Human Trypanosoma cruzi infection in the Argentinean Chaco: risk factors and identification of households with infected children for treatment

Abstract

Background: Chagas disease is a neglected tropical disease (NTD). Cost-effective strategies for large-scale implementation of diagnosis and etiological treatment are urgently needed to comply with NTD control goals. We determined the seroprevalence of Trypanosoma cruzi infection and associated risk factors in a well-defined rural population of Pampa del Indio municipality including creole and indigenous (Qom) households and developed two indices to identify houses harboring infected children.

Methods: We serodiagnosed and administered a questionnaire to 1337 residents (48.2% of the listed population) in two sections of the municipality (named Areas II and IV) 6-9 years after deploying sustained vector control interventions. Multiple logistic regression models were used to evaluate the relationship between human infection and a priori selected predictors. Two risk indices were constructed based on environmental and serostatus variables, and we used spatial analysis to test whether households harboring T. cruzi-seropositive children were randomly distributed.

Results: The global seroprevalence of T. cruzi infection was 24.8%. Human infection was positively and significantly associated with exposure time to triatomines, the household number of seropositive co-inhabitants, maternal seropositivity for T. cruzi, recent residence at the current house and the presence of suitable walls for triatomine colonization in the domicile. The pre-intervention mean annual force of infection (FOI) was 1.23 per 100 person-years. Creoles from Area IV exhibited the highest seroprevalence and FOI; Qom people from both areas displayed intermediate ones and creoles from Area II the lowest. Three hotspots of infected children were spatially associated with hotspots of triatomine abundance at baseline and persistent house infestation. No child born after vector control interventions was T. cruzi seropositive except for one putative transplacental case. Two simple risk indices (based on self-reported inhabiting an infested house and suitable walls for triatomines or maternal serostatus) identified 97.3-98.6% of the households with at least one T. cruzi-seropositive child.

Conclusions: We showed strong heterogeneity in the seroprevalence of T. cruzi infection within and between ethnic groups inhabiting neighboring rural areas. Developed indices can be used for household risk stratification and to improve access of rural residents to serodiagnosis and treatment and may be easily transferred to primary healthcare personnel.

Keywords: Chagas disease; Indigenous; Risk factor; Seroprevalence; Stratification; Trypanosoma cruzi.

Fig. 1

a Map of the study houses and communities from Areas II and IV shown as colored-shaded polygons. b Location of Pampa del Indio Municipality (star) within Chaco Province and the Gran Chaco ecoregion. CM, Colonia Mixta; CQ, Campo Cacique; CY, Campo Alemany; EP, Ex-Parque; H2, La Herradura; LA, Cancha Larga; LC, Lote Cuatro; LM, Las Muñecas; ME, Campo Medina; NU, Campo Nuevo; OM, Pampa Ombú; TCZ, Tacuruzal

Fig. 2

Timeline of key activities conducted at the study area. Pink and yellow boxes are vector surveys for Area II and IV, respectively. Purple boxes are the serosurveys at both areas

Fig. 3

Age-specific seroprevalence of Trypanosoma cruzi infection in residents from Areas II and IV born before the onset of interventions, observed (dots) and 95% CI (whiskers) and predicted according to an irreversible catalytic model seroprevalence (dashed line and dark envelope). a For all ages and b for children ≤ 18 years old at the onset of interventions

Fig. 4

a Spatial distribution of households harboring Trypanosoma cruzi-seropositive children ≤ 18 years of age at baseline, Area II and IV, Pampa del Indio, Chaco. Yellow circles indicate local hotspots. Hotspots of households harboring T. cruzi-seropositive children and triatomine house abundance at b baseline, c early period of intervention and d late period of intervention as defined in [22]