Global programme to eliminate lymphatic filariasis: progress report, 2020

Overview

Lymphatic filariasis (LF) is an avoidable, debilitating, disfiguring disease caused by infection with the filarial parasites Wuchereria bancrofti, Brugia malayi and B. timori. Globally, 51.4 million people are estimated to be infected.1 Lymphoedema and hydrocoele are the visible, chronic clinical consequences of the lymphatic vessel impairment caused by infection with these parasites. Mosquitos in the genera Culex, Anopheles, Mansonia and Aedes transmit the parasites from person to person. 2020 marked the 20th year since WHO established the Global Programme to Eliminate Lymphatic Filariasis (GPELF) which aims to stop transmission of infection with mass drug administration (MDA) and to alleviate suffering among people affected by the disease through morbidity management and disability prevention (MMDP). 

Achievements in 2020

Scale-up of mass drug administration

MDA involves treatment of all eligible people living in endemic areas. An implementation unit (IU) is the smallest administrative unit that countries use as a basis for making decisions about implementing MDA. The population in an IU no longer requires MDA when the prevalence of infection has been reduced to such low levels that transmission is considered no longer sustainable.2 Multiple rounds of MDA with effective coverage (≥65% coverage of the total population) are required to achieve the desired effect. This core strategy of GPELF is highly cost effective.3 WHO recommends sentinel and spot-check community surveys (preTAS), followed by a transmission assessment survey (TAS) to measure the impact of MDA and determine whether levels of infection have decreased below target thresholds.

Fewer people requiring mass drug administration

The population in an IU is considered to no longer require MDA once the criteria in preTAS and TAS have been met. The total population no longer requiring MDA was 692 million people. This represents a 49% reduction in the total population requiring interventions for LF: substantial progress towards achieving Sustainable Development Goal (SDG) 3.3.6 Figure 1 shows the cumulative proportion of known endemic IUs by region that have completed TAS and no longer require MDA. A total of 4017 endemic IUs were known globally. In 2020, TAS were conducted in 13 countries, covering 171 IUs (50 IUs in TAS1, 60 IUs in TAS2 and 61 IUs in TAS3). To date, 4316 TAS have been conducted in EUs, which may be larger or smaller than an IU. According to reports describing surveys completed in 2020, 100% of EUs passed a TAS (the proportion of children who tested positive for LF infection was below the threshold for considering transmission unsustainable). Many TAS due in 2020 were postponed to 2021 due to coronavirus 19 (COVID-19) pandemic related restrictions These accomplishments and the respective decline in population requiring MDA will be reflected in next year’s report.