Background: Schistosomiasis is endemic in 54 countries, but has one of the lowest coverages by mass drug
administration of all helminth diseases. However, with increasing drug availability through donation, the World
Health Organisation has set a goal of increasing coverage to 75 % of at-risk children in endemic countries and
elimination in some regions. In this paper, we assess the impact on schistosomiasis of the WHO goals in terms of
control and elimination.
Methods: We use an age-structured deterministic model of schistosome transmission in a human community and
the effect of mass drug administration. The model is fitted to baseline data from a longitudinal re-infection study in
Kenya and validated against the subsequent re-infection data. We examine the impact on host worm burden of the
current treatment trend, extrapolated to meet the WHO goals, and its sensitivity to uncertainty in important
parameters. We assess the feasibility of achieving elimination.
Results: Model results show that the current treatment trend, extrapolated to the WHO goals, is able to greatly
reduce host worm burdens. If coverage is continued at the same level beyond 2020, elimination is possible for low
to moderate transmission settings, where transmission intensity is defined by the basic reproduction number, R0.
Low levels of adult coverage have a significant impact on worm burden in all settings. Model validation against the
re-infection survey demonstrates that the age-structured model is able to match post-treatment data well in terms
of egg output, but that some details of re-infection among school children and young adults are not currently well
represented.
Conclusions: Our work suggests that the current WHO treatment goals should be successful in bringing about a
major reduction in schistosome infection in treated communities. If continued over a 15 year period, they are likely
to result in elimination, at least in areas with lower transmission.