Infestation of Rural Houses byTriatoma Infestans(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.

Factors Affecting Infestation by Triatoma infestans in a Rural Area of the Humid Chaco in Argentina: A Multi-Model Inference Approach

“…The frequent domestic use of insecticides in Pampa del Indio may explain, at least in part, why the observed prevalence of house infestation with T. infestans was much lower than expected, considering that the most recent residual spraying with insecticides conducted by the vector control program occurred 12 years earlier, and other areas in the dry Chaco experience fast reinfestation after insecticide spraying campaigns [4], [8], [9], [36]. Insecticide use may also reflect to some extent the economic status of householders and/or their concern for and response to the presence of bugs and other domestic pests [22].…”

Improved Chemical Control of Chagas Disease Vectors in the Dry Chaco Region

“…House infestations with T. infestans were mainly detected in peridomestic structures during the first year after community-wide spraying with pyrethroid insecticides in several studies (Dujardin et al 1996; Cecere et al 2002; Guillén et al 1997; Zerba et al 1997; Gürtler et al 2004; Porcasi et al 2006, 2007), including other triatomine bug species in arid and semiarid areas of Brazil and Mexico (Diotaiuti et al 2000, Ramsey et al 2003). In the Gran Chaco, community-wide residual spraying of different SC pyrethroid insecticides at standard dose have not reached the expected levels of effectiveness against T. infestans in peridomestic areas (Silveira 2002, Gürtler et al 2007).…”

“…The available evidence indicates that peridomestic structures are the weakest points of Chagas disease vector control programs in arid or semiarid areas throughout Latin America (Ronderos et al 1980; Cecere et al 2002, 2004, 2006a,b; Diotaiuti et al 2000; Ramsey et al 2003; Gürtler et al 2004; Porcasi et al 2006, 2007). Peridomestic ecotopes were identified as the main sources of residual T. infestans populations that increased the risk of domestic reinfestation after control interventions (Cecere et al 2002, 2004).…”

“…Furthermore, the lower, more variable effectiveness of pyrethroids in peridomestic areas may emerge from the presence of structures with numerous hiding places for triatomine bugs that are difficult to reach with insecticides (Diotaiuti and Texeira–Pinto 1991, Cecere et al 2002). Despite professional community-wide spraying of pyrethroids in the absence of insecticide resistance, lack of elimination of peridomestic foci promote fast domestic reinfestation with T. infestans followed by new cases of human infection with T. cruzi (Gürtler et al 1994, 2005, 2007; Cecere et al 2004, 2006a; Porcasi et al 2006). …”

Seasonal Variation in Spatial Distributions ofAnopheles gambiaein a Sahelian Village: Evidence for Aestivation

“…SatScan accounts for multiple tests based on the sequential Bonferroni approach. The input data included the weekly total of A. gambiae collected per house, considering mosquitoes in a house as “cases” in the Bernoulli model (Kulldorff and Nagarwalla 1995, Kulldorff et al 1997, Porcasi et al 2006). Buildings that served only as kitchens and those few that were not available for regular collection were excluded.…”