{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"institution":[{"name":"medRxiv"}],"indexed":{"date-parts":[[2026,2,22]],"date-time":"2026-02-22T01:52:45Z","timestamp":1771725165544,"version":"3.50.1"},"posted":{"date-parts":[[2026,2,17]]},"group-title":"Epidemiology","reference-count":29,"publisher":"openRxiv","license":[{"start":{"date-parts":[[2026,2,17]],"date-time":"2026-02-17T00:00:00Z","timestamp":1771286400000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"accepted":{"date-parts":[[2026,2,19]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                <jats:sec>\n                  <jats:title>Background<\/jats:title>\n                  <jats:p>Testing blood samples with multiplex bead assays can assess elimination and identify residual foci of transmission for multiple pathogens simultaneously. In Ecuador, onchocerciasis and yaws are presumed eliminated, and the status of trachoma is unknown. We assessed their elimination status by measuring IgG antibodies in children 6\u201324 months.<\/jats:p>\n                <\/jats:sec>\n                <jats:sec>\n                  <jats:title>Methods<\/jats:title>\n                  <jats:p>\n                    In a birth cohort of 404 children measured between 2021-2024 in Esmeraldas province, Ecuador, we tested dried blood spots at ages 6, 9, 12, 18, and 24 months using a multiplex IgG assay that included antigens to\n                    <jats:italic>Onchocerca volvulus<\/jats:italic>\n                    (Ov16),\n                    <jats:italic>Treponema pallidum<\/jats:italic>\n                    (rp17, tmpa), and\n                    <jats:italic>Chlamydia trachomatis<\/jats:italic>\n                    (Pgp3, Ct694). We estimated seroprevalence and incident seroconversion rates across an urban-rural gradient.\n                  <\/jats:p>\n                <\/jats:sec>\n                <jats:sec>\n                  <jats:title>Results<\/jats:title>\n                  <jats:p>\n                    Of 404 children enrolled, 370 contributed 1,606 samples. Seroprevalence was near zero for onchocerciasis (0.4%, 95% CI: 0.2% to 0.8%) and yaws (0.2%, 95% CI: 0.0% to 0.5%). Conversely,\n                    <jats:italic>C. trachomatis<\/jats:italic>\n                    Pgp3 seroprevalence increased along the urban-rural gradient from Esmeraldas city (3.4%, 95% CI: 1.8% to 5.8%) to remote, river-accessible rural villages (22.4%, 95% CI: 16.0% to 30.1%), and incident seroconversion was common in rural villages (16.1 per 100 child-years, 95% CI: 11.3 to 21.9).\n                  <\/jats:p>\n                <\/jats:sec>\n                <jats:sec>\n                  <jats:title>Conclusions<\/jats:title>\n                  <jats:p>\n                    Serologic surveillance found no evidence of\n                    <jats:italic>O. volvulus<\/jats:italic>\n                    or\n                    <jats:italic>T. pallidum<\/jats:italic>\n                    transmission, consistent with elimination. High Pgp3 seroconversion rates suggest ongoing\n                    <jats:italic>C. trachomatis<\/jats:italic>\n                    transmission in rural villages. Results highlight the value of integrated serologic surveillance and motivate in-depth trachoma surveillance in Esmeraldas.\n                  <\/jats:p>\n                <\/jats:sec>\n                <jats:sec>\n                  <jats:title>Lay Summary<\/jats:title>\n                  <jats:p>Antibodies measured in blood provide a sensitive measure of past infection. At the population-level, antibody responses are widely used to monitor pathogen elimination. Antibodies measured in blood samples from children along an urban-rural gradient in Ecuador showed no evidence of exposure to the pathogens that cause onchocerciasis or yaws, confirming their continued elimination in the region. However, antibody responses to chlamydia were common among children in rural villages during their first two years, motivating additional surveillance to assess trachoma endemicity in the area as its endemicity status is currently unknown. Trachoma is caused by ocular chlamydia infection, and these results indicate a need for additional surveillance to assess ocular infections and clinical signs of trachoma in this population.<\/jats:p>\n                <\/jats:sec>","DOI":"10.64898\/2026.02.16.26346420","type":"posted-content","created":{"date-parts":[[2026,2,18]],"date-time":"2026-02-18T01:30:22Z","timestamp":1771378222000},"source":"Crossref","is-referenced-by-count":1,"title":["Integrated serosurveillance to assess disease elimination in coastal Ecuador: onchocerciasis, yaws, and trachoma"],"prefix":"10.64898","author":[{"ORCID":"https:\/\/orcid.org\/0009-0002-1811-7808","authenticated-orcid":false,"given":"Lesly","family":"Simba\u00f1a Vivanco","sequence":"first","affiliation":[{"name":"Institute of Microbiology, Colegio de Ciencias Biol\u00f3gicas y Ambientales, Universidad de San Francisco de Quito, Quito, Ecuador"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0009-0007-2515-5227","authenticated-orcid":false,"given":"Stuart","family":"Torres Ayala","sequence":"additional","affiliation":[{"name":"Institute of Microbiology, Colegio de Ciencias Biol\u00f3gicas y Ambientales, Universidad de San Francisco de Quito, Quito, Ecuador"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6137-9275","authenticated-orcid":false,"given":"Nikolina","family":"Walas","sequence":"additional","affiliation":[{"name":"Francis I. Proctor Foundation, University of California, San Francisco, CA, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6224-3831","authenticated-orcid":false,"given":"Gretchen","family":"Cooley","sequence":"additional","affiliation":[{"name":"Division of Parasitic Diseases and Malaria, US Centers for Disease Control and Prevention, Atlanta, GA, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4816-9249","authenticated-orcid":false,"given":"Chabier","family":"Coleman","sequence":"additional","affiliation":[{"name":"Division of Parasitic Diseases and Malaria, US Centers for Disease Control and Prevention, Atlanta, GA, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2951-7607","authenticated-orcid":false,"given":"E. Brook","family":"Goodhew","sequence":"additional","affiliation":[{"name":"Division of Parasitic Diseases and Malaria, US Centers for Disease Control and Prevention, Atlanta, GA, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9417-5562","authenticated-orcid":false,"given":"Diana L.","family":"Martin","sequence":"additional","affiliation":[{"name":"Division of Parasitic Diseases and Malaria, US Centers for Disease Control and Prevention, Atlanta, GA, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Hadley","family":"Burroughs","sequence":"additional","affiliation":[{"name":"Francis I. Proctor Foundation, University of California, San Francisco, CA, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4285-2255","authenticated-orcid":false,"given":"Everlyn","family":"Kamau","sequence":"additional","affiliation":[{"name":"Francis I. 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