Monitoring of pyrethroid resistance in Aedes aegypti: first report of double and triple kdr mutations in Buenos Aires Province

Abstract

Background: Dengue is an emerging disease in Argentina, due to the colonization of Aedes aegypti, the mosquito vector. Buenos Aires Province is the biggest and most populated Province in Argentina, suffering dengue outbreaks of growing magnitude. During epidemic periods, pyrethroid insecticides are used in this country for the control of adult mosquitoes. Pyrethroid resistance in dengue vectors has been reported worldwide, making necessary the implementation of resistance management strategies in the control campaigns. The voltage-gated sodium channel is the target site of pyrethroids. Mutations in the gene encoding this protein, called kdr mutations, are usually the molecular cause of pyrethroid resistance in insects. In Ae. aegypti from the Americas, three kdr substitutions were described: V410L, V1016I and F1534C. The diagnostic of kdr markers is recommended for the early detection of pyrethroid resistance, and the consequent planning of evidence-based control policies. The study presented here aimed to provide essential information on the detection of pyrethroid resistance, facilitating the planning and evaluation of initiatives to control dengue vector populations, and providing evidence of kdr evolution in Ae. aegypti around their Southern distribution range in Latin America. Methodology and findings: This was a multicenter study carried out through a joint effort of academic and governmental institutions that have formed the Argentine Network for Surveillance of Resistance to Pesticides Exclusively for Public Health. We distributed ovitraps across 16 localities in Buenos Aires Province, collecting a total of 22,123 eggs. A total of 522 mosquitoes were genotyped in positions 1016 and 1534 of voltage-gated channel, by using multiplex-High Resolution Melting and/or TaqMan probe methods. A subset of 449 samples was also genotyped by a singleplex High-Resolution Melting method developed ad hoc, and/or Sanger sequencing. We documented for the first time in the central region of Argentina the presence of the 1016I^kdr + 1534C^kdr allele, probably due to the selective pressure exerted by pyrethroids during recent dengue outbreaks. Additionally, our study reports the first identification of the V410L mutation in Argentina. These results underscore a growing trend of pyrethroid resistance in Ae. aegypti, fueled by the widespread use of these insecticides. Conclusions and Significance: Our results indicate that the pressure exerted by pyrethroids led to the emergence and expansion of 1016I^kdr + 1534C^kdr mutations in Ae. aegypti from Buenos Aires. We also detected V410L mutation in Argentina for the first time, indicating that pyrethroid resistance is a serious problem in the country, such as in other countries of the region. We also improve the processivity and accuracy of genotyping methods. The results are both a tool for resistance monitoring and a sign of alarm to direct efforts in the finding of sustainable methods for vector control, to complement or replace pyrethroids in the near future. Joined efforts between academia and authorities in public policies for vector control is a productive way for the transference of scientific results to its application in public health.