VIABILITY AND FERTILITY OF ADULT ONCHOCERCA-VOLVULUS AFTER 6 YEARS OFTREATMENT WITH IVERMECTIN

Onchocerca volvulus nodules were removed from 77 fully compliant patie nts in a longitudinal study of ivermectin treatment in Sierra Leone. T he patients had participated in a randomized controlled trial and rece ived either 4 annual doses of ivermectin or ro 6-monthly doses over 6 years. Worms were examined 9 months after the last treatment for evide nce of changes in morphology, viability and reproductivity. The findin gs were compared with results for the 2 groups obtained at earlier sur veys of the same study population. Repeated treatment at 6 and 12-mont h intervals has resulted in a marked ageing of the male worm populatio n profile and a significant reduction in the proportion of live female worms found in the nodules. In addition, there has been a reduction i n reproductivity of 90% or more. However, most of the worms found were still alive and potentially fertile, underlining the need for the con tinuation of regular ivermectin treatment to maintain the benefits ach ieved.