UNLV researchers warn of rising mosquito resistance in Las Vegas

By Maryn Jane Belleza

LAS VEGAS (KLAS) — Mosquitoes are becoming an increasingly persistent problem across Southern Nevada, with rising populations and growing concerns about their impact.

Dr. Trishan Wickramasinghe, a physician and researcher at the University of Nevada, Las Vegas, has spent nearly two years studying insect resistance in Clark County. At UNLV’s parasitology and vector biology lab, he has tested thousands of mosquitoes and larvae as part of his ongoing research.

He said the common mosquito species, Culex quinquefasciatus, is developing resistance to certain pesticides, including deltamethrin and permethrin. A more aggressive species, Aedes aegypti, is expected to be tested next year.

The more we spray, the more exposed mosquitoes are to pesticides, which means more immunity.

“It depends on which insecticide works for different areas. Some only work in certain areas and some don’t,” Wickramasinghe said. “So we can give targeted advice for pest control agencies, and we are trying to come up with a mosquito abatement district for Clark County to control the mosquito population without increasing pesticide resistance.”

The common mosquito can be found across Las Vegas, from Summerlin down to Henderson, favoring stagnant water like golf courses, artificial lakes, or the Wetlands.

“Normally they are supposed to die at the dose the CDC recommends, let’s say hypothetically for deltamethrin is 0.75 grams per millimeter and they’re supposed to die within one hour, but these mosquitos I find in Clark County, they don’t die 100 times that dose and sometimes 24 hours later prolonged that exposure for dose, they’re still not dying and even 100 times that concentration,” Wickramasinghe said.

He also explained that these mosquitoes are already quite resistant, and that resistance continues to build as people blindly use insecticides without knowing whether they are actually effective.

Louis Messenger, an assistant professor from the School of Public Health, said mosquitoes can adapt and evolve.

“So while we have seen rainfall, we have seen extreme highs in temperatures; all of those climatic variables are going to impact whether or not mosquitoes can breed and proliferate,” Messenger said.

Medhi Zarhloul is a homeowner in Las Vegas and knows not to leave any standing water around, as it makes perfect breeding conditions for mosquitoes.

“This year we’ve kind of seen an increase in mosquitoes,” Zarhloul said. “If you have any plants, make sure they’re not overwatered, make sure you have them sealed so there’s not air, especially during the summertime. It’s so hot, so anything that’s outside wants to get cooler.”

As the director of the lab, Messenger said we need a coordinated effort as a community.

“The problem is once mosquito populations are established in a given environment, it’s really difficult to get rid of them. You want to stop them before they become established,” Messenger said. “We now have a situation where West Nile insect vectors are thriving along with invasive species that can transmit dengue, yellow fever, and Zika. We don’t have any of those diseases here yet in Las Vegas, but we have close to 50 million visitors that come through the doors, and we know pathogens don’t respect any borders, so we need better monitoring here in Southern Nevada. “

Messenger is asking the community to participate in a survey regarding mosquito control in hopes of implementing a mosquito control program, and if taxpayers would be willing to pay a small cost for mosquito abatement if the county provided the service.