How is the phenotype of antennae, wings, and heads modified in Triatoma infestans resistants to deltamethrin?

HERNÁNDEZ M.L; REMÓN C; LOBBIA P; MOUGABURE-CUETO G

La Plata

Congreso; II Congress of the Latin American Society for Vector Ecology; 2022

Triatoma infestans is an important vector of Trypanosoma cruzi, the etiologic agent of Chagas disease. This insect represents a serious public health problem in Argentina due to the high density populations that develop in domestic and peridomestic environments in rural areas and, recently, in urban areas. Chemical control through spraying with pyrethroid insecticides is the only method to reduce populations of T. infestans in endemic areas. Despite this, resistance to pyrethroid insecticides is a problem in some localities in Argentina and Bolivia, where control actions with pyrethroid insecticides are ineffective. The genetic changes that determine resistance mechanisms to insecticides in an individual can have pleiotropic effects on physiological processes, causing changes that can be observed as different morphotypes. The objective of this work was to estimate the possible morphometric changes of wings, heads and antennal phenotype of males and females of T. infestans resistant to pyrethroids, evaluating the implication of the changes of the different structures in the adaptive processes of this insect. Thirty-six resistant (RR) and 58 susceptible (SS) adults (35 males and 59 females) from Chaco (Argentina) and raised in the laboratory (first and second generation) were analyzed. In these adults, the variables of size and conformation of heads and wings were analyzed, and the antennal sensilla of the three distal segments of the antenna were quantified. The results indicate that the RR insects suffer a phenotypic simplification compared to the SS. The antennae of RR females showed a significant decrease in the number of chemo- and mechano-sensilla. Antennae from RR males did not show this differentiation compared to SS. The wings were shorter and thinner than those susceptible for both sexes. In heads, the changes were less marked although a smaller distance between eyes is observed in RR. Regarding the fluctuating asymmetry, the RR ones showed more asymmetry in the shape of wings and heads than the SS. This result indicates greater developmental stress and instability associated with resistance to deltamethrin. The changes in wings, heads, and antennae suggest a lower sensory capacity and a lower potential for dispersal by flight in resistant insects. Although resistant insects have an adaptive advantage over susceptible ones in the presence of the insecticide, the resistance may imply a cost that reduces the energy devoted to various physiological processes or the modification of their phenotype with adaptive consequences in the environment without insecticide.