P 33 - Mapping trends of pyrethroid resistance in Aedes aegypti from Mexico.

Current strategies to suppress arbovirus outbreaks in Mexico include eliminating larval breeding sites and insecticide treatment against larval and adult mosquito populations. The control of Aedes aegypti by insecticides is challenging due to a rapid increase in knockdown resistance (kdr) to pyrethroid insecticides. In this study, we located the focal points for kdr resistance in 45 populations of Ae aegypti from Mexico and with diagnostic dose (DD) bioassays in bottle bioassays with permethrin (10 mg) and deltamethrin (15 mg) in the same populations, a reliable geographical extrapolation was generated on the distribution of resistance to pyrethroid insecticides. Additionally, we evaluated the activity of enzymes associated with resistance, such as α-esterases, ß-esterases, mixed function oxidases (MFO), and glutathione S-transferases (GST). All populations of Ae. aegypti were found to have a high frequency of resistance to permethrin, with hotspots in the states of Veracruz and Tabasco in the southeast and Guerrero and Sinaloa in the Pacific. A high frequency of resistance to deltamethrin was obtained in 40% of the populations, 28% were moderately resistant, and 32% were susceptible, with the greatest focus of resistance in populations from Tabasco in the southeast. The most frequent genotype was VL/VI/CC, followed by the triple resistant LL/II/CC. The foci of greatest resistance to permethrin were significantly associated with the triple resistant genotype (LL/II/CC); however, for deltamethrin, the most frequent genotypes were the triple resistant (LL/II/CC) and double heterozygous for 410 and 1016 and resistant for 1534 (VL/VI/CC). CyP450 oxidases were altered in 72% of the populations and, to a lesser extent, the a-esterases with 41%; b-esterases and GST were altered in only 13% and 23% of the populations, respectively. The spatial identification of pyrethroid resistance foci provides a feasible tool to focus insecticide selection actions based on high-resistance risk areas identified as focal sites in Mexico.