SE Valley Times

Mosquitoes are the deadliest creatures on the planet, transmitting life-threatening diseases such as malaria, West Nile virus, dengue, and yellow fever. According to the U.S. Centers for Disease Control and Prevention, these insects kill more than 700,000 people each year and are becoming increasingly resistant to insecticides.

In preliminary studies, Arizona State University (ASU) researchers have found that 85% of a type of mosquito in Maricopa County are resistant to efforts to suppress them. “And that’s a huge problem,” said Silvie Huijben, an associate professor at ASU’s Center for Evolution and Medicine.

Researchers in the Huijben Lab are studying the evolutions and mutations of mosquitoes that make them immune to efforts to eliminate them. Huijben and her colleagues conduct research in the newly renamed Alex Eugene “Gene” Elefant Insectary, where they study different types of mosquitoes and West Nile virus carriers. The West Nile virus is carried by birds, and mosquitoes transmit the virus from birds to humans or other animals.

Huijben asks her students three important questions: Are these local mosquitoes resistant to insecticides? How do they develop resistance? And will they be able to easily develop resistance to new chemicals?

“We want to answer these questions prior to a major outbreak of disease,” said Huijben. “Because once we have another full-blown pandemic — and hopefully that will never happen again — we want to know what chemicals we should be using to suppress them.”

In recognition of World Mosquito Day on Aug. 20, attention is drawn to the work of two of Huijben's students.

ASU student researcher Don Ward has spent eight years studying mosquitoes. While he does not necessarily like them, he appreciates their importance. Ward studies insecticide resistance in various mosquito species in Maricopa County and focuses on the impact of fogging by vector control.

Using tweezers, third-year biology PhD student Donald Ward places mosquitoes into microcentrifuge tubes to extract their DNA at the Hujiben Lab in the Life Sciences Building on Tempe campus. Mosquito season in Arizona peaks from March to early June and again from late August through November. Despite Arizona's dry climate, mosquitoes can breed successfully in sewers, irrigated areas, and golf courses.

Ward has conducted field trials by setting up cages at various distances behind Maricopa County pickup trucks spraying insecticides. He also uses different materials such as wood, glass, and cement to observe varying deposition rates.

In his most recent study, Ward found that fogging killed only 15% of highly resistant mosquitoes; beyond that percentage its efficacy diminished significantly. “In my most recent trial ... we found that not many of them died at all,” said Ward. “The fogging efforts coming out of Maricopa County or anywhere in the country are not as effective as people think — especially with resistant populations.”

Mackenna Berg has been working in the Huijben Lab since 2022. She graduates in December with a bachelor’s degree in molecular biosciences and biotechnology and will pursue a master’s degree in biology at ASU.

Berg has been studying mosquitoes carrying dengue and Zika viruses secured from Maricopa County's Vector Control division by extracting their DNA for mutations analysis across geographic patterns within the county. For her master’s degree research she will focus on West Nile virus-carrying mosquitoes.

“It’s definitely frightening,” Berg said about her findings regarding insect resistance being a growing problem.

“This information is a wake-up call... We have to hurry things up and find a new solution.”