Diffuse retro-reflective imaging for improved video tracking of mosquitoes at human baited bednets.

Vitaly Voloshin,Chandrabhan Seniya,Philip J Mccall,Catherine E Towers,Gregory P D Murray,Christian Kröner,David P Towers,Amy Guy

doi:10.1098/rsos.191951

Vitaly Voloshin, Chandrabhan Seniya + Show 6 more

Open Access

https://doi.org/10.1098/rsos.191951

Copy DOI

Abstract

Robust imaging techniques for tracking insects have been essential tools in numerous laboratory and field studies on pests, beneficial insects and model systems. Recent innovations in optical imaging systems and associated signal processing have enabled detailed characterization of nocturnal mosquito behaviour around bednets and improvements in bednet design, a global essential for protecting populations against malaria. Nonetheless, there remain challenges around ease of use for large-scale in situ recordings and extracting data reliably in the critical areas of the bednet where the optical signal is attenuated. Here, we introduce a retro-reflective screen at the back of the measurement volume, which can simultaneously provide diffuse illumination, and remove optical alignment issues while requiring only one-sided access to the measurement space. The illumination becomes significantly more uniform, although noise removal algorithms are needed to reduce the effects of shot noise, particularly across low-intensity bednet regions. By systematically introducing mosquitoes in front of and behind the bednet in laboratory experiments, we are able to demonstrate robust tracking in these challenging areas. Overall, the retro-reflective imaging set-up delivers mosquito segmentation rates in excess of 90% compared to less than 70% with backlit systems.

Highlights

Voloshin1, Christian Kröner1, Chandrabhan Seniya1, Gregory P
Bednets treated with insecticide can be very effective in preventing transmission of these infections, and, in Africa, the factory-treated durable type of nets referred to as long-lasting insecticidal nets (LLINs), are the most effective method available and an essential element of malaria control and elimination strategies today
Optical imaging techniques have been used for decades in entomological studies in diverse settings in the laboratory and field, and recently a tracking system was used to characterize in detail how Anopheles gambiae mosquitoes, the vectors of human malaria in sub-Saharan Africa, interact with human-occupied bednet [1,2,5]

Summary

Introduction

Voloshin, Christian Kröner, Chandrabhan Seniya, Gregory P. Optical imaging techniques have been used for decades in entomological studies in diverse settings in the laboratory and field, and recently a tracking system was used to characterize in detail how Anopheles gambiae mosquitoes, the vectors of human malaria in sub-Saharan Africa, interact with human-occupied bednet [1,2,5]. Sustaining the required high level of efficacy against increasingly insecticide-resistant vector populations requires novel insecticide treatments on bednets, and vector biologists need to understand how hungry host-seeking mosquitoes interact with different treatments, or how net alterations (physical as well as chemical) might alter efficacy To investigate this, they are interested in visualising activity around the sleeping human body, the bednet suspended above it and the regions around this in order to examine details of approach, attack and departure [11,12]. The tracking in [22] relies on high levels of spatial sampling in order to extract position and orientation information of the animal as well as on the use of a network of processing computers (up to nine computers)

Methods

Results

Discussion

Conclusion