Current resistance status of Aedes aegypti and Aedes albopictus populations in Penang Island, Malaysia

• Main Authors: Kin Hoong Ng, Wan Fatma Zuharah
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wolters Kluwer Medknow Publications 2024
• Subjects: aedes; insecticide resistance; mosquito; organophosphates; pyrethroids; vector control; Arctic medicine. Tropical medicine; RC955-962; Arctic
• Online Access: https://doi.org/10.4103/apjtm.apjtm_806_23; https://doaj.org/article/19fe11001db84da1a2772228ee7432d9

Objective: To determine the current insecticide resistance status of Aedes (Ae.) aegypti and Ae. albopictus to four insecticides, namely 0.05% deltamethrin, 0.75% permethrin, 5% malathion and 0.25% pirimiphos–methyl using the World Health Organisation (WHO) susceptibility test kit. Methods: Adult bioassays were carried out using the standard protocol of the World Health Organisation. All F1 generation urban and suburban field strains of Ae. aegypti and Ae. albopictus were tested against pyrethroid and organophosphate insecticides, including the presence of piperonyl butoxide (PBO) in four replicates of 25 non-blood-fed female mosquitoes ranging from 3 to 5 days old. The Vector Control Research Unit (VCRU) laboratory strain served as a reference strain. Results: In this study, 0.05% deltamethrin demonstrated a lower value of knockdown time when 50% of the mosquito population died (KT50) and knockdown time when 95% of the mosquito population died (KT95), which is significantly more effective compared to 0.75% permethrin against adult female Ae. aegypti (urban and suburban) and Ae. albopictus (urban and suburban) (ANOVA, P<0.01). Meanwhile, 5% malathion was a more effective insecticide, amounting to the shorter KT50 and KT95 compared to 0.25% pirimiphos-methyl against Ae. aegypti (urban and suburban) and Ae. albopictus (urban and suburban). Ae. aegypti urban and Ae. aegypti suburban performed a higher resistance ratio (RR) towards both 0.05% deltamethrin and 0.75% permethrin due to the wide use of permethrin in dengue vector control programs in Malaysia. However, Ae. albopictus urban and suburban have lower resistance than Ae. aegypti urban and suburban towards 0.05% deltamethrin and 0.75% permethrin at 24 hours post-treatment. The addition of PBO with these insecticides successfully reduced knockdown time (KT50 and KT95) values of most of the Ae. aegypti and Ae. albopictus field strains except PBO+0.75% permethrin against Ae. aegypti suburban. Conclusions: The addition of PBO to insecticides has significantly ...