Researchers at the University of Warwick’s School of Engineering are using imaging technologies that are normally applied to automotive engines and sprays to image thousands of mosquitoes in order to help develop better netting and physical protection against the malaria-spreading insect. The engineers, David Towers, Natalia Angarita and Catherine Towers, are helping entomologist colleagues at the Liverpool School of Tropical Medicine, Philip McCall and Josie Parker, explore the best insecticide treatment and physical design of the protection for sleeping people in areas where mosquitoes are a problem.
In observing how mosquitoes engage with insecticide-treated barriers such as netting, researchers have in the past mainly relied on recording just the final landing location, which does not give a full picture of how they approach and handle the protective barriers.
The entomologists at the Liverpool School of Tropical Medicine are carrying out their latest experiments in a swamp in Tanzania. The site has a stable mixed population of mosquitoes, some resistant to insecticide, others not. This is particularly important as insecticide resistance is of significant interest when testing bed nets.
They have built a hut at this site mimicking the typical housing and sleeping arrangements for local people. They need to experiment at night when people are at greatest risk of being bitten by anopheles gambiae mosquitoes: the species responsible for transmission of the malaria parasite which is the most dangerous to humans.
The University of Warwick engineers devised a method that would capture a vast amount of data on the behavior of the tiny mosquitoes. Using a modified back lighting technique, the insects have been imaged throughout a 2.0 × 2.4 × 1.0 meter volume using illumination in the near infra-red. This is a wavelength that is not perceived by mosquitoes so it does not change their natural behavior. Two cameras are positioned so each captures images at a rate of 50 per second. For every hour of operation, 360,000 images are captured, each taken at 4 million pixels, or 1.4 terabytes (TB) in total size.
Until now, there was no software capable of analyzing such a large number of high resolution images, so it had to be specially written by the Warwick Engineers and it has now been used to process over 50 TB of data so far.
Professor David Towers said: “There is a lot of interest in the analysis of so-called ‘big data’ — here we have the added complexity of capturing information from the field with everything powered from petrol-fuelled generators, and we need very robust algorithms to be tolerant of the natural variability in behavior exhibited by wild mosquitoes.”
The current phase of the research grant is nearing its conclusion and some initial findings are published today September 1, 2015, in Nature Scientific Reports. The indications show that the mosquitoes do not realize a net is treated before they touch it, and future research will build on these findings.
The work is part of a €12M research project called AvecNet (www.avecnet.eu), funded by an FP7 grant and brings together a multidisciplinary team of European and African experts including biologists, engineers, epidemiologists and social scientists. The researchers are pleased to have received a further £0.9M support from the Medical Research Council (MRC) for their next project. The new experiments will use eight cameras, collecting up to 10 TB of data per hour, to map not just the sleeping area, but the hut as a whole. This will enable the team to fully map the behavior of the mosquitoes as they approach their targets.
A MRC Confidence in Concept grant has also been awarded to build the innovative new net which was patented as an outcome from the current research. The team are hoping to quantify the effectiveness of the net in the laboratory or at the field site.
The full paper in Nature Scientific Reports is entitled “Infrared video tracking of Anopheles gambiae at insecticide treated bed nets reveals rapid decisive impact after brief localized net contact.” Liverpool School of Tropical Medicine (LSTM) entomologists Philip McCall and Josie Parker are the lead authors.
