Three sites were investigated, namely the enclosure of the WHO/AFRO office, the surroundings of the Djoué hydroelectric dam, and the bridge’s surroundings over the Djoué. The results obtained indicate that the density of bites is on average 855 bites/man/day in the dry season against 560 bites/man/day in the rainy season. The most prolific site is the one located within the WHO/AFRO enclosure, with 1136 bites/man/day in the dry season and 721 bites/man/day in the rainy season. The parturity rate is on average 58.45% in the dry season, and 59.59% on average in the rainy season. The infestation rate was on average 1.4% in the dry season against 0.7% in the rainy season. The black flies from the WHO/AFRO site had the highest infestation rate with 1.6% in the dry season compared to 0.9% in the rainy season. The aggressiveness expressed by the black flies’ capture density indicates that August and September had the highest densities. Thus, 913 bites/man/day were obtained. Regarding the parturity rate, it appeared more important in September with 67.9%. The percentage of infestation was higher in July with 31 L3 stage larvae.

These results confirm the presence of onchocerciasis in the city of Brazzaville and the designated WHO/AFRO site appears to be the most infested site. In addition, these results show that it is important to carry out regular entomological evaluations coupled with a verification of the effectiveness of the treatments initiated with Ivermectin under the Community Directive (CDTI).