# Surveillance of pyrethroid resistance and detection of voltage-gated sodium channel gene mutations in Aedes albopictus populations from Shanghai, China

## TL;DR

This study examines pyrethroid resistance in Aedes albopictus mosquitoes in Shanghai and develops a rapid test to detect resistance-related gene mutations.

## Contribution

A novel LAMP assay is developed for rapid detection of the F1534S mutation in the voltage-gated sodium channel gene in Aedes albopictus.

## Key findings

- Pyrethroid resistance is widespread in Aedes albopictus populations across Shanghai.
- The F1534S mutation in the voltage-gated sodium channel gene is highly prevalent.
- The developed LAMP assay accurately detects the F1534S mutation with high sensitivity.

## Abstract

As a global hub for trade and tourism, Shanghai faces escalating risks of dengue fever due to imported and local transmission. Aedes albopictus, the primary dengue vector in the region, is predominantly controlled using pyrethroid insecticides. However, widespread resistance threatens their efficacy.

Resistance levels of Ae. albopictus to four pyrethroids (deltamethrin, permethrin, lambda-cyhalothrin, beta-cypermethrin) in 12 Shanghai districts were assessed via adult mosquito contact tube bioassays, with resistance categorized by mortality rates at diagnostic doses. Voltage-gated sodium channel (VGSC) gene mutations in 255 adult mosquitoes were identified through sequencing. A loop-mediated isothermal amplification (LAMP) assay was developed to rapidly detect the F1534S mutation in the VGSC gene.

The Baoshan district population exhibited resistance to cyhalothrin (mortality: 80.3%), while populations in all other districts displayed confirmed resistance (mortality < 80%) to all four pyrethroids. VGSC mutation analysis revealed high frequencies of F1534S (84.71%), moderate V1016G (21.96%), and rare I1532T (1.57%). An optimized LAMP assay for F1534S detection was established with the following parameters: 0.5 U/μl Bst DNA polymerase, 0.8 mM deoxynucleoside triphosphates (dNTPs), 3.00 mM Mg2+, 1.00 mM betaine, 2.00 μM forward/backward inner primers (FIP/BIP), 0.40 μM F3/B3 primers, 0.8 mM hydroxyl naphthol blue (HNB), and 60-min incubation at 63 °C. The assay demonstrated 100% concordance with sequencing results and high sensitivity.

Pyrethroid resistance is pervasive in Shanghai’s Ae. albopictus populations, driven by high-frequency VGSC mutations. The LAMP assay provides a rapid field-deployable tool for resistance monitoring, guiding targeted vector control strategies.