Posted by Vector and Vector-borne Disease Committee
May 2, 2022
Guofa Zhou,1,4, Yiji Li,1,3 Brook Jeang,1 Xiaoming Wang,1, Robert F. Cummings,2
Daibin Zhong,1 and Guiyun Yan1
1Program in Public Health, University of California, Irvine, CA, USA, 2Orange County Mosquito and Vector Control District, Garden Grove, CA, USA, 3Current address: Department of Pathogen Biology, Hainan Medical University, Haikou, Hainan, China, and
4Corresponding author, e-mail: zhoug@uci.edu
Paraphrased from the Abstract:
Mosquito mortalities and metabolic enzyme expressions were examined in mosquitoes with/without pre-exposure to different PBO concentrations and exposure durations. Except for malathion, wild strain Cx quinquefasciatus mosquitoes were resistant to all insecticides tested, including PBO-synergized pyrethroids (mortality range 3.7 ± 4.7% to 66.7 ± 7.7%). Wild strain mosquitoes had elevated levels of carboxylesterase (COE, 3.8-fold) and monooxygenase (P450, 2.1-fold) but not glutathione S-transferase (GST) compared to susceptible mosquitoes. When wild strain mosquitoes were pre-exposed to 4% PBO, the 50% lethal concentration of deltamethrin was reduced from 0.22% to 0.10%, compared to 0.02% for a susceptible strain. The knockdown resistance gene mutation (L1014F) rate was 62% in wild strain mosquitoes. The addition of PBO alone may not be enough to control highly pyrethroid-resistant mosquitoes due to multiple resistance mechanisms. Mosquito resistance to PBO-synergized insecticide should be closely monitored through a routine resistance management program for effective control of mosquitoes and the pathogens they transmit.
Journal of Medical Entomology, 59(2), 2022, 638–647
https://doi.org/10.1093/jme/tjab231
Highly pyrethroid resistant populations may be evolving multiple resistance pathways that allow them to be resistant not only to the insecticide but also to the synergist.