Lymphatic Filariasis (LF) is one of the oldest and most debilitating neglected tropical diseases. It is caused by three species of parasitic worms (Wuchereria bancrofti, Brugia malayi, and Brugia timori) which are transmitted to humans by mosquitoes. Based on tropical disease mapping from 2009, approximately 125 million people in 337 endemic districts across Indonesia were at risk of contracting LF. Although the number of endemic districts has been more than halved to 152 and people at risk significantly reduced to 50,785,500 as of 2017, LF remains an important public health problem in Indonesia that requires significant attention.
Earlier this year, WHO Indonesia partnered with the Directorate of Vector Borne and Zoonotic Diseases Prevention & Control, Ministry of Health (MoH), in a mission to assess the elimination programme and current situation of LF transmission in Mentawai Islands District in West Sumatra. Mentawai Islands District was classified as an LF endemic area after the 2003 baseline survey revealed an unexpectedly high rate of microfilaria in Simalegi Village.
During the mission (held from 28 April to 5 May 2019), a Transmission Assessment Survey examined 1,396 first and second grade students in 117 elementary schools. The survey was conducted based on the result of the 2018 Night-Blood Survey to measure the level of microfilaria prevalence post-Mass Drugs Administration (MDA). The microfilaria rate was less than 1%, indicating that the district could proceed to the post-MDA surveillance activities by conducting a Transmission Assessment Survey.
The Transmission Assessment Survey is important because it can help drive decisions on the continuation of administering MDA. It should be repeated at least twice post-MDA, at an interval of 2-3 years, to ensure that recrudescence has not occurred, and that transmission can therefore be considered interrupted.
Also recommended by WHO, a Survey Sample Builder was used to identify the selected schools and children for sampling purposes.
The results of the Transmission Assessment Survey showed that there was no transmission of LF in Mentawai Islands District after implementing the five rounds of MDA. Consequently, the district was then encouraged to perform an integrated vector control. Integrated vector control/management is a rational decision-making process for the optimum use of resources for vector control, using several tools to manage one or more vector-borne diseases. This approach can be beneficial in LF elimination in areas where local transmissions have been interrupted. The risk for recurrence of LF after terminating MDA is at a minimum level, but vector control may be useful as a complementary strategy to maintain a transmission-free status and reduce the risk for re-introduction.
Logo of National Campaign for Lymphatic Filariasis (LF) Elimination conducted annually in October