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Published on: August 23, 2018
Time-of-day changes in permethrin susceptibility and metabolic gene expression in Florida Aedes aegypti (Diptera:
Sierra M Schluep1, Tse-Yu Chen1,2, Shelley A Whitehead1
1Florida Medical Entomology Laboratory, Department of Entomology and Nematology, Institute of Food and Agricultural Sciences, University of Florida, Vero Beach, FL, USA.
Abstract:
Aedes aegypti (Linnaeus) is the principal mosquito vector for many of the most medically significant arboviruses that threaten global public health. A better understanding of time-of-day variation in insecticide resistance mediated by detoxifying enzymes in Ae. aegypti could allow for targeted insecticide applications when susceptibility is highest and the upregulation of detoxification enzymes is lowest. Using a susceptible and metabolically resistant field Ae. aegypti strain from Florida, we investigated simulated photoperiodic changes in permethrin susceptibility and upregulation of detoxification enzymes by measuring permethrin LD50 and expression of detoxification genes (GSTE7, GSTE2, CCEae3A, CYP9J28, and CYPBB2) for both strains every 4 h over a 24 h (12:12 h light: dark) cycle. We found that in both Ae. aegypti strains, permethrin susceptibility was lower during the day as compared to evening, with susceptibility lowest at dusk (18:00) and highest between 02:00 and 14:00. Although no significant changes in gene expression over time were observed in the susceptible Ae. aegypti strain, we documented increased expression of all investigated detoxification genes in the metabolically resistant field Ae. aegypti strain during the night (18:00 to 02:00) as compared to the day (06:00 to 14:00). These data suggest that permethrin applications made between midnight and dawn (06:00) may be more effective against Ae. aegypti as compared to applications made at dusk (approximately 18:00).
Insights
Mosquitoes like Aedes aegypti are less susceptible to permethrin insecticide during the day. Applying insecticides at night or dawn may be more effective against these disease vectors.
Area of Science:
- Medical entomology
- Vector-borne disease control
- Insecticide resistance
Background:
- Aedes aegypti mosquitoes transmit significant arboviruses globally.
- Understanding daily variations in insecticide resistance can optimize control strategies.
- Detoxifying enzymes in mosquitoes influence insecticide efficacy.
Purpose of the Study:
- To investigate the impact of time-of-day on permethrin susceptibility in Ae. aegypti.
- To examine the daily expression patterns of detoxification genes in Ae. aegypti.
- To determine optimal timing for insecticide applications against Ae. aegypti.
Main Methods:
- Tested permethrin susceptibility (LD50) and detoxification gene expression (GSTE7, GSTE2, CCEae3A, CYP9J28, CYPBB2) in susceptible and resistant Ae. aegypti strains.
- Collected samples every 4 hours over a 24-hour cycle under simulated light:dark conditions.
- Analyzed gene expression and mortality rates in relation to time of day.
Main Results:
- Permethrin susceptibility was lower during the day and highest between 02:00 and 14:00.
- Detoxification gene expression increased significantly during the night in the resistant strain.
- No significant time-dependent changes in gene expression were observed in the susceptible strain.
Conclusions:
- Permethrin efficacy varies with time of day in Ae. aegypti.
- Insecticide applications between midnight and dawn may be more effective.
- Targeted application timing can improve control of this important disease vector.
