Association between landscape transformation and the Chagas disease vector dynamics in a rural area with continuous surveillance and control.

BACKGROUND

The Gran Chaco Region of Argentina, a hotspot for neglected tropical diseases (NTDs) including Chagas disease (CD), has undergone significant landscape transformations due to deforestation and agricultural expansion. These changes have altered the dynamics of Triatoma infestans, the primary vector of Trypanosoma cruzi, the causative agent of CD. This study investigates the association between environmental changes and vector infestation patterns in a rural area of Añatuya, Santiago del Estero, Argentina, under continuous surveillance and control since 2005.

METHODS

Entomological data from 502 households across 13 rural settlements were collected over a decade (2009-2019). Spatial patterns of triatomine infestation were analyzed using kernel density estimation (KDE), and relationships between infestation, land use changes, household density, and proximity to deforested areas were assessed. Random Forest models were employed to identify key predictors of infestation, incorporating variables such as deforestation percentage, distance to agricultural plots, and domestic animal density.

RESULTS

Infestation patterns were highly heterogeneous, with significant hotspots identified in settlements such as Lote 27, Lote 47, and La Salamanca. Household density and distance to main roads emerged as the most important predictors of infestation, with higher infestation rates observed in areas with lower deforestation and greater distance from agricultural plots. Deforestation reduced sylvatic reservoirs of T. cruzi but influenced domestic triatomine populations, particularly in areas with intermediate household density. Continuous surveillance and control efforts, including insecticide application and house improvements, led to a significant reduction in infestation rates over time.

CONCLUSIONS

Landscape transformation plays a critical role in shaping T. cruzi transmission dynamics. While deforestation reduces sylvatic reservoirs, it also influences domestic triatomine populations, highlighting the complex interplay between environmental changes and vector ecology. Tailored control strategies that address both domestic and sylvatic cycles are essential for sustainable vector elimination. These findings underscore the importance of integrating environmental and spatial factors into CD control programs to achieve certification of transmission-free areas and reduce the burden of CD in endemic regions.