Testing a novel Optical Sensor for Aedes and Culex adult automatic count and identification and BG-trap capture rate determination

Introduction and Objectives Effective mosquito vector monitoring is increasingly needed to optimize control interventions and predicting risk of pathogen transmission. However, conventional methods are time- and labor-intensive and difficult to implement on a large spatial and temporal scale. Recently, an optical sensor combined with a supervised machine learning algorithm (Vectrack), was developed with the goal to allow automatic count and identification of adult mosquitoes in conventional BG-traps. Here we summarize the results of field experiments carried out in summer 2023 in Italy to evaluate: (i) the accuracy of Vectrack in counting and identifying Aedes and Culex adults, and (ii) whether BG-trap catching capacity is affected by the sensor presence. The experiments also provided the opportunity to estimate the capture rate of BG-traps based on the known capture rate of Sticky Traps. Materials and Methods The experimental design implied the rotation every 48h of three types of traps – one BG-Mosquitaire (BG-M), one BG-M equipped with the sensor, and 4 Sticky Traps (considered as a single trap due to their lower catching capacity) – in three sites within an area of about 1,000m2. The same experimental design was carried out in 4 Italian provinces (Bergamo, Padua, Rome, Naples) and replicated 3 times/area. Collected mosquitoes were counted and identified both automatically by the Vectrack and by visual inspections. Results, Discussion and Conclusion The capture performance of the BG-M with and without Vectrack was comparable both overall and when assessed against Aedes and Culex, or sexes (females, males) (Tukey’s Honest Significant Difference method, p-value NS). High correlation was observed in Aedes and Culex counts between Vectrack and operator (Pearson cor 0.985, pval <0.0001). Overall, results support Vectrack high potential for continuous monitoring with minimal human effort and opened the possibility of unprecedented studies on mosquito seasonal and circadian rhythms in 2024.