WHO lists the milestones towards validation of elimination beginning with stopping the spread of infection through mass drug administration (MDA), implementing MDA in all endemic areas (100% geographical coverage), reducing infection below a threshold at which transmission is not sustainable in all endemic areas and stop MDA, and finally demonstrating sustained reduction of infection below the threshold no earlier than 4 years after stopping MDA. WHO also encourages countries to alleviate suffering by managing morbidity such as lymphedema and preventing disability.
By 2015 the partners providing PCT achieved a milestone. As WHO reports, “Preventive chemotherapy is achievable, as proven by the increasing numbers of people being reached each year. In 2015, over 1.5 billion treatments were administered to almost 1 billion individuals for at least one of the targeted infections: lymphatic filariasis, onchocerciasis, schistosomiasis soil-transmitted helminthiases and trachoma.
At a low cost – between US$ 0.30 and US$ 0.50 per person treated in most settings – preventive chemotherapy remains the most affordable, cost-effective strategy for controlling and eliminating these diseases.” WHO also explains that to be fully sustainable and to maximize impact, PCT the strategy should be combined and delivered with other interventions, including improving access to safe drinking-water, hygiene, disease management and vector control.
USAID as one of the major NTD partners has spent nearly $700 million since 2006 to build the capacity of 33 endemic countries to plan and implement the MDA strategy for the five PCT diseases. By 2016, “USAID-assisted NTD programs had provided a total of more than 2 billion treatments in the respective countries, representing 935 million persons treated.” Over these years the number of persons living in implementation units (e.g. districts) that no longer require MDA has steadily increased.
Of the 25 countries USAID has supported for LF MDA, “Three had already stopped MDA treatment in 2015 (Togo, Cambodia, and Vietnam), Four were expected to stop MDA in 2017, and 10 more countries by 2020. There were eight countries where the date for stopping treatment was anticipated beyond 2020.” Likewise, “Most countries are on track to reach WHO 2020 elimination goals for trachoma,” and nearly all countries shown anticipate reaching post-MDA surveillance by 2021.
In conclusion, Robollo and Bockarie remind us that, “Interventions against neglected tropical diseases (NTD), including lymphatic filariasis (LF), (were) scaled up dramatically after the signing of the London Declaration (LD) in 2012… but some countries are considered not on track to meet the 2020 target using the recommended preventive chemotherapy and morbidity management strategies.” They believe that LF can be eliminated by 2020 “using cross-sectoral and integrated approaches” that incorporate the synergistic effect of the Sustainable Development Goals related to poverty reduction and water and sanitation.