Suramin and the time it takes to kill Onchocerca volvulus

Abstract

The paper records the numbers of 1-2 mm shotty papules developing in the author's skin after 2-day courses of diethylcarbamazine (DEC) repeated every 16 days before, during and after a 7.1 G suramin course for cutaneous onchocerciasis. Assuming, from biopsy evidence, that each papule represented a dead Onchocerca volvulus microfilaria (mf), the number of mfs reaching the skin every 16 days did not begin to fall until 96 days after the first full dose of suramin; and only reached zero by day 224. The histopathology of nodules excised from Cameroonian patients before, and at intervals of 56-335 days after, the start of a 7.1 G suramin course, revealed changes in the worms that correlated over time with the disappearance of mfs from the skin. Suramin sterilized and killed the male worms between days 77 and 105 and, in the females, it adversely affected the staining and subsequent development of small morulae from about day 56. It was estimated that new embryogenesis ceased about 56-77 days after the first full dose; development of the last viable embryos to mfs was complete by about 136 days; and the last mfs, perhaps having reduced vitality, emerged from the females by 160 days and reached the skin within 16-32 days.