Landscape Disturbance Impacts on Attalea Butyracea Palm Distribution in Central Panama: Implications for Chagas Disease Transmission

Abstract

Background: Chagas disease is a vector-borne zoonotic disease endemic to Latin America. In Panama, Attalea butyracea palm trees are the preferred habitat of the region’s primary Chagas disease vector (Rhodnius pallescens). Close proximity of these palms to human dwellings is linked to increased risk of Chagas disease transmission. However, these palms thrive in disturbed habitats associated with human settlement and agriculture. This study examines the relationship between landscape disturbance and mature A. butyracea spatial distribution, density, and proximity to susceptible populations and vector movement corridors in a heterogeneous tropical region in central Panama. Presence of A. butyracea does not guarantee corresponding presence of R. pallescens, but as the vectors’ preferred habitat, quantifying A. butyracea response to disturbance may provide new insight into Chagas disease transmission risks in changing landscapes. Methods: We remotely identified the locations of over 50,000 mature A. butyracea palms using high-resolution WorldView2 satellite imagery. A local Getis-Ord Gi* spatial analysis identified significant clusters of aggregated palms. Associations between palm and cluster abundance and a landscape disturbance gradient, derived from official Panama landcover data, were tested using Chi-square tests for Homogeneity and Z-test for proportions. Kruskall-Wallace non-parametric analysis of variance tests were run to assess whether palm cluster area varied by disturbance level, or whether disturbance influenced average proximity of palms and palm clusters to susceptible populations or vector movement corridors.Results: Our findings indicate a regional relationship between landscape disturbance and A. butyracea occurrence. We observe a significant increase in both individual and clustered A. butyracea in secondary forest, but a reduction in palms in agricultural settings. Notably, we do not detect evidence of any thinning in abundance of palms in residential settings. All but one household in our study area is within vector flight distance of potential vector habitat in palm crowns.Conclusions: We observe probable anthropogenic thinning of A. butyracea palms in agricultural, but not residential, settings. Even in heavily deforested regions, significant concentrations of mature palms remain in close proximity to human establishments. The potential of A. butyracea palms as a source of infectious Chagas disease vectors in this region warrants further study.