DAR ES SALAAM, Feb. 11 -- ALONG the shores of Lake Victoria, the banks of the Rufiji River, and countless streams and irrigation canals across Tanzania, freshwater is part of daily life. It is where children play, women wash clothes, and families draw water.

Yet hidden in these waters is a parasite that has quietly shaped the reproductive health of millions of Tanzanian women and girls often without their knowledge, and frequently beyond the recognition of the health systems meant to serve them. The condition is called Female Genital Schistosomiasis (FGS).

It is a chronic manifestation of schistosomiasis, a parasitic disease acquired through contact with freshwater contaminated by Schistosoma haematobium.

When the parasite enters the b...