General Abstract Submission
Disease/Vector Studies
The advent of efficient traps to capture gravid females of Aedes aegypti provides an opportunity to determine what is the number of mosquitoes per trap (mosquito density threshold) that prevents or reduces dengue virus transmission. This information can be then used by Vector Control Programs to evaluate the effectiveness of their operations. Using a cluster randomized study, we investigated if controlling the population of Ae. aegypti at various levels was associated with low or no local transmission of dengue viruses. Area-wide control was done by mass-trapping gravid females with Autocidal Gravid Ovitraps (AGO traps). There were 4 intervention levels with 3 replicate clusters per level and 300 houses per cluster: no trapping (control), one trap/house, two traps/house, and three traps/house in most houses ( >75% of houses in the clusters). We monitored the density of Ae. aegypti every week since May 2021 and collected pools of female mosquito that were analyzed by RT-PCR to detect the presence of dengue viruses. The results showed significant differences in the average number of female mosquitoes per treatment, where the density decreased from untreated clusters to clusters with three traps/home. Mean densities were 9.16, 5.85, 4.47, and 2.99 female mosquitoes/trap/week in clusters with no control, one, two, and three traps/home, respectively. There were reductions of 41 (25.7-53.1; 95% C. I.), 58 (46.1 – 66.3), and 77 (70.5 – 81.4) % in treatments with one, two, and three traps/home, respectively. The expected numbers of infected mosquitoes per one thousand mosquitoes were 2.8, 2.6, 0.6, and 0.8 in clusters with zero, one, two, and three traps/house. Our findings suggest that a threshold density of 4 or less Ae. aegypti/trap/week reduces dengue transmission.