The effect of ivermectin on the uptake and development of O. volvulus microfilariae in S. damnosum s.l
Chavasse, D.C.; Davies, J.B.
Acta Leidensia 59(1-2): 227-230
1990
ISSN/ISBN: 0065-1362 PMID: 2198754 Document Number: 364288
The effect of 6-monthly treatments with ivermectin on the transmission of onchocerciasis was determined by examining the number of Onchocerca volvulus microfilariae (mf) ingested by Simulium damnosum from treated persons, and the number of larvae that subsequently developed in the flies. 20 volunteers were treated at 6-monthly intervals with either 200 micro g/kg ivermectin or a placebo. Up to 30 wild caught S. damnosum were allowed to feed to repletion on each volunteer one or 2 days before and less than 10 days after each 6-monthly treatment. Half of the flies were dissected within 30 minutes and the number of mf counted. The remaining flies were maintained at ambient temperature for 4 days, and the larvae that developed were counted. Between 80% and 100% of flies that fed on the placebo group ingested one or more mf. Of flies that fed within a few days of ivermectin treatment, 5% or less ingested mf. But 6 months later this proportion had risen to between 30% and 71%. Ivermectin treatment immediately reduced the number of O. volvulus that survived 4 days post ingestion to almost zero, but there was some recovery by the end of the 6 month interval between treatments.