Seroprevalence of Chagas disease in urban and rural indigenous populations of the south of Gran Chaco

ABSTRACT Background: In Latin America, Chagas disease is endemic, with a high prevalence in rural indigenous communities and an increasing prevalence in urban areas owing to migration from rural areas with active vector transmission. This study aimed to assess differences in the prevalence of Chagas disease in urban and rural moqoit communities, one of the main ethnic indigenous groups in the south of Gran Chaco. Methods: A seroprevalence study was conducted in six moqoit populations in the Santa Fe province, Argentina. The variables studied were serology results for Chagas disease, residents of urban or rural areas, age, and sex. Results: The results showed that 9.26% of the 702 volunteers evaluated and 18.32% of the 131women of childbearing potential were seropositive. According to the calculated prevalence ratio, the prevalence of Chagas disease in urban communities was6.41 (95% confidence inverval: 3.73-11.02) times higher than that in rural communities: 21.59% in urban communities vs. 3.37%in rural communities. Conclusions: The seroprevalence found in the moqoit community was higher than the estimated level for the general population of the same region, with a greater impact in urban areas than in rural areas. The urbanization of groups of people with poor socio-sanitary conditions in the second half of the 20th century could have caused this higher seroprevalence of Chagas disease.

Chagas pediátrico en áreas rurales de la provincia de Santa Fe / Pediatric chagas disease in rural areas of Santa Fe province

INTRODUCCIÓN: la enfermedad de Chagas continúa siendo un importante problema de salud pública en la ecoregión del Gran Chaco. El norte de la provincia de Santa Fe, correspondiente al Sur de dicha región, se encuentra bajo control entomológico. Dado que se trata de una infección crónica, la seroprevalencia de esta endemia enniños es un marcador de la situación actual de la infección. OBJETIVOS:Determinar la seroprevalencia de infección chagásica en poblaciónpediátrica del Chaco santafesino. MÉTODOS: Se realizó un estudiodescriptivo de corte transversal sobre seroprevalencia de infección chagásica en niños de 5 a 14 años de edad. Comprendió un área aproximada de 38 000 km2 de distritos rurales de los departamentos 9 de Julio y Vera en la provincia de Santa Fe, y se llevó a cabo entre noviembre de 2010 y abril de 2013. RESULTADOS: Se muestreó al71,5% de los niños de la región (3765/5266). La prevalencia fue de1,8% (67/3765). Varió de 5,5% a 0% entre los distintos distritos. De5 a 9 años, fue 1,2% (21/1769); de 10 a 14 años, 2,3% (46/1996).CONCLUSIONES: La seroprevalencia hallada fue inferior a la de otrosestudios en el Gran Chaco. Se observa una gran heterogeneidad en laprevalencia entre los distritos, aun entre los vecinos. La distribución noobedecería a factores climáticos, sino a factores sociales y a la influenciade la actividad antrópica en cada localidad.

INTRODUCTION: chagas disease remains a major public health problem in the Gran Chaco region. The north of Santa Fe province, being the south of this region, is under entomologicalsurveillance. Being a chronic infection, the seroprevalence of this endemic disease in children serves as a marker of the current status. OBJECTIVES: To determine the seroprevalence of Chagasdisease in the pediatric population of Chaco region in Santa Fe. METHODS: A descriptive, cross-sectional seroprevalence study on Chagas infection was conducted for children aged 5-14 years old. It considered an area of 38 000 km2 belonging to ruraldistricts of 9 de Julio and Vera departments in Santa Fe province,between November 2010 and April 2013. RESULTS: The sampling included 71.5% of the children in the region (3765/5266). There was a prevalence of 1.8% (67/3765), ranged from 5.5% to 0% among districts. For 5-9 years, it was 1.2% (21/1769); for 10-14 years, 2.3% (46/1996). CONCLUSIONS: The seroprevalence was lower than in other studies performed in the Gran Chaco. A large heterogeneity is observed in the prevalence among districts, even among neighboring districts. The distribution does not seem to be due to climatic factors, but to social factors and the influence of human activity in each location.

Diagnostic reliability of an immunochromatographic test for Chagas disease screening at a primary health care centre in a rural endemic area

Many patients with Chagas disease live in remote communities that lack both equipment and trained personnel to perform a diagnosis by conventional serology (CS). Thus, reliable tests suitable for use under difficult conditions are required. In this study, we evaluated the ability of personnel with and without laboratory skills to perform immunochromatographic (IC) tests to detect Chagas disease at a primary health care centre (PHCC). We examined whole blood samples from 241 patients and serum samples from 238 patients. Then, we calculated the percentage of overall agreement (POA) between the two groups of operators for the sensitivity (S), specificity (Sp) and positive (PPV) and negative (NPV) predictive values of IC tests compared to CS tests. We also evaluated the level of agreement between ELISAs and indirect haemagglutination (IHA) tests. The readings of the IC test results showed 100% agreement (POA = 1). The IC test on whole blood showed the following values: S = 87.3%; Sp = 98.8%; PPV = 96.9% and NPV = 95.9%. Additionally, the IC test on serum displayed the following results: S = 95.7%; Sp = 100%; PPV = 100% and NPV = 98.2%. Using whole blood, the agreement with ELISA was 96.3% and the agreement with IHA was 94.1%. Using serum, the agreement with ELISA was 97.8% and the agreement with IHA was 96.6%. The IC test performance with serum samples was excellent and demonstrated its usefulness in a PHCC with minimal equipment. If the IC test S value and NPV with whole blood are improved, then this test could also be used in areas lacking laboratories or specialised personnel.

Alta frecuencia de DQ8 en la población celiaca de la provincia del Chaco, Argentina / [High frequency of DQ8 in the celiac population of Chaco province, Argentina].

BACKGROUND: There is a strong association between celiac disease (CD) and certain genes of the major histocompatibility complex (HLA). The CD specifically related alleles are those coding for HLA-DQ2 heterodimer and to a lesser degree for HLA-DQ8. OBJECTVE. The aim of this study was to evaluate the frequency of HLA-DQB1* and HLA-DRB1* alleles, haplotypes, and genotypes in patients diagnosed with CD and in control population of Chaco, in order to establish its distribution and compare it with that observed in other populations. METHODS: A total of 139 samples from patients diagnosed with CD and 119 healthy controls were typed for HLA-DQ and HLA-DR, using PCR and reverse hybridization (INNO-LiPA or Dynal). RESULTS: Comparing patients with CD vs. controls, the DQBI*0201 (P = 0.0002), DQBJ*0202 (P = 0.0046), DQBI*0302 (P = 0. 0006), DRBl *03 (P = 0.0002), DRBl *04 (P = 0.0199) and DRB1 *07 (P = 0.0062) were significantly increased, while a decrease was observed in HLA-DQB1*0301 (P = 0.0006), HLA-DQBI*0303 (P = 0.0070), DQBI*0501 (P = 0.0023), DQB1*0604 (P = 0.0140) DRB1*01 (P = 0.0023), DRB1*08 (P = 0.0165), DRB1*09 (P = 0.0362) and DRB1*16 (P = 0.0228). Within DQB1* genotypes associated with EC, 65.4

of patients had the DQB1*02 in linkage disequilibrium with DRB1*03 or DRB1*07 (DQ2), and 43.2

presented genotype DQB1*0302 in linkage disequilibrium with DRB1*04 (DQ8). Both genotypes were shared by 15.2

of them. CONCLUSIONS: We point out the high frequency of DQ8 associated with CD. Although the DQ2 is still the most common, this finding could be attributed to the Amerindian influence in our population.

Infección chagásica en niños de cuatro distritos de riesgo de la provincia de Santa Fe / Chagas' infection in children of four districts at risk in Santa Fe province / Infecgáo chagasica em changas de quatro distritos de risco da provincia de Santa Fe

El objetivo del presente estudio fue investigar infección chagásica en niños de 1 a 15 años que residen en zona de riesgo vectorial o con antecedentes migratorios en la provincia de Santa Fe, estimar la/s vía/s más probable/s de infección y comparar la prevalencia con trabajos anteriores. Se realizó un estudio seroepidemiológico en escuelas de los Distritos Garabato, Fortín Olmos y Gato Colorado y la escuela de la comunidad Com Caia del Departamento La Capital. A los seropositivos se les realizó una encuesta para determinar las probables vías de infección. Se comparó la prevalencia actual con la del último control de cada distrito. No se hallaron seropositivos en Com Caia (prevalencia 0%, 0/130). La prevalencia en Garabato fue 1,0% (6/604), Fortín Olmos 1,9% (13/688), Gato Colorado 3,0% (12/399). Disminuyó respecto de los últimos estudios: Garabato 11,2% (año 2000), Fortín Olmos 14,6% (2004), Gato Colorado 6,3% (2006). La vía de infección que se sospecha más frecuente es la congènita, seguida por la vectorial. Se concluye que, a pesar de la disminución de la prevalencia, se deben continuar las acciones de control, principalmente por vías vectorial y congènita.

The aim of the present study was to diagnose Chagas infection in children 1 to 15 years of age living in a risk area or with migrant background in Santa Fe province, to estimate the most probable way of infection and to compare the prevalence with previous works. A seroepidemiological study was conducted in schools in the districts Garabato, Fortin Olmos and Gato Colorado and the community Com Caia in La Capital Department. An inquiry was conducted in positive patients to determine the most probable way of infection. The current prevalence was compared with the last control in each district. No seropositive were found in Com Caia (prevalence 0%, 0/130). In Garabato the prevalence was 1.0% (6/604), Fortin Olmos 1.9% (13/688), Gato Colorado 3.0% (12/399). It decreased in comparison with the latest study: Garabato 11.2% (2000), Fortin Olmos 14.6% (2004), Gato Colorado 6.3% (2006). The most suspected way of infection was congenital, followed by vector one. We conclude that, although the prevalence decreased, it must be continued mainly vector and congenital controls actions.

O objetivo deste estudo foi investigar a infecgáo chagásica em criangas de 1 a 15 anos que moram em zona de risco vetorial ou com antecedentes de migragáo na provincia de Santa Fe, estimar a/as via/s mais provável/veis de infecgáo e comparar prevalencia com trabalhos anteriores. Foi realizado um estudo soroepidemiológico em escolas nos distritos Garabato, Fortin Olmos e Gato Colorado e na escola da comunidade Com Caia no departamento La Capital. Os soropositivos foram entrevistados para determinar as prováveis vias da infecgáo. A prevalencia atual foi comparada com a do último controle em cada distrito. Náo foram encontrados soropositivos em Com Caia (prevalencia 0%, 0/130). A prevalencia em Garabato foi 1,0% (6/604), Fortin Olmos 1,9% (13/688), Gato Colorado 3,0% (12/399). Diminuiu a respeito dos últimos estudos: Garabato 11,2% (ano 2000), Fortin Olmos 14,6% (2004), Gato Colorado 6,3% (2006). A via de infecgáo que se suspeita como sendo a mais frequente é a congenita, seguida pela vetorial. Concluise que, apesar da diminuigáo da prevalencia, devem continuar sendo realizadas agoes de controle, principalmente por vias vetorial e congenita.