Serological and Spatial Assessment of Lymphatic Filariasis Transmission Interruption in the Coastal Region of Kenya: Evidence from Pre-TAS and TAS Surveys

Background Lymphatic filariasis (LF) remains a health challenge specifically in resources limited settings. Objective This study evaluated previous LF exposure and the impact of MDA interventions in coastal Kenya using serological and spatial evidence. Methods A cross-sectional survey was conducted in four LF-endemic counties. Pre-Transmission Assessment Surveys (Pre-TAS) targeted individuals aged ≥15 years, while Transmission Assessment Surveys (TAS) targeted children aged 6-7 years. Wuchereria bancrofti antigen was detected using Filariasis Test Strip (FTS), while IgG4 antibodies against the Bm14 antigen were measured using ELISA. PCR was performed on FTS positive samples. Results Overall, ELISA positivity was 12.0% (95% CI: 10.8-13.3%), higher in males (14.4%, 95% CI: 12.4-16.6%), and increased with age, peaking at 20.0%, (95% CI: 15.2-25.7%) among those over 60 years old. Geographic variation was moderate, with Kilifi (12.2%, 95% CI: 10.7-13.9%) and Kwale (11.7%, 95% CI: 9.8-14.0%) showing similar antibody prevalence. At the subcounty level, Kaloleni (18.1%, 95% CI: 13.8-23.5%) and Magarini (15.2%, 95% CI: 10.9-20.8%) had the highest seropositivity, while Msambweni (8.0%, 95% CI: 5.0-12.4%), and Kilifi North had the lowest (8.4%, 95% CI: 5.5-12.8%). Conclusion These findings indicate persistence of anti-filarial antibodies, particularly in older populations, underscoring the need for robust post-MDA surveillance systems.