From pets to pests: Researchers explore new tool to fight disease-carrying insects

After switching to fluralaner as a veterinary medication for her dog, Emily McDermott, assistant professor of medical and veterinary entomology and a researcher for the Arkansas Agricultural Experiment Station, was curious about exploring other possible applications for it.

"The reason I put my dog on this fluralaner drug is because the spot-on treatments were not working very well," she said. "Fluralaner is exciting because it has a different mode of action than current insecticides."

The drug prevents insects' nerve cells from working properly, disrupting their nervous systems.

McDermott says previous studies had shown promising results when fluralaner was applied as a spray but that it's much more effective if ingested orally.

McDermott and Ph.D. student Blythe Lawson conducted research to find out if fluralaner would be effective as a larvicide and the best method to feed it to the larvae.

By treating larvae directly, they were able to use less chemicals and target specific areas where larvae are concentrated, reducing the need for widespread spraying and minimizing the risk of contaminating waterways and the environment.

The study "Successful yeast microencapsulation of fluralaner and its potential as a larvicide for vector control," was published in the Acta Tropica journal in August.

"Fluralaner is an up-and-coming synthetic chemical, and there's a lot of interest in expanding its use," Lawson said. "There's a big need for larvicides in the market; there are only a few for mosquitoes."

Flies and mosquitoes can carry diseases such as malaria, dengue and Zika virus. McDermott says disease vectors such as mosquitoes and flies have developed resistance to commonly used drugs and traditional methods often target adult insects. But Lawson and McDermott investigated ways to use fluralaner to target these insect's larvae before they develop into adults, which is when they are most likely to spread diseases or become pests.

"You can knock those populations down before they start causing problems," McDermott said.

Fluralaner is sold in chewable form for pets under the brand name Bravecto, currently the only labeled form of fluralaner in the United States.

The Trojan horse method

McDermott and Lawson used a yeast microencapsulation technique to investigate if fluralaner would work. They encapsulated yeast cells with the insecticide and then tested it on larvae of three species:

• Common house fly -- Musca domestica
• Asian tiger mosquito -- Aedes albopictus
• Biting midge -- Culicoides sonorensis, the most common midge in much of eastern U.S.

McDermott and Lawson said the larvae of these species naturally consume microorganisms such as yeast, making the microencapsulation an ideal delivery method.

"It acts like a Trojan horse," Lawson said.

Their research showed fluralaner is effective and long-lasting as a larvicide. The study found that a single application of microencapsulated fluralaner could control mosquito larvae for five weeks and midge larvae for eight weeks.

"We compared our product to a couple of commercially available mosquito larvicides, and we found that it was as effective or more effective than the products that are currently on the market," McDermott said.

The study also found that a higher concentration is needed to kill off housefly larvae compared to mosquitoes or biting midges, which McDermott says was not surprising given that houseflies are larger.

However, McDermott said the midges seemed to be less sensitive to the larvicide than mosquitoes, which was not expected because the midge larvae are much smaller than the mosquito larvae.

"So, we do think there's a size component to this, but it's not just size -- there's something about the physiology of the insects as well," she said.

Future use

McDermott envisions this research will lead to the development of a product that could be used around households and trash collection sites, for example.

"The way our product is formulated is that after we encapsulate the active ingredient in the yeast, we freeze-dry it and get it back down to a powdered yeast form," she said. "We envision this product could be in a backpack sprayer, and you would spray it like any other kind of insecticide."

McDermott says her team is engaging with industry partners to move forward with this patent-pending technology.

'We're still several steps away from a commercial application," she said. "With further testing and development, this yeast-based larvicide could provide a new tool for vector-control efforts and public health."

This study was supported by Deployed Warfighter Protection Program Award No. W911QY2210003. The DWFP is a research program tasked with developing and testing management tools for pest and vector species that transmit diseases to deployed war-fighters. It's administered by the Armed Forces Pest Management Board and sponsored by the Department of Defense.