Dengue fever is a viral infection that spreads from mosquitoes to people, and sewers have become breeding grounds for the tiny insects.

Now a study from Taiwan has shown that unmanned robotic vehicles can be highly effective in monitoring sewers for Aedes mosquitos and carrying out eradication. There are several mosquito species in the dengue-carrying genus Aedes, which also spread chikungunya, yellow fever and zika virus.

As populations have become more urbanised, sewers have become easy breeding grounds for Aedes mosquitos and most current mosquito monitoring programmes struggle to monitor and analyse the density of mosquitos in these hidden areas. In this new push to control them, researchers combined a crawling robot, wire-controlled cable car and real-time monitoring system into an unmanned ground vehicle (UGV) system that can take high-resolution images within sewers.

From May to August 2018, the system was deployed in five administrative districts in Kaohsiung City, Taiwan, with covered roadside sewer ditches suspected to be hotspots for mosquitos. Specially designed traps were placed above the sewers to monitor the effects of the UGVs on adult mosquitos in the area.

In 20.7% of inspected sewers, the system found traces of Aedes mosquitos in stages from larvae to adult. In sewers testing positive, additional prevention and control measures were carried out, using either insecticides or high-temperature water jets.

Immediately after these interventions, the nearby gravitrap index (GI)— a measure of the adult mosquito density — dropped significantly, from 0.62 to 0.19.

“The widespread use of UGVs can potentially eliminate some of the breeding sources of vector mosquitoes, thereby reducing the annual prevalence of dengue fever in Kaohsiung city,” say the authors.

The study, carried out by Wei-Liang Liu and colleagues at the Taiwan National Mosquito-Borne Diseases Control Research Center, is published in PLOS Neglected Tropical Diseases