HumanTrypanosoma cruziinfection risk is driven by eco-social interactions in rural communities of the Argentine Chaco
Authors: Pilar Fernández Maria del , Gaspe Maria Sol , Sartor Paula , Gürtler Ricardo E. 
Published: May 2019

The transmission ofTrypanosoma cruzito humans is determined by multiple ecological, socio-economic and cultural factors acting at different scales. Their effects on the human risk of infection withT. cruzihave often been examined separately or using a limited set of ecological and socio-demographic variables. Herein, we integrated the ecological and social dimensions of human disease risk with the spatial distribution patterns of human and vector (Triatoma infestans) infection withT. cruziin rural communities of the Argentine Chaco composed mainly of indigenous people (90% Qom) and a creole minority. Prior to the implementation of a vector control intervention, the estimated seroprevalence ofT. cruziamong 1,929 local residents examined in a cross-sectional study was 29.0%, and was twice as large in Qom than creoles. Using generalized linear mixed models, the risk of human infection increased by 60% with each additional infected triatomine and by 40% with each seropositive household co-inhabitant; increased significantly with increasing household social vulnerability (a multidimensional index of poverty), and decreased with increasing host availability in sleeping quarters. A significant negative interaction between household social vulnerability and the relative abundance of infectedT. infestansindicated that vulnerable household residents were exposed to a higher risk of infection even at low infected-vector abundances. Household mobility within the study area reduced the effects of domiciliary vector abundance, possibly due to less consistent exposures. Nonetheless, the seroprevalence rates of movers and non-movers were not significantly different. Human infection was clustered by household and at a larger spatial scale, with hotspots of human and vector infection matching areas of higher social vulnerability. These results were integrated in a risk map that shows high-priority areas for targeted interventions oriented to suppress house (re)infestations, treat infected children, and thus reduce the burden of future disease.

Author summary

Chagas disease is one of the main neglected tropical diseases (NTDs) affecting vulnerable communities in Latin America where transmission by triatomine vectors still occurs. Access to diagnosis and treatment is one of the remaining challenges for sustainable control of Chagas disease in endemic areas. In this study, we integrated the ecological and social determinants of human infection with the spatial component to identify individuals, households and geographic sectors at higher risk of infection. We found that the risk of human infection was higher in indigenous people compared to creoles, and increased with the abundance of infected vectors and with household social vulnerability (a multidimensional index of poverty). We also found that the social factors modulated the effect of the abundance of infected vectors: vulnerable-household residents were exposed to a higher risk of infection even at low infected-vector abundance, and human mobility within the area determined a lower and more variable exposure to the vector over time. These results were integrated in a risk map that showed high-priority areas, which can be used in designing cost-effective serological screening strategies adapted to resource-constrained areas.