Study Finds Insecticide-Resistant Mosquitoes Across New Mexico

New Mexico State University researchers collaborating with the New Mexico Department of Health recently published a paper that shows there is widespread resistance to insecticides in one type of mosquito found in southern New Mexico – Aedes aegypti, the yellow fever mosquito.

Researchers say insecticide resistance is a serious problem, which evolves in insect populations when they are repeatedly exposed to the same type of insecticide or insecticides. This resistance can undermine public health efforts. This study characterized for the first time insecticide resistance of the yellow fever mosquito across its range in New Mexico.

“With climate change, New Mexico will increasingly be seeing mosquito-borne disease,” said NMDOH state epidemiologist Michael Landen. “This paper provides an important warning of how insecticide resistance in the state will complicate our ability to control these diseases and that we need to work on alternatives.”

The article, which outlines widespread insecticide resistance of the state’s yellow fever mosquito population, was published Feb. 22 in PLos One, a peer-reviewed open access scientific journal. It was authored by a number of researchers in the NMSU Departments of Biology and Geography along with the NMDOH.

The research was part of the SouthWest Aedes Research and Mapping project funded by NMDOH with biology professors Kathryn Hanley, Jiannong Xu and Immo Hansen along with geography professor Michaela Buenemann as principal investigators. As part of the SWARM project, yellow fever mosquitoes were collected from around the state and taken to Hansen’s Molecular Vector Physiology Lab at NMSU where bottle tests were conducted.

“It’s very easy, you take a bottle, put a certain amount of insecticide in there and let it dry,” said Hansen. “Then you put mosquitoes inside and record the time it takes them to die. A resistant strain takes maybe an hour until all of them are dead. If you have a susceptible strain they die in the first 5 minutes.” 

In addition to trapping and testing mosquitoes, the study also elicited data from some vector control entities in counties and cities across New Mexico about pesticides used in 2017 for mosquito control as well as methods used over the previous five years. 

Overall, results of the study demonstrate widespread resistance to pyrethroid insecticides.The majority of the mosquito populations analyzed were resistant to the permethrin and deltamethrin, with one exception ––Alamogordo, a city that did not use pyrethroids or chemical pesticides but instead used the bacterial larvicide Vectobac.

“In Alamogordo we did not find resistence in our study, you can see they are not resistant at all, which is good news for vector control,” Hansen said. “In Roswell and Deming, the mosquitoes we tested were highly insecticide-resistant. In other places we saw mixed populations. To address this issue of insecticide resistance, we suggest vector control have a management plan to rotate periodically from one active ingredient to another and consider exploring alternative approaches to mosquito control that do not involve insecticides.”

Source: New Mexico State University (NMSU)