Phenotypic Variability of Peridomestic Triatoma Infestans Populations in Areas of the Chaco Region in Northwestern Argentina

Abstract

Triatoma infestans is one of the main vectors for Trypanosoma cruzi transmission, a serious health problem in the Gran Chaco region. Triatomine persistence is partly due to peridomestic populations, which are the main source of house reinfestation and thus prevent vector control. The aim of this study was to determine phenotypic variations in peridomestic T. infestans populations from different geographical areas of the Chaco region in northwestern Argentina. Adult male and female T. infestans m orphotypes were collected in chicken coops from four departments of the provinces of Chaco (Güemes, GU), San Luis (Junín, JU), Córdoba (Cruz del Eje, CE) and Santiago del Estero (Choya, CH). The shape and size of right wings (n = 266) and heads (n = 269) were analyzed using landmark-based geometric morphometrics. Sexual dimorphism was significantly larger in females (GU, JU and CE wings shape and GU, CE and CH head size). The centroid (Cs) size of wings differed significantly in most T. infestans populations (H = 187.28, df = 3; p = 0.001), whereas differences in the Cs size of heads were found between CE and GU and JU and CH, with the highest mean Cs in CE and the smallest ones in CH (H = 123.12, df = 3, p = 0.00 between males; H = 79.92, df = 3, p = 0.001 between females). Discriminant analysis showed that wing conformation differed significantly between females and males from the study populations, excepting CH vs JU females and males (d2 = 1.47; p = 0.092 and d2 = 1.23; p = 0.169) and between CH vs. GU females and GU vs. JU in males. No differences were found in males from GU and JU. Mahalanobis distance (d2) showed significant differences in heads among all departments, without discriminating by sex. These results suggest sexual dimorphism in T. infestans head size and wing conformation as well as different population structures (high, low or no exchange of individuals) in peridomestic areas of the four Chaco region departments studied, probably due to geographic isolation.