Rat-borne leptospirosis is an emerging zoonotic disease in urban slum settlements for which there are no adequate control measures. The challenge in elucidating risk factors and informing approaches ...for prevention is the complex and heterogeneous environment within slums, which vary at fine spatial scales and influence transmission of the bacterial agent.
We performed a prospective study of 2,003 slum residents in the city of Salvador, Brazil during a four-year period (2003-2007) and used a spatiotemporal modelling approach to delineate the dynamics of leptospiral transmission. Household interviews and Geographical Information System surveys were performed annually to evaluate risk exposures and environmental transmission sources. We completed annual serosurveys to ascertain leptospiral infection based on serological evidence. Among the 1,730 (86%) individuals who completed at least one year of follow-up, the infection rate was 35.4 (95% CI, 30.7-40.6) per 1,000 annual follow-up events. Male gender, illiteracy, and age were independently associated with infection risk. Environmental risk factors included rat infestation (OR 1.46, 95% CI, 1.00-2.16), contact with mud (OR 1.57, 95% CI 1.17-2.17) and lower household elevation (OR 0.92 per 10m increase in elevation, 95% CI 0.82-1.04). The spatial distribution of infection risk was highly heterogeneous and varied across small scales. Fixed effects in the spatiotemporal model accounted for the majority of the spatial variation in risk, but there was a significant residual component that was best explained by the spatial random effect. Although infection risk varied between years, the spatial distribution of risk associated with fixed and random effects did not vary temporally. Specific "hot-spots" consistently had higher transmission risk during study years.
The risk for leptospiral infection in urban slums is determined in large part by structural features, both social and environmental. Our findings indicate that topographic factors such as household elevation and inadequate drainage increase risk by promoting contact with mud and suggest that the soil-water interface serves as the environmental reservoir for spillover transmission. The use of a spatiotemporal approach allowed the identification of geographic outliers with unexplained risk patterns. This approach, in addition to guiding targeted community-based interventions and identifying new hypotheses, may have general applicability towards addressing environmentally-transmitted diseases that have emerged in complex urban slum settings.
Leptospirosis has become an urban health problem as slum settlements have expanded worldwide. Efforts to identify interventions for urban leptospirosis have been hampered by the lack of ...population-based information on Leptospira transmission determinants. The aim of the study was to estimate the prevalence of Leptospira infection and identify risk factors for infection in the urban slum setting.
We performed a community-based survey of 3,171 slum residents from Salvador, Brazil. Leptospira agglutinating antibodies were measured as a marker for prior infection. Poisson regression models evaluated the association between the presence of Leptospira antibodies and environmental attributes obtained from Geographical Information System surveys and indicators of socioeconomic status and exposures for individuals. Overall prevalence of Leptospira antibodies was 15.4% (95% confidence interval CI, 14.0-16.8). Households of subjects with Leptospira antibodies clustered in squatter areas at the bottom of valleys. The risk of acquiring Leptospira antibodies was associated with household environmental factors such as residence in flood-risk regions with open sewers (prevalence ratio PR 1.42, 95% CI 1.14-1.75) and proximity to accumulated refuse (1.43, 1.04-1.88), sighting rats (1.32, 1.10-1.58), and the presence of chickens (1.26, 1.05-1.51). Furthermore, low income and black race (1.25, 1.03-1.50) were independent risk factors. An increase of US$1 per day in per capita household income was associated with an 11% (95% CI 5%-18%) decrease in infection risk.
Deficiencies in the sanitation infrastructure where slum inhabitants reside were found to be environmental sources of Leptospira transmission. Even after controlling for environmental factors, differences in socioeconomic status contributed to the risk of Leptospira infection, indicating that effective prevention of leptospirosis may need to address the social factors that produce unequal health outcomes among slum residents, in addition to improving sanitation.
Leptospirosis has emerged as an urban health problem as slum settlements have rapidly spread worldwide and created conditions for rat-borne transmission. Prospective studies have not been performed ...to determine the disease burden, identify risk factors for infection and provide information needed to guide interventions in these marginalized communities.
We enrolled and followed a cohort of 2,003 residents from a slum community in the city of Salvador, Brazil. Baseline and one-year serosurveys were performed to identify primary and secondary Leptospira infections, defined as respectively, seroconversion and four-fold rise in microscopic agglutination titers. We used multinomial logistic regression models to evaluate risk exposures for acquiring primary and secondary infection. A total of 51 Leptospira infections were identified among 1,585 (79%) participants who completed the one-year follow-up protocol. The crude infection rate was 37.8 per 1,000 person-years. The secondary infection rate was 2.3 times higher than that of primary infection rate (71.7 and 31.1 infections per 1,000 person-years, respectively). Male gender (OR 2.88; 95% CI 1.40-5.91) and lower per capita household income (OR 0.54; 95% CI, 0.30-0.98 for an increase of $1 per person per day) were independent risk factors for primary infection. In contrast, the 15-34 year age group (OR 10.82, 95% CI 1.38-85.08), and proximity of residence to an open sewer (OR 0.95; 0.91-0.99 for an increase of 1 m distance) were significant risk factors for secondary infection.
This study found that slum residents had high risk (>3% per year) for acquiring a Leptospira infection. Re-infection is a frequent event and occurs in regions of slum settlements that are in proximity to open sewers. Effective prevention of leptospirosis will therefore require interventions that address the infrastructure deficiencies that contribute to repeated exposures among slum inhabitants.
We report the emergence of leptospirosis-associated severe pulmonary hemorrhagic syndrome (SPHS) in slum communities in Salvador, Brazil. Although active surveillance did not identify SPHS before ...2003, 47 cases were identified from 2003 through 2005; the case-fatality rate was 74%. By 2005, SPHS caused 55% of the deaths due to leptospirosis.
The Cerrado biome is a biodiversity hotspot with a rich biota, and intense anthropogenic pressures. Despite its importance, it is still poorly understood how insects occupy different spatial ...dimensions of the landscape.
We investigated how the beta diversity of plants influences the beta diversity of nymphalids at the regional‐scale (gallery forest vs. savannah) and local‐scale (transects). We expected greater beta‐diversity in nymphalid assemblages in gallery forests given the heterogeneity of plants and canopy structure.
We sampled nymphalids in each habitat monthly for 1 year and observed 3459 individuals from 62 species. Nymphalidae abundance was significantly higher in the understory than in the canopy. Specifically, only 18% of the individuals were captured in the canopy of gallery forests compared to 11% in savannah canopies. Species richness was higher in gallery forests (55 species) compared to savannahs (34 species).
Savannah transects were very similar in plant species composition and butterfly assemblages within the understory and canopy, whereas the species composition of plants and butterflies in gallery forests was highly heterogeneous which is consistent with the habitat heterogeneity hypothesis.
Gallery forests are spatially more complex, which probably results in higher niche availability that may contribute to reduce the community saturation and help to maintain greater beta diversity in these habitats.
The Cerrado biome has different habitat types ranging from grasslands to forests. In the present study, we have investigated how spatial heterogeneity influences the beta diversity of Nymphalidae species.
Nymphalidae species composition has changed from understory to canopy in gallery forests. Moreover, beta diversity of both plants and nymphalids were greater in gallery forest than in savannah transects.
Gallery forests are spatially more complex, which probably reflects in higher niche availability that may contribute to reduce community saturation, thus maintaining greater beta diversity in this habitat.
Chagas disease discovered more than a century ago remains an incurable disease. The objective of this work was to investigate the therapeutic potential of cardiomyocytes derived from mouse embryonic ...stem cells (CM-mESC) in a model of chronic Chagasic cardiomyopathy (CCC). Mouse embryonic stem cells (mESC) were characterized, transduced with luciferase, and submitted to cardiac differentiation. CM-mESC were labeled with superparamagnetic iron oxide particles. To induce CCC, mice were infected with Brazil strain trypomastigotes. At 150 days post-infection (dpi), infected animals were treated with CM-mESC or PBS. Cells were detected by magnetic resonance imaging (MRI) and bioluminescence. Cardiac function was evaluated by MRI and electrocardiogram at 150 and 196 dpi. CCC mice showed significant differences in MRI and ECG parameters compared to non-infected mice. However, no differences were observed in contractile and electrical parameters between cell and PBS injected groups, 45 days after cell transplantation. Cells were detected 24 h after transplantation by MRI. CM-mESC bioluminescence tracking demonstrated over 90% decrease in signal 8 days after treatment. Nevertheless, the Infected + CM-mESC group showed a significant reduction in the percentage of collagen fibers when compared to the Infected + PBS group. In conclusion, CM-mESC therapy was not effective in reversing cardiac functional changes induced by Chagas disease despite some improvement in myocardial fibrosis.
Induced pluripotent stem (iPS) cells are somatic cells that have been reprogrammed to a pluripotent state via the introduction of defined transcription factors. Although iPS is a potentially valuable ...resource for regenerative medicine and drug development, several issues regarding their pluripotency, differentiation propensity and potential for tumorigenesis remain to be elucidated. Analysis of cell surface glycans has arisen as an interesting tool for the characterization of iPS. An appropriate characterization of glycan surface molecules of human embryonic stem (hES) cells and iPS cells might generate crucial data to highlight their role in the acquisition and maintenance of pluripotency. In this study, we characterized the surface glycans of iPS generated from menstrual blood-derived mesenchymal cells (iPS-MBMC). We demonstrated that, upon spontaneous differentiation, iPS-MBMC present high amounts of terminal β-galactopyranoside residues, pointing to an important role of terminal-linked sialic acids in pluripotency maintenance. The removal of sialic acids by neuraminidase induces iPS-MBMC and hES cells differentiation, prompting an ectoderm commitment. Exposed β-galactopyranose residues might be recognized by carbohydrate-binding molecules found on the cell surface, which could modulate intercellular or intracellular interactions. Together, our results point for the first time to the involvement of the presence of terminal sialic acid in the maintenance of embryonic stem cell pluripotency and, therefore, the modulation of sialic acid biosynthesis emerges as a mechanism that may govern stem cell differentiation.
Leptospirosis is an important public health problem affecting vulnerable urban slum populations in developing country settings. However, the complex interaction of meteorological factors driving the ...temporal trends of leptospirosis remain incompletely understood.
From March 1996-March 2010, we investigated the association between the weekly incidence of leptospirosis and meteorological anomalies in the city of Salvador, Brazil by using a dynamic generalized linear model that accounted for time lags, overall trend, and seasonal variation. Our model showed an increase of leptospirosis cases associated with higher than expected rainfall, lower than expected temperature and higher than expected humidity. There was a lag of one-to-two weeks between weekly values for significant meteorological variables and leptospirosis incidence. Independent of the season, a weekly cumulative rainfall anomaly of 20 mm increased the risk of leptospirosis by 12% compared to a week following the expected seasonal pattern. Finally, over the 14-year study period, the annual incidence of leptospirosis decreased significantly by a factor of 2.7 (8.3 versus 3.0 per 100,000 people), independently of variations in climate.
Strategies to control leptospirosis should focus on avoiding contact with contaminated sources of Leptospira as well as on increasing awareness in the population and health professionals within the short time window after low-level or extreme high-level rainfall events. Increased leptospirosis incidence was restricted to one-to-two weeks after those events suggesting that infectious Leptospira survival may be limited to short time intervals.
The interaction between high fire frequency and long flooding seasons maintains open vegetation in floodplains, while low fire frequency and no flooding can lead to forest development. In the Kadiwéu ...Indigenous Territory (IT), in the ecotone between the Cerrado and the Pantanal biomes in Brazil, the diversified spatio-temporal patterns of fire activity affect the diversity of floral functional traits and plant phenological strategies. Given this scenario, we sampled tree and non-tree species abundance data in 156 plots subject to different flood levels and fire frequencies in the Kadiwéu IT. Based on flooding regimes and fire frequency data series from 2001 to 2021, we classify the sample sites as floodable or flood-free areas under high (annual or biennial burn), moderate (three-yearly burn), or low (burning at four-year intervals or more) fire frequency. We analyzed the effects of flooding and fire frequency on plant species richness, abundance, and beta diversity (β). In general, tree density did not affect non-tree species richness. The species richness on the patches with different fire frequency category was generally similar, especially regarding the tree species. However, the combined effect of fire and flooding shifted the species composition. Variability in fire frequency across the landscapes support β-diversity maintenance in ecotonal vegetation between tropical wetlands and savannas. Furthermore, the similarity in species composition between floodable and flood-free areas at the same fire frequency category is low due to differences in abundance and species replacement. As part of adaptive fire management, we suggest maintaining a heterogeneous mosaic of fire frequencies in the landscape.
•The megafires frequency has been increasing globally.•The biodiversity protection needs planning for adaptive fire management.•In tropical wetlands, the interaction between fire and flooding maintains open vegetation.•The heterogeneity of the landscape is linked to the great diversity of tree and non-tree species.•Different fire frequencies and their interaction with floods are related to beta diversity.
Streptococcus pneumoniae
causes invasive diseases of significant public health concern, such as meningitis. The culture of cerebrospinal fluid (CSF) samples, the standard technique for meningitis ...diagnoses, is not always positive. Consequently, meaningful information about the etiological agent is lost, which can compromise effective epidemiological surveillance and the improvement of immunization policies. This study aims to standardize a method to genotype pneumococcus in the CSF samples which could mitigate the absence of isolated strains, and also evaluate the prediction of this assay. We applied eight multiplex PCR (mPCR) assays to CSF samples paired with the Quellung reaction applied to the isolated strains. We also compared different master mix kits in the mPCR. Moreover, a retrospective study was conducted with CSF samples considered pneumococcus positive due to the presence of the
lytA
gene. Results showed that genotyping by the mPCR correlated 100% with the Quellung reaction, and genotyping was dependent on the master mix applied. In the retrospective study (2014–2020), 73.4% were successfully genotyped. The analyses of the receiver operating characteristic curve showed that the cycle threshold (Ct value) around 30 for the
lytA
gene had a 75% positive chance of successful genotyping, whereas with a Ct value > 35, the chance was 12.5%. Finally, we observed that genotype 19A was prevalent in the period (12%), information unknown until now due to the lack of isolated strains. Therefore, the mPCR of CSF samples can efficiently predict
S. pneumoniae
serotypes, especially in the absence of isolated strains, which can be a great tool for pneumococcal serotype surveillance.
PDF
