Excretion/defecation patterns in Triatoma infestans populations that are, respectively, susceptible and resistant to deltamethrin

Abstract

Pyrethroid resistance has been detected in Triatoma infestans (Klug) (Hemiptera: Reduviidae) specimens from different areas of Argentina and Bolivia. Genes conferring resistance can have a pleiotropic effect with epidemiological and evolutionary consequences. This research studied excretion/defecation patterns in deltamethrin-resistant T. infestans in order to elucidate its biological performance, adaptive consequences and role in the transmission of Chagas' disease. One deltamethrin-susceptible strain and two deltamethrin-resistant strains were used. Fifth-instar nymphs were fed ad libitum and their defecations recorded during and after the first or second feeding in the stadium. Resistant insects began to defecate later, defecated less, showed a lower proportion of defecating individuals and lower defecation indices compared with susceptible insects during the first hour after feeding. The number of bloodmeals in the stadium did not affect the main variables determining the pattern of defecation. The present study suggests that alterations in the excretion/defecation pattern in resistant insects entail an adaptive cost and, considering only this pattern, determine a lower capacity for transmission of Trypanosoma cruzi (Kinetoplastida: Trypanosomatidae) compared with susceptible insects.

Effects of the infection with Trypanosoma cruzi on the feeding and excretion/defecation patterns of Triatoma infestans

“…The experiments were carried out with infected (n = 31) and uninfected (n = 44) fifth-instar nymphs, 15-20 days old and fasted since the last molt. In order to characterize the feeding and excretion/defecation patterns, each insect was fed ad libitum on pigeons and its behavior was observed during and after feeding according to Lobbia et al (2018). Briefly, a pigeon was placed on a device that kept the pigeon 20 cm away from the laboratory table with its ventral side exposed underneath.…”

“…Many authors have studied the patterns of feeding and defecation/excretion in many species of triatomines (Wood, 1951; Zeledón et al ., 1977; Trumper & Gorla, 1991; Crocco & Catalá, 1996; Nattero et al ., 2002; Biral dos Santos et al ., 2006; Rodríguez et al ., 2008; Reisenman et al ., 2011; Lobbia et al ., 2018). However, considering the mode of transmission of T. cruzi , strikingly only two studies investigated these two patterns together in triatomines infected with T. cruzi .…”

Resistance to deltamethrin in Triatoma infestans: microgeographical distribution, validation of a rapid detection bioassay and evaluation of a fumigant canister as control alternative strategy

“…This control strain was toxicologically characterized by Lobbia et al . (2018) [LD 50 = 0.5 (0.17–0.91); RR = 2.7 (0.9–6.2)]. Field and reference population insects were raised at the laboratory under controlled temperature (26 ± 1°C), humidity (50–70%), and a photoperiod of 12:12 (L:D) h. A chicken was weekly provided as a blood meal source.…”

“…So, the studies approached the resistance mechanisms, cross-resistance patterns, heritance and heritability, expression during ontogeny, pleiotropic effects (e.g. adaptive costs), macro and micro-geographical distribution and environmental influence (González-Audino et al ., 2004; Santo Orihuela et al ., 2008; Germano et al ., 2010 a ; Roca-Acevedo et al ., 2013; Gomez et al ., 2015; Germano and Picollo, 2015, 2018; Bustamante-Gomez et al ., 2016; Sierra et al ., 2016; Lobbia et al ., 2018, 2019 a ; Fronza et al ., 2019).…”

“…While most pleiotropic effects of resistance reported in several species were interpreted as adaptive costs for the natural environment (i.e. adaptive resistance costs) (Rivero et al, 2011;Kliot and Ghanim, 2012), including in resistant T. infestans (Germano and Picollo, 2015;Lobbia et al, 2018Lobbia et al, , 2019aLobbia et al, , 2019b, pleiotropic effects with positive adaptive consequences were described for Tribolium castaneum and Musca domestica (Arnaud et al, 2005;McCart et al, 2005). In triatomines, Lobbia et al (2019b) studied the reproductive efficiency after dispersal in susceptible and resistant T. infestans and showed that the dispersed resistant females had a higher reproductive efficiency than the dispersed susceptible females and the non-dispersed resistant females.…”