Cuticular thickening associated with insecticide resistance in dengue vector, Aedes aegypti L.

Aedes aegypti is a globally spread disease vector of supreme concern, primarily controlled by chemical insecticides. Current study investigates the comparative rate of acetamiprid and deltamethrin resistance development in Ae. aegypti larvae and; possible correlation between resistance and cuticular thickening. The larvae were selected with LC90 level of the respective insecticide for 10 successive generations and the level of resistance induced was estimated. The larvae of parent (PS), acetamiprid-selected (ACSF-10) and deltamethrin-selected (DLSF-10) strains were sectioned through first abdominal segment to elucidate the variation in cuticular thickness. The PS larvae of Ae. aegypti were 229.26-fold higher susceptible to deltamethrin as compared to acetamiprid, exhibiting corresponding LC50 values of 0.00082 mg/L and 0.18799 mg/L. Larval selections induced 9.91-fold and 19.74-fold resistance to deltamethrin and acetamiprid, respectively; indicating multifactorial and heterozygous pattern. Cuticular analysis of the larval sections demonstrated a significantly thicker cuticle in selected strains, the mean thickness in PS, ACSF-10 and DLSF-10 was 2.891 ± 0.243, 4.288 ± 0.508 and 5.695 ± 0.437 μm, respectively revealing 1.48-fold and 1.97-fold thicker cuticle in the ACSF-10 and DLSF-10 strains, respectively in comparison to PS strain. The increased cuticular thickness possibly inhibited the insecticide penetration in selected larvae resulting in the resistance development. This is the first such report which demonstrates the association between acetamiprid/deltamethrin resistance in Ae. aegypti larvae with the cuticular thickness.