Spatial Stratification of House Infestation by Triatoma infestans in La Rioja, Argentina

Abstract

Vectorial transmission of Chagas disease has been decreasing over the past few decades because of effective vector control programs in the southern cone of South America. However, the disease is still actively transmitted within the Gran Chaco region. In this area, vector populations are abundant and highly prevalent in poor rural houses. This study analyses the spatial pattern of rural house infestation by Triatoma infestans in a 56,000 km(2) area in the province of La Rioja, Argentina, before the re-initiation of systematic activity on vector control intervention. Data on 5,045 rural houses show that infestation has high spatial heterogeneity, with highly infested localities concentrated in a few areas. House infestation has a negative significant relationship with locality size. Rural houses in the region are highly dispersed and this feature has been and will remain a challenge for any vigilance system to be installed in the region.

Origins of house reinfestation with Triatoma infestans after insecticide spraying in the Argentine Chaco using wing geometric morphometry

“…One of the main obstacles to the success of some of the ongoing elimination programs of domestic Triatominae vectors of T. cruzi is the reinfestation of houses after insecticide spraying (Cecere et al, 2006, in press; Dujardin et al, 1997; Dumonteil et al, 2004; Gorla et al, 2009; Gurevitz et al, 2012; Gürtler et al, 2007). It is often unclear whether the vectors found after control interventions are derived from residual subpopulations that either survived treatment or re-invaded the area from external sources such as untreated communities or sylvatic foci (Dujardin et al, 1997; Romaña 1963; Schofield, 1988).…”

“…Of the wide variety of peridomestic structures frequently infested with T. infestans , goat and pig corrals were identified as key ecotopes and sources of reinfestant insects in the dry Argentine Chaco (Cecere et al, 2004; Gorla et al, 2009; Gürtler et al, 2004). In contrast, domiciles, kitchens, storerooms and other peridomestic ecotopes used by chickens were the structures most frequently infested before and after insecticide spraying in Pampa del Indio, in the humid Argentine Chaco (Gurevitz et al, 2011, 2012).…”

Hidden Sylvatic Foci of the Main Vector of Chagas Disease Triatoma infestans: Threats to the Vector Elimination Campaign?

“…The Gran Chaco, an ecoregion of 1.3 million km 2 mainly spanning northern Argentina, Bolivia and Paraguay, has high levels of poverty and is hyperendemic for Chagas disease [9]. Recurrent reinfestation after residual spraying with insecticides and lack of a sustainable vector surveillance program result in renewed parasite transmission 3–5 years after community-wide vector control campaigns [10]–[13]. The obstacles to the elimination of T. infestans in the Gran Chaco may stem from different processes yet to be identified conclusively.…”

Spatial Heterogeneity and Risk Maps of Community Infestation by Triatoma infestans in Rural Northwestern Argentina

“…Rather, district-wide (e.g., state or county equivalents) entomologic and epidemiologic information collected at the community-level may represent the best compromise between the level of empirical detail needed and potential applicability for the design of vector control interventions. Unfortunately, to date few studies have quantified the spatial distribution of T. infestans and the factors associated with the distribution of bug infestation at the district level [7], [18], and none have developed risk maps of T. infestans distribution and T. cruzi transmission at this scale.…”