Sewer robots identify and destroy dengue dens
A new study shows how unmanned ground vehicles could be deployed to monitor sewers for dengue-transmitting Aedes mosquitoes and help eradicate their breeding sites.
- 9 June 2023
- 3 min read
- by Linda Geddes
Taiwanese researchers are deploying robots to take high-resolution, real-time images of sewers to identify the breeding sites of mosquitoes that carry dengue fever. Once detected, these are destroyed using high-temperature water jets or insecticides.
Dengue is a viral infection that causes a severe flu-like illness and can be lethal. It is spread by several species of Aedes mosquito, which also transmit chikungunya, yellow fever and Zika virus.
The UGV system found traces of Aedes mosquitoes in 20.7% of inspected sewers, leading to the deployment of either insecticides or high-temperature water jets to try and destroy these breeding sites.
Sewers have become easy breeding grounds for Aedes mosquitoes in urban areas, yet most current mosquito monitoring programmes struggle to keep tabs on the density of mosquitoes and their larvae in these hidden areas. So, researchers at Taiwan's National Mosquito-Borne Diseases Control Research Center are pioneering a different approach.
Wei-Liang Liu and colleagues combined a crawling robot, wire-controlled cable car and real-time monitoring system into an unmanned ground vehicle system (UGV) that enables them to capture images of mosquito larvae and adults, improving their detection and eradication. "Widespread use of advanced UGV designs may be effective in protecting the population from mosquito-borne diseases," they said.
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From May to August 2018, the system was deployed in covered roadside sewer ditches suspected to be hotspots for mosquitoes in five administrative districts of Kaohsiung city in southern Taiwan.
"A few decades ago, the ditches in Kaohsiung city would not have constituted an important factor in the dengue epidemic, but in recent years they have become a driver for outbreaks of dengue fever," the team said, citing increased urbanisation and migration to cities as contributing factors.
"Because Kaohsiung is a metropolitan city with a mix of old and new building developments, and the previous drainage system was rarely modified when old neighbourhoods were rebuilt, the ditches in these areas were prone to ponding and siltation. Years later, the water in the recesses of these ditches turned them into large breeding sources for Aedes mosquitoes," they explained.
The UGV system found traces of Aedes mosquitoes in 20.7% of inspected sewers, leading to the deployment of either insecticides or high-temperature water jets to try and destroy these breeding sites. Mosquito traps placed above the sewers suggested that these efforts had a significant impact on adult mosquito numbers in all but one of the districts, Fengshan.
"This may be because the Aedes mosquitoes in this area are resistant to insecticides, in which case other effective anti-epidemic actions may need to be employed to reduce the density of vector mosquitoes," the team said. Their research is published in PLOS Neglected Tropical Diseases.
Future modifications to the system could help. For instance, it could be equipped with a granular spreader that contains growth inhibitors to impede mosquito larvae growth. The release of mosquitoes infected with Wolbachia – naturally occurring bacteria that infect many insect species and make it harder for viruses to reproduce inside them – could also help to reduce the density of mosquitoes in areas such as Fengshan, Liu suggested.