High Pyrethroid Resistance in Triatoma infestans Is Strongly Associated with kdr Variants: A Multiplex High-Resolution Melting Tool for Vector Surveillance

Abstract

Simple Summary Chagas disease affects millions of people worldwide; it is spread by blood-feeding insects known as kissing bugs, which are endemic in Latin America. In the Southern Cone, the main vector is Triatoma infestans, which lives inside houses and is controlled by spraying dwellings with pyrethroid insecticides. In some regions of Argentina and Bolivia, these insects have become highly resistant to those insecticides, so spraying no longer kills them and transmission continues. In this species, resistance has been closely associated with mutations in the gene that encodes the voltage-gated sodium channel, which is the target site of pyrethroids. Detecting those changes early, before they spread through a whole population, would let health authorities adjust their strategy in time. Here, we developed a cost-effective assay that identifies the two known resistance-causing changes at once, in a single reaction. We examined insects from several Argentine and Bolivian regions and found that these genetic changes appeared only in populations highly resistant to the insecticide, never in susceptible ones. The new test is quicker and cheaper than existing methods based on enzymatic digestion or allele-specific PCR, despite the requirement of more expensive equipment. It could be incorporated into control programs to monitor resistance routinely.