Temephos susceptibility assay against Culex quinquefasciatus larvae in Odisha, India.
TL;DR
The mortality rate of Culex quinquefasciatus mosquitoes exposed to temephos was significantly below the anticipated 98% susceptibility of the mosquitoes, indicating resistance to this insecticide.
Abstract
Background
Objectives
Insecticide bioassays are often used to assess the degree of insecticide resistance in mosquito populations, examining the ability of mosquitoes to withstand exposure to insecticides. In this study, laboratory bioassays were carried out to measure responses in F 1 larvae of field-collected Culex quinquefasciatus mosquito populations to the insecticide temephos as per the guidelines of the World Health Organization.
Methods
Culex quinquefasciatus mosquitoes were collected from the coastal and inland areas in and around Berhampur, Ganjam, Odisha. Fourth instar larvae of Cx. quinquefasciatus were exposed to temephos with various concentrations, from 0.01 to 0.05 ppm, and the response (mortality) was recorded at 12 and 24 hours after the exposure.
Results
The obtained LC 50 , LC 90 , and LC 99 values were 0.017, 0.027, and 0.040 ppm, respectively, after 24 hours of temephos exposure.
Interpretation
Conclusion
After 24 hours of treatment with the WHO-recommended diagnostic dose of 0.02 ppm of temephos, the mortality rate was found to be 58.7%, which was significantly below the anticipated 98% susceptibility of the mosquitoes, indicating resistance to this insecticide. Therefore, temephos insecticide resistance should be monitored at regular intervals for mosquito vector control management.