Abstract
Background
Onchocerciasis, a parasitic disease caused by the filarial worm Onchocerca volvulus transmitted through the bite of Simulium (black flies), is a cause of global concern, with the African population being majorly affected. This study focused on the bite rates, bite cycle, and transmission potential of Simulium damnosum s.l. in two sites with river blindness outbreaks in Kinshasa, DRC: Gombe (S1) and Mont-Ngafula at Kimwenza (S2).
Methods
From August 1, 2019, to July 31, 2020, we captured adult female black flies near breeding sites along the Congo River at S1 and Lukaya Valley at S2. Collections using human baits at the two sites were conducted for five days/month.
Results
A total of 6082 black flies of species Simulium squamosum (classified based on other entomological surveys) were captured during the study period. The daily cycle of aggression revealed two peaks: one between 8 and 9 a.m. and the other between 4 and 5 p.m. Low bite rates were observed between 11 a.m. and 1 p.m. The annual biting rate/person reached 13,463 in S1 and 23,638 in S2, with a total of 37,101 bites/person. The average daily biting rate, 37 ± 10 and 69 ± 23 bites/day/person in S1 and S2, respectively, did not differ significantly (P = 0.8901). The high density of the host population can disrupt the transmission of vector-borne diseases by diluting the transmission indices. There was no evidence of onchocerciasis transmission at the study sites because of inadequate laboratory facilities in the DRC. Various larval supports have been identified: at Gombe: aquatic plants, plastic bags, dead leaves, and rocks; at Kimwenza: Ledermaniella ledermanii (the most abundant species at the site), plastic bags, artificial waste, and aquatic plants.
Conclusions
The study provides further evidence for the need for alternative strategies to eliminate the parasite in the formerly hyper-endemic foci.
Macrofilaricidal Efficacy of Repeated Doses of Ivermectin for the Treatment of River Blindness
