Significant 24 h recovery and survival of Culex mosquitoes exposed to pyrethroid insecticides using the CDC bottle bioassay
Loading...
Date
2023
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Insecticides deployed for mosquito vector control rely on the susceptibility of the targeted vector
population for continued efficacy and public health protection. The Centers for Disease Control and
Prevention (CDC) bottle bioassay is a standard method used for rapid mosquito insecticide resistance
assessment without measuring sublethal or delayed insecticidal effects. Ignored sublethal or delayed
mortality effects may affect the accuracy of susceptibility test outcomes and appropriateness of
insecticide selection decisions. This study found significant recovery and survival among Culex mosquito
populations initially immobilized after pyrethroid insecticide exposures using the CDC bottle bioassay.
Adult female Culex mosquitoes, reared from three different larval collection sites, were exposed to x1
and x2 intensities of deltamethrin and alphacypermethrin insecticides using the CDC bottle bioassay
method. Exposed mosquitoes were held for 24 hours for comparison of 30 min exposure time and 24 h
post-exposure mortalities. Subsamples of exposed mosquitoes were identified with Polymerase Chain
Reaction (PCR) technique. For both x1 (P ≤ 0.009) and x2 (P ≤ 0.048) insecticide intensities, the percentage
mosquito mortalities at 30 min exposure time (20-24%, 21-27%) reduced significantly after the 24 h postexposure
period (3-9%, 6-13%) respectively. However, after both 30 min (P ≥ 0.475) and 24 h (P ≥ 0.090)
periods, mosquito mortalities at x2 intensity (21-27%, 6-13%) were not significantly higher than mortality
at x1 (20-24%, 3-9%). All PCR-identified samples were found to be Culex quinquefasciatus. The significantly
reduced mortality at 24 h post exposure time indicates delayed recovery and survival of mosquitoes,
usually not captured when using the CDC bottle bioassay method. This result provides evidence to
suggest further discussions and review of the CDC bottle bioassay procedures for improved measure of
mosquito susceptibility/resistance.