Spatiotemporal Determinants of Urban Leptospirosis Transmission: Four-Year Prospective Cohort Study of Slum Residents in Brazil

Detection of pathogenic Leptospira spp. in unconventional pets

Leptospirosis is a disease caused by Leptospira spp. responsible for considerable impacts on the public and animal health. In the past two decades, non-domesticated species of pets (unconventional pets) have become popular. However, the role of these unconventional pets on maintaining diseases still unclear. Therefore, the objective of this study was to survey the presence of Leptospira spp. DNA in unconventional pets. Samples of kidney tissues from 29 animals belonging to the Mammalia class (including Orders Carnivora, Lagomorpha and Rodentia) were analyzed for the presence of the gene lipL32. As a result, DNA of pathogenic Leptospira spp. from specie L. interrogans was detected in four (13,80%) of the analyzed samples: three from Oryctolagus cuniculus and one from Mesocricetus auratus. This study highlights the importance of epidemiological surveillance of leptospirosis, as it identified in species of unconventional pets, that may possibly act as reservoirs of Leptospira spp.

Palma F, Santana R, Nery N, C. Quintero-Vélez J, Zeppelini CG, Almeida do Sacramento G, Cruz JS, Lustosa R, Santana Ferreira I, Carvalho-Pereira T, Diggle PJ, Wunder EA, I. Ko A, Alzate Lopez Y, Begon M, G. Reis M, Costa F. Factors associated with differential seropositivity to Leptospira interrogans and Leptospira kirschneri in a high transmission urban setting for leptospirosis in Brazil

BACKGROUND

Leptospirosis is a zoonosis caused by pathogenic species of bacteria belonging to the genus Leptospira. Most studies infer the epidemiological patterns of a single serogroup or aggregate all serogroups to estimate overall seropositivity, thus not exploring the risks of exposure to distinct serogroups. The present study aims to delineate the demographic, socioeconomic and environmental factors associated with seropositivity of Leptospira serogroup Icterohaemorraghiae and serogroup Cynopteri in an urban high transmission setting for leptospirosis in Brazil.

METHODS/PRINCIPAL FINDINGS

We performed a cross-sectional serological study in five informal urban communities in the city of Salvador, Brazil. During the years 2018, 2020 2021, we recruited 2.808 residents and collected blood samples for serological analysis using microagglutination assays. We used a fixed-effect multinomial logistic regression model to identify risk factors associated with seropositivity for each serogroup. Seropositivity to Cynopteri increased with each year of age (OR 1.03; 95% CI 1.01-1.06) and was higher in those living in houses with unplastered walls (exposed brick) (OR 1.68; 95% CI 1.09-2.59) and where cats were present near the household (OR 2.00; 95% CI 1.03-3.88). Seropositivity to Icterohaemorrhagiae also increased with each year of age (OR 1.02; 95% CI 1.01-1.03) and was higher in males (OR 1.51; 95% CI 1.09-2.10), in those with work-related exposures (OR 1.71; 95% CI 1.10-2.66) or who had contact with sewage (OR 1.42; 95% CI 1.00-2.03). Spatial analysis showed differences in distribution of seropositivity to serogroups Icterohaemorrhagiae and Cynopteri within the five districts where study communities were situated.

CONCLUSIONS/SIGNIFICANCE

Our data suggest distinct epidemiological patterns associated with the Icterohaemorrhagiae and Cynopteri serogroups in the urban environment at high risk for leptospirosis and with differences in spatial niches. We emphasize the need for studies that accurately identify the different pathogenic serogroups that circulate and infect residents of low-income areas.

Spatiotemporal assessment of pathogenic Leptospira in subtropical coastal watersheds

The World Health Organization classifies leptospirosis as a significant public health concern, predominantly affecting impoverished and unsanitary regions. By using the Pensacola Bay System as a case study, this study examines the underappreciated susceptibility of developed subtropical coastal ecosystems such as the Pensacola Bay System to neglected zoonotic pathogens such as Leptospira. We analyzed 132 water samples collected over 12 months from 44 distinct locations with high levels of Escherichia coli (>410 most probable number/100 mL). Fecal indicator bacteria (FIB) concentrations were assessed using IDEXX Colilert-18 and Enterolert-18, and an analysis of water physiochemical characteristics and rainfall intensity was conducted. The LipL32 gene was used as a quantitative polymerase chain reaction (qPCR) indicator to identify the distribution of Leptospira interrogans. The results revealed 12 instances of the presence of L. interrogans at sites with high FIB over various land cover and aquatic ecosystem types. Independent of specific rainfall events, a seasonal relationship between precipitation and elevated rates of fecal bacteria and leptospirosis was found. These findings highlight qPCR's utility in identifying pathogens in aquatic environments and the widespread conditions where it can be found in natural and developed areas.

Gender differences in the perception of leptospirosis severity, behaviours, and Leptospira exposure risk in urban Brazil: a cross-sectional study

Background

Vulnerability to climate hazards and infectious diseases are not gender-neutral, meaning that men, women, boys, girls, and other gender identities experience different health risks. Leptospirosis, a zoonotic climate sensitive infectious disease, is commonly transmitted to humans via contact with animals and the environment, particularly soil and flood water. Gender differences in leptospiral infection risk are reported globally, with men consistently found to be at higher risk than women. However, the drivers of this difference in risk are poorly understood. Previous studies suggest that the interplay of knowledge, perceptions, and behaviours may shape differential infection risk among genders.

Methodology/Principal Findings

To examine gender differences in Leptospira exposure risk we conducted a cross-sectional serosurvey among adult participants (n = 761) in four urban, marginalised, informal settlements in the city of Salvador, Brazil. We found that seroprevalence was 14.6% and 9.4% across men and women respectively. We then applied causal inference methodology to a two-part sex-disaggregated analysis to investigate: 1) the association of perceptions and behaviours with Leptospira seropositivity and 2) the association of perceptions with behaviours. We found that men who perceived leptospirosis as extremely serious had lower odds of seropositivity, walking through sewage water, or walking barefoot, suggesting an important link between perceptions, behaviours, and exposure risk. These associations were not found in women, and these behaviours were not associated with seropositivity in men or women.

Conclusions

Our results highlight perceived severity of disease as a potential driver of behaviour in men, and perceptions of disease may be an important target for health education programs. Furthermore, our study identifies evidence gaps in the understanding of infection risks in women. As the first sex-disaggregated study investigating Leptospira infection risks, we advocate for a gendered lens in future studies to further understand risks specific to different gender identities.

Leptospira borgptersenii and Leptospira interrogans identified in wild mammals in Rio Grande do Sul, Brazil

Leptospira spp. are bacteria responsible for leptospirosis, a zoonotic disease with considerable impacts on the economy, animal health, and public health. This disease has a global distribution and is particularly prevalent in Brazil. Both rural and urban environments are habitats for Leptospira spp., which are primarily transmitted through contact with the urine of infected animals. Consequently, domestic and wild species can harbor these prokaryotes and serve as infection sources for other hosts. In the context of wild animals, there is a dearth of molecular studies elucidating the roles of various animal and bacterial species in the epidemiology of leptospirosis. Therefore, this study aimed to evaluate the presence of Leptospira spp. DNA in different species of free-living and captive wild animals and to assess the phylogenetic relationships of the identified microorganisms in Rio Grande do Sul, Brazil. The samples were evaluated for the presence of the gene lipL32 by polymerase chain reaction (PCR) and sequencing of the amplified fragment after which phylogenetic analyzes were carried out. DNA from Leptospira spp. was extracted from kidney tissue from wild animals (Mammalia class). Pathogenic Leptospira spp. DNA was detected in 9.6% (11/114) of the samples, originating from nine species of wild animals, including the white-eared opossum (Didelphis albiventris), skunk (Conepatus chinga), geoffroy's cat (Leopardus geoffroyi), margay (Leopardus wiedii), pampas fox (Lycalopex gymnocercus), capybara (Hydrochoerus hydrochaeris), common marmoset (Callithrix jacchus), neotropical river otter (Lontra longicaudis), and european hare (Lepus europaeus). Phylogenetic analysis revealed the presence of Leptospira borgpetersenii and Leptospira interrogans in these animals. This research is the first study contributing to the epidemiology of leptospirosis by identifying L. borgpetersenii and L. interrogans in free-living and captive wild animals in Rio Grande do Sul, Brazil, potentially acting as bacterial reservoirs. Additionally, our findings can inform sanitary measures for controlling and preventing the disease, thereby safeguarding public health.

Overestimation of Severe Acute Respiratory Syndrome Coronavirus 2 Household Transmission in Settings of High Community Transmission: Insights From an Informal Settlement Community in Salvador, Brazil

Background

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant has spread globally. However, the contribution of community versus household transmission to the overall risk of infection remains unclear.

Methods

Between November 2021 and March 2022, we conducted an active case-finding study in an urban informal settlement with biweekly visits across 1174 households with 3364 residents. Individuals displaying coronavirus disease 2019 (COVID-19)-related symptoms were identified, interviewed along with household contacts, and defined as index and secondary cases based on reverse-transcription polymerase chain reaction (RT-PCR) and symptom onset.

Results

In 61 households, we detected a total of 94 RT-PCR-positive cases. Of 69 sequenced samples, 67 cases (97.1%) were attributed to the Omicron BA.1* variant. Among 35 of their households, the secondary attack rate was 50.0% (95% confidence interval [CI], 37.0%-63.0%). Women (relative risk [RR], 1.6 [95% CI, .9-2.7]), older individuals (median difference, 15 [95% CI, 2-21] years), and those reporting symptoms (RR, 1.73 [95% CI, 1.0-3.0]) had a significantly increased risk for SARS-CoV-2 secondary infection. Genomic analysis revealed substantial acquisition of viruses from the community even among households with other SARS-CoV-2 infections. After excluding community acquisition, we estimated a household secondary attack rate of 24.2% (95% CI, 11.9%-40.9%).

Conclusions

These findings underscore the ongoing risk of community acquisition of SARS-CoV-2 among households with current infections. The observed high attack rate necessitates swift booster vaccination, rapid testing availability, and therapeutic options to mitigate the severe outcomes of COVID-19.

Systematic surveillance tools to reduce rodent pests in disadvantaged urban areas can empower communities and improve public health

Rodents are notorious pests, known for transmitting major public health diseases and causing agricultural and economic losses. The lack of site-specific and national standardised rodent surveillance in several disadvantaged communities has rendered interventions targeted towards rodent control as often ineffective. Here, by using the example from a pilot case-study in the Bahamas, we present a unique experience wherein, through multidisciplinary and community engagement, we simultaneously developed a standardised national surveillance protocol, and performed two parallel but integrated activities: (1) eight days of theoretical and practical training of selected participants; and (2) a three-month post-training pilot rodent surveillance in the urban community of Over-the-Hill, Nassau, The Bahamas. To account for social and environmental conditions influencing rodent proliferation in the Bahamas, we engaged selected influential community members through a semi-structured interview and gathered additional site-specific information using a modified Centers for Diseases Control and Prevention (CDC) exterior and interior rodent evaluation form, along with other validated instruments such as tracking plates and snap trapping, to test and establish a standardised site-specific rodent surveillance protocol tailored for the Bahamas. Our engagement with community members highlighted poor disposal of animal and human food, irregular garbage collection, unapproved refuse storage, lack of accessible dumpsters, poor bulk waste management, ownership problems and structural deficiencies as major factors fuelling rodent proliferation in the study areas. Accordingly, results from our pilot survey using active rodent signs (that is, the presence of rodent runs, burrows, faecal material or gnawed material) as a proxy of rodent infestation in a generalized linear model confirmed that the variables earlier identified during the community engagement program as significantly correlated with rodent activities (and capturing) across the study areas. The successful implementation of the novel site-specific protocol by trained participants, along with the correlation of their findings with those recorded during the community engagement program, underscores its suitability and applicability in disadvantaged urban settings. This experience should serve as a reference for promoting a standardised protocol for monitoring rodent activities in many disadvantaged urban settings of the Global South, while also fostering a holistic understanding of rodent proliferation. Through this pilot case-study, we advocate for the feasibility of developing sustainable rodent control interventions that are acceptable to both local communities and public authorities, particularly through the involvement of a multidisciplinary team of professionals and community members.

"People are now working together for a common good": The effect on social capital of participatory design for community-level sanitation infrastructure in urban informal settlements

Communities with higher levels of social capital perform better than communities with lower social capital in community-level water and sanitation interventions and have better health outcomes. Although research recommends bolstering social capital to improve intervention outcomes, few studies provide empirical evidence on the effect of intervention activities on social capital. This study aimed to evaluate the effect of participatory design and community engagement activities on social capital among urban informal settlements in Suva, Fiji and Makassar, Indonesia enrolled in the Revitalizing Informal Settlements and their Environments trial using the Short Adapted Social Capital Assessment Tool. We performed confirmatory factor analyses (CFA) to test tool performance and built structural equation models to assess intervention effect on CFA-informed, sub-scale scores for cognitive and structural social capital. Qualitative in-depth interviews in Fiji and Indonesia and focus group discussions in Fiji provided nuanced understanding of intervention effects on social capital from residents' perspectives. Results confirmed the hypothesized two-factor solution but revealed differences by country and by gender in Indonesia. The intervention appeared positively related to cognitive social capital among men and women in Indonesia and negatively related to cognitive and structural social capital among men and women in Fiji. While effect sizes were small and cluster-adjustment for a small number of settlements yielded non-significant effects, trends were consistent across models and bivariate analyses and were corroborated by qualitative findings. Several contextual factors may explain these results, including timing and duration of intervention activities and influence of COVID-19. Qualitative data suggested that the relationship between participatory design and social capital may be bidirectional, helping to explain why certain settlements appeared to be better equipped to benefit from intervention activities. Practitioners and program designers should carefully consider the social pre-conditions of communities in which they intend to work to optimize program outcomes and avoid unintended consequences.

Environmental and Occupational Factors Associated with Leptospirosis: A Systematic Review

Background

Leptospirosis is a neglected emerging zoonotic disease with a profound public health impact worldwide with higher burden of disease in resource-poor countries. The environmental and occupational exposures contribute to human and animal transmission, but the interaction was less explored. A deeper understanding of the critical environmental and occupational drivers in different contexts will provide useful information for disease control and prevention measures.

Objective

This review aimed to summarize the potential environmental and occupational risk factors associated with leptospirosis infection.

Methods

Four databases (Scopus, Web of Science, Ovid MEDLINE, EBSCOhost) were searched for articles published from 2012 to 2021. Eligible articles were assessed using a checklist for assessing the quality of the studies. The quality of the articles was assessed based on the laboratory diagnosis approach and statistical analysis method.

Results

A total of 32 studies were included in this systematic review. Water-related risk factors such as natural water as the primary water source (AOR 1.8-18.28), water-related recreational activities (AOR 2.36-10.45), flood exposure (AOR 1.54-6.04), contact with mud (AOR 1.57-4.58) and stagnant water (AOR 2.79-6.42) were associated with increased risk of leptospirosis. Infrastructural deficiencies such as un-plastered house walls and thatched houses presented a higher risk (AOR 2.71-5.17). Living in low-lying areas (AOR 1.58-3.74), on clay loam soil (OR 2.72), agricultural land (OR 2.09), and near rubber tree plantations (AOR 11.65) is associated with higher risk of leptospirosis. Contact with rats (AOR 1.4-3.5), livestock (AOR 1.3-10.4), and pigs (AOR 1.54-7.9) is associated with an increased risk of leptospirosis. Outdoor workers (AOR 1.95-3.95) and slaughterhouse workers (AOR 5.1-7.5) have higher risk of leptospirosis.

Conclusion

The environmental and occupational components related to water, infrastructure, landscape, agriculture, and exposed animals play an essential role in leptospirosis transmission. The magnitude of those risk factors differs with geographical region, climate factor, urbanization and population growth, and the country's socioeconomic status.

Landscape, Socioeconomic, and Meteorological Risk Factors for Canine Leptospirosis in Urban Sydney (2017-2023): A Spatial and Temporal Study

Leptospirosis is a potentially fatal zoonotic disease caused by infection with pathogenic Leptospira spp. We described reported clinical cases of canine leptospirosis in the council areas of the Inner West and the City of Sydney, Australia, from December 2017 to January 2023 and tested the association with urban spatial (landscape and socioeconomic factors, community seroprevalence, and urban heat island effect) and temporal (precipitation and minimum and maximum temperature) factors and the cases using log-transformed Poisson models, spatially stratified population-adjusted conditional logistic models, General Additive Models (GAMs), and Autoregressive Integrated Moving Average (ARIMA) models. The results suggested that canine leptospirosis is now endemic in the study area. A longer distance to the nearest veterinary hospital (RR 0.118, 95% CI -4.205--0.065, p < 0.05) and a mildly compromised Index of Economic Resources (IER) (RR 0.202, 95% CI -3.124--0.079, p < 0.05) were significant protective factors against leptospirosis. In areas proximal to the clinical cases and seropositive samples, the presence of tree cover was a strong risk factor for higher odds of canine leptospirosis (OR 5.80, 95% CI 1.12-30.11, p < 0.05). As the first study exploring risk factors associated with canine leptospirosis in urban Sydney, our findings indicate a potential transmission from urban green spaces and the possibility of higher exposure to Leptospira-or increased case detection and reporting-in areas adjacent to veterinary hospitals.

Dynamics of chikungunya virus transmission in the first year after its introduction in Brazil: A cohort study in an urban community

BACKGROUND

The first chikungunya virus (CHIKV) outbreaks during the modern scientific era were identified in the Americas in 2013, reaching high attack rates in Caribbean countries. However, few cohort studies have been performed to characterize the initial dynamics of CHIKV transmission in the New World.

METHODOLOGY/PRINCIPAL FINDINGS

To describe the dynamics of CHIKV transmission shortly after its introduction in Brazil, we performed semi-annual serosurveys in a long-term community-based cohort of 652 participants aged ≥5 years in Salvador, Brazil, between Feb-Apr/2014 and Nov/2016-Feb/2017. CHIKV infections were detected using an IgG ELISA. Cumulative seroprevalence and seroincidence were estimated and spatial aggregation of cases was investigated. The first CHIKV infections were identified between Feb-Apr/2015 and Aug-Nov/2015 (incidence: 10.7%) and continued to be detected at low incidence in subsequent surveys (1.7% from Aug-Nov/2015 to Mar-May/2016 and 1.2% from Mar-May/2016 to Nov/206-Feb/2017). The cumulative seroprevalence in the last survey reached 13.3%. It was higher among those aged 30-44 and 45-59 years (16.1% and 15.6%, respectively), compared to younger (12.4% and 11.7% in <15 and 15-29 years, respectively) or older (10.3% in ≥60 years) age groups, but the differences were not statistically significant. The cumulative seroprevalence was similar between men (14.7%) and women (12.5%). Yet, among those aged 15-29 years, men were more often infected than women (18.1% vs. 7.4%, respectively, P = 0.01), while for those aged 30-44, a non-significant opposite trend was observed (9.3% vs. 19.0%, respectively, P = 0.12). Three spatial clusters of cases were detected in the study site and an increased likelihood of CHIKV infection was detected among participants who resided with someone with CHIKV IgG antibodies.

CONCLUSIONS/SIGNIFICANCE

Unlike observations in other settings, the initial spread of CHIKV in this large urban center was limited and focal in certain areas, leaving a high proportion of the population susceptible to further outbreaks. Additional investigations are needed to elucidate the factors driving CHIKV spread dynamics, including understanding differences with respect to dengue and Zika viruses, in order to guide prevention and control strategies for coping with future outbreaks.

Leptospirosis and the Environment: A Review and Future Directions

Leptospirosis is a zoonotic disease of global importance with significant morbidity and mortality. However, the disease is frequently overlooked and underdiagnosed, leading to uncertainty of the true scale and severity of the disease. A neglected tropical disease, leptospirosis disproportionately impacts disadvantaged socioeconomic communities most vulnerable to outbreaks of zoonotic disease, due to contact with infectious animals and contaminated soils and waters. With growing evidence that Leptospira survives, persists, and reproduces in the environment, this paper reviews the current understanding of the pathogen in the environment and highlights the unknowns that are most important for future study. Through a systematic Boolean review of the literature, our study finds that detailed field-based study of Leptospira prevalence, survival, and transmission in natural waters and soils is lacking from the current literature. This review identified a strong need for assessment of physical characteristics and biogeochemical processes that support long-term viability of Leptospira in the environment followed by epidemiological assessment of the transmission and movement of the same strains of Leptospira in the present wildlife and livestock as the first steps in improving our understanding of the environmental stage of the leptospirosis transmission cycle.

Using model-based geostatistics for assessing the elimination of trachoma

BACKGROUND

Trachoma is the commonest infectious cause of blindness worldwide. Efforts are being made to eliminate trachoma as a public health problem globally. However, as prevalence decreases, it becomes more challenging to precisely predict prevalence. We demonstrate how model-based geostatistics (MBG) can be used as a reliable, efficient, and widely applicable tool to assess the elimination status of trachoma.

METHODS

We analysed trachoma surveillance data from Brazil, Malawi, and Niger. We developed geostatistical Binomial models to predict trachomatous inflammation-follicular (TF) and trachomatous trichiasis (TT) prevalence. We proposed a general framework to incorporate age and gender in the geostatistical models, whilst accounting for residual spatial and non-spatial variation in prevalence through the use of random effects. We also used predictive probabilities generated by the geostatistical models to quantify the likelihood of having achieved the elimination target in each evaluation unit (EU).

RESULTS

TF and TT prevalence varied considerably by country, with Brazil showing the lowest prevalence and Niger the highest. Brazil and Malawi are highly likely to have met the elimination criteria for TF in each EU, but, for some EUs, there was high uncertainty in relation to the elimination of TT according to the model alone. In Niger, the predicted prevalence varied significantly across EUs, with the probability of having achieved the elimination target ranging from values close to 0% to 100%, for both TF and TT.

CONCLUSIONS

We demonstrated the wide applicability of MBG for trachoma programmes, using data from different epidemiological settings. Unlike the standard trachoma prevalence survey approach, MBG provides a more statistically rigorous way of quantifying uncertainty around the achievement of elimination prevalence targets, through the use of spatial correlation. In addition to the analysis of existing survey data, MBG also provides an approach to identify areas in which more sampling effort is needed to improve EU classification. We advocate MBG as the new standard method for analysing trachoma survey outputs.

Simplified sewerage to prevent urban leptospirosis transmission: a cluster non-randomised controlled trial protocol in disadvantaged urban communities of Salvador, Brazil

INTRODUCTION

Leptospirosis is a globally distributed zoonotic and environmentally mediated disease that has emerged as a major health problem in urban slums in developing countries. Its aetiological agent is bacteria of the genus Leptospira, which are mainly spread in the urine of infected rodents, especially in an environment where adequate sanitation facilities are lacking, and it is known that open sewers are key transmission sources of the disease. Therefore, we aim to evaluate the effectiveness of a simplified sewerage intervention in reducing the risk of exposure to contaminated environments and Leptospira infection and to characterise the transmission mechanisms involved.

METHODS AND ANALYSIS

This matched quasi-experimental study design using non-randomised intervention and control clusters was designed to assess the effectiveness of an urban simplified sewerage intervention in the low-income communities of Salvador, Brazil. The intervention consists of household-level piped sewerage connections and community engagement and public involvement activities. A cohort of 1400 adult participants will be recruited and grouped into eight clusters consisting of four matched intervention-control pairs with approximately 175 individuals in each cluster in baseline. The primary outcome is the seroincidence of Leptospira infection assessed through five serological measurements: one preintervention (baseline) and four postintervention. As a secondary outcome, we will assess Leptospira load in soil, before and after the intervention. We will also assess Leptospira exposures before and after the intervention, through transmission modelling, accounting for residents' movement, contact with flooding, contaminated soil and water, and rat infestation, to examine whether and how routes of exposure for Leptospira change following the introduction of sanitation.

ETHICS AND DISSEMINATION

This study protocol has been reviewed and approved by the ethics boards at the Federal University of Bahia and the Brazilian National Research Ethics Committee. Results will be disseminated through peer-reviewed publications and presentations to implementers, researchers and participating communities.

TRIAL REGISTRATION NUMBER

Brazilian Clinical Trials Registry (RBR-8cjjpgm).

Culture-Independent Detection and Identification of Leptospira Serovars

Pathogenic Leptospira, the causative agents of leptospirosis, comprise >200 serotypes (called serovars). Most have a restricted reservoir-host range, and some, e.g., serovar Copenhageni, are cosmopolitan and of public health importance owing to their propensity to produce severe, fatal disease in humans. Available serotyping approaches-such as multilocus sequence typing, core genome sequence typing, pulsed-field gel electrophoresis, and the cross-agglutination absorption test-are tedious and expensive, and require isolation of the organisms in culture media-a protracted and incredibly inefficient process-precluding their use in prospective studies or outbreak investigations. The unavailability of culture-independent assays capable of distinguishing Leptospira serotypes remains a crucial gap in the field. Here, we have developed a simple yet specific real-time qPCR assay-targeting a Leptospira-unique gene encoding a putative polysaccharide flippase-that provides intraspecies, serotype-defining (i.e., epidemiologically useful) information, and improves upon the sensitivity of preferred lipL32-based qPCR-based diagnostic tests. The assay, dubbed RAgI ("rage one"), is rapid and affordable, and reliably and specifically detects group I pathogenic Leptospira in culture, serum, and urine, with no detectable off-target amplification-even of the genetically related but low virulence group II pathogenic (formerly "intermediate") or nonpathogenic Leptospira. It retained 100% diagnostic specificity when tested against difficult sample types, including field-collected dog urine samples and environmental samples containing varied and complex microbial species-consortia. This assay holds considerable promise in the clinical setting, and for routine epidemiological and environmental surveillance studies. IMPORTANCE Leptospirosis is caused by a diverse group of pathogenic spirochetes comprising over 200 different serotypes. Some are widely reported and of public health importance owing to their propensity to produce severe, fatal disease in humans. Apart from their tedium and expense, current serotyping approaches require isolation of the organisms in culture media-a protracted and incredibly inefficient process-rendering them useless clinically and limiting their utilization in prospective studies or outbreak investigations. The unavailability of culture-independent assays capable of distinguishing Leptospira serotypes remains a crucial gap in the field. The 11108 qPCR-assay overcomes this barrier to progress via direct taxonomic and serotype classification of Leptospira from urine and serum samples, and hence, is the first qPCR-based prognostic test for human leptospirosis.

Leptospira Infection in Rural Areas of Urabá Region, Colombia: A Prospective Study

The objective of this study was to analyze the eco-epidemiological aspects of Leptospira seroprevalence and seroincidence and its associated factors in two municipalities of northwest Colombia. A prospective study was performed in rural areas of Urabá, Antioquia, Colombia. The study enrolled 597 people between November 2015 and January 2016, of which 274 were followed up 1 year later. Serologic testing was performed by a microscopic agglutination. The outcomes were seroprevalent and seroincident cases, and the primary exposure was an outdoor occupation. A binary and mixed-effect multinomial logistic regression model was used to estimate factors associated with seroprevalent or seroincident cases of Leptospira infection. The overall Leptospira seroprevalence was 27.81% (95% confidence interval: 23.62-32.49), and the overall cumulative seroincidence for Leptospira was 14.60% (95% confidence interval: 10.33-20.23). Multivariable analysis showed that factors associated with L. interrogans serogroups seropositivity were outdoor occupation, male gender, older age, the presence of dirt floor in the household, and the presence of piglets and opossums. It also showed that factors associated with other Leptospira species serogroups were the presence of pit latrines and of turkeys. In addition, the multivariable model of seroincident cases of L. interrogans serogroups evidenced outdoor occupations, the presence of rats, and corn cultivation as risk factors. Likewise, the multivariable model for seroincident cases of other Leptospira species showed that the presence of hunting canines and cassava cultivation were risk factors. We found specific factors associated with the transmission of Leptospira serogroups contribute to the understanding of the epidemiology of Leptospira infection in rural areas of Urabá, Colombia.

Why is leptospirosis hard to avoid for the impoverished? Deconstructing leptospirosis transmission risk and the drivers of knowledge, attitudes, and practices in a disadvantaged community in Salvador, Brazil

Several studies have identified socioeconomic and environmental risk factors for infectious disease, but the relationship between these and knowledge, attitudes, and practices (KAP), and more importantly their web of effects on individual infection risk, have not previously been evaluated. We conducted a cross-sectional KAP survey in an urban disadvantaged community in Salvador, Brazil, leveraging on simultaneously collected fine-scale environmental and epidemiological data on leptospirosis transmission. Residents' knowledge influenced their attitudes which influenced their practices. However, different KAP variables were driven by different socioeconomic and environmental factors; and while improved KAP variables reduced risk, there were additional effects of socioeconomic and environmental factors on risk. For example, males and those of lower socioeconomic status were at greater risk, but once we controlled for KAP, male gender and lower socioeconomic status themselves were not direct drivers of seropositivity. Employment was linked to better knowledge and a less contaminated environment, and hence lower risk, but being employed was independently associated with a higher, not lower risk of leptospirosis transmission, suggesting travel to work as a high risk activity. Our results show how such complex webs of influence can be disentangled. They indicate that public health messaging and interventions should take into account this complexity and prioritize factors that limit exposure and support appropriate prevention practices.

Reliable estimation of SARS-CoV-2 anti-spike protein IgG titers from single dilution optical density values in serologic surveys

Reliable and scalable seroepidemiology methods are needed to estimate SARS-CoV-2 incidence and monitor the dynamics of population-level immunity as the pandemic evolves. We aimed to evaluate the reliability of SARS-CoV-2 normalized ELISA optical density (nOD) at a single dilution compared to titers derived from serial dilutions. We conducted serial serosurveys within a community-based cohort in Salvador, Brazil. Anti-S IgG ELISA (Euroimmun AG) was performed with 5 serial 3-fold dilutions of paired sera from 54 participants. Changes in nOD reliably predicted increases and decreases in titers (98.1% agreement, κ = 95.8%). Fitting the relationship between nOD and interpolated titers to a log-log curve yields highly accurate predictions of titers (r2 = 0.995) and changes in titers (r2 = 0.975), using only 1 to 2 dilutions. This approach can significantly reduce the time, labor and resources needed for large-scale serosurveys to ascertain population-level changes in exposure and immunity.

An Overview of Anthropogenic Actions as Drivers for Emerging and Re-Emerging Zoonotic Diseases

Population growth and industrialization have led to a race for greater food and supply productivity. As a result, the occupation and population of forest areas, contact with wildlife and their respective parasites and vectors, the trafficking and consumption of wildlife, the pollution of water sources, and the accumulation of waste occur more frequently. Concurrently, the agricultural and livestock production for human consumption has accelerated, often in a disorderly way, leading to the deforestation of areas that are essential for the planet's climatic and ecological balance. The effects of human actions on other ecosystems such as the marine ecosystem cause equally serious damage, such as the pollution of this habitat, and the reduction of the supply of fish and other animals, causing the coastal population to move to the continent. The sum of these factors leads to an increase in the demands such as housing, basic sanitation, and medical assistance, making these populations underserved and vulnerable to the effects of global warming and to the emergence of emerging and re-emerging diseases. In this article, we discuss the anthropic actions such as climate changes, urbanization, deforestation, the trafficking and eating of wild animals, as well as unsustainable agricultural intensification which are drivers for emerging and re-emerging of zoonotic pathogens such as viral (Ebola virus, hantaviruses, Hendravirus, Nipah virus, rabies, and severe acute respiratory syndrome coronavirus disease-2), bacterial (leptospirosis, Lyme borreliosis, and tuberculosis), parasitic (leishmaniasis) and fungal pathogens, which pose a substantial threat to the global community. Finally, we shed light on the urgent demand for the implementation of the One Health concept as a collaborative global approach to raise awareness and educate people about the science behind and the battle against zoonotic pathogens to mitigate the threat for both humans and animals.

Rickettsial Infections Causing Acute Febrile Illness in Urban Slums, Brazil

We conducted enhanced acute febrile illness surveillance in an urban slum community in Salvador, Brazil. We found that rickettsial infection accounted for 3.5% of urgent care visits for acute fever. Our results suggest that rickettsiae might be an underrecognized, treatable cause of acute febrile illness in impoverished urban populations in Brazil.

Linking rattiness, geography and environmental degradation to spillover Leptospira infections in marginalised urban settings: An eco-epidemiological community-based cohort study in Brazil

Background

Zoonotic spillover from animal reservoirs is responsible for a significant global public health burden, but the processes that promote spillover events are poorly understood in complex urban settings. Endemic transmission of Leptospira, the agent of leptospirosis, in marginalised urban communities occurs through human exposure to an environment contaminated by bacteria shed in the urine of the rat reservoir. However, it is unclear to what extent transmission is driven by variation in the distribution of rats or by the dispersal of bacteria in rainwater runoff and overflow from open sewer systems.

Methods

We conducted an eco-epidemiological study in a high-risk community in Salvador, Brazil, by prospectively following a cohort of 1401 residents to ascertain serological evidence for leptospiral infections. A concurrent rat ecology study was used to collect information on the fine-scale spatial distribution of 'rattiness', our proxy for rat abundance and exposure of interest. We developed and applied a novel geostatistical framework for joint spatial modelling of multiple indices of disease reservoir abundance and human infection risk.

Results

The estimated infection rate was 51.4 (95%CI 40.4, 64.2) infections per 1000 follow-up events. Infection risk increased with age until 30 years of age and was associated with male gender. Rattiness was positively associated with infection risk for residents across the entire study area, but this effect was stronger in higher elevation areas (OR 3.27 95% CI 1.68, 19.07) than in lower elevation areas (OR 1.14 95% CI 1.05, 1.53).

Conclusions

These findings suggest that, while frequent flooding events may disperse bacteria in regions of low elevation, environmental risk in higher elevation areas is more localised and directly driven by the distribution of local rat populations. The modelling framework developed may have broad applications in delineating complex animal-environment-human interactions during zoonotic spillover and identifying opportunities for public health intervention.

Funding

This work was supported by the Oswaldo Cruz Foundation and Secretariat of Health Surveillance, Brazilian Ministry of Health, the National Institutes of Health of the United States (grant numbers F31 AI114245, R01 AI052473, U01 AI088752, R01 TW009504 and R25 TW009338); the Wellcome Trust (102330/Z/13/Z), and by the Fundação de Amparo à Pesquisa do Estado da Bahia (FAPESB/JCB0020/2016). MTE was supported by a Medical Research UK doctorate studentship. FBS participated in this study under a FAPESB doctorate scholarship.

Structural factors associated with SARS-CoV-2 infection risk in an urban slum setting in Salvador, Brazil: A cross-sectional survey

BACKGROUND

The structural environment of urban slums, including physical, demographic, and socioeconomic attributes, renders inhabitants more vulnerable to Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection. Yet, little is known about the specific determinants that contribute to high transmission within these communities. We therefore aimed to investigate SARS-CoV-2 seroprevalence in an urban slum in Brazil.

METHODS AND FINDINGS

We performed a cross-sectional serosurvey of an established cohort of 2,041 urban slum residents from the city of Salvador, Brazil between November 2020 and February 2021, following the first Coronavirus Disease 2019 (COVID-19) pandemic wave in the country and during the onset of the second wave. The median age in this population was 29 years (interquartile range [IQR] 16 to 44); most participants reported their ethnicity as Black (51.5%) or Brown (41.7%), and 58.5% were female. The median size of participating households was 3 (IQR 2 to 4), with a median daily per capita income of 2.32 (IQR 0.33-5.15) US Dollars. The main outcome measure was presence of IgG against the SARS-CoV-2 spike protein. We implemented multilevel models with random intercepts for each household to estimate seroprevalence and associated risk factors, adjusting for the sensitivity and specificity of the assay, and the age and gender distribution of our study population. We identified high seroprevalence (47.9%, 95% confidence interval [CI] 44.2% to 52.1%), particularly among female residents (50.3% [95% CI 46.3% to 54.8%] versus 44.6% [95% CI 40.1% to 49.4%] among male residents, p < 0.01) and among children (54.4% [95% CI 49.6% to 59.3%] versus 45.4% [95% CI 41.5% to 49.7%] among adults, p < 0.01). Adults residing in households with children were more likely to be seropositive (48.6% [95% CI 44.8% to 52.3%] versus 40.7% [95% CI 37.2% to 44.3%], p < 0.01). Women who were unemployed and living below the poverty threshold (daily per capita household income <$1.25) were more likely to be seropositive compared to men with the same employment and income status (53.9% [95% CI 47.0% to 60.6%] versus 32.9% [95% CI 23.2% to 44.3%], p < 0.01). Participation in the study was voluntary, which may limit the generalizability of our findings.

CONCLUSIONS

Prior to the peak of the second wave of the COVID-19 pandemic, cumulative incidence as assessed by serology approached 50% in a Brazilian urban slum population. In contrast to observations from industrialized countries, SARS-CoV-2 incidence was highest among children, as well as women living in extreme poverty. These findings emphasize the need for targeted interventions that provide safe environments for children and mitigate the structural risks posed by crowding and poverty for the most vulnerable residents of urban slum communities.

Determining the spatial distribution of environmental and socio-economic suitability for human leptospirosis in the face of limited epidemiological data

Background

Leptospirosis is among the leading zoonotic causes of morbidity and mortality worldwide. Knowledge about spatial patterns of diseases and their underlying processes have the potential to guide intervention efforts. However, leptospirosis is often an underreported and misdiagnosed disease and consequently, spatial patterns of the disease remain unclear. In the absence of accurate epidemiological data in the urban agglomeration of Santa Fe, we used a knowledge-based index and cluster analysis to identify spatial patterns of environmental and socioeconomic suitability for the disease and potential underlying processes that shape them.

Methods

We geocoded human leptospirosis cases derived from the Argentinian surveillance system during the period 2010 to 2019. Environmental and socioeconomic databases were obtained from satellite images and publicly available platforms on the web. Two sets of human leptospirosis determinants were considered according to the level of their support by the literature and expert knowledge. We used the Zonation algorithm to build a knowledge-based index and a clustering approach to identify distinct potential sets of determinants. Spatial similarity and correlations between index, clusters, and incidence rates were evaluated.

Results

We were able to geocode 56.36% of the human leptospirosis cases reported in the national epidemiological database. The knowledge-based index showed the suitability for human leptospirosis in the UA Santa Fe increased from downtown areas of the largest cities towards peri-urban and suburban areas. Cluster analysis revealed downtown areas were characterized by higher levels of socioeconomic conditions. Peri-urban and suburban areas encompassed two clusters which differed in terms of environmental determinants. The highest incidence rates overlapped areas with the highest suitability scores, the strength of association was low though (CSc r = 0.21, P < 0.001 and ESc r = 0.19, P < 0.001).

Conclusions

We present a method to analyze the environmental and socioeconomic suitability for human leptospirosis based on literature and expert knowledge. The methodology can be thought as an evolutive and perfectible scheme as more studies are performed in the area and novel information regarding determinants of the disease become available. Our approach can be a valuable tool for decision-makers since it can serve as a baseline to plan intervention measures.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40249-022-01010-x.

Evaluation of the impact of chemical control on the ecology of Rattus norvegicus of an urban community in Salvador, Brazil

BACKGROUND

The presence of synanthropic rodents, such as Rattus norvegicus, in urban environments generates high costs of prophylaxis and control, in large part due to the environmental transmission of the pathogenic spirochete Leptospira interrogans, which causes leptospirosis. In Salvador, Brazil, The Center for Control of Zoonosis (CCZ) is responsible for planning and implementing Rodent Control Programs (RCP) which are based on chemical rodenticide. However, these strategies have not been standardized for use in developing countries.

AIM

This study aimed to identify the effect of a chemical control campaign on the demographic variables of urban R. norvegicus, analyzing relative abundance, sex structure, body mass, and age of the population, as well as the characterization of spatial distribution among households, rodent capture campaigns and interventions.

METHODS

This study was carried out during 2015 in three valleys of an urban poor community in Salvador. Individuals of R. norvegicus were systematically captured before (Pre-intervention) and three months (1st post-intervention) and six months (2nd post-intervention) after a chemical control intervention conducted by the CCZ in two valleys of the study area while the third valley was not included in the intervention campaign and was used as a non-intervention reference. We used analysis of variance to determine if intervention affected demographic variables and chi-square to compare proportions of infested households (Rodent infestation index-PII).

RESULTS

During the chemical intervention, 939 households were visited. In the pre-intervention campaign, an effort of 310 trap nights resulted in 43 rodents captured, and in the 1st and 2nd, post-intervention campaigns resulted in 47 rodents captured over 312 trap nights and 36 rodents captured over 324 traps-nights, respectively. The rodent infestation index (PII) points did not show a reduction between the period before the intervention and the two periods after the chemical intervention (70%, 72%, and 65%, respectively). Regarding relative abundances, there was no difference between valleys and period before and two periods after chemical intervention (trap success valley 1: 0,18; 0,19; 0,18 / Valley 3 0,15; 0,17; 0,13/ P>0,05). Other demographic results showed that there was no difference in demographic characteristics of the rodent population before and after the intervention, as well as there being no influence of the application of rodenticide on the areas of concentration of capture of rodents between the campaigns.

CONCLUSION

Our study indicates that the chemical control was not effective in controlling the population of R. norvegicus and provides evidence of the need for re-evaluation of rodent control practices in urban poor community settings.

Factors affecting preventive behavior against leptospirosis among the population at risk in Si Sa Ket, Thailand

Leptospirosis is a major public health problem in Si Sa Ket, Thailand. Humans can become infected via direct contact with the urine of infected animal reservoir hosts or by indirect contact with contaminated soil and water in the environment. This study examined the factors affecting preventive behavior against leptospirosis among the population at risk in Si Sa Ket, Thailand. A cross-sectional questionnaire was conducted by a representative population survey using a four-stage stratified random sampling to select 350 respondents aged 18–65 years from the fifth districts with the highest morbidity rate in 2010–2019. Data were analyzed by descriptive statistics and stepwise multiple regression. The majority of the respondents were male (53.40%), aged 46–55 years (31.20%), and agricultural workers (76.00%). Their knowledge (M = 10.78, SD = 1.60), perceived severity (M = 2.91, SD = 0.60), perceived probability (M = 2.98, SD = 0.64), self-efficacy expectations (M = 3.18, SD = 0.63), responses-efficacy expectations (M = 3.16, SD = 0.71), social support (M = 3.19, SD = 0.52), and preventive behavior against leptospirosis (M = 3.29, SD = 0.49) were at moderate level. Significant factors affecting leptospirosis preventive behaviors were history of leptospirosis illness (β = 0.312), social support (β = 0.240), perceived probability (β = 0.238), household members with a history of leptospirosis illness (β = 0.158), perceived severity (β = 0.114), self-efficacy expectations (β = 0.094) and knowledge (β = 0.088) regarding leptospirosis. All of these factors could together predict the preventive behavior against leptospirosis up to 42.8% (Adjusted R² = 0.428). Public health interventions should be strengthening people's perception and awareness regarding leptospirosis and the promotion of preventive health behavior to prevent potential outbreaks.

Biannual and Quarterly Comparison Analysis of Agglutinating Antibody Kinetics on a Subcohort of Individuals Exposed to Leptospira interrogans in Salvador, Brazil

Introduction

Leptospirosis is a zoonosis with a worldwide spread that leads to clinical manifestations ranging from asymptomatic infection to a life-threatening disease. The immune response is predominantly humoral mediated limited to the infecting serovar. Individuals living in an area endemic for leptospirosis are often exposed to an environment contaminated with leptospires and there is a paucity of information on naturally acquired immunity. In the present study, we evaluated the kinetics of agglutinating antibodies in individuals from an endemic area for leptospirosis in Salvador, Brazil comparing two different intersample collection times.

Methods

Between 2017–2018, we carried out a biannual prospective cohort with 2,086 individuals living in an endemic area for leptospirosis in Salvador, Brazil. To compare agglutinating antibody kinetics using microscopic agglutination test (MAT) with different collection times, a subcohort of 72 individuals with quarterly follow-up was carried out in parallel.

Results

The results revealed that using a shorter time for intersample collection led to the detection of a higher number of infections and reinfection events. Furthermore, we observed a higher rate of titer decay indicating partial and short protection. However, there was no indication of major changes in risk factors for the disease.

Conclusions

We evaluated antibody kinetics among residents of an endemic area for leptospirosis comparing two sample collection times. The constant exposure to the contaminated environment increases the risk for leptospirosis infection with reinfection events being more common than expected. This indicates that the burden of leptospirosis might be underestimated by serological surveys, and further studies are necessary to better characterize the humoral response after infection.

Spatial distribution models of seroreactive sheep to Leptospira spp. in Veracruz, Mexico

Leptospirosis is an infectious zoonotic disease of special importance in tropical regions of the world and is closely related to climatic conditions. In Mexico, at least eight Leptospira serogroups are known to affect sheep, but little is known about their distribution. The aim was to analyze the spatial distribution of seroreactive sheep to eight serogroups of Leptospira spp. through ecological niche modeling from the state of Veracruz. We carried out a cross-sectional, multi-stage, and stratified epidemiological study, sampling 405 sheep in different regions of the state (north, center, and south). The sera were analyzed using the Microscopic Agglutination Test (MAT) to identify seropositivity to eight Leptospira serogroups (Icterohaemorrhagiae, Pyrogenes, Grippotyphosa, Canicola, Pomona, Hardjo, Wolffi, and Tarassovi). Management variables in the sampled herds were evaluated through a survey among the producers, which was analyzed using the Chi-square test for cross-tabulation. Geospatial modeling was conducted using MAXENT and 19 climatic variables and the validation was carried out using the area under the curve (AUC). No positive animals were found for Pomona in any area of Veracruz and there was only one case of seroreactivity to Grippotyphosa. The total seroprevalence found was 53.83% (95% CI: 48.84-58.75). The main serogroup found was Sejroe (55.31%, 95% CI 50.32 - 60.20%), followed by Canicola (8.64%, 95% CI 6.17 - 11.92%), Icterohaemorrhagiae (4.69%, 95% CI 2.93 - 7.36%), Tarassovi (3.95%, 95% CI 2.35 - 6.47%), Pyrogenes (2.47%, 95% CI 1.26 - 4.64%), Australis (0.99%, 95% CI 0.32 - 2.69%) and Grippotyphosa (0.25%, 95% CI 0.01 - 1.59%). The predictive model for Australis was not significant. Acceptable predictive models (AUC>0.7-0.8) were found for Canicola, Icterohaemorrhagiae, Pyrogenes, and Tarassovi; while for Sejroe it was excellent (AUC> 0.85); consequently, the climatic variables that most contributed to the model were those related to precipitation. The potential distribution of Pyrogenes, Icterohaemorrhagiae, and Canicola was located to a greater extent in the three regions; Pyrogenes and Tarassovi were distributed mostly in the north and central regions and Sejroe is mostly located in the center and south of the state. Ecological niche modeling could support epidemiological control and surveillance programs for affected sheep herds in the state of Veracruz. This article is protected by copyright. All rights reserved.

EA, Reis MG, Diggle PJ, Ko AI. Rainfall and other meteorological factors as drivers of urban transmission of leptospirosis

BACKGROUND

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.

METHODS AND FINDINGS

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.

CONCLUSIONS

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.

Detection of Leptospira interrogans in Wild Sambar Deer (Rusa unicolor), Brazil

Leptospirosis is an emerging zoonotic disease caused by bacteria of the genus Leptospira. Wild animals may present acute disease or become chronic hosts. The present study aimed to identify Leptospira spp. infection and determine circulating serogroups in free-ranging sambar deer (Rusa unicolor) in a fragment of peri-urban tropical forest in northeastern Brazil. Blood samples were collected and subjected to microscopic agglutination testing (MAT) and PCR analysis (genes lipL32 and secY). Anti-Leptospira antibodies were detected in 60% of the animals tested, with serogroups Cynopteri (33.4%), Hebdomadis (22.2%) and Grippotyphosa (22.2%) identified as most prevalent. DNA corresponding to the pathogenic species Leptospira interrogans was detected in 2/15 (13.3%) of the samples tested. Sambar deer experience a high level of exposure to Leptospira spp. in our epidemiological setting. It is important to emphasize the implementation of effective measures (i.e., maintaining habitats and reducing human contact) for the conservation of endangered species.

Structural factors contributing to SARS-CoV-2 infection risk in the urban slum setting.. [PMID: 35194620 PMCID: PMC8863166 DOI: 10.1101/2022.02.13.22270856] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Background

The structural environment of urban slums, including physical, demographic and socioeconomic attributes, renders inhabitants more vulnerable to SARS-CoV-2 infection. Yet, little is known about the specific determinants that contribute to high transmission within these communities.

Methods and findings

We performed a serosurvey of an established cohort of 2,035 urban slum residents from the city of Salvador, Brazil between November 2020 and February 2021, following the first COVID-19 pandemic wave in the country. We identified high SARS-CoV-2 seroprevalence (46.4%, 95% confidence interval [CI] 44.3–48.6%), particularly among female residents (48.7% [95% CI 45.9–51.6%] vs. 43.2% [95% CI 39.8–46.6%] among male residents), and among children (56.5% [95% CI 52.3–60.5%] vs. 42.4% [95% CI 39.9–45.0%] among adults). In multivariable models that accounted for household-level clustering, the odds ratio for SARS-CoV-2 seropositivity among children was 1.96 (95% CI 1.42–2.72) compared to adults aged 30–44 years. Adults residing in households with children were more likely to be seropositive; this effect was particularly prominent among individuals with age 30–44 and 60 years or more. Women living below the poverty threshold (daily per capita household income <$1.25) and those who were unemployed were more likely to be seropositive.

Conclusions

During a single wave of the COVID-19 pandemic, cumulative incidence as assessed by serology approached 50% in a Brazilian urban slum population. In contrast to observations from industrialized countries, SARS-CoV-2 incidence was highest among children, as well as women living in extreme poverty. These findings emphasize the need for targeted interventions that provide safe environments for children and mitigate the structural risks posed by crowding and poverty for the most vulnerable residents of urban slum communities.

Effect of Sewerage on the Contamination of Soil with Pathogenic Leptospira in Urban Slums

Leptospirosis is an environmentally transmitted zoonotic disease caused by pathogenic Leptospira spp. that affects poor communities worldwide. In urban slums, leptospirosis is associated with deficient sanitary infrastructure. Yet, the role of sewerage in the reduction of the environmental contamination with pathogenic Leptospira has not been explored. Here, we conducted a survey of the pathogen in soils surrounding open and closed sewer sections in six urban slums in Brazil. We found that soils surrounding conventionally closed sewers (governmental interventions) were 3 times less likely to contain pathogenic Leptospira (inverse OR 3.44, 95% CI = 1.66-8.33; p < 0.001) and contained a 6 times lower load of the pathogen (0.82 log₁₀ units difference, p < 0.01) when compared to their open counterparts. However, no differences were observed in community-closed sewers (poor-quality closings performed by the slum dwellers). Human fecal markers (BacHum) were positively associated with pathogenic Leptospira even in closed sewers, and rat presence was not predictive of the presence of the pathogen in soils, suggesting that site-specific rodent control may not be sufficient to reduce the environmental contamination with Leptospira. Overall, our results indicate that sewerage expansion to urban slums may help reduce the environmental contamination with the pathogen and therefore reduce the risk of human leptospirosis.

Earth Observations and Statistics: Unlocking Sociodemographic Knowledge through the Power of Satellite Images

The continuous urbanisation in most Low-to-Middle-Income-Country (LMIC) cities is accompanied by rapid socio-economic changes in urban and peri-urban areas. Urban transformation processes, such as gentrification as well as the increase in poor urban neighbourhoods (e.g., slums) produce new urban patterns. The intersection of very rapid socio-economic and demographic dynamics are often insufficiently understood, and relevant data for understanding them are commonly unavailable, dated, or too coarse (resolution). Traditional survey-based methods (e.g., census) are carried out at low temporal granularity and do not allow for frequent updates of large urban areas. Researchers and policymakers typically work with very dated data, which do not reflect on-the-ground realities and data aggregation hide socio-economic disparities. Therefore, the potential of Earth Observations (EO) needs to be unlocked. EO data have the ability to provide information at detailed spatial and temporal scales so as to support monitoring transformations. In this paper, we showcase how recent innovations in EO and Artificial Intelligence (AI) can provide relevant, rapid information about socio-economic conditions, and in particular on poor urban neighbourhoods, when large scale and/or multi-temporal data are required, e.g., to support Sustainable Development Goals (SDG) monitoring. We provide solutions to key challenges, including the provision of multi-scale data, the reduction in data costs, and the mapping of socio-economic conditions. These innovations fill data gaps for the production of statistical information, addressing the problems of access to field-based data under COVID-19.

Leptospirosis as a cause of fever associated with jaundice in the Democratic Republic of the Congo

Background

Fever with jaundice is a common symptom of some infectious diseases. In public health surveillance within the Democratic Republic of the Congo (DRC), yellow fever is the only recognized cause of fever with jaundice. However, only 5% of the surveillance cases are positive for yellow fever and thus indicate the involvement of other pathogens. Leptospira spp. are the causative agents of leptospirosis, a widespread bacterial zoonosis, a known cause of fever with jaundice. This study aimed to determine the seropositivity of anti-Leptospira antibodies among suspected yellow fever cases and map the geographical distribution of possible leptospirosis in the DRC.

Methods

We conducted a retrospective study using 1,300 samples from yellow fever surveillance in the DRC from January 2017 to December 2018. Serum samples were screened for the presence of IgM against Leptospira spp. by a whole cell-based IgM ELISA (Patoc-IgM ELISA) at the Institut National de Recherche Biomedicale in Kinshasa (INRB) according to World Health Organization (WHO) guidance. Exploratory univariable and multivariable logistic regression analyses were undertaken to assess associations between socio-demographic factors and the presence of Leptospira IgM.

Results

Of the 1,300 serum samples screened, 88 (7%) showed evidence of IgM against Leptospira spp. Most positive cases (34%) were young adult males in the 20–29-year group. There were statistically significant associations between having Leptospira IgM antibodies, age, sex, and living area. Observed positive cases were mostly located in urban settings, and the majority lived in the province of Kinshasa. There was a statistically significant association between seasonality and IgM Leptospira spp. positivity amongst those living in Kinshasa, where most of the positive cases occurred during the rainy season.

Conclusions

This study showed that leptospirosis is likely an overlooked cause of unexplained cases of fever with jaundice in the DRC and highlights the need to consider leptospirosis in the differential diagnosis of fever with jaundice, particularly in young adult males. Further studies are needed to identify animal reservoirs, associated risk factors, and the burden of human leptospirosis in the DRC.

Leptospirosis is an important bacterial zoonosis with a worldwide distribution. Each year there are an estimated one million cases, with about 60,000 deaths. The true burden of the disease, however, is unknown. The burden of leptospirosis is probably underestimated due to the lack of specific clinical symptoms and diagnostic techniques that are not readily available. Clinical diagnosis of leptospirosis is difficult because of the diversity of symptoms, ranging from asymptomatic forms to severe multivisceral icteric states. Differential diagnoses with infections presenting with fever or fever and jaundice are numerous and may mislead the clinician. Leptospirosis is considered endemic in sub-Saharan Africa and is known to cause fever with jaundice in African countries; however, for most countries, available epidemiologic data are scarce, including in the Democratic Republic of Congo (DRC). An improved understanding of the epidemiology of leptospirosis will improve clinical management, lead to policy formulation, and have implications for national surveillance of infectious diseases in these countries. We conducted a retrospective seroepidemiological study to extend the description of the pathogens responsible for fever with jaundice in the DRC and to clarify the circulation of possible leptospirosis in the country. This study showed that leptospirosis is a likely cause of fever with jaundice in the DRC.

Angiostrongylus cantonensis in urban populations of terrestrial gastropods and rats in an impoverished region of Brazil

The nematode Angiostrongylus cantonensis is the most common cause of neuroangiostrongyliasis (manifested as eosinophilic meningitis) in humans. Gastropod molluscs are used as intermediate hosts and rats of various species are definitive hosts of this parasite. In this study, we identified several environmental factors associated with the presence and abundance of terrestrial gastropods in an impoverished urban region in Brazil. We also found that body condition, age and presence of co-infection with other parasite species in urban Rattus norvegicus, as well as environmental factors were associated with the probability and intensity of A. cantonensis infection. The study area was also found to have a moderate prevalence of the nematode in rodents (33% of 168 individuals). Eight species of molluscs (577 individuals) were identified, four of which were positive for A. cantonensis. Our study indicates that the environmental conditions of poor urban areas (presence of running and standing water, sewage, humidity and accumulated rain and accumulation of construction materials) influenced both the distribution and abundance of terrestrial gastropods, as well as infected rats, contributing to the maintenance of the A. cantonensis transmission cycle in the area. Besides neuroangiostrongyliasis, the presence of these hosts may also contribute to susceptibility to other zoonoses.

Is Carriage of Leptospira interrogans by Rats Influenced by the Urban Environment or Population Density?

Leptospira interrogans is one of the most important zoonotic pathogens globally. In urban settings, Norway rats (Rattus norvegicus) are important reservoirs of L. interrogans, but it is unclear how this bacterium is transmitted among rats. Both environmental features and rat population density may determine the prevalence of this pathogen in rat populations as well as the spillover risk to people. While these factors could play an important role in transmission between rats, it is unknown whether such factors influence prevalence among rats at a fine scale. Our objective was to determine if carriage of L. interrogans by rats could be explained by variation in the environment or in rat population density. Rats were live-trapped in a single neighborhood of Vancouver, Canada during two study periods (2011-12; 2016-17) and were tested for L. interrogans. The physical environment of each city block was recorded using a comprehensive, in-person environmental survey. Using generalized linear mixed modelling, we found no evidence of an association between carriage of L. interrogans and environmental features or rat population density, suggesting that these were not the primary drivers of its distribution among rats within this neighborhood. Understanding factors that promote L. interrogans transmission can be used to inform management approaches to minimize public health risks.

Transmission of Chikungunya Virus in an Urban Slum, Brazil

After a chikungunya outbreak in Salvador, Brazil, we performed a cross-sectional, community-based study of 1,776 inhabitants to determine chikungunya virus (CHIKV) seroprevalence, identify factors associated with exposure, and estimate the symptomatic infection rate. From November 2016 through February 2017, we collected sociodemographic and clinical data by interview and tested serum samples for CHIKV IgG. CHIKV seroprevalence was 11.8% (95% CI 9.8%–13.7%), and 15.3% of seropositive persons reported an episode of fever and arthralgia. Infections were independently and positively associated with residences served by unpaved streets, a presumptive clinical diagnosis of chikungunya, and recall of an episode of fever with arthralgia in 2015–2016. Our findings indicate that the chikungunya outbreak in Salvador may not have conferred sufficient herd immunity to preclude epidemics in the near future. The unusually low frequency of symptomatic disease points to a need for further longitudinal studies to better investigate these findings.

Genetic evidence for a potential environmental pathway to spillover infection of rat-borne leptospirosis

In this study, we genotyped samples from environmental reservoirs (surface water and soil), colonized rat specimens and cases of human severe leptospirosis from an endemic urban slum in Brazil, to determine the molecular epidemiology of pathogenic Leptospira and identify pathways of leptospirosis infection. We identified a well-stablished population of Leptospira interrogans serovar Copenhageni common to human leptospirosis cases, and animal and environmental reservoirs. This finding provides genetic evidence for a potential environmental spillover pathway for rat-borne leptospirosis through the environment in this urban community and highlights the importance of environmental and social interventions to reduce spillover infections.

Effects of Accounting for Interval-Censored Antibody Titer Decay on Seroincidence in a Longitudinal Cohort Study of Leptospirosis

Accurate measurements of seroincidence are critical for infections undercounted by reported cases, such as influenza, arboviral diseases, and leptospirosis. However, conventional methods of interpreting paired serological samples do not account for antibody titer decay, resulting in underestimated seroincidence rates. To improve interpretation of paired sera, we modeled exponential decay of interval-censored microscopic agglutination test titers using a historical data set of leptospirosis cases traced to a point source exposure in Italy in 1984. We then applied that decay rate to a longitudinal cohort study conducted in a high-transmission setting in Salvador, Brazil (2013-2015). We estimated a decay constant of 0.926 (95% confidence interval: 0.918, 0.934) titer dilutions per month. Accounting for decay in the cohort increased the mean infection rate to 1.21 times the conventionally defined rate over 6-month intervals (range, 1.10-1.36) and 1.82 times that rate over 12-month intervals (range, 1.65-2.07). Improved estimates of infection in longitudinal data have broad epidemiologic implications, including comparing studies with different sampling intervals, improving sample size estimation, and determining risk factors for infection and the role of acquired immunity. Our method of estimating and accounting for titer decay is generalizable to other infections defined using interval-censored serological assays.

Poverty, sanitation, and Leptospira transmission pathways in residents from four Brazilian slums

Residents of urban slums suffer from a high burden of zoonotic diseases due to individual, socioeconomic, and environmental factors. We conducted a cross-sectional sero-survey in four urban slums in Salvador, Brazil, to characterize how poverty and sanitation contribute to the transmission of rat-borne leptospirosis. Sero-prevalence in the 1,318 participants ranged between 10.0 and 13.3%. We found that contact with environmental sources of contamination, rather than presence of rat reservoirs, is what leads to higher risk for residents living in areas with inadequate sanitation. Further, poorer residents may be exposed away from the household, and ongoing governmental interventions were not associated with lower transmission risk. Residents at higher risk were aware of their vulnerability, and their efforts improved the physical environment near their household, but did not reduce their infection chances. This study highlights the importance of understanding the socioeconomic and environmental determinants of risk, which ought to guide intervention efforts.

Globally, more than 1 billion residents live in urban slums, where inadequate sanitation increases the spread of pathogens and their animal hosts. Leptospirosis is a globally distributed bacterial disease, and in urban areas the bacteria is spread by brown rats. Humans become infected upon exposure to water or soil/mud that was contaminated with the urine of infected rats. In four urban slums in the city of Salvador, Brazil, we used a range of individual, socioeconomic, and environmental variables to understand how they influence to one another and define o leptospirosis exposure in residents. Poverty and sanitation influenced the degree to which residents were exposed to sewer water and mud. Further, we found that while residents tried to improve the physical environment near their household, living in an area with poor sanitation mean that their infection risk remained high. This work highlight the importance of socioeconomic and environmental factors in determining disease risk, and suggests that governmental interventions should focus on improving sanitation changes in the poorest parts of the community.

Leptospirosis diagnosis among patients suspected of dengue fever in Brazil

Background:

The early symptoms of leptospirosis and dengue fever are difficult to distinguish and can cause diagnostic confusion. Due to the large dengue epidemics that has occurred in Brazil in recent years, it is possible that cases of leptospirosis were unreported. Therefore, we performed a retrospective study to detect leptospirosis in patients who were tested for dengue, but whose laboratory diagnoses were negative.

Methods:

Sera samples from 2,017 patients from 48 cities located in the central region of São Paulo state, Brazil, were studied. All samples were subjected to the microscopic agglutination test (MAT), 305 of which were taken from patients five days or less since the onset of symptoms, and were additionally subjected to real-time polymerase chain reaction (PCR).

Results:

The overall prevalence of leptospirosis cases was 21 (1.04%), with 20 through MAT (18 for Icterohaemorrhagiae and two for the Cynopteri serogroup) and one through PCR (amplicon sequencing compatible with Leptospira interrogans). According to previously established criteria, eight cases of leptospirosis were classified as “confirmed” and 13 as “probable”. The Brazilian notification system for health surveillance had no records for 16 patients positive for leptospirosis and, thus, they were considered unreported cases. Statistical analyses revealed that the prevalence of leptospirosis was higher in men (1.56%) than in women (0.56%), and the mean age was higher in positive patients (43.7 years) than in negative ones (32.3 years).

Conclusion:

The results indicated that patients suspected of dengue fever had evidence of leptospirosis or Leptospira infection, and most of these cases were unreported in the Brazilian notification system. The high burden of dengue may contribute to the misdiagnosis of leptospirosis, and health professionals should increase their awareness of leptospirosis as an important differential diagnosis of patients with suspicion of dengue.

Anti-Leptospira immunoglobulin profiling in mice reveals strain specific IgG and persistent IgM responses associated with virulence and renal colonization

Leptospira interrogans is a pathogenic spirochete responsible for leptospirosis, a neglected, zoonotic reemerging disease. Humans are sensitive hosts and may develop severe disease. Some animal species, such as rats and mice can become asymptomatic renal carriers. More than 350 leptospiral serovars have been identified, classified on the basis of the antibody response directed against the lipopolysaccharide (LPS). Similarly to whole inactivated bacteria used as human vaccines, this response is believed to confer only short-term, serogroup-specific protection. The immune response of hosts against leptospires has not been thoroughly studied, which complicates the testing of vaccine candidates. In this work, we studied the immunoglobulin (Ig) profiles in mice infected with L. interrogans over time to determine whether this humoral response confers long-term protection after homologous challenge six months post-infection. Groups of mice were injected intraperitoneally with 2×10⁷ leptospires of one of three pathogenic serovars (Manilae, Copenhageni or Icterohaemorrhagiae), attenuated mutants or heat-killed bacteria. Leptospira-specific immunoglobulin (IgA, IgM, IgG and 4 subclasses) produced in the first weeks up to 6 months post-infection were measured by ELISA. Strikingly, we found sustained high levels of IgM in mice infected with the pathogenic Manilae and Copenhageni strains, both colonizing the kidney. In contrast, the Icterohaemorrhagiae strain did not lead to kidney colonization, even at high dose, and triggered a classical IgM response that peaked at day 8 post-infection and disappeared. The virulent Manilae and Copenhageni serovars elicited high levels and similar profiles of IgG subclasses in contrast to Icterohaemorrhagiae strains that stimulated weaker antibody responses. Inactivated heat-killed Manilae strains elicited very low responses. However, all mice pre-injected with leptospires challenged with high doses of homologous bacteria did not develop acute leptospirosis, and all antibody responses were boosted after challenge. Furthermore, we showed that 2 months post-challenge, mice pre-infected with the attenuated M895 Manilae LPS mutant or heat-killed bacterin were completely protected against renal colonization. In conclusion, we observed a sustained IgM response potentially associated with chronic leptospiral renal infection. We also demonstrated in mice different profiles of protective and cross-reactive antibodies after L. interrogans infection, depending on the serovar and virulence of strains.

Leptospira interrogans is a pathogenic spirochete responsible for leptospirosis, a neglected zoonotic reemerging disease. The immune response of hosts against these bacteria has not been thoroughly studied. Here, we studied over 6 months the antibody profiles in mice infected with L. interrogans and determined whether this humoral response confers long-term protection after homologous challenge six months after primary infection. Groups of mice were infected intraperitoneally with 2×10⁷ bacteria of one of three different pathogenic serovars (Manilae, Copenhageni and Icterohaemorrhagiae) and some corresponding attenuated avirulent mutants. We measured by ELISA each type of Leptospira-specific immunoglobulin (Ig) (IgA, IgM, IgG and 4 subclasses) produced in the first weeks up to 6 months post-infection and studied their cross-reactivities among serovars. We showed different profiles of antibody response after L. interrogans challenge in mice, depending on the serovar and virulence of strains. However, all infected mice, including the ones harboring low antibody levels, like mice vaccinated with an inactivated, heat-killed strain, were protected against leptospirosis after challenge. Notably, we also showed an unusual sustained IgM response associated with chronic leptospiral colonization. Altogether, this long-term immune protection is different from what is known in humans and warrants further investigation.

Genomic and Epidemiological Surveillance of Zika Virus in the Amazon Region

Zika virus (ZIKV) has caused an explosive epidemic linked to severe clinical outcomes in the Americas. As of June 2018, 4,929 ZIKV suspected infections and 46 congenital syndrome cases had been reported in Manaus, Amazonas, Brazil. Although Manaus is a key demographic hub in the Amazon region, little is known about the ZIKV epidemic there, in terms of both transmission and viral genetic diversity. Using portable virus genome sequencing, we generated 59 ZIKV genomes in Manaus. Phylogenetic analyses indicated multiple introductions of ZIKV from northeastern Brazil to Manaus. Spatial genomic analysis of virus movement among six areas in Manaus suggested that populous northern neighborhoods acted as sources of virus transmission to other neighborhoods. Our study revealed how the ZIKV epidemic was ignited and maintained within the largest urban metropolis in the Amazon. These results might contribute to improving the public health response to outbreaks in Brazil.

Epidemiology of human leptospirosis in urban and rural areas of Brazil, 2000-2015

Background

Leptospirosis is one of the most widespread zoonosis in the world and Brazil has the highest number of cases in Latin America. Transmission occurs mainly through exposure to water and soil contaminated by the urine of infected animals. The goals of this study are to describe the geographic distribution, demographic characteristics and exposure factors of urban and rural cases of leptospirosis, and identify spatial clusters in urban and rural areas of Brazil.

Methods/results

A retrospective epidemiological study was carried out using 16 years (2000–2015) of surveillance data from the Brazilian Ministry of Health. Cases were described by age, sex and race, and exposure factors were characterized in urban and rural areas. A spatial autocorrelation analysis was conducted using local Moran’s I to identify urban and rural clusters of disease. On average 3,810 leptospirosis cases were reported annually with higher numbers in urban areas. National urban and rural incidence rates were the same (1.9 cases/100,000 population), however, regional differences were observed. Urban incidence rates were higher in the North and Northeast regions, while rural incidence rates were higher in the Southeast and South. The main exposure factor reported in urban and rural areas was exposure to places with signs of rodents, followed by flood in urban areas and agriculture and animal farming in rural areas. Clusters of leptospirosis were identified in densely populated urban areas of the North, Southeast and South regions, while rural clusters were concentrated in of the Southern region with large agriculture and animal farming practices.

Conclusions

This study highlights that leptospirosis is an important public health problem in both urban and rural areas of Brazil. The results provide decision-makers with detailed information about where disease incidence is high and can be used in the development of prevention and control strategies for priority areas and risk groups.

Household rat infestation in urban slum populations: Development and validation of a predictive score for leptospirosis

Domestic rats are the principal reservoir for urban leptospirosis. However, few studies have identified infestation markers in slums and evaluated their predictivity for leptospirosis risk. We compared households with leptospirosis cases in Salvador, Brazil between 2007 and 2009 and their neighbors using a case control design, surveying for rodent infestation signs and environmental characteristics. With the 2007-2008 data, a conditional logistic regression modeling identified the peridomiciliar presence of rodent burrows (OR, 3.30; 95% CI, 1.50-7.26), rat feces (2.86; 1.24-6.59), runs (2.57; 1.06-6.22), households bordering abandoned houses (2.48; 1.04-6.02), and unplastered walls (2.22; 1.02-6.02) as risk factors and developed a predictive score for leptospirosis. With an independent data set from 2009, a receiver operating characteristic (ROC) curve analysis evaluated the prediction score performance, with the area under the curve being 0.70 (95% CI, 0.64-0.76) for score development and 0.71 (0.65-0.79) for validation. Results indicate that high proportions of urban slum households are infested with R. norvegicus. The score performed well when identifying high-risk households within slums. These findings need confirmation in other urban centers, but suggest that community-based screening for rodent infestation can allow to target rodent and environmental control measures in populations at highest risk for leptospirosis.

Histopathology of the kidney and seroprevalence of leptospirosis in wild rats in Baghdad Province, Iraq

Background and Aim: Leptospirosis, caused by pathogenic leptospires, is a globally emerging infectious disease affecting both humans and animals, which act as reservoirs, with large outbreaks worldwide. The role of rats in dispersing leptospirosis was never investigated in Iraq. Because of the seriousness of the disease and the scarce data regarding this disease in Iraq, this study determines the incidence of leptospirosis in rats and its renal histopathological profile. Materials and Methods: Of 211 captured rats, 82 apparently healthy rats were included in this study. After euthanatizing, 3-5-ml blood was collected by cardiac puncture. Approximately 0.5 cm3 of the kidney was collected for routine histopathology and stained using hematoxylin and eosin (H&E) and Warthin–Starry (WS) stains. Blood smears were prepared and stained with the WS stain. Results: All rats (100%) with different age groups were immunoglobulin G (IgG)-positive, and 90.24% of them had the IgG against leptospiral antigens in kidney tissues. The juvenile age group had higher IgG levels than other age groups. Considering sex, no significant differences in the overall results were observed. Serum concentrations of blood urea nitrogen and creatinine showed significant increments in the sub-adult and adult IgG- positive groups compared with the IgG-negative groups. No significant alterations were observed in the juvenile group. Using WS stains, 13 and 1 blood smears and 0 and 8 kidney tissues were positive for leptospires in the sub-adult and adult groups, respectively. Microscopical findings of the renal cortex and medulla in the sub-adult IgG-positive group showed hemorrhage, glomerular deterioration, tubular cell degeneration and necrosis with cast formation, periarterial edema, and focal hemorrhage with congestion of peritubular arteries. The adult IgG-positive group revealed deterioration similar to that in the sub-adult group and tended to be chronic. No leptospires were observed using H&E staining. Conclusion: IgG-positive carrier rats refer to previously exposed or infected rats. Understanding the risk of transmitting the disease to human and animals through a carrier rat's urine is highly predicted and possible mitigation of zoonotic transmission.

Human, animal, water source interactions and leptospirosis in Thailand

In Thailand, leptospirosis is primarily associated with those who work in agricultural occupations. Leptospirosis control is hampered by a poor understanding of the complex interactions between humans, animal reservoirs, Leptospira, and the variable spatial environment in which these factors coexist. We aimed to address key knowledge gaps concerning leptospirosis disease dynamics and the human–animal–water-source interface in two high-risk areas in Thailand. We conducted a cross-sectional survey among 746 study participants in two high-risk areas for leptospirosis in Thailand: Sisaket (SSK) and Nakhon Si Thammarat (NST). Interactions among humans, animals and water sources were quantified and analyzed. The presence of different animal species and thus contact patterns were different in NST and SSK. The consumption of water from the shared sources between the two areas was different. Those whose occupations were related to animals or environmental water and those who consumed water from more than two sources were more likely to have been infected with leptospirosis, with adjusted odds ratios 4.31 (95% CI 1.17–15.83) and 10.74 (95% CI 2.28–50.53), respectively. Understanding specific water-source sharing networks and human–animal contact patterns is useful when designing national and area-specific control programmes to prevent and control leptospirosis outbreaks.

Almeida AR, Reis MG, Harris E, Ko AI, Costa F. Developmental outcomes in children exposed to Zika virus in utero from a Brazilian urban slum cohort study

Background

The prevalence of developmental alterations associated with in-utero Zika virus (ZIKV) exposure in children is not well understood. Furthermore, estimation of the Population Attributable Fraction (PAF) of developmental alterations attributed to ZIKV has not been performed due to lack of population-based cohorts with data on symptomatic and asymptomatic ZIKV exposures and an appropriate control group. The aim of this study was to characterize neurodevelopmental outcomes of children at 11 to 32 months of age with intrauterine ZIKV exposure and estimate the PAF of alterations secondary to ZIKV exposure.

Methodology/Principal findings

We performed a cohort of biannual community-based prospective serosurveys in a slum community in Salvador, Brazil. We recruited women participating in our cohort, with a documented pregnancy from January 2015 to December 2016 and children born to those mothers. Children were classified as ZIKV exposed in utero (born from women with ZIKV seroconversion during pregnancy) or unexposed (born from women without ZIKV seroconversion or that seroconverted before/after pregnancy) by using an IgG monoclonal antibody blockade-of-binding (BoB). We interviewed mothers and performed anthropometric, audiometric, ophthalmological, neurologic, and neurodevelopmental evaluations of their children at 11 to 32 months of age. Among the 655 women participating in the cohort, 66 (10%) were pregnant during the study period. 46 (70%) of them completed follow-up, of whom ZIKV seroconversion occurred before, during, and after pregnancy in 25 (54%), 13 (28%), and 1 (2%), respectively. The rest of women, 7 (21.2%), did not present ZIKV seroconversion. At 11 to 32 months of life, the 13 ZIKV-exposed children had increased risk of mild cognitive delay (RR 5.1; 95%CI 1.1–24.4) compared with the 33 children unexposed, with a PAF of 53.5%. Exposed children also had increased risk of altered auditory behavior (RR 6.0; 95%CI 1.3–26.9), with a PAF of 59.5%.

Conclusions

A significant proportion of children exposed in utero to ZIKV developed mild cognitive delay and auditory behavioral abnormalities even in the absence of gross birth defects such as microcephaly and other neurodevelopmental domains. Furthermore, our findings suggest that over half of these abnormalities could be attributed to intrauterine ZIKV exposure.

ZIKV is a neurotropic virus associated with congenital abnormalities that have been grouped under congenital Zika syndrome (CZS), the most prominent being microcephaly. Recent studies have uncovered a spectrum of other abnormalities. However, what remains unclear is the Population Attributable Fraction (PAF) of developmental alterations attributable to ZIKV intrauterine exposure in children (> one year of life). In this population-based cohort study, we found that children (without microcephaly) exposed in utero to ZIKV have an increased incidence of mild cognitive delay and auditory behavior abnormalities, with over half of these events attributable to intrauterine exposure. The results of this study suggest that more than half of alterations found in the population study can be attributed to intrauterine ZIKV exposure, thus demonstrating the importance of monitoring apparently healthy children born during the epidemic, even to asymptomatic mothers. Health services should implement early interventions to limit the morbidity of congenital ZIKV infection.