Identification of an antigen of Onchocerca volvulus of possible diagnostic use.

Adult Onchocerca volvulus worms obtained by enzyme digestion from nodules of infected Mexicans were radio-isotope labelled by the chloramine-T or Bolton-Hunter methods. No antigenic determinants were detected in extracts of worms labelled by the chloramine-T method but 3 antigens were detected in extracts of the Bolton-Hunter labelled worms. Two were present in such small amounts that it was impractical to investigate them further, but a major component of mol. wt 20 kDa was purified by gel filtration and used in a serological survey of inhabitants of villages in Southern Mexico. Using the 20 kDa antigen, which is superficially located on both sexes of O. volvulus, sera from both non-endemic and endemic regions were analysed by radio-immunoprecipitation of this antigen. In Southern Mexico, the average sensitivity of the test was 92%, and the specificity 98%. Whilst the 20 kDa antigen did not detect antibodies in the sera of Trinidadians infected with Wuncheria bancrofti or Mansonella ozzardi, this antigen detected high levels of antibodies in Indians exposed to W. bancrofti.

Comparison of flubendazole and diethylcarbamazine in treatment of onchocerciasis.

Flubendazole, an injectable benzimidazole drug, was compared with diethylcarbamazine (DEC) in a prospective double-blind study of the treatment of onchocerciasis. Nineteen Mexican men were randomly assigned to receive either flubendazole 750 mg intramuscularly once a week for 5 doses, or DEC 100 mg twice daily for 14 days, and they were then followed up for 12 months. Major systemic side-effects during the first 3 weeks were common in the DEC group but not in the flubendazole group in which there was considerable inflammation at the injection site instead. Ocular complications (limbitis, punctate keratitis, and uveitis) were also common in the DEC group, whereas in the flubendazole group they consisted only of one new punctate opacity at day 4 in one subject. One DEC patient also had several new areas of chorioretinal changes on day 2 but these had disappeared by 2 months. Skin microfilaria counts fell rapidly in the DEC group, but returned to the pretreatment levels. In contrast, skin microfilaria counts in the flubendazole group fell slowly, but by 6 and 12 months were lower than in the DEC group (at 12 months 0.2 vs 7.3 mf/mg, p less than 0.001). In addition, by 6 months none of the flubendazole subjects had intracorneal microfilariae, and only one had microfilariae in the anterior chamber, whereas the numbers of intraocular microfilariae in the DEC group had returned to pretreatment levels. The results suggest that flubendazole is safer and more effective than DEC in the treatment of onchocerciasis.