I assume you already looked at https://forum.effectivealtruism.org/search?terms=filariasis
But just in case, there seem to be a bunch of interesting posts on the topic:
This post has some links to sources.
Mass Drug Administration to combat Lymphatic filariasis (MDA LF): MDA LF is much less cost-effective (unpublished CEA estimate) compared to other intervention areas we looked at. Since the program is a mass drug administration rather than a targeted approach, the prevalence has to be above a certain rate for it to be cost-effective. The microfilaria prevalence is too low for MDA LF to be cost-effective in India (9). Infection rates in other countries are also not sufficiently high. The majority of those infected never exhibit symptoms (10), of those who do, only a small percentage develop severe symptoms that cause large problems like social ostracization and depression. Furthermore, crowdedness in this intervention is fairly high. There are already eight charities active in the area, and the crowdedness in the areas of greater microfilaria prevalence is especially high. The Indian government claims to cover 85% (11) of the country with preventative medication. While there is a problem of people not taking the medication once receivedthey receive it (12), this is not a straightforward or cost-effective problem to solve.
And this post
There has been a large decline in the number of people with lymphatic filariasis, a neglected tropical disease. From ~200 million people in 2000 to ~50 million people in 2018
GSK recently announced its commitment to eradicating lymphatic filariasis (GSK Announces £1 Billion, 2022)