Effects of Multiple Monthly Doses of Ivermectin on Adult Onchocerca volvulus

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  • American Registry of Pathology, World Health Organization Collaborating Centre for the Histopathology of Filarial Diseases in Man, Armed Forces Institute of Pathology, Servicio de Oncocercosis, College of Agriculture, University of Arizona, Dana Center for Preventive Ophthalmology, Wilmer Institute, Johns Hopkins University School of Hygiene and Public Health, Washington, DC

This paper assesses the effects on adult Onchocerca volvulus of monthly doses of ivermectin (150 µg/kg) given over 4, 8, and 12 months to patients in Guatemala. Nodules were removed 4 months after the last dose; the adult O. volvulus were extracted by collagenase digestion, studied by histological techniques, and compared with worms from untreated patients. Twelve monthly doses killed a proportion of the adult worms (12% of males and 22% of females), leaving the remainder relatively unaffected and the females slowly resuming embryogenesis. After 8 and 12 doses, a number of female worms had resumed embryogenesis in 1 genital tract only, and in 1 female a total degeneration of 1 ovary was seen. Ivermectin also led to a marked drop in the number of male worms in nodules. No serious adverse reactions occurred and the treatment was well accepted.