Researchers tracked the movement of black flies capable of carrying onchocerciasis throughout the 2023 and 2024 wet seasons. The study focused on historical breeding areas located in Benin and Ghana to determine the range of the disease-carrying insects. Field data collected during these observations showed that infective black flies traveled up to 19 km from the Bétérou breeding site. This distance indicates an extended reach for the flies compared to previous assessments of their typical flight range. Scientists involved in the research monitored these populations to better understand the transmission patterns near established water sources. The findings provide new data on how far these vectors move from their primary habitats during periods of high rainfall in the region.
Survey Methodology and Scope
Researchers selected 40 settlements within a 25-km radius of each of the two breeding sites to conduct their analysis. This spatial arrangement allowed teams to monitor insect populations across a wide geographic area surrounding the primary habitats in Benin and Ghana. Field operations involved the collection of 76,050 black flies over a total of 656 sampling days. Personnel focused these collection efforts primarily around the Bétérou breeding site to capture data on vector density and movement. The systematic gathering of these insects provided the necessary sample size to evaluate the transmission potential in the vicinity of the selected locations. These activities were completed to ensure the resulting data accurately reflected the distribution patterns of the flies throughout the study period.
Findings at Bétérou Site
Laboratory analysis of the insect samples identified positive O-150 PCR pools at 31 of the 41 sites examined in the areas surrounding Bétérou. These findings indicate a significant presence of the parasite within the vector population across the surveyed locations.
The prevalence of infective flies at the Bétérou site fluctuated between the two years of the study. Data recorded by the research team showed an infective fly prevalence of 0.11% in 2023, which shifted to 0.08% in 2024. These percentages reflect the proportion of captured black flies found to be carrying the parasite during the respective wet seasons.
In contrast to the results obtained near the Bétérou breeding site, investigations at the Asubende site in Ghana produced different outcomes. Researchers reported that no infective flies were detected through PCR testing at the Asubende location. This absence of positive results in the Ghana-based samples suggests variations in transmission risk between the two monitored regions during the study period.
