Comparative Trial of Effectiveness of Pyrethroid Insecticides Against Peridomestic Populations ofTriatoma infestansin Northwestern Argentina

Abstract

The effects of different pyrethroid insecticides, formulations, and doses on peridomestic populations of Triatoma infestans (Klug) were evaluated in 128 houses with 148 identified infested peridomestic sites in northwestern Argentina between October 2003 and March 2005. Four treatments were randomly assigned within each community: two doses of 5% suspension concentrate beta-cypermethrin in water applied with manual compression sprayers, the standard dose (S) at 50 mg and a double dose (2S) at 100 mg active ingredient (AI)/m2; and two emulsifiable concentrates diluted in diesel fuel and applied with power sprayers, 25% cypermethrin (100 mg [AI] /m2) (CF) and 10% permethrin (170 mg [AI]/m2) (DF). Infestation was assessed by timed manual collections with a dislodging agent at baseline, 5, 12, and 17 mo postspraying, and the sites found to be reinfested at 5 mo postspraying were selectively resprayed. Only 2S eliminated T. infestans from all peridomestic sites up to 12 mo postspraying, and it was significantly more effective than all other treatments. At 5 mo postspraying, more sites treated with CF or DF rather than S had bug colonies that probably represented residual foci, which they also failed in eliminating after a second spray. At 17 mo postspraying, the prevalence of reinfested peridomestic sites was 5% for 2S, 29% for S, 43% for CF, and 54% for DF. The application of suspension concentrate pyrethroids in dose twice as large as that currently in use in the attack phase produces a greater initial impact and may eliminate peridomestic populations of T. infestans.

Domestic Animal Hosts Strongly Influence Human-Feeding Rates of the Chagas Disease Vector Triatoma infestans in Argentina

“…Field work was carried out in October-November 2003 in eight neighboring rural communities with 270 houses in Figueroa Department (27° 23′S, 63° 29′W), Province of Santiago del Estero, Argentina, described elsewhere [39]. The study area was selected for an insecticide trial in 2003–2005 because it had high infestation with T. infestans and recent occurrence of human acute cases of T. cruzi despite a previous community-wide residual spraying with pyrethroid insecticides conducted in 2000.…”

“…A cross-sectional survey of house infestation was conducted before control interventions in October-November 2003 [39]. Each of the 270 houses was visited and georeferenced.…”

“…All triatomine bugs collected were stored in labeled plastic bags and kept in a cooler at 10–12°C between capture and arrival at the field laboratory to stop excretion, and then were identified to species and counted by stage [39]. Timing of bug catches and time of processing of the bugs from each study house were recorded.…”

Toxicological, Enzymatic, and Molecular Assessment of the Insecticide Susceptibility Profile ofTriatoma infestans(Hemiptera: Reduviidae, Triatominae) Populations From Rural Communities of Santa Cruz, Bolivia

“…Pyrethroids are currently the main tool for vector control because of their high efficacy and residual activity, together with low risk of environmental contamination and lower health risks associated to them (Pinchin et al 1980, Zerba 1997, Gürtler et al 2004, Cécere et al 2006). …”

“…Several areas of the Gran Chaco have been targeted with intensive vector control efforts without success (Gürtler et al 2007, Mougabure-Cueto and Picollo 2015, Pessoa et al 2015). Abundant populations of T. infestans live in peridomestic structures of the Gran Chaco rural houses, habitats where the pyrethroid formulations showed lower efficacy probably due to no persistent residual effect outdoors (Gürtler et al 2004, Cécere et al 2006). The recommended strategy of repeating an insecticide application every six months is usually not met in these areas for a number of reasons, including infrastructure, material, and human resources availability, among the main operational problems.…”