The reappearance, rate of increase and distribution of the microfilariae of onchocerca volvulus following treatment with diethylcarbamazine

Ten African volunteers with onchocerciasis were submitted to examination by multiple skin snips to assess the distribution and concentration of microfilariae of Onchocerca volvulus in the skin. Each was then given a course of diethylcarbamazine (banocide) sufficient to destroy virtually all the microfilariae, and at intervals of from 3 to 13 months afterwards further examinations of multiple skin snips were made to assess the rate of increase in the numbers of microfilariae and their distribution in the skin. It is estimated that the pre-treatment concentration of microfilariae can be built up within 1 to 3 years of the cessation of treatment, and the original pattern of microfilarial distribution is maintained during the post-treatment build-up. The use of diethylcarbamazine in the treatment of onchocerciasis and in the prevention of anterior segment eye lesions is discussed in the light of these findings.