Similar blackfly attraction by onchocerciasis patients and individuals putatively immune to Onchocerca volvulus

In areas endemic for onchocerciasis, a small number of individuals show no detectable infection with Onchocerca volvulus despite an apparently similar exposure to the transmitting blackflies. Such individuals have been termed putatively immune. Since several studies have indicated marked host differ ences in attractiveness for blood-seeking insects, putative immunity in O, volvulus infection may result, at least in part, from low vector attractive ness of the respective individuals. In an area hyperendemic for onchocercia sis (Guinea), where Simulium yahense is the predominant vector, we organize d fly catches by putatively immune individuals and individuals with moderat e-to-high worm counts. No differences were found between the 2 groups with respect to (i) the attraction of blackflies, (ii) the attraction of blackfl ies infected with O. volvulus, or (iii) the numbers of O. volvulus larvae c arried by the attracted blackflies.