Introduction

Chagas disease (CD) is a neglected, anthropozoonosis caused by the protozoan parasite Trypanosoma cruzi, first described in the early 20th century [1]. Despite major advances in vector control and blood-borne transmission screening, CD remains a substantial public health challenge in Latin America [2] and disproportionately affects socially and economically vulnerable populations [3]. In Brazil, the persistence of CD reflects not only historical exposure but also structural barriers to timely diagnosis, access to care, and longitudinal clinical follow-up, particularly in rural and resource-limited settings [4–6]. These barriers contribute to underdiagnosis, delayed treatment, and the progression to advanced cardiac and gastrointestinal forms of the disease.

Transmission of T. cruzi occurs predominantly through hematophagous triatomine insects (kissing bugs); however, congenital, oral, transfusion- and transplant-related, and laboratory-acquired routes continue to play a relevant epidemiological role [7]. Independent of the route of infection, CD typically begins with an acute phase that is often asymptomatic or oligosymptomatic. In untreated individuals, the infection may progress to a chronic phase marked by low or intermittent parasitemia and progressive tissue damage. Although 60–70% of chronically infected individuals remain in the indeterminate form, approximately one-third develop clinically significant manifestations, most commonly Chagas cardiomyopathy and, less commonly, digestive involvement such as megaesophagus or megacolon [8]. Chagas cardiomyopathy arises from chronic myocardial inflammation, progressive fibrosis, autonomic dysfunction, and microvascular disease driven by persistent parasite-induced and immune-mediated injury, leading to conduction abnormalities, ventricular dysfunction, arrhythmias, and heart failure. Digestive manifestations arise from progressive destruction of the enteric nervous system caused by chronic T. cruzi infection, leading to severe motility disorders of the esophagus and colon. Both forms of chronic CD lead to substantial morbidity, reduced quality of life, and increased mortality, underscoring the need for early diagnosis and continuous clinical monitoring [9–11].

In Brazil, the elimination of Triatoma infestans as a domiciliary vector in 2006 represented a milestone in vector control [12]. Nevertheless, native triatomine species capable of sustaining domestic and peridomestic transmission cycles persist in several regions, including the state of Bahia. Tremedal and Novo Horizonte remain historically recognized endemic municipalities where residual transmission and the cumulative burden of chronic CD continue to occur. Although T. infestans has not been detected in these municipalities since 2011 and 2015, respectively, entomological surveys have documented the continued capture of secondary triatomine species in both settings. In Tremedal, species identified include Triatoma sordida, T. pseudomaculata, Panstrongylus geniculatus, and P. lutzi, with T. cruzi infection confirmed in specimens of T. sordida and P. geniculatus [13]. In Novo Horizonte, T. sordida, T. lenti, T. pseudomaculata, T. melanocephala, T. lutzi, P. diasi, and P. geniculatus have been captured, with T. cruzi infection confirmed in a specimen of T. pseudomaculata [14]. The recurrent capture of infected secondary species indicates an ongoing risk of vectorial transmission in both municipalities.

These municipalities constitute key sites of the Oxente Chagas Bahia Project [15], an initiative designed to address critical gaps in CD control through strengthened surveillance, validation of rapid diagnostic tests under real-world conditions, and expanded access to clinical evaluation and treatment within the Brazilian Unified Health System (SUS). The integration of epidemiological, clinical, and health-system components within this framework enables a reassessment of the baseline status of CD in endemic municipalities prior to large-scale interventions. This baseline is necessary to accurately interpret the effects of diagnostic innovations and to identify structural and clinical limitations in disease management.

This retrospective analysis describes clinical management of CD in Tremedal and Novo Horizonte between 2019 and 2023, prior to full implementation of the Oxente Chagas Bahia Project. Specifically, we review sociodemographic features of the municipalities, access to CD diagnosis, CD testing turnaround time, and the spectrum of chronic cardiac and gastrointestinal disease in individuals with confirmed CD in these regions. This pre-intervention characterization seeks to guide targeted clinical strategies, strengthen surveillance, and support evidence-based public health decision-making in endemic settings.

Methods

Study area

The study took place in the municipalities of Tremedal and Novo Horizonte, in the state of Bahia, northeastern Brazil (Fig 1). Tremedal (14°58′21″S, 41°24′52″W) lies approximately 590 km from Salvador and has an estimated population of 15,996 inhabitants; it ranks among the lowest Brazilian municipalities for per capita income, with an economy based on subsistence agriculture in a semi-arid caatinga setting, and delivers primary care through three urban and seven rural health units. Novo Horizonte (12°48′28″S, 42°10′04″W), has an estimated population of 12,522 inhabitants and an economy based on rutile quartz extraction and garlic cultivation, and delivers primary care through two urban and four rural health units.

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Fig 1. Map of Bahia showing the study area.

A public domain digital map was obtained from the IBGE (https://www.ibge.gov.br/geociencias/organizacao-do-territorio/malhas-territoriais/15774-malhas.html) cartographic database in shapefile format (.shp) and then reformatted and analyzed using QGIS version 3.22.16 (Geographic Information System, Open-Source Geospatial Foundation Project: http://qgis.org). IBGE: Brazilian Institute of Geography and Statistics.

https://doi.org/10.1371/journal.pntd.0014569.g001

Results

Seropositivity and confirmed cases

Among the 472 serological tests performed, 14 individuals (3.0%) tested positive for CD, all from Tremedal. These cases originated from two healthcare units: São Felipe and Manoel Inácio Pereira. One case was excluded from further analysis due to incomplete clinical information, yielding a final sample of 13 confirmed chronic CD cases (Table 1). The median age of confirmed cases was 52 years (IQR 49–67.5), with a predominance of female individuals (61.5%; n = 8).

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Table 1. Demographic characteristics of confirmed CD cases.

https://doi.org/10.1371/journal.pntd.0014569.t001

Clinical evaluation and disease classification

All 13 individuals underwent ECG assessment. Transthoracic ECHO reports were available for 10 of the 13 individuals; ECHO was not documented in the electronic medical records for remaining three (Table 2). When performed, ECHO was conducted without contrast agents. One individual underwent colonoscopy, and chest radiography results were unavailable for all cases. ECG abnormalities were identified in eight individuals and included right bundle branch block (RBBB), sinus bradycardia, QRS axis deviation, prolonged QT interval, second-degree atrioventricular block, ectopic rhythm, and ventricular repolarization changes. ECHO abnormalities were identified in one individual and consisted of mild aortic, mitral, and tricuspid valve insufficiency occurring concurrently. Other ECHO findings typically associated with Chagas cardiomyopathy, such as apical aneurysm, regional wall motion abnormalities, intracardiac thrombus, or diastolic dysfunction, were not reported.

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Table 2. Narrative clinical profiles of chronic Chagas disease cases from Tremedal, Bahia, Brazil.

https://doi.org/10.1371/journal.pntd.0014569.t002

Clinical classification identified the indeterminate form in eight individuals (61.5%), the cardiac form in two (15.4%), the mixed form in two (15.4%), and the digestive form in one (7.7%). Among the eight individuals classified with the indeterminate form, two had a normal or nonspecific ECG without an available ECHO report; in these cases, subclinical cardiac involvement could not be entirely excluded, and they were retained in the indeterminate group with this caveat (Table 2). Application of standardized ECG criteria for chronic Chagas cardiomyopathy reclassified several conduction and repolarization findings as nonspecific rather than typical of Chagas cardiomyopathy, supporting the predominance of the indeterminate form.

Discussion

This retrospective analysis reveals marked disparities in the detection and clinical management of Chagas disease between the municipalities of Tremedal and Novo Horizonte, Bahia, during the period preceding the full implementation of the Oxente Chagas Bahia Project [15]. Although both municipalities are historically endemic, serological testing expanded substantially only in Tremedal, whereas it remained minimal in Novo Horizonte until 2023. These findings illustrate how local health system organization, professional engagement, and programmatic prioritization strongly influence access to diagnosis in endemic settings.

Among the 13 confirmed cases analyzed, the clinical spectrum was broad, encompassing cardiac, digestive, mixed and indeterminate forms, consistent with long-standing infection and delayed diagnosis. Importantly, the identification of a pediatric case (aged 10–19 years) with confirmed CD raises concerns for ongoing transmission, either through residual vectorial activity or congenital infection, and highlights persistent surveillance gaps that extend beyond the adult population. Because maternal infection status was not available in the records, congenital transmission could not be assessed.

In Tremedal, the concentration of 39.0% of serological tests among three family physicians suggests that Chagas disease screening was largely driven by a small group of particularly engaged clinicians, consistent with the concept of local “Chagas champions” within primary care. These physicians worked within family health strategy teams and had no additional specialization, indicating that their contribution likely reflected individual clinical awareness and local leadership rather than specialist-driven care. Their heightened engagement in CD screening predated the formal activities of the Oxente Chagas Bahia Project, which began influencing testing practices in Tremedal only from 2022 onward. In contrast, testing in Novo Horizonte relied on a single professional from one urban health unit, despite both national guidelines [16] and a 2022 joint technical note from the Bahia State Health Secretariat explicitly recommending routine Chagas disease screening, including during prenatal care, in endemic municipalities [20]. This marked asymmetry suggests inconsistency implementation of guideline-directed care across the primary healthcare network and underscores the importance of continuous professional training, locally empowered clinical leadership, and individual accountability within primary care teams to ensure effective Cd detection in endemic regions.

Turnaround time for serological testing also differed between municipalities, with a median of 14 days in Tremedal and 10 days in Novo Horizonte. This difference likely reflects variations in laboratory processing capacity, transport logistics, and testing frequency. Samples from Novo Horizonte are processed at the Central Public Health Laboratory of Bahia (LACEN-BA) in Salvador, whereas samples from Tremedal are sent to a regional LACEN branch in Vitória da Conquista, which operates with lower testing volumes and does not perform daily analyses. Although no direct clinical consequences of delayed results were documented, prolonged turnaround times may discourage test requests, delay confirmatory diagnosis, hinder timely clinical staging, and make it more difficult to contact individuals after testing, particularly in rural settings with limited follow-up infrastructure.

Clinical characterization of confirmed cases revealed a predominance of the indeterminate form, consistent with reports from highly endemic rural areas, where the indeterminate form is the most frequent clinical presentation of chronic CD [21,22]. Among individuals with cardiac involvement, ECG abnormalities such as second-degree atrioventricular block, left anterior fascicular block, bradyarrhythmia, and ventricular repolarization changes represent classical findings associated with Chagas cardiomyopathy [23]. In the present series, second-degree atrioventricular block, right bundle branch block associated with left anterior fascicular block, and primary ventricular repolarization changes were regarded as typical of chronic Chagas cardiomyopathy, whereas isolated right bundle branch block, sinus bradycardia, QT prolongation, QRS axis deviation, left atrial enlargement, and ectopic rhythm were considered nonspecific. Specific ECG abnormalities, including atrial fibrillation, electrically inactive areas, and non-sustained ventricular tachycardia, carry adverse prognostic implications, as they have been associated with ventricular dysfunction, heart failure, and sudden cardiac death in chronic Chagas cardiomyopathy [17]. Valvular insufficiency, reported in one seropositive individual, is not a typical manifestation of Chagas cardiomyopathy; in the absence of left ventricular ejection fraction data, it cannot be attributed to Chagas-related myocardial dysfunction. The cardiac manifestations observed are consistent with patterns described in both Brazilian [24,25] and international cohorts [26]. The relative frequency of digestive forms, by contrast, varies across geographic and epidemiological contexts [27].

In the present cohort, digestive involvement was notably frequent. Three of the 13 confirmed cases (23.1%) presented with megaesophagus or megacolon, a proportion higher than the 10–15% typically reported in endemic cohorts; megavisceral disease, however, spans a spectrum of severity, and not all affected individuals progress to advanced or surgically managed forms [27–29]. One individual underwent Duhamel surgery for Chagasic megacolon, while two others presented with advanced esophageal disease, including megaesophagus with a history of surgical intervention and persistent dyspepsia, and megaesophagus secondary to achalasia. These conditions carry profound consequences for patients’ daily lives. Progressive dysphagia and chronic constipation impair nutritional intake and restrict physical capacity, often limiting individuals’ ability to perform occupational tasks and sustain income-generating activities, a particularly significant burden in the rural, low-income communities where these patients reside. The need for surgical intervention further compounds this impact through prolonged recovery, healthcare costs, and potential loss of productive capacity.

Despite the identification of individuals eligible for etiological treatment according to the Brazilian Clinical Protocol and Therapeutic Guidelines [16], documentation of benznidazole use was limited to two cases. Both treated individuals were older than 50 years. One presented a mixed cardiac–digestive form with established cardiac involvement; the other had only an unspecified arrhythmia and was classified as the indeterminate form. The treatment of an individual with established cardiac involvement is noteworthy in light of the BENEFIT trial, which demonstrated that benznidazole did not significantly reduce cardiac clinical deterioration in patients with established Chagas cardiomyopathy [30], suggesting that the individuals treated in this cohort may not have been the optimal candidates for etiological therapy. In addition, the Brazilian PCDT explicitly states that etiological treatment is not recommended as routine practice for individuals over 50 years of age, given the greater uncertainty of benefit in this group [16]. The absence of documented adverse drug reactions in these two individuals is noteworthy; however, given the retrospective nature of the study and the limitations of routine clinical records, this finding cannot be interpreted as evidence of tolerability. Conversely, several younger individuals, who would be more likely to benefit from treatment in terms of parasitological response and prevention of disease progression, did not receive benznidazole. Notably, the pediatric patient (aged 10–19 years)had no documented treatment, and available records suggest that the family relocated from the municipality before treatment could be initiated, precluding follow-up and care. These findings highlight an important gap in guideline-concordant care and have direct implications for physician education and the design of future screening interventions in endemic settings.

Detection of CD in a child further emphasizes the urgency of strengthening integrated surveillance strategies. Pediatric infection indicates either recent transmission or failure to identify congenital cases. Despite advances in vector control, the continued capture of native triatomine species, including T. cruzi-infected specimens, in both municipalities suggests that vectorial transmission risk has not been fully eliminated [13,14]. However, as congenital transmission could not be excluded in this case, the source of infection in the pediatric patient remains uncertain. Intensive vector surveillance, systematic household investigation, maternal screening, and community engagement remain essential to prevent new infections and interrupt transmission cycles [31,32].

The age distribution of confirmed cases in this cohort may partly reflect the impact of vector control programs in the region, but it should also be interpreted in light of healthcare-seeking and testing bias. The absence of confirmed cases in the 20–39-year age group is consistent with the progressive reduction in domiciliary triatomine burden that occurred during the formative years of individuals now in this age range, as intensified control efforts preceded the last detection of Triatoma infestans in Tremedal and Novo Horizonte in 2011 and 2015, respectively. However, adults aged 20–39 years may also be underrepresented in routine primary care-based testing because they are often generally healthy, economically active, and less likely to seek medical care, except in contexts such as prenatal care. Therefore, the absence of confirmed cases in this age group should not be interpreted as definitive evidence of absence of infection. In contrast, the predominance of confirmed cases among individuals aged 40 years and older likely reflects cumulative exposure acquired prior to the consolidation of vector control. Together, these observations underscore the importance of maintaining active vector surveillance and systematic screening across all age groups in endemic settings.

The case of an individual aged 70–79 whose cause of death could not be determined illustrates broader structural deficiencies in rural healthcare systems, including limited diagnostic capacity, poor integration of clinical information, and restricted access to specialized care, all of which compromise comprehensive management of Chagas disease in endemic settings. Early diagnosis and etiological treatment remain critical to prevent progression to advanced chronic forms of CD, in which symptoms become more severe, cumulative, and less predictable. Rapid diagnostic tests represent essential tools to expand early screening and improve timely access to care.

This study presents limitations inherent to its retrospective design. Because testing was initiated at the discretion of individual clinicians rather than through systematic population-based screening, the 3.0% seropositivity rate reflects outcomes among those who sought or were offered testing and should not be interpreted as a prevalence estimate. In addition, diagnostic procedures and specialist evaluations performed outside the municipalities frequently lacked documentation in local electronic health systems. This limitation may have led to an underestimate of disease severity, as complications and specialist findings from referral centers were not necessarily captured. Conversely, management gaps may have been overestimated, as some referrals, follow-up, or treatment may have occurred outside the local public primary care records and therefore remained undocumented. Clinical classification was further constrained by the incomplete availability of echocardiographic data: ECHO reports were not documented for three of the 13 individuals, so subclinical cardiac involvement could not be fully excluded in the two individuals with a normal or nonspecific ECG who were classified with the indeterminate form. Moreover, the ECHO examinations that were available had been performed without contrast, which reduces sensitivity for detecting abnormalities specifically associated with Chagas cardiomyopathy, such as apical aneurysm and intracardiac thrombus. Nonetheless, these limitations reflect real-world structural deficiencies in rural health networks.

This analysis documented a persistent burden of chronic CD in Tremedal prior to the implementation of the Oxente Chagas Bahia Project, with a predominance of the indeterminate form alongside cardiac and severe digestive manifestations and critical gaps in treatment uptake. In Novo Horizonte, the absence of confirmed cases most likely reflects limited screening rather than true absence of disease. The identification of a pediatric case (aged 10–19 years), together with the age distribution of confirmed cases, suggests that transmission may be ongoing and reinforces the need for active vector surveillance and screening across all age groups. These findings establish a real-world baseline for evaluating the impact of the Oxente Chagas Bahia Project and identify actionable gaps in screening, diagnosis, and guideline-concordant management in endemic settings.

Acknowledgments

We thank the health officials and health personnel of the municipalities of Tremedal and Novo Horizonte for their assistance in accessing the GAL and PEC systems.