Global programme to eliminate lymphatic filariasis: progress report, 2024

Overview

Lymphatic filariasis (LF) is a vector-borne, parasitic disease in humans that results in immense suffering among people affected. This neglected tropical disease is caused by infection with the filarial parasites Wuchereria bancrofti, Brugia malayi and B. timori which damage the lymphatic vessels and impair vessel function, leading to clinical manifestations such as lymphoedema and hydrocele. Member States called for the elimination of LF as a public health problem and in response WHO established the Global Programme to Eliminate Lymphatic Filariasis (GPELF) to stop transmission of infection by mass drug administration (MDA) of anthelminthics and to alleviate the suffering of people affected by the disease through morbidity management and disability prevention (MMDP).

MDA is the recommended, cost–effective strategy for stopping transmission by treating all people living in areas in which infections are prevalent. Multiple rounds of MDA with effective coverage (≥65% of the total population) are required to reduce levels of infection below thresholds where transmission is considered no longer sustainable. The smallest administrative unit at which national programmes deliver MDA is referred to as the implementation unit (IU). Once the prevalence of infection has been reduced below target thresholds, the population of an IU is considered no longer requiring MDA. WHO recommends a strategy of repeat epidemiological surveys including the transmission assessment survey (TAS) or the ivermectin (I), diethylcarbamazine (D) and albendazole (A) (IDA) impact survey (IIS) to measure infection levels in target age groups and determine when to stop MDA.2 The results of these surveys in each endemic IU and documentation of the quality of care for people with lymphoedema and hydrocele is required for validation by WHO and acknowledgement of having achieved elimination of LF as a public health problem.

Progress towards the 2030 NTD road map targets

The LF specific 2030 targets are for all countries to be conducting surveillance after MDA has ceased and for 80% of endemic countries to have achieved elimination as a public health problem. The status of each country in delivery of MDA and achieving these targets is presented in Table 1. In 2024, 35 countries had not met either target and were considered to require MDA (sum of columns 1, 2 and 3). There remained 5 countries where MDA had not yet been delivered in all areas where warranted (sum of columns 1 and 2). As of the end of 2024, 37 countries (sum of columns 4 and 5) had met the target of no longer requiring MDA. Sixteen (column 4) are under surveillance but not yet validated and 21 countries have met criteria for elimination as a public health problem and are under post-validation surveillance (column 5). Timor-Leste and Brazil were the most recent countries to be validated for the elimination of LF as a public health problem. A cross-cutting target of both the NTD road map and Sustainable Development Goal 3.3.5 is to see a 90% reduction in the population requiring interventions for NTDs.4,5 As of 2024, there has been a 69.2% reduction in the population requiring MDA. In 2024, the cumulative population living in IUs that no longer require MDA was 924.4 million.