As summer approaches and temperatures rise, it is hard to ignore the increasing number of ticks and mosquitoes in communities around the world. And because they can spread infectious diseases - including Zika, dengue and malaria - they pose a significant threat to global health.
To limit the spread of these dangerous diseases, Indiana University South Bend researcher Molly Scheel has developed a genetically based RNA interference insecticide. RNAi is a cellular mechanism that "turns off" a gene using its own DNA. Working with the IU Innovation and Commercialization Office, Scheel is filing patents to protect her research and collaborating with industry partners to get her discovery to market, allowing her important work to potentially be used across the globe to reduce the spread of disease.
With recent outbreaks of mosquito-borne diseases in South America, Southeast Asia and Africa, controlling mosquitoes is the main defense for disease control. According to the World Health Organization, malaria alone claims half a million lives annually. By April, the number of dengue cases reported this year already surpassed the annual high of 4.6 million, which was set in 2023.
"With the current inadequate insecticides and increasing insecticide resistance, these outbreaks will continue to spread rapidly, and the death toll will escalate at an alarming rate," said Scheel, the Navari Family Professor in the Department of Medical and Molecular Genetics at the IU School of Medicine-South Bend. "There is a critical need to develop insecticides that are effective in combating mosquito-borne diseases, yet safe for the environment."
Scheel has studied mosquito development since 2007 and began working with RNAi technology in 2009. Her team sequenced genomes of mosquitoes and selected genes known to be required for survival in other insects. Essentially, they were able to "turn off" the genes required for a mosquito to mature into a reproducing adult that can spread disease-causing pathogens.
To deliver the insecticide, Scheel's team chose to use an environmentally friendly method: yeast.
"We decided to take a different approach in creating an effective and environmentally safe insecticide that not only solves resistance issues but also solves the problems that pesticides pose on the environment," Scheel said. "Pesticides use harmful chemicals that contaminate soil, water and crops, and they are often toxic to non-target organisms. Through the use of yeast that makes species-specific interfering RNA, our insecticide mitigates environmental impact. We can also heat-kill the yeast before it is applied, so we aren't releasing live yeast into the environment."
Yeast is an attractive food source for mosquitoes, so the team discovered that adding yeast to water will kill juvenile mosquitoes before they are able to mature. The yeast can also be mixed with sugar baits to attract and kill adult mosquitoes upon consumption.
Scheel and her team have collaborated with international teams in the field in Trinidad, Tobago and Thailand since 2016 to successfully demonstrate, per World Health Organization guidelines, significant larvicide activity in treated water containers with respect to untreated control containers.
By working with industry partners to commercialize this technology, Scheel hopes to use these insecticides for disease prevention on a global scale. Considering that yeast is economically feasible and has the ability to be packed and shipped in shelf-stable forms, this new generation of insecticides can be used in countries that have significant mosquito-borne disease outbreaks.
While mosquitoes may be the primary focus of Scheel's team, they aren't the only insects this methodology can control. They have discovered that insecticides delivered through yeast work well in protecting against a number of species, including ants.
Scheel and IU South Bend's Keshava Mysore are targeting the nervous system genes in ants to create a genetically modified RNAi insecticide that will kill the ants when lured to the insecticidal sugar bait.
"Ants are often at the root of numerous problems," said Mysore, an assistant research professor of medical and molecular genetics at the IU School of Medicine-South Bend. "They can cause significant property damage to wood and other building materials, harm crops, contaminate stored food, and inflict painful and sometimes life-threatening stings."
Scheel hopes to secure funding to investigate more species of pest ants, including fire ants. She is also seeking commercial partners to further develop and commercialize the technology.
