Geographical Variation of Deltamethrin Susceptibility ofTriatoma infestans(Hemiptera: Reduviidae) in Argentina With Emphasis on a Resistant Focus in the Gran Chaco

Abstract

Chagas disease is one of the most important parasitic infections in Latin America. The main vector of the protozoan Trypanosoma cruzi in America is Triatoma infestans, a blood-sucking triatomine bug who is widely distributed in the Gran Chaco ecoregion. Control programs in endemic countries are focused in the elimination of triatomine vectors with pyrethroid insecticides. However, chemical control has failed in the Gran Chaco over the last two decades because of several factors. Previous studies have reported the evolution of different levels of resistance to deltamethrin in Tri. infestans Recently, very high resistance has been found in the central area of the Argentine Gran Chaco. However, the origin and the extension of this remarkably resistant focus remain unknown. The aim of this study was to evaluate the geographical variation of deltamethrin susceptibility of Tri. infestans in different endemic provinces of Argentina, with emphasis in the center of the Argentine Gran Chaco ecoregion where this main vector has not been reduced. Populations of Mendoza, San Juan, Santiago del Estero, and Tucumán provinces were all susceptible. Resistant populations were only detected in the province of Chaco, where a mosaic resistant focus was described at the Güemes Department. It was characterized into three pyrethroid resistance categories: susceptible, low, and highly resistant populations. We found the populations with the highest resistance levels to deltamethrin, with resistant ratios over 1000.

Novel Kdr mutations (K964R and A943V) in pyrethroid‐resistant populations of Triatoma mazzottii and Triatoma longipennis from Mexico and detoxifying enzymes

“…Variations in susceptibility to deltamethrin have been reported for Triatoma infestans Klug from Argentina with LD 50 ’s from 0.02 to >200 ng/I (Vieira‐Sonoda et al ., ; Fronza et al ., ), Brazil with LD 50 ’s from 0.26 to 0.70 ng/I (Vassena et al ., ; Vieira‐Sonoda et al ., ), Paraguay with LD 50 values from 0.1 to 0.5 ng/I (Fronza et al ., ), and Bolivia with LD 50 values from 0.25 to 119.12 ng/i (Lardeux et al ., ; Obara, ).…”

“…PAHO () has defined as resistant all populations with RR 50 >5, Fronza et al . () considered a low resistance in populations of T. infestans with RR 50 >10, and the last criteria suggested that a population should be considered resistant when RR 50 >2 (Zerba & Picollo, ). On the other hand, D'Ávila Pessoa et al .…”

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

“…The susceptible strain (S) originated from the vicinity of 25 de Mayo (26°52′42″ S, 60°13′52″ W) in the department of Quitilipi, and the resistant strains came from La Rinconada (LR) (24°55′14″ S, 61°24′15″ W) and El Asustado (EA) (26°5′10″ S, 60°18′22″ W) in the neighbouring department of Güemes (Fronza et al . ). Deltamethrin susceptibility was determined by topical application according to the World Health Organization protocol (WHO, 1994).…”

“…() using the reference Stariolo strain (LD 50 = 0.18 ng/i) (Fronza et al . ). Populations are considered susceptible if the RR 95% CI includes the number 1.…”

A motorized vehicle-mounted sprayer as a new tool for Chagas disease vector control

“…However, triatomines collected at the Lavalle study area showed no evidence of pyrethroid resistance 35 . Regarding bug immigration from external sources (iii), house reinfestation may derive from the intrusion of sylvatic adult bugs followed by house colonization.…”