Macro- and microfilariae in nodules from onchocerciasis patients in the Yemen Arab Republic.

Fourteen subcutaneous nodules from five patients with severe localized onchocerciasis, from one person with a mild dermatitis and from two men with the generalized form of the disease were studied. Ten nodules contained adult parasites with an average sex ratio of 1.6 for female to male worms. The median worm burden was two filariae per person. The onchocercomata of two patients with severe localized onchocerciasis comprised one or two pairs of microfilariae producing worms whereas the microfilaria load in the skin of these patients was estimated to have been less than 100 000 microfilariae. One nodule contained no intact microfilariae but more than 10 000 small granulomas with all stages of degenerating microfilariae whereas the density of 0.08 live microfilariae per milligram in the skin near to the nodule was very low. None of the patients had received antifilarial drugs before nodulectomy. It is concluded, therefore, that these patients with severe localized onchocerciasis possessed the capacity naturally to kill microfilariae. In the nodules of these patients many degenerating microfilariae were observed which were surrounded by eosinophils or macrophages or which lay in small abscesses with neutrophil leucocytes or in small granulomas. The adherence of eosinophil leucocytes to only slightly altered microfilariae could be observed as a first stage.