{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,28]],"date-time":"2026-07-28T02:16:43Z","timestamp":1785205003437,"version":"3.55.0"},"reference-count":32,"publisher":"Public Library of Science (PLoS)","issue":"6","license":[{"start":{"date-parts":[[2025,6,25]],"date-time":"2025-06-25T00:00:00Z","timestamp":1750809600000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001411","name":"Indian Council of Medical Research","doi-asserted-by":"publisher","award":["RFC.P.No.4 ECD\/Adhoc\/4\/22-23"],"award-info":[{"award-number":["RFC.P.No.4 ECD\/Adhoc\/4\/22-23"]}],"id":[{"id":"10.13039\/501100001411","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["www.plosntds.org"],"crossmark-restriction":false},"short-container-title":["PLoS Negl Trop Dis"],"abstract":"\nBackground<\/jats:title>\nIndia is moving towards the Lymphatic Filariasis (LF) elimination goal in 2027. Documentation on LF transmission status in the non-endemic and unsurveyed areas is crucial for WHO to certify that LF has been eliminated as a public health problem in the country. Appropriate sampling strategy is necessary to determine LF transmission status in the areas not under mass drug administration (MDA). We evaluated four different sampling strategies to identify the best tool(s) and indicator(s) that could be used to assess transmission interruption in a non-MDA district.<\/jats:p>\n<\/jats:sec>\n\nMethodology<\/jats:title>\nThis study was conducted in Salem district in Tamil Nadu, India, during the period from June 2022 to June 2023. Four different sampling strategies, namely: (i) School based Mini-TAS (Mini-sTAS, n\u2009=\u2009480), (ii) Community based Mini-TAS (Mini-cTAS, n\u2009=\u2009480), (iii) Molecular xenomonitoring surveys (MX, n\u2009=\u20097500), and (iv) Purposive sampling of five high-risk sites (human, n\u2009=\u20091500 and vector surveys, n\u2009=\u20093750), were evaluated for their ability to assess LF transmission status in the area. These strategies were compared with a large-scale community survey (n\u2009=\u200910200) in 30 randomly selected sites (villages\/wards) assessing human infection in the study area. While Filariasis Test strips (FTS) were used to assess circulating filarial antigen (CFA), night blood smears from CFA positives were collected to assess microfilaraemia (Mf). Mosquito samples collected from MX surveys were subjected to polymerase chain reaction (PCR) assays to assess the infection in vectors.<\/jats:p>\n<\/jats:sec>\n\nResults<\/jats:title>\nThe results of the large-scale survey showed that the overall prevalence of CFA was 0.2% (95% CI: 0.1%\u20130.3%), below the critical threshold of 2%. Mini-sTAS and Mini-cTAS both showed that the CFA prevalence among children was below the elimination threshold of 2%. MX surveys showed the vector infection prevalence of 0.03% (95% CI: 0.01%\u20130.09%). These three strategies showed that the district is non-endemic and corroborate the results of a large-scale community survey. However, under the purposive sampling strategy, in two high-risk sites, either human or vector infection prevalence was above the respective elimination thresholds. Further, the administrative blocks in which these sites were situated shared borders with known LF endemic districts.<\/jats:p>\n<\/jats:sec>\n\nConclusions<\/jats:title>\nThe sampling strategies that may be recommended for a non-MDA or unsurveyed district to assess LF transmission status would be to use (i) school- or community-based Mini-TAS or (ii) conduct MX surveys to classify them as endemic or non-endemic based on the pre-defined thresholds by WHO. For further confirmation, serosurveys among adults may be conducted in five purposively selected high-risk sites to identify pockets of LF transmission, if any.<\/jats:p>\n<\/jats:sec>","DOI":"10.1371\/journal.pntd.0013192","type":"journal-article","created":{"date-parts":[[2025,6,25]],"date-time":"2025-06-25T17:45:46Z","timestamp":1750873546000},"page":"e0013192","update-policy":"https:\/\/doi.org\/10.1371\/journal.pntd.corrections_policy","source":"Crossref","is-referenced-by-count":2,"title":["Evaluation of sampling strategies for assessing lymphatic filariasis endemic status of a non-MDA district in South India"],"prefix":"10.1371","volume":"19","author":[{"given":"Adinarayanan","family":"Srividya","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Rajendran","family":"Dhanalakshmi","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3359-3039","authenticated-orcid":true,"given":"Raja Jeyapal","family":"Dinesh","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Palappurath Maliyakkal","family":"Azad","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ramalingam","family":"Balasubramaniyan","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sivaprakasam T.","family":"Selvavinayagam","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Palani","family":"Sampath","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Masilamani","family":"Senthilkumar","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Dhandapani","family":"Bharani Kumar","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Brindha","family":"Balan","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Philip Raj","family":"Abraham","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ashwani","family":"Kumar","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Swaminathan","family":"Subramanian","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Manju","family":"Rahi","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"340","published-online":{"date-parts":[[2025,6,25]]},"reference":[{"key":"pntd.0013192.ref001","volume-title":"Weekly epidemiological report","author":"WHO","year":"2023"},{"key":"pntd.0013192.ref002","volume-title":"List of state-wise lf endemic districts","author":"NCVBDC","year":"2024"},{"key":"pntd.0013192.ref003","volume-title":"Guideline: Alternative mass drug administration regimens to eliminate lymphatic filariasis","author":"WHO","year":"2017"},{"key":"pntd.0013192.ref004","author":"NCVBDC","year":"2023"},{"issue":"9","key":"pntd.0013192.ref005","doi-asserted-by":"crossref","first-page":"657","DOI":"10.1089\/vbz.2012.1238","article-title":"Lymphatic filariasis transmission risk map of India, based on a geo-environmental risk model","volume":"13","author":"S Sabesan","year":"2013","journal-title":"Vector Borne Zoonotic Dis"},{"key":"pntd.0013192.ref006","volume-title":"Validation of elimination of lymphatic filariasis as a public health problem","author":"World Health Organization","year":"2017"},{"issue":"10","key":"pntd.0013192.ref007","article-title":"The rationale and cost-effectiveness of a confirmatory mapping tool for lymphatic filariasis: Examples from Ethiopia and Tanzania","volume":"11","author":"KM Gass","year":"2017","journal-title":"PLoS Negl Trop Dis"},{"issue":"3","key":"pntd.0013192.ref008","doi-asserted-by":"crossref","DOI":"10.1371\/journal.pntd.0006325","article-title":"Results of a confirmatory mapping tool for Lymphatic filariasis endemicity classification in areas where transmission was uncertain in Ethiopia","volume":"12","author":"H Sime","year":"2018","journal-title":"PLoS Negl Trop Dis"},{"issue":"2","key":"pntd.0013192.ref009","doi-asserted-by":"crossref","first-page":"78","DOI":"10.1016\/j.pt.2006.12.001","article-title":"Diagnostic tools for filariasis elimination programs","volume":"23","author":"GJ Weil","year":"2007","journal-title":"Trends Parasitol"},{"issue":"11","key":"pntd.0013192.ref010","article-title":"Seroprevalence and spatial epidemiology of Lymphatic Filariasis in American Samoa after successful mass drug administration","volume":"8","author":"CL Lau","year":"2014","journal-title":"PLoS Negl Trop Dis"},{"issue":"1","key":"pntd.0013192.ref011","doi-asserted-by":"crossref","first-page":"99","DOI":"10.1186\/s13071-017-2044-5","article-title":"Assessment of lymphatic filariasis prior to re-starting mass drug administration campaigns in coastal Kenya","volume":"10","author":"SM Njenga","year":"2017","journal-title":"Parasit Vectors"},{"issue":"2","key":"pntd.0013192.ref012","doi-asserted-by":"crossref","first-page":"156","DOI":"10.1016\/S0035-9203(97)90205-4","article-title":"A polymerase chain reaction-based assay for detection of Wuchereria bancrofti in human blood and Culex pipiens","volume":"91","author":"RM Ramzy","year":"1997","journal-title":"Trans R Soc Trop Med Hyg"},{"key":"pntd.0013192.ref013","article-title":"Development and standardization of a rapid, PCR-based method for the detection of Wuchereria bancrofti in mosquitoes, for xenomonitoring the human prevalence of bancroftian filariasis","author":"SA Williams","year":"2002","journal-title":"Ann Trop Med Parasitol"},{"issue":"1","key":"pntd.0013192.ref014","doi-asserted-by":"crossref","DOI":"10.1371\/journal.pntd.0007862","article-title":"Molecular xenomonitoring as a post-MDA surveillance tool for global programme to eliminate lymphatic filariasis: Field validation in an evaluation unit in India","volume":"14","author":"S Subramanian","year":"2020","journal-title":"PLoS Negl Trop Dis"},{"key":"pntd.0013192.ref015","author":"COR-NTD","year":"n.d"},{"key":"pntd.0013192.ref016","doi-asserted-by":"crossref","first-page":"107801","DOI":"10.1016\/j.ijid.2025.107801","article-title":"Confirmatory mapping for lymphatic filariasis in districts previously considered nonendemic in Ghana","volume":"152","author":"JL Opare","year":"2025","journal-title":"Int J Infect Dis"},{"key":"pntd.0013192.ref017","volume-title":"Filariasis Test Strip (FTS) Bench Aid","author":"COR-NTD","year":"2021"},{"key":"pntd.0013192.ref018","volume-title":"Monitoring and epidemiological assessment of mass drug administration in the global programme to eliminate lymphatic filariasis: a manual for national elimination programmes","author":"WHO","year":"2011"},{"issue":"2","key":"pntd.0013192.ref019","first-page":"325","article-title":"A revised version of the CDC Gravid Mosquito Trap","volume":"3","author":"P Reiter","year":"1987","journal-title":"J Am Mosq Control Assoc"},{"issue":"4","key":"pntd.0013192.ref020","doi-asserted-by":"crossref","DOI":"10.1371\/journal.pntd.0005519","article-title":"Application of a household-based molecular xenomonitoring strategy to evaluate the lymphatic filariasis elimination program in Tamil Nadu, India","volume":"11","author":"S Subramanian","year":"2017","journal-title":"PLoS Negl Trop Dis"},{"issue":"1","key":"pntd.0013192.ref021","doi-asserted-by":"crossref","first-page":"77","DOI":"10.4103\/0972-9062.179266","article-title":"Molecular xenomonitoring of Wuchereria bancrofti in Culex quinquefasciatus from an endemic area: Comparison of two DNA extraction methods for realtime PCR assay","volume":"53","author":"V Vasuki","year":"2016","journal-title":"J Vector Borne Dis"},{"issue":"1","key":"pntd.0013192.ref022","doi-asserted-by":"crossref","first-page":"109","DOI":"10.1016\/S0001-706X(02)00267-X","article-title":"A simple and rapid DNA extraction method for the detection of Wuchereria bancrofti infection in the vector mosquito, Culex quinquefasciatus by Ssp I PCR assay","volume":"86","author":"V Vasuki","year":"2003","journal-title":"Acta Trop"},{"issue":"5","key":"pntd.0013192.ref023","doi-asserted-by":"crossref","first-page":"826","DOI":"10.4269\/ajtmh.2006.74.826","article-title":"A real-time PCR-based assay for detection of Wuchereria bancrofti DNA in blood and mosquitoes","volume":"74","author":"RU Rao","year":"2006","journal-title":"Am J Trop Med Hyg"},{"key":"pntd.0013192.ref024","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.envsoft.2021.105158","article-title":"PoolTestR: An R package for estimating prevalence and regression modelling for molecular xenomonitoring and other applications with pooled samples","volume":"145","author":"A McLure","year":"2021","journal-title":"Environmental Modelling & Software"},{"key":"pntd.0013192.ref025","volume-title":"The role of polymerase chain reaction techniques for assessing lymphatic filariasis transmission","author":"WHO","year":"2009"},{"key":"pntd.0013192.ref026","volume-title":"ArcGIS Desktop: Release 10.2","author":"ESRI","year":"2013"},{"key":"pntd.0013192.ref027","volume-title":"Stata Statistical Software: Release 18","author":"STATA","year":"2020"},{"issue":"11","key":"pntd.0013192.ref028","doi-asserted-by":"crossref","DOI":"10.1371\/journal.pone.0293641","article-title":"Mini-TAS as a confirmatory mapping tool for remapping areas with uncertain filarial endemicity to exclude\/ include for mass drug administration: A report from field validation in India","volume":"18","author":"BB Panda","year":"2023","journal-title":"PLoS One"},{"issue":"2","key":"pntd.0013192.ref029","doi-asserted-by":"crossref","first-page":"109","DOI":"10.1016\/j.trstmh.2010.10.006","article-title":"High prevalence of Wuchereria bancrofti infection as detected by immunochromatographic card testing in five districts of Orissa, India, previously considered to be non-endemic","volume":"105","author":"PK Foo","year":"2011","journal-title":"Trans R Soc Trop Med Hyg"},{"key":"pntd.0013192.ref030","doi-asserted-by":"crossref","DOI":"10.1016\/j.parepi.2023.e00300","article-title":"Morbidity hotspot surveillance: A novel approach to detect lymphatic filariasis transmission in non-endemic areas of the Tillab\u00e9ry region of Niger","volume":"21","author":"X Badia-Rius","year":"2023","journal-title":"Parasite Epidemiol Control"},{"issue":"1","key":"pntd.0013192.ref031","doi-asserted-by":"crossref","first-page":"89","DOI":"10.4269\/ajtmh.13-0407","article-title":"Ongoing surveillance for lymphatic filariasis in Togo: assessment of alternatives and nationwide reassessment of transmission status","volume":"90","author":"PJ Budge","year":"2014","journal-title":"Am J Trop Med Hyg"},{"issue":"2","key":"pntd.0013192.ref032","doi-asserted-by":"crossref","DOI":"10.1371\/journal.pntd.0012802","article-title":"Changes in circulating filarial antigen status in previously positive individuals: Lessons for treatment monitoring and pre-transmission assessment surveys","volume":"19","author":"DA Mensah","year":"2025","journal-title":"PLoS Negl Trop Dis"}],"container-title":["PLOS Neglected Tropical Diseases"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/dx.plos.org\/10.1371\/journal.pntd.0013192","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,6,25]],"date-time":"2025-06-25T17:46:02Z","timestamp":1750873562000},"score":1,"resource":{"primary":{"URL":"https:\/\/dx.plos.org\/10.1371\/journal.pntd.0013192"}},"subtitle":[],"editor":[{"given":"Feng","family":"Xue","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"editor"}]}],"short-title":[],"issued":{"date-parts":[[2025,6,25]]},"references-count":32,"journal-issue":{"issue":"6","published-online":{"date-parts":[[2025,6,25]]}},"URL":"https:\/\/doi.org\/10.1371\/journal.pntd.0013192","relation":{},"ISSN":["1935-2735"],"issn-type":[{"value":"1935-2735","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,6,25]]}}}