Prevalence of Mansonella perstans in western Uganda and its detection using the QBC-fluorescence method.

The prevalence of the apathogenic filaria Mansonella perstans was studied in four parishes in western Uganda as part of an onchocerciasis control programme to avoid futile treatment. Blood samples from 1543 persons aged over 14 years from 19 villages were examined for the presence of microfilariae using a modified Knott method. The prevalence of microfilaraemic persons ranged between the parishes from 39% (95% CI 35.9-42.0%) to 81% (95% CI 76.2-84.8%). With exception of single microfilariae of Onchocerca volvulus no other filaria species was detected. Onchocerciasis mass treatment campaigns did not reduce the prevalence of M. perstans infection, since 6-12 months after treatment with a single dose of 150 micrograms/kg ivermectin the prevalence in 124 persons was about the same as before treatment. The QBC-fluorescence technique was employed for the detection of microfilariae in samples from outpatients of the government hospital in Fort Portal: in 16% of 120 children and 24% of 369 adults microfilariae of M. perstans were detected.