Early Formation of the Nodule in Guatemalan Onchocerciasis

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  • Medical Entomology Research and Training Unit/Guatemala, Center for Infectious Diseases, Centers for Disease Control (CDC), Public Health Service (PHS), U. S. Department of Health and Human Services (USDHHS), Instituto de Investigaciones, Universidad del Valle de Guatemala, Department of Robles Disease, National Malaria Eradication Service, Ministry of Health, Vector Biology and Control Division, Center for Infectious Diseases, CDC, PHS, USDHHS, Guatemala, Guatemala

Thirty-eight nodules containing adults of Onchocerca volvulus were removed from 36 patients who had no detectable microfilariae in skin snips. Worms were digested from nodules in collagenase solution, maintained alive in vitro, and the number, sex, and state of fecundity were recorded. A total of 48 female and 8 male worms were recovered; 39 females were in the nodules without the presence of a male. Eleven females (22.9%) had microfilariae in utero or produced microfilariae in vitro; seven of these were found together with males in the nodules while four were not. No nodules were found around male worms unless a female was also present. These observations indicate that the nodule forms only around female worms and that mating probably occurs before or early during nodule formation. Furthermore, the production of microfilariae by the female is not essential for nodule formation since many nodules contained non-fecund, living females.