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ARS Home » Southeast Area » Gainesville, Florida » Center for Medical, Agricultural and Veterinary Entomology » Mosquito and Fly Research » Research » Publications at this Location » Publication #391794
Research Project: Integrated Pest Management of Mosquitoes and Biting Flies

Location: Mosquito and Fly Research

Title: Assessing pyrethroid resistance status in the Culex pipiens complex (Diptera: Culicidae) from the northwest suburbs of Chicago, Illinois using Cox regression of bottle bioassays and other detection tools

Author
item BURGESS, EDWIN - University Of Florida
item LOPEZ, KRISTINA - University Of Wisconsin
item IRWIN, PATRICK - Northwest Mosquito Abatement District
item JAEGAR, COLLIN - McHenry County College
item Estep Iii, Alden

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/10/2022
Publication Date: 6/29/2022
Citation: Burgess, E., Lopez, K., Irwin, P., Jaegar, C., Estep III, A.S. 2022. Assessing pyrethroid resistance status in the Culex pipiens complex (Diptera: Culicidae) from the northwest suburbs of Chicago, Illinois using Cox regression of bottle bioassays and other detection tools. PLoS ONE. 17(6): e0268205. https://doi.org/10.1371/journal.pone.0268205.
DOI: https://doi.org/10.1371/journal.pone.0268205

Interpretive Summary: Culex pipiens is a known vector of West Nile Virus in the Chicago area. Effective mosquito control is crucial for limiting public health risk but insecticide resistance can cause control failure or can significantly the reduce effectiveness of insecticide sprays. In this study, we examined several populations collected in the Chicago area and conducted CDC bottle bioassays that determined resistance was present to Sumithrin. We subsequently conducted enzymatic and genetic assays to understand the mechanisms that underly the resistance observed in the bioassays. We also developed a method using Cox proportional hazards to generate additional information on significant factors that could affect resistance levels. The results indicate that the synergist-sumithrin combination, Anvil, restored susceptibility to most strains. Mosquito control programs frequently use synergized products and thus should have relatively high efficacy.

Technical Abstract: Culex pipiens complex is an important vector of many human and animal pathogens, including West Nile virus. Historically, Chicago has been affected by heavy incidence of human infection with West Nile virus. This makes abatement programs in and around the Chicago area an essential service. The control of Cx. pipiens is often complicated by rapidly evolving resistance to pyrethroids, which are the most widely used chemical class in mosquito abatement in the US. The present study assessed Sumithrin resistance in Cx. pipiens collected from five locations around Cook County, Illinois, neighboring the city limits of Chicago. According to CDC guidelines, samples from all five sites were resistant to Sumithrin. When assessed with formulated product made of Sumithrin synergized with piperonyl butoxide (PBO), three out of five tested sites were considered susceptible, suggesting involvement of mixed-function oxidases and/or carboxylesterases in Sumithrin resistance. Not all sites had susceptibility rescued by the addition of PBO with Sumithrin, suggesting other mechanisms such as knockdown resistance may be playing a stronger role in resistance in these strains. Enzyme activities did not reveal any marked trends that could be related back to mortality in the bottle bioassays, which highlights the need for multiple types of assays to infer enzymatic involvement in resistance. Future directions in pyrethroid resistance management in Chicago area Cx. pipiens are discussed further.