Mosquitoes are really on the radar

The quest to curb the spread of malaria rightly knows no bounds, and now we’re even turning to radar technology – with promising results.

An international team of scientists from nine countries has used LiDAR (Light Detection and Ranging) to remotely track wild mosquito populations from a village in southwest Tanzania. 

They found the insects were most active during morning and evening “rush hour” periods, suggesting these may be the most effective times to target them with sprays.

The technology was able to distinguish mosquitoes from moths, flies, midges, and bees based on their high wingbeat frequency, and even to differentiate between different mosquito species and sexes.

“These unprecedented findings demonstrate how LiDAR-based monitoring of distinct mosquito activities could advance our understanding of vector ecology,” the researchers write in a paper in the journal Science Advances.

The team set up a 596-metre LiDAR transect hovering three to five metres above ground, detecting 312,191 insects over five days. They estimated changes in relative abundance throughout each day by tracking a range of frequencies between 85 and 850 hertz to identify the tell-tale signatures of insect wingbeats. 

They also studied mosquito activity during the 2016 pan-African solar eclipse, finding males to be 87 times more active and females 7.4 times more active than usual during daytime hours. 

“We were able to compare the fine-scale spatiotemporal activity patterns of malaria vectors during ordinary days and an eclipse to disentangle phototactic activity patterns from the circadian mechanism,” they write.

These findings suggest, they say, that light levels affect the prevalence of mosquitoes in flight, creating opportunities for the development of light-based measures to modify their behaviour and prevent the spread of malaria. 

Since both the insects and the malaria-causing parasite they carry can evolve rapidly, resistance to existing measures can quickly develop, resulting in a need for new measures that target all mosquito life stages. 

Detecting and quantifying wild mosquito activities in situ and mapping their distribution remains a challenge, the researchers note.

“Further progress toward malaria vector control and elimination will undoubtedly require new measures that target all life stages of the vectors, notably those that occur outdoors and are widely distributed in the landscape,” they write.

“It will also require a greatly improved understanding of mosquito population ecology, so that the design and deployment of new tools may be rationally optimised.”

The research was led by Mikkel Brydegaard, from Norsk Elektro Optikk AS in Norway, and involved scientists from Norway, Sweden, Denmark, Tanzania, Switzerland, South Africa, England, Scotland and Ireland.