High levels of human infection with Trypanosoma cruzi associated with the domestic density of infected vectors and hosts in a rural area of northeastern Argentina

Abstract

BackgroundInsecticide spraying campaigns designed to suppress the principal vectors of the Chagas disease usually lack an active surveillance system that copes with house reinvasion. Following an insecticide campaign with no subsequent surveillance over a 12-year period, we implemented a longitudinal intervention programme including periodic surveys for Triatoma infestans, full-coverage house spraying with insecticides, and selective control in a well-defined rural area of the Argentinean Chaco inhabited by Creoles and one indigenous group (Qom). Here, we conducted a cross-sectional study and report the age-specific seroprevalence of human T. cruzi infection by group, and examine the association between human infection, the onset of the intervention, the relative density of infected domestic bugs, and the household number of infected people, dogs, or cats.ResultsThe seroprevalence of infection among 691 residents examined was 39.8% and increased steadily with age, reaching 53–70% in those older than 20 years. The mean annual force of infection was 2.5 per 100 person-years (95% CI: 1.8–3.3%). Infection in children younger than 16 years born before the intervention programme was two to four times higher in houses with infected T. infestans than in houses without them and was six times higher when there were both infected dogs or cats and bugs than when they were absent. The model-averaged estimate of the intervention effect suggests that the odds of seropositivity were about nine times smaller for those born after the onset of the intervention than for those born before it, regardless of ethnic background, age, gender, household wealth, and cohabitation with T. cruzi-infected vectors or human hosts. Human infection was also closely associated with the baseline abundance of infected domestic triatomines and the number of infected cohabitants. Two of 43 children born after interventions were T. cruzi-seropositive; since their mothers were seropositive and both resided in apparently uninfested houses they were attributed to vertical transmission. Alternatively, these cases could be due to non-local vector-borne transmission.ConclusionsOur study reveals high levels of human infection with T. cruzi in the Argentinean Chaco, and the immediate impact of sustained vector surveillance and selective control actions on transmission.Electronic supplementary materialThe online version of this article (10.1186/s13071-018-3069-0) contains supplementary material, which is available to authorized users.

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

“…To this end, we used the abundance of T. cruzi -infected vectors because it is more closely related to the prevalence and incidence of human infection with T. cruzi [30, 32, 33, 62] than other indices, but the main outcomes with other indices (domiciliary infestation and vector abundance) were qualitatively congruent. In adjacent rural communities the relative risk of human infection increased almost three times with every infected vector collected in the domicile [26]. Households with both greater social vulnerability and host availability had the highest abundance of infected vectors, corroborating the occurrence of between- and within-group variations in transmission risks.…”

“…The present study stems from a broader long-term research programme on the eco-epidemiology and control of Chagas disease in the municipality of Pampa del Indio, a highly endemic, mostly rural area of the Argentine Chaco where creoles and an indigenous people (Qom) live in structural poverty. In this region the seroprevalence of T. cruzi in indigenous peoples tends to exceed that of creoles [18–26]. Particularly in Pampa del Indio, house infestation rates with the main vector of Chagas disease, Triatoma infestans , were higher in Qom than in creole households [27–29] and dogs and cats from Qom households exhibited a higher T. cruzi- infection prevalence than those owned by creoles [30].…”

“…This study addresses the gap in our understanding of the combined effects of structural and intermediary SDHs on key vector indices closely associated with the risk of vector-borne transmission of T. cruzi [26, 32, 33]. We assessed socio-economic inequalities between creole and Qom households and within these groups in a well-defined rural section of Pampa del Indio in order to identify the most vulnerable groups by evaluating their demographic profiles, mobility and migration patterns, and access to health services.…”

Cultural perception of triatomine bugs and Chagas disease in Bolivia: a cross-sectional field study

“…The Gran Chaco has the highest prevalence of CD in the world [50]. Despite the presence of insecticide spraying campaigns in the last 15 years in this region, T. cruzi prevalence remains extraordinarily high, with close to universal infection among adults over 30 years-old [15, 49, 59, 60]. In this region T. infestans , T. sordida and T. guasayana have been shown to infest houses [61, 62] and sylvatic populations of these tree species have been described [56, 57, 63–65].…”

Chagas Disease in the United States: a Public Health Approach

“…Canine Chagas disease. Dogs are important in peridomestic cycles in Latin America, both as vector blood meal sources and T. cruzi infection reservoirs (85,86). In the hyperendemic Chaco region of Argentina, dogs have been shown to be highly infective to vectors and are thought to be a key reservoir sustaining transmission to humans (87).…”