Renato M. Oliveira

Spatial point analysis based on dengue surveys at household level in central Brazil

BackgroundDengue virus (DENV) affects nonimunne human populations in tropical and subtropical regions. In the Americas, dengue has drastically increased in the last two decades and Brazil is considered one of the most affected countries. The high frequency of asymptomatic infection makes difficult to estimate prevalence of infection using registered cases and to locate high risk intra-urban area at population level. The goal of this spatial point analysis was to identify potential high-risk intra-urban areas of dengue, using data collected at household level from surveys.MethodsTwo household surveys took place in the city of Goiania (~1.1 million population), Central Brazil in the year 2001 and 2002. First survey screened 1,586 asymptomatic individuals older than 5 years of age. Second survey 2,906 asymptomatic volunteers, same age-groups, were selected by multistage sampling (census tracts; blocks; households) using available digital maps. Sera from participants were tested by dengue virus-specific IgM/IgG by EIA. A Generalized Additive Model (GAM) was used to detect the spatial varying risk over the region. Initially without any fixed covariates, to depict the overall risk map, followed by a model including the main covariates and the year, where the resulting maps show the risk associated with living place, controlled for the individual risk factors. This method has the advantage to generate smoothed risk factors maps, adjusted by socio-demographic covariates.ResultsThe prevalence of antibody against dengue infection was 37.3% (95%CI [35.5–39.1]) in the year 2002; 7.8% increase in one-year interval. The spatial variation in risk of dengue infection significantly changed when comparing 2001 with 2002, (ORadjusted = 1.35; p < 0.001), while controlling for potential confounders using GAM model. Also increasing age and low education levels were associated with dengue infection.ConclusionThis study showed spatial heterogeneity in the risk areas of dengue when using a spatial multivariate approach in a short time interval. Data from household surveys pointed out that low prevalence areas in 2001 surveys shifted to high-risk area in consecutive year. This mapping of dengue risks should give insights for control interventions in urban areas.

Molecular epidemiology and risk factors for nasal carriage of Staphylococcus aureus and methicillin-resistant S. aureus in infants attending day care centers in Brazil.

ABSTRACT Investigations regarding Staphylococcus aureus carriage among Brazilian children are scarce. We evaluated the determinants of S. aureus and methicillin-resistant S. aureus (MRSA) nasal carriage in infants attending day care centers (DCCs) and the molecular features of the MRSA strains. A total of 1,192 children aged 2 months to 5 years attending 62 DCCs were screened for S. aureus and MRSA nasal carriage. MRSA isolates were characterized by pulsed-field gel electrophoresis, multilocus sequence typing, spa typing, staphylococcal cassette chromosome (SCC) mec typing and the presence of the Panton-Valentine leukocidin gene. Logistic regression was performed to determine risk factors associated with S. aureus and MRSA colonization. S. aureus and MRSA carriage were detected in 371 (31.1%) and 14 (1.2%) children, respectively. Variables found to be independently associated with an increased risk for S. aureus carriage included being older than 24 months (odds ratio [OR], 1.8; 95% confidence interval [CI], 1.3 to 2.6) and previous DCC attendance (OR, 1.5; 95% CI, 1.0 to 2.2). Having a mother with a high level of education was a protective factor for nasal colonization (OR, 0.4; 95% CI, 0.2 to 0.8). Moreover, we observed that more children carrying MRSA had younger siblings than children not colonized by MRSA. Among the 14 MRSA strains, three SCCmec types (IIIA, IV, and V) were detected, together with a multidrug-resistant dominant MRSA lineage sharing 82.7% genetic similarity with the Brazilian clone (ST239-MRSA-IIIA; ST indicates the sequence type determined by multilocus sequence typing). Although SCCmec type V was recovered from one healthy child who had been exposed to known risk factors for hospital-associated MRSA, its genetic background was compatible with community-related MRSA. Our data suggest that DCC attendees could be contributing to MRSA cross-transmission between health care and community settings.

Population-based surveillance of pediatric pneumonia: use of spatial analysis in an urban area of Central Brazil

This study examined the spatial distribution of childhood community-acquired pneumonia detected through prospective surveillance in Goiânia, Brazil. Three spatial analysis techniques were applied to detect intra-urban geographic aggregation of pneumonia cases: Kernel method, nearest neighbor hierarchical technique, and spatial scan statistic. A total of 724 pneumonia cases confirmed by chest radiography were identified from May 2000 to August 2001. All cases were geocoded on a digital map. The annual pneumonia risk rate was estimated at 566 cases/100,000 children. Analysis using traditional descriptive epidemiology showed a mosaic distribution of pneumonia rates, while GIS methodologies showed a non-random pattern with hot spots of pneumonia. Cluster analysis by spatial scan statistic identified two high-risk areas for pneumonia occurrence, including one most likely cluster (RR = 2.1; p < 0.01) and one secondary cluster (RR = 1.3; p = 0.01). The data used for the study are in line with recent WHO-led efforts to improve and standardize pediatric pneumonia surveillance in developing countries and show how GIS and spatial analysis can be applied to discriminate target areas of pneumonia for public heath intervention.

Computer-aided diagnosis in chest radiography for detection of childhood pneumonia.

OBJECTIVES This article presents a novel approach based on computer-aided diagnostic (CAD) scheme and wavelet transforms to aid pneumonia diagnosis in children, using chest radiograph images. The prototype system, named Pneumo-CAD, was designed to classify images into presence (PP) or absence of pneumonia (PA). MATERIALS AND METHODS The knowledge database for the Pneumo-CAD comprised chest images confirmed as PP or PA by two radiologists trained to interpret chest radiographs according to the WHO guidelines for the diagnosis of pneumonia in children. The performance of the Pneumo-CAD was evaluated by a subset of images randomly selected from the knowledge database. The retrieval of similar images was made by feature extraction using wavelets transform coefficients of the image. The energy of the wavelet coefficients was used to compose the feature vector in order to support the computational classification of images as PP or PA. Methodology I worked with a rank-weighted 15-nearest-neighbour scheme, while methodology II employed a distance-dependent weighting for image classification. The performance of the prototype system was assessed by the ROC curve. RESULTS Overall, the Pneumo-CAD using the Haar wavelet presented the best accuracy in discriminating PP from PA for both, methodology I (AUC=0.97) and methodology II (AUC=0.94), reaching sensitivity of 100% and specificity of 80% and 90%, respectively. CONCLUSION Pneumo-CAD could represent a complementary tool to screen children with clinical suspicion of pneumonia, and so to contribute to gather information on the burden of-pneumonia estimates in order to help guide health policies toward preventive interventions.

Haemophilus influenzae Resistance in Latin America: Systematic Review of Surveillance Data

Haemophilus influenzae is a relevant cause of morbidity and mortality among children under 5 years of age in the developing world. In Latin America, H. influenzae type b (Hib) conjugate vaccine and surveillance of H. influenzae antimicrobial susceptibility have been implemented in recent years. We have undertaken a systematic review and a pooled analysis on H. influenzae antimicrobial resistance, including reports of 15 Latin America countries over a 10-year period (1990-2000). We have found that 450 (21.4%) of 2,100 invasive isolates were beta-lactamase producers compared to 145 (14.5%) of 998 isolates of noninvasive isolates (p < 0.05). Ampicillin resistance was detected among 783 (21.9%) of 3,577 invasive isolates compared to 111 (17.2%) of 646 noninvasive strains (p < 0.05). In contrast, 568 (41.9%) of 1,355 noninvasive strains were trimethoprim-sulfamethoxazole (TMP-SMX) resistance against 241 (26.9%) of 897 invasive ones (p < 0.05). Therefore, TMP-SMX resistance was more common in nonsterile fluids than in sterile fluids. Over time, rates of beta-lactamase-producing strains were stable in Brazil and Mexico, whereas rates of TMP-SMX resistance were increasing in Brazil. It is predictable that following the Hib immunization, Latin America countries will be faced with increased nontypeable H. influenzae infection. Although standing by the nontypeable H. influenzae vaccine, in this novel epidemiological scenario of post-Hib vaccination in Latin America settings there is a need to improve H. influenzae resistance monitoring to guide clinicians to choose efficacious antimicrobial therapy.

Seroprevalence of Trypanosoma cruzi infection among unskilled urban workers in central Brazil

A cross-sectional survey of the prevalence of Trypanosoma cruzi infection was carried out among urban unskilled workers in an endemic area in central Brazil as part of a study to assess the health impact of Chagas disease and to identify risk factors for the evolution of cardiopathy. Blood samples from 5425 male and female workers, aged 15-61 years, from 5 public institutions, were screened by indirect immunofluorescence, enzyme-linked immunosorbent assay and indirect haemagglutination for antibodies to T. cruzi. Seroprevalence varied from 8.8% to 15.6% in the different institutions and increase with age up to 55 years. More stable jobs were associated with lower seroprevalence. Migrants from São Paulo and Minas Gerais presented higher prevalence and a relative risk associated with seropositivity in relation to workers from Goiás of 2.2 (95% confidence limits, 1.4-3.5) and 1.9 (1.6-2.3), respectively.

A randomized clinical trial with high dose of chloroquine for treatment of Plasmodium falciparum malaria in Brazil

This clinical trial compared parasitological efficacy, levels of in vivo resistance and side effects of oral chloroquine 25 mg/Kg and 50 mg/Kg in 3 days treatment in Plasmodium falciparum malaria with an extended followed-up of 30 days. The study enrolled 58 patients in the 25 mg/Kg group and 66 in the 50 mg/Kg group. All eligible subjects were over 14 years of age and came from Amazon Basin and Central Brazil during the period of August 1989 to April 1991. The cure rate in the 50 mg/Kg group was 89.4% on day 7 and 71.2% on day 14 compared to 44.8% and 24.1% in the 25 mg/Kg group. 74.1% of the patients in the 25 mg/Kg group and 48.4% of the patients in the 50 mg/Kg group had detectable parasitaemia at the day 30. However, there was a decrease of the geometric mean parasite density in both groups specially in the 50 mg/Kg group. There was 24.1% of RIII and 13.8% of RII in the 25 mg/Kg group. Side effects were found to be minimum in both groups. The present data support that there was a high level resistance to chloroquine in both groups, and the high dose regimen only delayed the development of resistance and its administration should not be recommended as first choice in malaria P. falciparum therapy in Brazil.

Exercise electrocardiogram tests in manual workers with and without antibodies to Trypanosoma cruzi: a population-based study.

Blood pressure, heart rate and electrocardiographic responses to exercise were compared in a group of 125 subjects with antibodies to Trypanosoma cruzi and in 153 seronegative subjects, randomly selected from persons with no evidence of heart disease in a resting electrocardiogram during a cross-sectional survey among apparently healthy manual workers. The mean heart rates and diastolic and systolic blood pressures of those in each group did not differ statistically at different phases of the exercise test and there was no evidence of a difference in physical fitness between those in the 2 groups. An abnormal test was recorded in 26.2% of seropositive, and in 16.1% of seronegative, subjects (odds ratio adjusted for age, sex and body mass index [OR] = 2.0, 95% confidence interval [95% CI] = 1.1-3.8). No significant difference was observed between the 2 groups in the occurrence of hypertensive response to exercise (6.4% among seropositives and 5.9% among seronegatives), ST depression greater than 1 mm (0.8% and 2.0%), supraventricular premature beats (4.8% and 2.6%) or conduction defects (0.8% and 1.3%). Complex ventricular premature beats were recorded more often in seropositive subjects (12.8% and 3.9%; OR = 3.7, 95% CI = 1.4-9.8, P less than 0.01). The risk of an abnormal test increased with age in both groups. A history of cardiovascular symptoms, gender and body mass was not associated with the risk of an abnormal response in the test. The findings suggest that exercise testing might be a routine procedure when subjects with antibodies to T. cruzi are being assessed for participation in potentially high risk activities, such as heavy manual work.

EFFICACY OF BENZNIDAZOL TREATMENT IN TRYPANOSOMA CRUZI INFECTED CHILDREN: A RANDOMIZED DOUBLE BLIND CLINICAL TRIAL CONDUCTED IN CENTRAL BRAZIL

EFFICACY OF BENZNIDAZOL TREATMENT IN TRYPANOSOMA CRUZI INFECTED CHILDREN: A RANDOMIZED DOUBLE BLIND CLINICAL TRIAL CONDUCTED IN CENTRAL BRAZIL