Active dispersal in Triatoma infestans (Klug, 1834) (Hemiptera: Reduviidae: Triatominae): Effects of nutritional status, the presence of a food source and the toxicological phenotype.

In Argentina, the main vector of Chagas disease is Triatoma infestans (Klug, 1834). In recent years, the presence of T. infestans was reported in human dwelling after spraying with pyrethroids in several locations in Argentina. The presence of these insects can be attributed, among other factors, to colonization by bugs from sylvatic or peridomestic populations or to the evolution of resistance to insecticides. In both cases, the dispersal of insects is a determining factor. The aim was to determinate the interaction of dispersal with feeding, food resource and resistance to insecticides. Three nutritional states were obtained with the number of feeds (NF) offered (0, 1 or 2). The resistant females were evaluated only with NF1. The experimental arena was 10 m long and contained two shelters. Groups of 30 virgin females of each NF were released in one of the shelters and were able to move during 3 days/nights. Females without possibility of dispersal were the controls. Results showed that the individuals dispersed mainly walking regardless of the number of feeds, the presence of food resource and toxicological phenotype. This type of dispersal presented energy costs in susceptible individuals but not in resistant ones. The numbers of feeds that determined low nutritional states showed greater dispersal and activity associated with the shelter. The presence of a food source had an effect on the dispersal capacity and this depended on the number of feeds. There was a decrease in the dispersal in individuals with one feeding and an absence of response in fasted individuals and with two feeds. On the other hand, a lower dispersal tendency were found in resistant females compared to susceptible females, suggesting that resistance to deltamethrin is associated with adaptive costs.