Analysis of the transmission level of onchocerciasis in a health area in Kinshasa, Democratic Republic of Congo (DRC)

Abstract

The present study was designed to investigate the current level of onchocerciasis transmission in Mont-Ngafula I area, a health area of Kinshasa from October 7, 2014 and November 27, 2015. Pre-imaginal black flies were collected at breeding sites for adult fly collection on Lukaya River and in the most appropriate place for human-fly contacts. Entomological prospections showed that Simulium squamosum was the only vector species present in the focus. A total of 2,573 female flies were trapped (1,296 at S1 and 1,277 at S2). The daily aggressiveness cycle showed two peaks: the highest peak was registered between 7:00 and 8:00, while the second (lower) peak was observed between 17:00 and 18:00 at both trapping sites. Out of all dissected females, 5.4% were parous. The number of parous females varied according to the site (5% at S1 vs. 6% at S2), but not significantly (p=0.663). Only 27% of parous females were infectious, among them, 11% at S1 and 16% at S2. The annual biting rate per person reached 5,269 at S1 and 5,183 at S2. The females black flies density was not different in sites 1 and 2, with a mean of 14.4±4.3 and 14.2±3.6 bites per human per day. The Monthly Transmission Potential (MTP) was null during the period of study, when Simulium multiply and become more harmful. Various substrates were identified for larvae: aquatic plants, plastic bags, dead leaves and rocks.