transmission model, EPIONCHO-IBM: Implications for elimination and data needs","author":"JID Hamley","year":"2019","journal-title":"PLoS Negl Trop Dis"},{"key":"pntd.0009011.ref021","article-title":"Structural Uncertainty in Onchocerciasis Transmission Models Influences the Estimation of Elimination Thresholds and Selection of Age Groups for Seromonitoring","author":"JID Hamley","year":"2020","journal-title":"J Infect Dis"},{"key":"pntd.0009011.ref022","article-title":"Modelling Anti-Ov16 IgG4 Antibody Prevalence as an Indicator for Evaluation and Decision Making in Onchocerciasis Elimination Programmes","author":"YL Lont","year":"2017","journal-title":"PLoS Negl Trop Dis"},{"key":"pntd.0009011.ref023","article-title":"Feasibility of Onchocerciasis Elimination Using a \u201cTest-and-not-treat\u201d Strategy in Loa loa Co-endemic Areas","author":"DJ Blok","year":"2020","journal-title":"Clin Infect Dis"},{"key":"pntd.0009011.ref024","article-title":"Are alternative strategies required to accelerate the global elimination of lymphatic filariasis? 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