Posted October 13, 2021

Molly Duman Scheel, Ph.D., Indiana University
David Severson, Ph.D., University of Notre Dame

Dr. Molly Duman Scheel

Dr. David Severson

Illnesses transmitted by mosquitoes are a significant public health concern and are of particular importance for the military. There are currently no approved vaccines against many of the diseases spread by mosquitoes, such as Chikungunya, Dengue fever, malaria, West Nile virus, and Zika virus, so mosquito control measures remain critical for protection. Service Members are at higher risk of mosquito exposure during deployment, especially to locations where mosquito-transmitted illnesses are common. Additionally, many commonly used pesticides can cause health and safety issues in both humans and to the local environment, and resistance to these pesticides often emerges in mosquito populations. Therefore, creative, effective, and safe mosquito control measures are needed to prevent the spread of dangerous mosquito-borne illnesses within both the military and the general public.

Aedes mosquito drinks sugar bait containing RNAi insecticides.

Drs. Molly Duman Scheel and David Severson were awarded a Fiscal Year 2016 (FY16) Peer Reviewed Medical Research Program (PRMRP) Investigator-Initiated Research Award with Partnering PI Option to develop and test ovitraps (i.e., containers to lure and kill female mosquitoes that are carrying eggs). These ovitraps utilize RNA interference (RNAi) technology to create pesticides that kill mosquito larvae. RNAi is the introduction of double-stranded RNA into an organism to turn off or “silence” specific, targeted genes.¹ The research team identified interfering RNAs that could silence genes required for mosquito survival, creating novel interfering RNA pesticides (IRPs) that could kill mosquito larvae when ingested. This technology has been shown to be highly effective in mosquito control by Drs. Duman Scheel and Severson’s team and is a new type of pesticide, designed to kill only the target organism, with minimal to no effect on the environment or other insects and humans. Advances in oral RNAi for mosquito control by Dr. Duman Scheel are detailed in a 2020 publication in Current Opinion in Insect Science.

Dr. David Severson inspects a water storage container for mosquito larvae. Aedes larvae are often found in water storage containers located next to homes.

Dr. Molly Duman Scheel tests RNAi-based yeast larvicides at the University of the West Indies, St. Augustine, Trinidad and Tobago field site.

The FY16 PRMRP award funded research that showed the validity, scalability, and low overall cost of the IRP system. Dr. Duman Scheel and her team selected Saccharomyces cerevisiae (Baker's yeast) as the delivery system for the IRPs because it can be produced inexpensively in large quantities. Analysis of the yeast delivery system is detailed in a publication in Current Drug Targets in 2019. The research team also showed that the system attracted mosquitoes to lay their eggs in the ovitraps containing the yeast interfering RNA technology. Mosquito larvae were killed after hatching and eating the yeast IRPs. This system was tested in the Caribbean, where both the effectiveness of larvae control and general public perception were evaluated. Consumers in the local area provided valuable feedback for implementation and acceptance of this new mosquito control system. One of the most significant concerns was that consumers wanted pesticide systems that last for a long time after initial application and are inexpensive to maintain. They also hoped for an expanded system that could also kill adult mosquitoes.