A Tool for Monitoring Epidemiological Impact of Mass Drug Administration (MDA) in the Elimination of Lymphatic Filariasis- an Indian Experience

Lymphatic filariasis (LF) is a mosquito- transmitted parasitic disease, which is a leading cause of permanent disability. LF affects an estimated 120 million people in 81 countries, with over 1 billion at risk for filarial infection. During 1997, Lymphatic filariasis was considered for elimination in the 50th WHA resolution. The Global Programme to Eliminate Lymphatic Filariasis (GPELF) was launched in 2000 with the goal of eliminating LF as a public health problem worldwide by 2020. The programme is centred on annual mass drug administration (MDA), which is done through community- based administration of diethylcarbamazine (DEC) and albendazole tablets to all the population at risk. The main components of GPELF comprised of (i) interruption of LF transmission by MDA and (ii) Management of Morbidity and prevention of disability. Five to six rounds of MDA, with at least 60? 70% treatment coverage (consumption), are adequate to interrupt transmission. In India, programme to eliminate lymphatic filariasis was launched in 2004 covering 202 endemic districts in 20 states/ union territories and subsequently scaled up to cover all the 250 endemic districts targeting a population of about 600 million. The current benchmark for assessing the impact of the programme is a microfilaria prevalence of less than 1% in the community covered under MDA. This is considered as the critical level below which the transmission is not sustained. Current WHO Transmission Assessment Survey (TAS) protocol recommends conducting cluster surveys of young children (6- 7 years) to confirm the interruption of transmission and absence of recent cases. Immuno- Chromatographic Test (ICT) is the recommended diagnostic tool. In India, the programme evaluation has been initiated to make programmatic decision on stopping further rounds of MDA. So far 21 districts (4 districts partially) have been evaluated using the TAS protocol and the results were encouraging as all the Evaluation Units were qualified for stopping MDA. Training of Trainers (TOTs) has already been conducted at the National and four sub- national levels in Maharashtra, Odisha, Tamil Nadu and Karnataka. Action plans are prepared by the respective states to undertake evaluation in the qualifying districts based on eligiblity criteria. The prospects and operational issues in conducting TAS are discussed.