‘Mosquito toilets’: How scientists are using mosquito poop to detect viruses

Researchers have developed a “mosquito toilet” — a tool to analyse mosquito waste for pathogens — that could be an early warning system for emerging health threats. Mosquitoes are considered the world’s deadliest animals because of the diseases they transmit. Monitoring them could help scientists detect viruses circulating in the environment before they pose a threat to humans. To gain a better understanding of the viruses and bacteria circulating in the environment, Dana Price, an entomologist at Rutgers University in the United States, developed a tool to analyse mosquito waste. The device, which Price calls a “mosquito toilet”, collects small amounts of liquid excreted by mosquitoes, which can then be analysed for genetic traces of pathogens. “Our question is, is this virus in the environment?” Price told Euronews. “You just have to look for it. If you don't look for it, you won't find it,” he said, adding that the findings suggest the range of viruses that mosquitoes may be naturally infected with is much broader than previously thought. Having such a tool could give scientists an advantage in responding to new viruses, Price explained. Detecting traces of COVID-19 before it jumped to humans, he said, could have given researchers “a large head start” in understanding the virus and developing vaccines. The mosquito toilet is a 3D-printed funnel coated with a water-repelling material that causes liquid to bead up and slide into a collection tube. Researchers placed 50 Culex mosquitoes collected from a garden in New Jersey into the container, where they drank from a cotton pad soaked with sugar water and red food colouring. Their excrement, containing genetic traces of viruses and other organisms, collected over 18 hours, was later analysed in a lab. Unlike traditional methods, which involve trapping and grinding up mosquitoes, analysing their waste reduces the amount of mosquito DNA in samples, making viral genetic material easier to detect. Using this seemingly simple device, the team identified the first known evidence of a Hedwig-like virus in the Americas and detected several viruses that may be new to science. They also recovered a complete West Nile virus genome, which shows that mosquito waste contains enough high-quality genetic material to rebuild an entire virus's genetic code and allows researchers to identify specific variants or mutations of the virus. Yet, Price said there is no reason to be alarmed by anything the study found. Identifying previously unknown viruses, or detecting them in places where they have not been found before, does not necessarily mean they pose a threat, he added. Instead, it may just indicate that they have been circulating undetected. What’s next? While Price’s tool has shown promise in detecting viruses carried by mosquitoes in a limited area, the team’s next step is to expand the geographical scope of its research and improve the device to keep samples stable for longer, enabling extended collection periods. “The idea is that you could go, place these traps kind of in the middle of nowhere or some place that's really hard to reach and then go back in a few days or maybe even a week,” Price said. Being able to leave traps in remote locations for longer could make it easier to monitor pathogens in areas that are difficult to access regularly. However, further research is needed to establish how effectively the approach could be used for ongoing disease surveillance. The researchers are also working to develop devices that can be deployed in the field and combine mosquito trapping with excreta collection in a single step.