The Persistent Gap in Mass Drug Administration Uptake Among Known Microfilaria-Positive Individuals in India's Lymphatic Filariasis Elimination Program: A Call for Strengthened Follow-Up Strategies

India’s lymphatic filariasis elimination program has achieved high mass drug administration (MDA) coverage and substantial reductions in transmission across endemic districts. As the program transitions toward transmission assessment surveys (TAS) and post-MDA surveillance, the strategic focus is shifting from expanding coverage to sustaining verified interruption of transmission. However, reliance solely on aggregate coverage metrics may overlook an important endgame vulnerability: incomplete longitudinal follow-up of individuals identified as microfilaria (Mf) positive or filarial test strip (FTS) positive during surveillance activities. Although defined epidemiologic thresholds (microfilaremia <1% or antigenemia <2% in young children) guide decisions to stop MDA, achieving these benchmarks does not necessarily ensure that all previously identified infected individuals have cleared infection. In low-prevalence settings, even small numbers of untreated or inadequately treated individuals may sustain localized transmission. Strengthening case-based registries, treatment verification mechanisms, and structured follow-up of confirmed positives can enhance epidemiologic confidence in validated elimination and reduce the risk of recrudescence.