Inequalities in the social determinants of health and Chagas disease transmission risk in indigenous and creole households in the Argentine Chaco

Abstract

Background: The social determinants of health (SDHs) condition disease distribution and the ways they are handled. Socio-economic inequalities are closely linked to the occurrence of neglected tropical diseases, but empirical support is limited in the case of Chagas disease, caused by the protozoan Trypanosoma cruzi. Herein we assessed the relationship between key structural SDHs and the risk of T. cruzi vector-borne transmission in rural communities of the Argentine Chaco occupied by creoles and an indigenous group (Qom). We used multiple correspondence analysis to quantify the household-level socio-economic position (social vulnerability and assets indices), access to health and sanitation services, and domestic host availability. We identified the most vulnerable population subgroups by comparing their demographic profiles, mobility patterns and distribution of these summary indices, then assessed their spatial correlation and household-level effects on vector domiciliary indices as transmission risk surrogates.

Results: Qom households had higher social vulnerability and fewer assets than creoles, as did local movers and migrant households compared with non-movers. We found significantly positive effects of social vulnerability and domestic host availability on infected Triatoma infestans abundance, after adjusting for ethnicity. Access to health and sanitation services had no effect on transmission risk. Only social vulnerability displayed significant global spatial autocorrelation up to 1 km. A hotspot of infected vectors overlapped with an aggregation of most vulnerable households.

Conclusions: This synthetic approach to assess socio-economic related inequalities in transmission risk provides key information to guide targeted vector control actions, case detection and treatment of Chagas disease, towards sustainability of interventions and greater reduction of health inequalities.

Keywords: Integrated vector control; Neglected tropical diseases; Social vulnerability; Socio-economic inequalities; Triatoma infestans; Trypanonoma cruzi.

Fig. 1

Age-sex pyramid and sex ratio per five-year age group in Area III of Pampa del Indio, Chaco, Argentina in 2015

Fig. 2

Migration and mobility patterns by age group, gender (a, b) and ethnic group (c, d) in Area III of Pampa del Indio, Chaco, Argentina, for the 2012–2015 period. Out-migrants and in-migrants refer to those who moved out or into the study area, respectively, regardless of whether they moved within the same municipality or to another town or city. Local movers changed their residential location within Area III

Fig. 3

Household social vulnerability vs the asset index in 2015 (a), host availability in 2008 (b) and health access and sanitation index in 2015 (c), by ethnic group in Area III of Pampa del Indio, Chaco, Argentina

Fig. 4

Household distribution according to host availability, social vulnerability and vector indices in 2008 prior to implementation of vector control and surveillance in Area III of Pampa del Indio, Chaco, Argentina

Fig. 5

Global spatial analysis of quantitative and qualitative marks: social vulnerability (a), host availability (b), occurrence of at least one T. cruzi-infected T. infestans (c), and the relative abundance of infected vectors (d), area III of Pampa del Indio, Chaco, Argentina. The observed values correspond to the full dark circles and the lines correspond to the expected random pattern and its confidence envelopes

Fig. 6

Heatmaps of the social vulnerability and host availability indices, and the relative abundance of T. cruzi-infected T. infestans in domicile at baseline (2008) in Area III of Pampa del Indio, Chaco, Argentina