As more districts stop mass drug administration (MDA) for lymphatic filariasis, maintaining strong surveillance is needed to ensure transmission does not return. Post-MDA monitoring requires several years of regular transmission assessment surveys (TAS), supported by skilled health workers, reliable diagnostics and sustained local commitment. Yet delays in MDA, low coverage and limited resources continue to challenge elimination efforts in many areas.
Indonesia has identified 236 endemic districts for lymphatic filariasis and more than 200 have now stopped MDA. Since the national scale-up of MDA in 2014, the population requiring preventive chemotherapy has declined by around 98%, reflecting major progress toward elimination. While many districts have achieved elimination status, others continue MDA or are in post-MDA phases requiring sustained monitoring. The World Health Organization (WHO) recommends repeated TAS and strong laboratory networks to ensure transmission remains below critical thresholds and to guide decisions on continuing or stopping interventions. By 2024, at least 128 districts that had stopped MDA were awaiting surveys to validate their elimination status.
In 2025, WHO supported the Ministry of Health to strengthen post-MDA surveillance and frontline capacity through a coordinated package of activities across multiple provinces. From August to September, TAS were conducted in six endemic districts – OKU Timur, Ketapang, Buton, Kutai Barat, Kubu Raya and Subulussalam – involving more than 9 000 schoolchildren. All districts passed the first TAS, allowing them to proceed to the next survey stage. This was complemented by hands-on laboratory training in October at the University of Indonesia for staff from 19 districts, strengthening quality assurance and diagnostic readiness for surveillance. In Tana Tidung district, WHO also provided technical briefings to health managers and frontline workers to strengthen preparation, community engagement, drug administration and adverse event management for additional MDA rounds using the triple-drug regimen.
.jpg?sfvrsn=9f932db0_5 "webstory feb 2 (1)")
Laboratory staff take part in hands-on microscopy training for the diagnosis of lymphatic filariasis as part of capacity building for post-MDA surveillance.
Credit: WHO/Ajib Diptyanusa
Districts that passed the first TAS will proceed to the second round after two to three more years of surveillance. Continued laboratory mentorship and supervision of MDA implementation are planned to support data quality, community confidence and long-term programme sustainability.
Eliminating filariasis is not only about stopping treatment, but ensuring systems remain strong enough to detect any resurgence early. As districts transition to post-MDA phases, periodic surveys, strong routine surveillance and well-trained health workers are critical to sustain elimination gains. Through a combination of post-MDA surveys, laboratory strengthening and programme supervision, Indonesia is building the systems needed to protect communities while supporting districts still completing MDA. For communities, this means fewer disabilities, reduced stigma and greater confidence that the disease will not return, keeping the country firmly on track for national elimination by 2030.
Written by Ajib Diptyanusa, National Consultant (Malaria and Vector-Borne Diseases), and Budiarto, National Professional Officer (HIV, Hepatitis, and Sexually-Transmitted Infections), WHO Indonesia