Efficacy of ivermectin in the treatment of Wuchereria bancrofti infection:a model-based analysis of trial results

Ivermectin is a promising drug for the treatment of lymphatic filariasis. A meta-analysis of trials investigating the effects of a single treatment su ggested a dose-dependent effect on the production of microfilariae (mf) by adult Wuchereria bancrofti parasites. A mathematical model that describes t he parasite dynamics in the human host and the impact of ivermectin treatme nt is presented and its outputs compared with these trials. The calculated trend in mf density after treatment appears to be particularly sensitive to the assumption about the mean life-span of mf. Adopting 0.5-2 pears as a r ange of plausible values for this mf life-span, the model is used to estima te the impact of treatment on the parasite. It is found that irrespective o f dosage, ivermectin eliminates 100 % of the blood mf from a patient. Furth ermore, at a dosage level of 400 mu g/kg a single treatment irreversibly re duces the mf production of the adult parasites by at least 65 %. For a dosa ge of 200 mu g/kg this reduction is at least 35 %. No such effect can be co ncluded from the results of trials using lower dosages.