Infestation of Rural Houses by <I>Triatoma Infestans</I> (Hemiptera: Reduviidae) in Southern Area of Gran Chaco in Argentina

Abstract

The impact of control activities against Triatoma infestans (Klug) (Hemiptera: Reduviidae) in South America has a marked contrast within and outside the Gran Chaco region. Development of a geographic information system, as part of an improvement in control program activities, allowed analysis of the spatial pattern of house infestations by T. infestans before and after house spraying with deltamethrin in the San Martin Department (an arid Chaco region of central Argentina). The overall peridomestic infestation index decreased from 48.2 to 28.2% after insecticide application. House infestation was spatially clustered in regions with low or high infestation levels that were located east and southwest of the department, respectively. This pattern was detected both before and after the insecticide application. Three environmental variables calculated from a temporal series of MODIS imagery (average of night temperature, maximum of day temperature, and temporal variation of vegetation index) were capable of correctly discriminating 96% of the places belonging to either high or low house infestation observed after the insecticide application.

Toxicity of non-pyrethroid insecticides against Triatoma infestans (Hemiptera: Reduviidae)

“…However, in the Gran Chaco ecoregion, T. infestans numbers have not been reduced and this area is considered to represent the last main barrier to be conquered (Gürtler 2009). The lack of efficacy in this area may be attributable to several factors, such as incomplete insecticide coverage and entomological surveillance, interruption of local control programs due to economic problems and harsh environmental working conditions, such as temperatures ranging from -10-50ºC and the increasing desertification of some areas (Porcasi et al 2006, Gürtler 2009, Vazquez-Prokopec et al 2009). As noted by Gürtler et al (2004), peridomestic populations of T. infestans in the Gran Chaco ecoregion may exhibit a high rate of survival after chemical control actions, leading to a low efficacy of these treatments.…”

Susceptibility of Triatoma sordida Stal, 1859 (Hemiptera: Reduviidae) to alpha-cypermethrin under natural climatic conditions

“…Spraying the peridomicile is exhausting work in which unshackling all of the material accrued is operationally impossible for the fi eld agent in charge. After insecticide application, eggs and triatomines (nymphs and adults) may either be completely free of contact with active chemicals, or could be in contact with sub-lethal doses, thus selecting for the specimens less susceptible to the chemicals and allowing for the survival of those insects in such ecotopes (17) (18) . This underscores the fi nding that different pyrethroids exhibit ovicidal action when the insecticide is applied directly to the exochorial components of eggs (19) .…”

“…Operational failures cover the insecticide dilution errors, failures in applications as well problems with spraying machines (5) . One should also consider the discontinuity of spraying cycles for administrative, budgetary, and logistical reasons (17) (18) (20) . Finally, the presence of wild foci of T. sordida in the region should be considered, as it is associated with signifi cant mobility of this triatomine (mostly adults), which facilitates the process of dispersal and colonization of artifi cial ecotypes (20) , thereby hindering control.…”

New structures for goat corrals to control peridomestic populations of Triatoma infestans (Hemiptera: Reduviidae) in the Gran Chaco of Argentina

“…This is usually the case for intradomestic populations (Schofield et al 2006). A number of factors contribute to this result, as has been shown by several studies (Gürtler et al 2004, Porcasi et al 2006. The inefficacy of pyrethroid insecticides on these types of structures encouraged evaluations of alternative approaches to eliminate the peridomestic populations of T. infestans.…”