Discussion

In 2002 Uganda began praziquantel Mass Drug Administration (MDA) in Schistosoma endemic communities across 79 districts. The World Health Organization recommends community-wide treatment in areas where prevalence in school-aged children (SAC) is >50%, aiming to reach >75% of SAC and adults/year in these areas. Most mathematical models assume the untreated proportion are randomly distributed. While others assume a small proportion are systematic non-compliers, and the rest are randomly distributed. MDA coverage is often only reported at a district level. To address a gap in our understanding of individual's annual and lifetime treatment, we undertook detailed mapping and household surveys in two villages, Bugoto A and B, in Mayuge District, Uganda, a high endemicity area (92% SAC infected, 2017) on the shores of Lake Victoria which has received community-wide MDA for 15 years. From Feb-March 2017, a total of 676 households (>90%) and all associated pit latrines were GPS mapped. Comprehensive data on praziquantel coverage, socio-economic indicators, and other individual-level risk factors were collected from 3,335 individuals. Praziquantel uptake was low compared to other studies, especially among adults, with an overall 2016 coverage of 35% (61% in SAC). Only 70% of SAC and 50% of adults had ever taken praziquantel. Side effects were rarely the reason for not taking it. Most untreated individuals were either not offered the drug, not bothered, or absent from the village during MDA. Other risk factors linked with never being treated included living in Bugoto A (the predominantly lakeside, fishing community, with higher infection levels), being >15y, and not sleeping under a mosquito net. To our knowledge, this is the first study to record lifetime coverage, reporting chronically untreated individuals, who, contrary to expectation are rarely systematic non-compliers but are better described as systematically not-offered. This has implications for human disease reservoirs and ethical issues associated with morbidity. Improved interventions may be able to better reach these people and easier to implement than side effects education.