Evaluating the effectiveness of mass drug administration on lymphatic filariasis transmission and assessment of post-mass drug administration surveillance in Nigeria's Federal Capital Territory.

Abstract

Background: Nigeria's Federal Capital Territory (FCT) launched annual mass drug administration (MDA) in its four lymphatic filariasis (LF)-endemic councils in 2011, achieving sustained high coverage and pre-transmission assessment survey success. This study aimed to confirm transmission interruption in Bwari and Gwagwalada and to evaluate post-MDA surveillance efficacy in Abaji and Kuje.

Methods: Transmission Assessment Surveys (TAS) were systematically conducted in four distinct evaluation units (EUs) within the FCT. TAS 1 was carried out in Bwari and Gwagwalada EUs that had recently achieved pre-TAS thresholds indicating potential interruption of transmission, whereas TAS 2 was conducted in Abaji and Kuje EUs, where MDA had been discontinued since 2021 following successful TAS 1 evaluations. Abbott Filarial Test Strips (FTS) were employed to test children aged 6-7 years attending selected schools. Data collection adhered to standardized WHO guidelines, utilizing both paper-based and electronic data-capture tools to enhance accuracy and reduce human error.

Results: A total of 6,448 children participated in surveys across the four EUs, with gender distribution closely balanced (53% male, 47% female). In TAS 1 (Bwari and Gwagwalada), no LF-positive cases were identified well below the WHO-defined critical cutoff of 18 cases. In TAS 2 (Abaji and Kuje), a single LF-positive case was detected in Abaji, still below the critical threshold. Participant refusal rates were minimal, reflecting strong community support and engagement.

Conclusions: The findings provide compelling evidence of significant progress toward LF elimination in Nigeria's FCT; however, the single positive case in Abaji underscores the continued importance of vigilant surveillance and integrated vector-management strategies to maintain elimination status and guard against residual transmission.