The dynamic effect of a single dose of ivermectin (A) and moxidectin (B) on skin microfilarial load. The data points are derived from skin microfilarial loads (the mean of four microfilarial counts ) collected from (A) the 45 control participants (who took ivermectin) and (B) the 38 treated participants (who took moxidectin) as part of the Phase II clinical safety trial of moxidectin for the treatment of onchocerciasis . The effect of a single dose of ivermectin previously fitted to microfilarial load data collated as part of a meta-analysis  is shown as the solid blue line in (A) (note that the microfilarial dynamics induced by ivermectin are not re-estimated here and hence provide a validation of the previous parameterization). The dynamical effect precipitated by moxidectin was fitted to the trial data on microfilarial loads from treated participants using the same approach as in  (described in the Supporting information (Additional file 1: Text S.2)) and is shown as the solid red line in (B). Error bars show the 95% confidence intervals which in some circumstances were narrower that the plotted data point and so are not discernible.