Urbanisation, risk stratification and house infestation with a major vector of Chagas disease in an endemic municipality of the Argentine Chaco

Abstract

Background: The occurrence of the major vectors of Chagas disease has historically been linked to poor rural housing, but urban or peri-urban infestations are increasingly being reported. We evaluated a simple risk index to detect houses infested with Triatoma infestans and tested whether house infestation and vector abundance increased across the urban-to-rural gradient in Avia Terai, an endemic municipality of the Argentine Chaco; whether the association between infestation and selected ecological determinants varied across the gradient; and whether urban and periurban infestations were associated with population settlement history. Methods: We conducted a screening survey of house infestation in 2296 urban, peri-urban and rural dwellings to identify high-risk houses based on a simple index, and then searched for triatomines in all high-risk houses and in a systematic sample of low-risk houses. Results: The risk index had maximum sensitivity and negative predictive value, and low specificity. The combined number of infested houses in peri-urban and urban areas equalled that in rural areas. House infestation prevalence was 4.5%, 22.7% and 42.4% across the gradient, and paralleled the increasing trend in the frequency of domestic animals and peridomestic structures. Multiple logistic regression analysis showed that house infestation was positively and significantly associated with the availability of poultry and bug refuges in walls, and was negatively associated with domestic insecticide use. Several pieces of evidence, including absence of spatial aggregation of house infestation, support that T. infestans has been a long-established occupant of urban, peri-urban and rural settings in Avia Terai. Conclusions: An integrated vector management strategy targeting chicken coops and good husbandry practices may provide more cost-effective returns to insecticide-based vector elimination efforts.

Trypanosoma cruzi infection in Triatoma infestans and high levels of human–vector contact across a rural-to-urban gradient in the Argentine Chaco

“…A cross-sectional survey was conducted in all environments to evaluate house and domestic infestation with triatomines at baseline between October 2015 and March 2016, as described elsewhere [25]. In total, 2296 inhabited houses were surveyed.…”

“…Fieldwork was conducted in the municipality of Avia Terai (26°42′ S, 60°44′ W), Chaco Province, Argentina, which has been described elsewhere [25]. The last house spraying campaign with pyrethroid insecticides conducted by Chagas vector control personnel was carried out in 2011-2013 (2-4 years prior to our survey) and did not achieve full coverage.…”

“…The last house spraying campaign with pyrethroid insecticides conducted by Chagas vector control personnel was carried out in 2011-2013 (2-4 years prior to our survey) and did not achieve full coverage. For the purpose of this study, we divided the municipality into three environments based on house arrangement patterns: urban (blocks), peri-urban (blocks and dispersed houses) and rural (dispersed houses) [25]. The peri-urban environment was highly heterogeneous and was further subclassified into established and recent neighborhoods [25].…”

“…As part of an intervention program aimed at suppressing house infestation with T. infestans in a sustainable manner and reducing disease burden in Avia Terai, Argentine Chaco, we conducted a survey that found a decreasing prevalence of house infestation (i.e. domestic or/and peridomestic infestation) with T. infestans, ranging from 42.4% in rural houses to 22.5 and 4.5% in periurban and urban areas, respectively [25]. Domestic infestation, defined as the occurrence of T. infestans in human sleeping quarters or domiciles, also decreased across the rural-to-urban gradient, from 9.9 to 1.1%, respectively, as did the household number of domestic animals and peridomestic structures.…”

“…Domestic infestation, defined as the occurrence of T. infestans in human sleeping quarters or domiciles, also decreased across the rural-to-urban gradient, from 9.9 to 1.1%, respectively, as did the household number of domestic animals and peridomestic structures. Triatoma infestans seemed to be long established in Avia Terai, unlike in Arequipa and Cochabamba [17,25,26].…”