The yellow fever mosquito (Aedes aegypti) is a major vector of deadly diseases such as dengue, chikungunya, and the Zika virus, which cause hundreds of thousands of deaths worldwide each year. Because Ae. Aegypti prefers to bite people and there are no vaccines for many of these diseases that carry them. Developing methods to control these insects is essential in the fight against disease.
In a study recently published in Proceedings of the National Academy of Sciences, a Yale-led research team developed a new method to track how Ae. Aegypti move through the environment. By combining genetic data from mosquitoes and environmental data from satellites, the authors mapped “landscape connectivity” – defined as the way a landscape facilitates the movement of organisms and their genes across large areas. In particular, the researchers developed a new workflow that models Ae more effectively. Aegypti move through the countryside in the southern United States
“Connectivity maps enable managers to make informed decisions based on how mosquitoes are likely to move through a landscape,” said Evlyn Pless, a postdoctoral fellow at the University of California at Davis and a PhD student in the Yale Department of Ecology and Evolutionary Biology. “Our results suggest that Ae. Aegypti in the southern United States is traveling through a mix of natural and human-assisted dispersal, utilizing regions that are warmer and shallower, as well as human transportation networks.”
Plessco co-authored the paper with Giuseppe Amatulli, a research scientist at the Center for Research Computing and the Yale School of the Environment. Norah Saarman, assistant professor of biology at Utah State University; and Jeffrey Powell and Adalgisa Caccone of the Department of Ecology and Evolutionary Biology at Yale.
Now the most common way to combat invasive, disease-causing species like Ae. Aegypti uses pesticides that are not environmentally friendly. “We now know that some pesticides cause environmental damage, including harm to humans,” Saarman says. “At the same time, mosquitoes develop a resistance to the pesticides that we have found to be environmentally friendly.
“This creates a challenge that can only be solved with more information about where mosquitoes live and how they move.”
A state-of-the-art control method is the release of genetically modified mosquitoes into existing populations to stop the disease from reproducing and spreading. The authors expect connectivity maps like the one they created to be useful for developing more strategic versions of modified mosquitos.
“By incorporating machine learning into an optimization process, our approach overcomes the limitations of previous methods and should be useful for more accurate planning of vector control actions,” says Amatulli.
The authors also believe that this novel advance could have wider applications, including in conservation and environmental protection.
“Connectivity maps can also be crucial in protecting endangered native species,” says Pless, “for example when designing corridors to connect fragmented populations.”
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