Risk factors for human leptospirosis following flooding: A meta-analysis of observational studies

Are Pathogenic Leptospira Species Ubiquitous in Urban Recreational Parks in Sydney, Australia?

Leptospirosis is a zoonotic disease caused by the spirochete bacteria Leptospira spp. From December 2017 to December 2023, a total of 34 canine leptospirosis cases were reported in urban Sydney, Australia. During the same spatio-temporal frame, one locally acquired human case was also reported. As it was hypothesised that human residents and companion dogs might both be exposed to pathogenic Leptospira in community green spaces in Sydney, an environmental survey was conducted from December 2023 to January 2024 to detect the presence of pathogenic Leptospira DNA in multipurpose, recreational public parks in the council areas of the Inner West and City of Sydney, Australia. A total of 75 environmental samples were collected from 20 public parks that were easily accessible by human and canine visitors. Quantitative PCR (qPCR) testing targeting pathogenic and intermediate Leptospira spp. was performed, and differences in detection of Leptospira spp. between dog-allowed and dog-prohibited areas were statistically examined. The global Moran's Index was calculated to identify any spatial autocorrelation in the qPCR results. Pathogenic leptospires were detected in all 20 parks, either in water or soil samples (35/75 samples). Cycle threshold (Ct) values were slightly lower for water samples (Ct 28.52-39.10) compared to soil samples (Ct 33.78-39.77). The chi-squared test and Fisher's exact test results were statistically non-significant (p > 0.05 for both water and soil samples), and there was no spatial autocorrelation detected in the qPCR results (p > 0.05 for both sample types). Although further research is now required, our preliminary results indicate the presence of pathogenic Leptospira DNA and its potential ubiquity in recreational parks in Sydney.

Analysing the outbreaks of leptospirosis after floods in Kerala, India

A growing number of studies have linked the incidence of leptospirosis with the occurrence of flood events. Nevertheless, the interaction between flood and leptospirosis has not been extensively studied to understand the influence of flood attributes in inducing new cases. This study reviews leptospirosis cases in relation to multiple flood occurrences in Kerala, India. Leptospirosis data were obtained for three years: 2017 (non-flood year) and two years with flooding-2018 (heavy flooding) and 2019 (moderate flooding). We considered the severity of flood events using the discharge, duration and extent of each flooding event and compared them with the leptospirosis cases. The distribution of cases regarding flood discharge and duration was assessed through descriptive and spatiotemporal analyses, respectively. Furthermore, cluster analyses and spatial regression were completed to ascertain the relationship between flood extent and the postflood cases. This study found that postflood cases of leptospirosis can be associated with flood events in space and time. The total cases in both 2018 and 2019 increased in the post-flood phase, with the increase in 2018 being more evident. Unlike the 2019 flood, the flood of 2018 is a significant spatial indicator for postflood cases. Our study shows that flooding leads to an increase in leptospirosis cases, and there is stronger evidence for increased leptospirosis cases after a heavy flood event than after a moderate flooding event. Flood duration may be the most important factor in determining the increase in leptospirosis infections.

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.

Bacterial community profiles within the water samples of leptospirosis outbreak areas

Background

Leptospirosis is a water-related zoonotic disease. The disease is primarily transmitted from animals to humans through pathogenic Leptospira bacteria in contaminated water and soil. Rivers have a critical role in Leptospira transmissions, while co-infection potentials with other waterborne bacteria might increase the severity and death risk of the disease.

Methods

The water samples evaluated in this study were collected from four recreational forest rivers, Sungai Congkak, Sungai Lopo, Hulu Perdik, and Gunung Nuang. The samples were subjected to next-generation sequencing (NGS) for the 16S rRNA and in-depth metagenomic analysis of the bacterial communities.

Results

The water samples recorded various bacterial diversity. The samples from the Hulu Perdik and Sungai Lopo downstream sampling sites had a more significant diversity, followed by Sungai Congkak. Conversely, the upstream samples from Gunung Nuang exhibited the lowest bacterial diversity. Proteobacteria, Firmicutes, and Acidobacteria were the dominant phyla detected in downstream areas. Potential pathogenic bacteria belonging to the genera Burkholderiales and Serratia were also identified, raising concerns about co-infection possibilities. Nevertheless, Leptospira pathogenic bacteria were absent from all sites, which is attributable to its limited persistence. The bacteria might also be washed to other locations, contributing to the reduced environmental bacterial load.

Conclusion

The present study established the presence of pathogenic bacteria in the river ecosystems assessed. The findings offer valuable insights for designing strategies for preventing pathogenic bacteria environmental contamination and managing leptospirosis co-infections with other human diseases. Furthermore, closely monitoring water sample compositions with diverse approaches, including sentinel programs, wastewater-based epidemiology, and clinical surveillance, enables disease transmission and outbreak early detections. The data also provides valuable information for suitable treatments and long-term strategies for combating infectious diseases.

Climate-driven models of leptospirosis dynamics in tropical islands from three oceanic basins

BACKGROUND

Leptospirosis is a neglected zoonosis which remains poorly known despite its epidemic potential, especially in tropical islands where outdoor lifestyle, vulnerability to invasive reservoir species and hot and rainy climate constitute higher risks for infections. Burden remains poorly documented while outbreaks can easily overflow health systems of these isolated and poorly populated areas. Identification of generic patterns driving leptospirosis dynamics across tropical islands would help understand its epidemiology for better preparedness of communities. In this study, we aim to model leptospirosis seasonality and outbreaks in tropical islands based on precipitation and temperature indicators.

METHODOLOGY/PRINCIPAL FINDINGS

We adjusted machine learning models on leptospirosis surveillance data from seven tropical islands (Guadeloupe, Reunion Island, Fiji, Futuna, New Caledonia, and Tahiti) to investigate 1) the effect of climate on the disease's seasonal dynamic, i.e., the centered seasonal profile and 2) inter-annual anomalies, i.e., the incidence deviations from the seasonal profile. The model was then used to estimate seasonal dynamics of leptospirosis in Vanuatu and Puerto Rico where disease incidence data were not available. A robust model, validated across different islands with leave-island-out cross-validation and based on current and 2-month lagged precipitation and current and 1-month lagged temperature, can be constructed to estimate the seasonal dynamic of leptospirosis. In opposition, climate determinants and their importance in estimating inter-annual anomalies highly differed across islands.

CONCLUSIONS/SIGNIFICANCE

Climate appears as a strong determinant of leptospirosis seasonality in tropical islands regardless of the diversity of the considered environments and the different lifestyles across the islands. However, predictive and expandable abilities from climate indicators weaken when estimating inter-annual outbreaks and emphasize the importance of these local characteristics in the occurrence of outbreaks.

Factors mediating the association between recurring floods and child chronic undernutrition in northern Bangladesh

OBJECTIVES

Although there is some evidence that flood exposure in Bangladesh and other developing countries increases the risk of chronic undernutrition in children, the underlying mechanisms are, to our knowledge, unknown. The objectives of this research are to examine the association between recurrent flood exposure and the likelihood of chronic undernutrition in children and to investigate the mediators of this association.

METHODS

This cross-sectional study was conducted in the Naogaon District in northern Bangladesh. Purposive sampling was used to choose 800 children between the ages of 12 and 59 mo in equal numbers in the specified flood-affected and flood-unaffected areas: 400 children from the flood-affected area and 400 from the flood-unaffected area. The nutrition indicator height for age, expressed as z scores, was used to define child chronic undernutrition. Our study focused on children who have been exposed to multiple floods in the past 5 y.

RESULTS

In our sample data, children who had experienced flooding had a 1.74-times higher chance of having chronic undernutrition (95% CI, 1.53-2.28) than children who had not experienced flooding. The mediation analyses found inadequate minimum dietary diversity, history of diarrhea, not being fully vaccinated, not using clean cooking fuel, and not having a separate kitchen contributed 19.5%, 10%, 9.8%, 14.8%, and 10%, respectively, to the flood exposure-child undernutrition association.

CONCLUSIONS

Flood exposure was found associated with the likelihood of child chronic undernutrition, and this relationship was mediated through lack of having a separate kitchen, history of diarrhea, insufficient vaccination, use of unclean cooking fuel, and poor minimum dietary diversity. Interventions to reduce the prevalence of these risk factors could contribute to reducing the disparities in child undernourishment brought on by exposure to flooding.

A Cross Sectional Study on the Bidirectional Interactions Between Leptospirosis and HIV Infection Among Patients from Maputo Central Hospital, Mozambique

Introduction

This study aims to determine the baseline seroprevalence of leptospirosis, a zoonotic and neglected disease, in people living with HIV (PWH) in Maputo, Mozambique, and to evaluate the relationship between selected HIV-related factors that might influence risk of coinfection with leptospirosis, such as degree of immunosuppression, as assessed by CD4 cell count, World Health Organization (WHO) HIV/AIDS clinical stage and antiretroviral therapy (ART) intake.

Methods

This was a descriptive cross-sectional analysis of 157 PWH, aged over 18 years old, admitted to the Maputo Central Hospital, in Maputo, Mozambique, between March 2020 and October 2021. The study participants were recruited as a convenience sample regardless of the reasons for their admission. We collected sociodemographic and clinical data, including ART and WHO HIV/AIDS clinical stage, and blood for CD4 cell count and detection of Leptospira IgG antibodies using a commercial Kit ab247199 Leptospira IgG ELISA (www.abcam.com/ab247199) with sensitivity and specificity of 100% and 97.3%, respectively. Laboratory testing was performed at the Faculty of Medicine, Eduardo Mondlane University and Laboratory of Clinical Analysis, in Maputo.

Results

Participants were aged 18 to 72 years (median age 39 years; SD ± 10.5), the majority were female 100 (63.7%), from urban areas 138 (87.9%), with secondary-level education 80 (51%). The overall seroprevalence of Leptospira IgG antibodies was 40.1%. The median CD4 cell count was 385 cells/µl (02 to 2297; SD ± 378.47). Higher seroprevalence of Leptospira antibodies was found among participants with CD4 cell counts <250 cells/µl (54.8%), WHO HIV/AIDS stage IV (70.2%) and those on ART (92%), though there were no statistically significant differences between groups with and without Leptospira antibodies.

Conclusion

Our study confirmed that Leptospira antibodies are highly prevalent in PWH in Maputo; however, Leptospira infection was not associated with the degree of immunosuppression, WHO HIV/AIDS clinical stage, or the use of ART. Our data support the need for routine screening for leptospirosis in PWH in Mozambique. Future studies are warranted to characterize the incidence and outcomes of symptomatic leptospirosis in this patient population and to identify circulating serovars and species in the country and region, as well as the implicated reservoirs.

Rainfall-driven resuspension of pathogenic Leptospira in a leptospirosis hotspot

Leptospirosis is a zoonosis caused by Leptospira bacteria present in the urine of mammals. Leptospira is able to survive in soils and can be resuspended during rain events. Here, we analyzed the pathogenic Leptospira concentration as a function of hydrological variables in a leptospirosis hot spot. A total of 226 samples were collected at the outlet of a 3 km2 watershed degraded by ungulate mammals (deer and feral pigs) and rats which are reservoirs for leptospirosis. Water samples collected at the beginning of a rain event following a dry period contained high concentrations of pathogenic Leptospira. The concentration was generally correlated with the water level and the suspended matter concentration (SMC) during the main flood event. A secondary peak of pathogenic Leptospira was sometimes detected after the main flood and in slightly turbid waters. Lastly, the pathogenic Leptospira concentration was extremely high at the end of a wet season. The pathogenic Leptospira concentrations could not be explained by a linear combination of hydrological variables (e.g. the rainfall, water level, SMC and soil moisture). However, nonlinear machine learning models of rainfall data only provided a fair fit to the observations and explained 75 % of the variance in the log10-transformed pathogenic Leptospira concentration. A comparison of identical machine learning models for the water level, SMC and pathogenic Leptospira concentration showed that the residual error in the Leptospira concentration was due to not only the small dataset but also the intrinsic characteristics of the signal. Our results support the hypothesis whereby pathogenic Leptospira survive at different depths in soils and superficial river sediments (depending on their water saturation) and are transferred to surface water during erosion. These results might help to refine leptospirosis warnings given to the local population. Future research should be focused on larger watersheds in more densely populated areas.

Outcome of severe leptospirosis presenting with ARDS in respiratory ICU

Introduction

Acute Respiratory Distress Syndrome (ARDS) is a rare presentation and a major complication of leptospirosis associated with high mortality despite advances in management.

Methods

We conducted a retrospective observational study, in 48 patients presenting with ARDS due to leptospirosis. Clinical presentation, risk factors, management and outcome of patients were noted. Factors associated with survival and mortality were studied.

Results

Our study showed a male preponderance (87%) with a mean age of presentation of 31.5 years. All patients presented with multiorgan failure. PaO2/FiO2 ratio less than 100 on 3rd day was associated with 90% mortality. The requirement for invasive mechanical ventilation carried a mortality risk of 70.4%. Overall mortality was 39.6%.

Conclusion

Leptospirosis can cause serious ARDS with a high case fatality. Prompt treatment with non-invasive mechanical ventilation to maintain haemodynamic stability and intravenous steroids can improve the outcome.

Quantifying the relationship between climatic indicators and leptospirosis incidence in Fiji: A modelling study

Leptospirosis, a global zoonotic disease, is prevalent in tropical and subtropical regions, including Fiji where it's endemic with year-round cases and sporadic outbreaks coinciding with heavy rainfall. However, the relationship between climate and leptospirosis has not yet been well characterised in the South Pacific. In this study, we quantify the effects of different climatic indicators on leptospirosis incidence in Fiji, using a time series of weekly case data between 2006 and 2017. We used a Bayesian hierarchical mixed-model framework to explore the impact of different precipitation, temperature, and El Niño Southern Oscillation (ENSO) indicators on leptospirosis cases over a 12-year period. We found that total precipitation from the previous six weeks (lagged by one week) was the best precipitation indicator, with increased total precipitation leading to increased leptospirosis incidence (0.24 [95% CrI 0.15-0.33]). Negative values of the Niño 3.4 index (indicative of La Niña conditions) lagged by four weeks were associated with increased leptospirosis risk (-0.2 [95% CrI -0.29 --0.11]). Finally, minimum temperature (lagged by one week) when included with the other variables was positively associated with leptospirosis risk (0.15 [95% CrI 0.01-0.30]). We found that the final model was better able to capture the outbreak peaks compared with the baseline model (which included seasonal and inter-annual random effects), particularly in the Western and Northern division, with climate indicators improving predictions 58.1% of the time. This study identified key climatic factors influencing leptospirosis risk in Fiji. Combining these results with demographic and spatial factors can support a precision public health framework allowing for more effective public health preparedness and response which targets interventions to the right population, place, and time. This study further highlights the need for enhanced surveillance data and is a necessary first step towards the development of a climate-based early warning system.

Infectious diseases following hydrometeorological disasters: current scenario, prevention, and control measures

Natural disasters are catastrophic occurrences that can seriously harm infrastructure, inflict property damage, and even result in fatalities. Water supply and sanitation systems can be disrupted in flooded areas, raising the risk of infectious diseases. It is advised that public health responders do a disease risk assessment of such a catastrophic event to ascertain the disaster's consequences and the health requirements. This editorial provides an overview of the transmission of infectious illnesses after hydrometeorological disasters. It also discusses the effects of such catastrophes on individuals' psychological and physical health who live in disaster-prone locations.

Seroprevalence of leptospirosis among blood donors in an endemic area

Thailand is known to be endemic for leptospirosis. This bacterium may pose a potential risk to transfusion safety. This study was a cross-sectional study examining the seroprevalence of leptospirosis among Thai blood donors. A total of 1053 serum specimens collected from blood donors residing in 5 regions of Thailand during March to September 2020 were included in this study. All samples were tested for the presence of antibodies to 22 leptospiral serovars using the microscopic agglutination test (MAT) and anti-Leptospira IgG antibodies using commercially available enzyme immunoassay. We found no evidence of recent exposure to Leptospira spp. in sera of healthy Thai blood donors by MAT, including those in higher-risk areas. However, in this same group, we did find small numbers of past exposure (1.7%) to Leptospira spp. by IgG ELISA. According to the findings of this study, there is currently no evidence for implementing new blood banking procedures to identify possible carriers in Thailand, however these should be continually monitored and revised according to the infectious disease burden in each country. It should be noted that there was a difference in the occupation rate between the general population reported in Thailand and blood donors in this study; it may not reflect the actual situation in the country.

Spatio-Temporal Analysis of Leptospirosis Hotspot Areas and Its Association With Hydroclimatic Factors in Selangor, Malaysia: Protocol for an Ecological Cross-sectional Study

BACKGROUND

Leptospirosis is considered a neglected zoonotic disease in temperate regions but an endemic disease in countries with tropical climates such as South America, Southern Asia, and Southeast Asia. There has been an increase in leptospirosis incidence in Malaysia from 1.45 to 25.94 cases per 100,000 population between 2005 and 2014. With increasing incidence in Selangor, Malaysia, and frequent climate change dynamics, a study on the disease hotspot areas and their association with the hydroclimatic factors would further enhance disease surveillance and public health interventions.

OBJECTIVE

This study aims to examine the association between the spatio-temporal distribution of leptospirosis hotspot areas from 2011 to 2019 with the hydroclimatic factors in Selangor using the geographical information system and remote sensing techniques to develop a leptospirosis hotspot predictive model.

METHODS

This will be an ecological cross-sectional study with geographical information system and remote sensing mapping and analysis concerning leptospirosis using secondary data. Leptospirosis cases in Selangor from January 2011 to December 2019 shall be obtained from the Selangor State Health Department. Laboratory-confirmed cases with data on the possible source of infection would be identified and georeferenced according to their longitude and latitudes. Topographic data consisting of subdistrict boundaries and the distribution of rivers in Selangor will be obtained from the Department of Survey and Mapping. The ArcGIS Pro software will be used to evaluate the clustering of the cases and mapped using the Getis-Ord Gi* tool. The satellite images for rainfall and land surface temperature will be acquired from the Giovanni National Aeronautics and Space Administration EarthData website and processed to obtain the average monthly values in millimeters and degrees Celsius. Meanwhile, the average monthly river hydrometric levels will be obtained from the Department of Drainage and Irrigation. Data are then inputted as thematic layers and in the ArcGIS software for further analysis. The artificial neural network analysis in artificial intelligence Phyton software will then be used to obtain the leptospirosis hotspot predictive model.

RESULTS

This research was funded as of November 2022. Data collection, processing, and analysis commenced in December 2022, and the results of the study are expected to be published by the end of 2024. The leptospirosis distribution and clusters may be significantly associated with the hydroclimatic factors of rainfall, land surface temperature, and the river hydrometric level.

CONCLUSIONS

This study will explore the associations of leptospirosis hotspot areas with the hydroclimatic factors in Selangor and subsequently the development of a leptospirosis predictive model. The constructed predictive model could potentially be used to design and enhance public health initiatives for disease prevention.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

PRR1-10.2196/43712.

In Silico Approaches for the Identification of Aptamer Binding Interactions to Leptospira spp. Cell Surface Proteins

Aptamers are nucleic acids that can bind with high affinity and specificity to a range of target molecules. However, their functionality relies on their secondary and tertiary structures such that the combination of nucleotides determines their three-dimensional conformation. In this study, the binding mechanisms of candidate aptamers and their interactions with selected target proteins found in the cell surface of Leptospira were predicted to select high-affinity aptamers. Four aptamers were evaluated through molecular modeling and docking using available software and web-based tools, following the workflow previously designed for in silico evaluation of DNA aptamers. The most predominant and highly conserved surface-exposed proteins among pathogenic Leptospira species were used as aptamer targets. The highest number of interactions was seen in aptamers AP5 and AP1. Hydrogen bonds, along with a few hydrophobic interactions, occur in most aptamer-protein complexes. Further analysis revealed serine, threonine, glutamine, and lysine as main protein residues. H-bond interactions occur mostly with polar amino acids, as reflected in the predicted interaction profiles of aptamer-protein complexes. In silico strategies allowed the identification of key residues crucial in aptamer-target interaction during aptamer screening. Such information can be used in aptamer modification for improved binding affinity and accuracy for diagnostics application.

Surveillance for arboviruses and leptospirosis among non-malarial acute febrile illness outpatients in areas affected by Cyclones Idai and Kenneth in Mozambique

The floods associated with the landfall of cyclones Idai and Kenneth in Mozambique between March and April 2019 had a major impact on the country’s public health and placed the affected population at risk for vector- and rodent-borne diseases. Aiming to improve the diagnostic capacity, yield information to guide public health responses, and assess potential short-term effects of cyclones Idai and Kenneth on arboviruses (dengue, Zika, and chikungunya) and leptospirosis, a clinical and laboratory surveillance for non-malarial acute febrile illness was established in six health units located in different districts within the two provinces (Sofala and Cabo Delgado) affected by the cyclones. Patients were tested using real-time reverse transcriptase polymerase chain reaction (qRT-PCR) for dengue (DENV), Zika (ZIKV), and chikungunya (CHIKV) viruses and using enzyme linked immunoassays (ELISA) to detect nonstructural DENV protein 1 (NS1), as well as DENV, ZIKV, CHIKV, and Leptospira IgM antibodies. From April to September 2019, 305 patients aged ≥15 years were enrolled, of which 58.4% were women and the median age was 30 years old. All patients were qRT-PCR negative for the targeted arboviruses, but three (1.0%) were positive for DENV NS1 ELISA. Specific IgM antibodies against DENV, ZIKV, CHIKV or Leptospira were found in the serum of 104 (34.1%) patients. Our results indicate that vector- and rodent-borne disease transmission occurred in all districts under investigation in the wake of cyclones Idai and Kenneth, including some regions where cases had not been previously detected. The investigation provided useful information for post-cyclone emergency response purposes.

Commensal Rodents: Still a Current Threat

Commensal rodents live in human habitats where they can find essential elements, including food, water, shelter, and space [...].

One health approach on serosurvey of anti-Leptospira spp. in homeless persons and their dogs in South Brazil

Although leptospirosis has been described as a worldwide bacterial zoonosis primarily affecting vulnerable populations, to date no study has focused on concomitant serosurvey of homeless persons and their dogs. The aim of the present study was, to use a One Health approach to serologically assess homeless persons and their dogs in 3 major cities of south Brazil (São Paulo, Curitiba, and Foz do Iguaçu). Environmental information was obtained with an epidemiological questionnaire given to all participants. A total of 200 human and 75 dog samples were tested for anti-Leptospira spp. antibodies to thirty different serovars using the microscopic agglutination test. None of the homeless persons were positive while 5 of the 75 (6.7%) dogs were positive. Among homeless population, 89% (177 of 200) were male, 61% (122 of 200) self-declared Non-white, and 67% (134 of 200) were educated up to the 8th school grade. Lower exposure of homeless persons to Leptospira spp. in the present study when compared to other vulnerable populations (slum and low-income residents) may be result of less direct exposure as they are able to rapidly change locations in response to flooding events. In addition, these results may reflect the effectiveness of a specific healthcare service provided to people living in the streets in the 3 cities. While dogs may be used as environmental sentinels for leptospirosis, the low seropositivity results found in this report may indicate low transmission risk to homeless owners in direct daily contact with their dogs.

Seroprevalence, distribution, and risk factors for human leptospirosis in the United States Virgin Islands

BACKGROUND

The first documented human leptospirosis cases in the U.S. Virgin Islands (USVI) occurred following 2017 Hurricanes Irma and Maria. We conducted a representative serosurvey in USVI to estimate the seroprevalence and distribution of human leptospirosis and evaluate local risk factors associated with seropositivity.

METHODOLOGY/PRINCIPAL FINDINGS

A stratified, two-stage cluster sampling design was used and consisted of three island strata and random selection of census blocks and then households. All eligible members of selected households were invited to participate (≥5 years old, resided in USVI ≥6 months and ≥6 months/year). Household and individual-level questionnaires were completed, and serum collected from each enrolled individual. Microscopic agglutination test serology was conducted, and bivariate and logistic regression analyses completed to identify risk factors for seropositivity. In March 2019, 1,161 individuals were enrolled from 918 households in St. Croix, St. Thomas, and St. John. The territory-wide weighted seroprevalence was 4.0% (95% CI:2.3-5.7). Characteristics/exposures independently associated with seropositivity using logistic regression included contact with cows (OR: 39.5; 95% CI: 9.0-172.7), seeing rodents/rodent evidence or contact with rodents (OR: 2.6; 95% CI: 1.1-5.9), and increasing age (OR: 1.02; 95% CI: 1.002-1.04); full or partial Caucasian/White race was negatively correlated with seropositivity (OR: 0.02, 95% CI: 0.04-0.7). Bivariate analysis showed self-reported jaundice since the 2017 hurricanes (pRR: 5.7; 95% CI: 1.0-33.4) was associated with seropositivity and using a cover/lid on cisterns/rainwater collection containers (pRR: 0.3; 95% CI: 0.08-0.8) was protective against seropositivity.

CONCLUSIONS/SIGNIFICANCE

Leptospirosis seropositivity of 4% across USVI demonstrates an important human disease that was previously unrecognized and emphasizes the importance of continued leptospirosis surveillance and investigation. Local risk factors identified may help guide future human and animal leptospirosis studies in USVI, strengthen leptospirosis public health surveillance and treatment timeliness, and inform targeted education, prevention, and control efforts.

Infectious Diseases Associated with Hydrometeorological Hazards in Europe: Disaster Risk Reduction in the Context of the Climate Crisis and the Ongoing COVID-19 Pandemic

Hydrometeorological hazards comprise a wide range of events, mainly floods, storms, droughts, and temperature extremes. Floods account for the majority of the related disasters in both developed and developing countries. Flooding alters the natural balance of the environment and frequently establish a favorable habitat for pathogens and vectors to thrive. Diseases caused by pathogens that require vehicle transmission from host to host (waterborne) or a host/vector as part of their life cycle (vector-borne) are those most likely to be affected by flooding. Considering the most notable recent destructive floods events of July 2021 that affected several Central Europe countries, we conducted a systematic literature review in order to identify documented sporadic cases and outbreaks of infectious diseases in humans in Europe, where hydrometeorological hazards, mainly floods, were thought to have been involved. The occurrence of water-, rodent-, and vector-borne diseases in several European countries is highlighted, as flooding and the harsh post-flood conditions favor their emergence and transmission. In this context, strategies for prevention and management of infectious disease outbreaks in flood-prone and flood-affected areas are also proposed and comprise pre- and post-flood prevention measures, pre- and post-outbreak prevention measures, as well as mitigation actions when an infectious disease outbreak finally occurs. Emphasis is also placed on the collision of floods, flood-related infectious disease outbreaks, and the evolving COVID-19 pandemic, which may result in unprecedented multi-hazard conditions and requires a multi-hazard approach for the effective disaster management and risk reduction.

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.

A global one health perspective on leptospirosis in humans and animals

Leptospirosis is a quintessential one health disease of humans and animals caused by pathogenic spirochetes of the genus Leptospira. Intra- and interspecies transmission is dependent on 1) reservoir host animals in which organisms replicate and are shed in urine over long periods of time, 2) the persistence of spirochetes in the environment, and 3) subsequent human-animal-environmental interactions. The combination of increased flooding events due to climate change, changes in human-animal-environmental interactions as a result of the pandemic that favor a rise in the incidence of leptospirosis, and under-recognition of leptospirosis because of nonspecific clinical signs and severe signs that resemble COVID-19 represents a "perfect storm" for resurgence of leptospirosis in people and domestic animals. Although often considered a disease that occurs in warm, humid climates with high annual rainfall, pathogenic Leptospira spp have recently been associated with disease in animals and humans that reside in semiarid regions like the southwestern US and have impacted humans that have a wide spectrum of socioeconomic backgrounds. Therefore, it is critical that physicians, veterinarians, and public health experts maintain a high index of suspicion for the disease regardless of geographic and socioeconomic circumstances and work together to understand outbreaks and implement appropriate control measures. Over the last decade, major strides have been made in our understanding of the disease because of improvements in diagnostic tests, molecular epidemiologic tools, educational efforts on preventive measures, and vaccines. These novel approaches are highlighted in the companion Currents in One Health by Sykes et al, AJVR, September 2022.

Survey for Leptospira and Brucella in Amazonian manatees, Amazon river dolphins, and a tucuxi in the Brazilian Amazon

Leptospirosis and brucellosis are zoonotic diseases with global distributions that represent severe hazards to humans and animals. We investigated exposure to Leptospira spp. and Brucella spp. in samples from Amazonian manatees Trichechus inunguis, Amazon river dolphins Inia geoffrensis, and a tucuxi Sotalia fluviatilis. The animals were free-ranging or undergoing in situ rehabilitation in the mid-Solimões River region, Brazilian Amazon. Serum samples from 19 Amazonian manatees were tested by microscopic agglutination test, Rose Bengal test, and 2-mercaptoethanol Brucella agglutination test. Antibodies against Leptospira spp. were detected in 63% of the manatees tested and serovar Patoc was considered the infecting serovar in all positive samples. Titers were generally low, indicating chronic exposure, but higher titers indicative of an active infection were detected in 3 animals. Anti-Brucella spp. antibodies were not detected. Tissue and/or body fluid samples from 12 Amazon river dolphins, a tucuxi, and 2 Amazonian manatees were investigated by multiplex PCR and bacteriology for Leptospira spp. and Brucella spp. All samples were negative. However, Enterococcus faecalis was isolated from uterine fluid, lymph node, and lung of 3 Amazon river dolphins. Bacillus spp. were isolated from milk and synovial fluid from 2 Amazon river dolphins and from a milk sample from 1 Amazonian manatee. Knowledge of the pathogens present in Amazonian manatees, Amazon river dolphins, and tucuxis is of great relevance to species conservation and environmental health. Although no clinical signs were noted, further research is needed to elucidate the clinical relevance of infection by Leptospira sp. serovar Patoc in Amazonian aquatic mammals.

Spatial-temporal patterns and risk factors for human leptospirosis in Thailand, 2012-2018

Leptospirosis is a globally important zoonotic disease. The disease is particularly important in tropical and subtropical countries. Infections in humans can be caused by exposure to infected animals or contaminated soil or water, which are suitable for Leptospira. To explore the cluster area, the Global Moran's I index was calculated for incidences per 100,000 population at the province level during 2012-2018, using the monthly and annual data. The high-risk and low-risk provinces were identified using the local indicators of spatial association (LISA). The risk factors for leptospirosis were evaluated using a generalized linear mixed model (GLMM) with zero-inflation. We also added spatial and temporal correlation terms to take into account the spatial and temporal structures. The Global Moran's I index showed significant positive values. It did not demonstrate a random distribution throughout the period of study. The high-risk provinces were almost all in the lower north-east and south parts of Thailand. For yearly reported cases, the significant risk factors from the final best-fitted model were population density, elevation, and primary rice crop arable areas. Interestingly, our study showed that leptospirosis cases were associated with large areas of rice production but were less prevalent in areas of high rice productivity. For monthly reported cases, the model using temperature range was found to be a better fit than using percentage of flooded area. The significant risk factors from the model using temperature range were temporal correlation, average soil moisture, normalized difference vegetation index, and temperature range. Temperature range, which has strongly negative correlation to percentage of flooded area was a significant risk factor for monthly data. Flood exposure controls should be used to reduce the risk of leptospirosis infection. These results could be used to develop a leptospirosis warning system to support public health organizations in Thailand.

Leptospira Is an Environmental Bacterium That Grows in Waterlogged Soil

Leptospirosis is a zoonotic disease caused by infection with pathogenic leptospires. Consistent with recent studies by other groups, leptospires were isolated from 89 out of 110 (80.9%) soil or water samples from varied locations in the Philippines in our surveillance study, indicating that leptospires might have a life cycle that does not involve animal hosts. However, despite previous work, it has not been confirmed whether leptospires multiply in the soil environment under various experimental conditions. Given the fact that the case number of leptospirosis is increased after flood, we hypothesized that waterlogged soil, which mimics the postflooding environment, could be a suitable condition for growing leptospires. To verify this hypothesis, pathogenic and saprophytic leptospires were seeded in the bottles containing 2.5 times as much water as soil, and bacterial counts in the bottles were measured over time. Pathogenic and saprophytic leptospires were found to increase their number in waterlogged soil but not in water or soil alone. In addition, leptospires were reisolated from soil in closed tubes for as long as 379 days. These results indicate that leptospires are in a resting state in the soil and are able to proliferate with increased water content in the environment. This notion is strongly supported by observations that the case number of leptospirosis is significantly higher in rainy seasons and increased after flood. Therefore, we reached the following conclusion: environmental soil is a potential reservoir of leptospires.

IMPORTANCE Since research on Leptospira has focused on pathogenic leptospires, which are supposed to multiply only in animal hosts, the life cycle of saprophytic leptospires has long been a mystery. This study demonstrates that both pathogenic and saprophytic leptospires multiply in the waterlogged soil, which mimics the postflooding environment. The present results potentially explain why leptospirosis frequently occurs after floods. Therefore, environmental soil is a potential reservoir of leptospires and leptospirosis is considered an environment-borne as well as a zoonotic disease. This is a significant report to reveal that leptospires multiply under environmental conditions, and this finding leads us to reconsider the ecology of leptospires.

Serological survey of anti-Leptospira spp. antibodies in individuals with animal hoarding disorder and their dogs in a major city of Southern Brazil

Background

Individuals with hoarding disorder (HD) presented a persistent difficulty in detaching from objects and/or animals. Unhealthy conditions, frequently found in cases of animal HD (AHD), may favour environmental contamination and the spread of zoonotic pathogens. Despite that, only one study of zoonotic diseases in individuals with AHD and their companion animals has been conducted to date.

Objectives

This study aimed to assess the seroprevalence of anti‐Leptospira spp. antibodies in individuals with AHD and their dogs in a major city of Southern Brazil.

Methods

Blood samples were obtained from 264 dogs (21 households) and 19 individuals with AHD (11 households) and tested by microscopic agglutination test.

Results

All human samples were seronegative. Seropositivity was found in 16/264 (6.1%; CI 95% 3.3–9.6%) dogs from 11/21 (52.38%) households, with titres ranging from 100 up to 400, and Copenhageni (10/16; 62.5%) was the most frequent serovar. Surprisingly, seropositivity of hoarded dogs found herein was among the lowest reportedly observed in other dog populations of Brazil. Two epidemiological variables were significantly associated with seropositivity in dogs: the presence of cat hoarding (p = 0.004) and the report of flood occurrence in the household (p = 0.031).

Conclusions

No individuals with AHD were seropositive, and besides the lower seroprevalence of dogs, they probably had contact with Leptospira spp. at some point in their life. Since dogs can be considered potential sentinels in leptospirosis, public health programs must become aware of the risk of leptospirosis cases in households of individuals with AHD and nearby communities.

Socio-ecological drivers of multiple zoonotic hazards in highly urbanized cities

The ongoing COVID-19 pandemic is a stark reminder of the devastating consequences of pathogen spillover from wildlife to human hosts, particularly in densely populated urban centers. Prevention of future zoonotic disease is contingent on informed surveillance for known and novel threats across diverse human-wildlife interfaces. Cities are a key venue for potential spillover events because of the presence of zoonotic pathogens transmitted by hosts and vectors living in close proximity to dense human settlements. Effectively identifying and managing zoonotic hazards requires understanding the socio-ecological processes driving hazard distribution and pathogen prevalence in dynamic and heterogeneous urban landscapes. Despite increasing awareness of the human health impacts of zoonotic hazards, the integration of an eco-epidemiological perspective into public health management plans remains limited. Here we discuss how landscape patterns, abiotic conditions, and biotic interactions influence zoonotic hazards across highly urbanized cities (HUCs) in temperate climates to promote their efficient and effective management by a multi-sectoral coalition of public health stakeholders. We describe how to interpret both direct and indirect ecological processes, incorporate spatial scale, and evaluate networks of connectivity specific to different zoonotic hazards to promote biologically-informed and targeted decision-making. Using New York City, USA as a case study, we identify major zoonotic threats, apply knowledge of relevant ecological factors, and highlight opportunities and challenges for research and intervention. We aim to broaden the toolbox of urban public health stakeholders by providing ecologically-informed, practical guidance for the evaluation and management of zoonotic hazards.

Diversity of bacterial pathogens and their antimicrobial resistance profile among commensal rodents in Qatar

Rodents are sources of many zoonotic pathogens that are of public health concern. This study investigated bacterial pathogens and assessed their antimicrobial resistance (AMR) patterns in commensal rodents in Qatar. A total of 148 rodents were captured between August 2019 and February 2020, and blood, ectoparasites, and visceral samples were collected. Gram-negative bacteria were isolated from the intestines, and blood plasma samples were used to detect antibodies against Brucella spp., Chlamydophila abortus, and Coxiella burnetii. PCR assays were performed to detect C. burnetii, Leptospira spp., Rickettsia spp., and Yersinia pestis in rodent tissues and ectoparasite samples. Antimicrobial resistance by the isolated intestinal bacteria was performed using an automated VITEK analyzer. A total of 13 bacterial species were isolated from the intestine samples, namely Acinetobacter baumannii, Aeromonas salmonicida, Citrobacter freundii, Citrobacter koseri, Enterobacter aerogenes, Enterobacter cloacae, Escherichia coli, Hafnia alvei, Klebsiella pneumoniae, Providencia stuartii, Proteus mirabilis, Pseudomonas aeruginosa, and Salmonella enterica. The majority of them were E. coli (54.63%), followed by P. mirabilis (17.59%) and K. pneumoniae (8.33%). Most of the pathogens were isolated from rodents obtained from livestock farms (50.46%), followed by agricultural farms (26.61%) and other sources (22.94%). No antibodies (0/148) were detected against Brucella spp., C. abortus, or C. burnetii. In addition, 31.58% (6/19) of the flea pools and one (1/1) mite pool was positive for Rickettsia spp., and no sample was positive for C. burnetii, Leptospira spp., and Y. pestis by PCR. A total of 43 (38%) bacterial isolates were identified as multidrug resistant (MDR), whereas A. salmonicida (n = 1) did not show resistance to any tested antimicrobials. Over 50% of bacterial MDR isolates were resistant to ampicillin, cefalotin, doxycycline, nitrofurantoin, and tetracycline. The presence of MDR pathogens was not correlated with rodent species or the location of rodent trapping. Seven (11.86%) E. coli and 2 (22.2%) K. pneumoniae were extended-spectrum beta-lactamases (ESBL) producers. These findings suggest that rodents can be a source of opportunistic bacteria for human and animal transmission in Qatar. Further studies are needed for the molecular characterization of the identified bacteria in this study.

Climate Change and Infections on the Move in North America

Climate change is increasingly recognized for its impacts on human health, including how biotic and abiotic factors are driving shifts in infectious disease. Changes in ecological conditions and processes due to temperature and precipitation fluctuations and intensified disturbance regimes are affecting infectious pathogen transmission, habitat, hosts, and the characteristics of pathogens themselves. Understanding the relationships between climate change and infectious diseases can help clinicians broaden the scope of differential diagnoses when interviewing, diagnosing, and treating patients presenting with infections lacking obvious agents or transmission pathways. Here, we highlight key examples of how the mechanisms of climate change affect infectious diseases associated with water, fire, land, insects, and human transmission pathways in the hope of expanding the analytical framework for infectious disease diagnoses. Increased awareness of these relationships can help prepare both clinical physicians and epidemiologists for continued impacts of climate change on infectious disease in the future.

A Scoring Tool to Predict Pulmonary Complications in Severe Leptospirosis with Kidney Failure

Rapid identification of patients likely to develop pulmonary complications in severe leptospirosis is crucial to prompt aggressive management and improve survival. The following article is a cohort study of leptospirosis patients admitted at the National Kidney and Transplant Institute (NKTI). Logistic regression was used to predict pulmonary complications and obtain a scoring tool. The Kaplan-Meir method was used to describe survival rates. Among 380 patients with severe leptospirosis and kidney failure, the overall mortality was 14%, with pulmonary hemorrhage as the most common cause. In total, there were 85 (22.4%) individuals who developed pulmonary complications, the majority (95.3%) were observed within three days of admission. Among the patients with pulmonary complications, 56.5% died. Patients placed on mechanical ventilation had an 82.1% mortality rate. Multivariate analyses showed that dyspnea (OR = 28.76, p < 0.0001), hemoptysis (OR = 20.73, p < 0.0001), diabetes (OR = 10.21, p < 0.0001), renal replacement therapy (RRT) requirement (OR = 6.25, p < 0.0001), thrombocytopenia (OR = 3.54, p < 0.0029), and oliguria/anuria (OR = 3.15, p < 0.0108) were significantly associated with pulmonary complications. A scoring index was developed termed THe-RADS score (Thrombocytopenia, Hemoptysis, RRT, Anuria, Diabetes, Shortness of breath). The odds of developing pulmonary complications were 13.90 times higher among patients with a score >2 (63% sensitivity, 88% specificity). Pulmonary complications in severe leptospirosis with kidney failure have high mortality and warrant timely and aggressive management.

Eco-epidemiological scaling of Leptospirosis: Vulnerability mapping and early warning forecasts

Infectious disease epidemics are plaguing the world and a lot of research is focused on the development of models to reproduce disease dynamics for eco-environmental and biological investigation, and disease management. Leptospirosis is an example of a neglected zoonosis strongly mediated by ecohydrological dynamics with emerging endemic and epidemic patterns worldwide in both animal and human populations. By accounting for large heterogeneities of affected areas we show how exponential endemics and scale-free epidemics are largely predictable and linked to common socio-environmental features via scaling laws with different exponents that inform about vulnerability factors. This led to the development of a novel pattern-oriented integrated model that can be used as an early-warning signal (EWS) tool for endemic-epidemic regime classification, risk determinant attribution, and near real-time forecast of outbreaks. Forecasts are grounded on expected outbreak recurrence time dependent on exceedance probabilities and statistical EWS that sense outbreak onset. A stochastic spatially-explicit model is shown to comprehensively predict outbreak dynamics (early sensing, timing, magnitude, decay, and eco-environmental determinants) and derive a spreading factor characterizing endemics and epidemics, where average over maximum rainfall is the critical factor characterizing disease transitions. Dynamically, case cross-correlation considering neighboring communities senses 2-weeks in advance outbreaks. Eco-environmental scaling relationships highlight how predicted host suitability and topographic index can be used as epidemiological footprints to effectively distinguish and control Leptospirosis regimes and areas dependent on hydro-climatological dynamics as the main trigger. The spatio-temporal scale-invariance of epidemics - underpinning persistent criticality and neutrality or independence among areas - is emphasized by the high accuracy in reproducing sequence and magnitude of cases via reliable surveillance. Further investigations of robustness and universality of eco-environmental determinants are required; nonetheless a comprehensive and computationally simple EWS method for the full characterization of Leptospirosis is provided. The tool is extendable to other climate-sensitive zoonoses to define vulnerability factors and predict outbreaks useful for optimal disease risk prevention and control.

Understanding the transmission of Mycobacterium ulcerans: A step towards controlling Buruli ulcer

Mycobacterium ulcerans is the causative agent of Buruli ulcer, a rare but chronic debilitating skin and soft tissue disease found predominantly in West Africa and Southeast Australia. While a moderate body of research has examined the distribution of M. ulcerans, the specific route(s) of transmission of this bacterium remain unknown, hindering control efforts. M. ulcerans is considered an environmental pathogen given it is associated with lentic ecosystems and human-to-human spread is negligible. However, the pathogen is also carried by various mammals and invertebrates, which may serve as key reservoirs and mechanical vectors, respectively. Here, we examine and review recent evidence from these endemic regions on potential transmission pathways, noting differences in findings between Africa and Australia, and summarising the risk and protective factors associated with Buruli ulcer transmission. We also discuss evidence suggesting that environmental disturbance and human population changes precede outbreaks. We note five key research priorities, including adoption of One Health frameworks, to resolve transmission pathways and inform control strategies to reduce the spread of Buruli ulcer.

Buruli ulcer is a debilitating skin and soft tissue disease characterised by large ulcerative wounds that are treated with antibiotics or with adjunctive surgery for advanced cases. Found predominantly in West Africa and Southeast Australia, the causative agent is the environmental bacterial pathogen Mycobacterium ulcerans. Lack of understanding of transmission pathways, combined with the absence of a vaccine, has hindered efforts to control the spread of M. ulcerans. Here, in order to identify probable transmission pathways and inform future studies, we review literature linking M. ulcerans to environmental reservoirs, mammalian hosts, and potential invertebrate vectors. We also summarise factors and behaviours that reduce the risk of developing Buruli ulcer, to inform effective prevention strategies and further shed light on transmission pathways.

An Analysis of Leptospirosis Control in a Flood-Affected Region of Kerala and the Role of Accredited Social Health Activists - A Questionnaire Study

BACKGROUND

Chengannur, a town in the south Indian state of Kerala, was 1 of the worst affected towns during the floods of 2018. Post-flood, Kerala state was under the threat of many infectious diseases including leptospirosis, but did not report any leptospirosis infections.

OBJECTIVES

This study was conducted with the following objectives: (1) Assess the knowledge, attitude and practices regarding the prevention of leptospirosis among the flood affected population and Accredited Social Health Activists (ASHAs) of Chengannur; and (2) Analyze the factors responsible for and contributing to leptospirosis control in the area post flood.

METHODOLOGY

A cross-sectional questionnaire based observational study was conducted among 2 groups: the flood affected population, and ASHA. The questionnaire was divided into 3 parts. Part A contained the socio-demographic information. Part B contained questions on assessment of knowledge, attitude, and practices regarding the prevention, and control of leptospirosis. Part C was only for the ASHA involved.

RESULTS

The final sample size was 331 (244 from the general population and 87 ASHAs). With respect to knowledge, attitude, and practice, the responses were dichotomized into correct and wrong responses. The mean knowledge score was 9.01 ± 1.08 (maximum score of 10), mean attitude score was of 3.61 ± 0.55 (maximum score of 4) and the mean practice score was 4.12 ± 1.05 (maximum score of 5).

CONCLUSION

Knowledge and attitude scores did not significantly differ between the general population and ASHA, but the practice score showed a higher score among the ASHA, all of which could have probably contributed to the prevention of a leptospirosis outbreak in the region.

Serological and molecular study of Leptospira in pediatric patients at a tertiary care centre of northern India

Leptospirosis is considered as one of the most neglected zoonotic tropical diseases. Animals and humans acquire this infection through direct contact with contaminated urine or body fluids of infected animals. This prospective study was undertaken to know the proportion of leptospirosis in pediatric patients presented with acute febrile illness at the Post Graduate Department of Microbiology, King George's Medical University, Lucknow, Uttar Pradesh. Blood samples were collected over a period of one year from January to December 2018 from 70 pediatric patients aged up to 0-12 years presented with febrile illness for 3-14 days. Out of the 70 samples, 7 (10%) samples were found positive by IgM ELISA, 4 (5.7%) samples were positive by MAT and 3(4.3%) were found positive by PCR. Risk factors such as contact with infected animals and contaminated environment were highly associated with seropositivity of leptospirosis. Clinical symptoms such as fever, chills, myalgia, headache, abdominal pain and cough were significantly associated (p < 0.05) with the seropositivity of leptospirosis.

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.

The effects of flooding and weather conditions on leptospirosis transmission in Thailand

The epidemic of leptospirosis in humans occurs annually in Thailand. In this study, we have developed mathematical models to investigate transmission dynamics between humans, animals, and a contaminated environment. We compared different leptospire transmission models involving flooding and weather conditions, shedding and multiplication rate in a contaminated environment. We found that the model in which the transmission rate depends on both flooding and temperature, best-fits the reported human data on leptospirosis in Thailand. Our results indicate that flooding strongly contributes to disease transmission, where a high degree of flooding leads to a higher number of infected individuals. Sensitivity analysis showed that the transmission rate of leptospires from a contaminated environment was the most important parameter for the total number of human cases. Our results suggest that public education should target people who work in contaminated environments to prevent Leptospira infections.

Significant Clinical Presentation of Leptospirosis in Relation to Sociodemographic and Risk Factors in a Tertiary Hospital, Malaysia

Introduction: Incidence of leptospirosis has increased within the past few years in many countries. Its clinical presentations were generally nonspecific, making it difficult to assist in the diagnosis. Besides the determination of the common clinical features, the sociodemographic background is essential to identify high-risk populations to assist in prevention. Methods: Data for this study were obtained from electronic medical records among patients clinically diagnosed with leptospirosis at a tertiary hospital in Malaysia from the years 2011 to 2015 and were recorded using standard pro forma. Associations between clinical features and sociodemographics were performed using bivariate analysis and logistic regression. Results: Data were collected from 283 patients. Their mean age was 30.71 years old. Out of 283 patients, 206 (72.8%) were male. Involvement in outdoor events and water activities was the highest risk factor of acquiring leptospirosis in 64 (22.7%) patients followed by 59 (20.8%) patients who were staying in crowded housing areas with poor sanitation. Although fever was the main clinical presentation in 274 (96.8%) patients with leptospirosis, gastrointestinal (GIT) symptoms were the second most frequent in 159 (56.2%) patients followed by pulmonary symptoms, myalgia, headache, and jaundice. From the total number of 283 patients, only 21 (92.6%) presented with severe leptospirosis. GIT symptoms were a significant predictor for leptospirosis severity, while the age group was the significant sociodemographic factor toward GIT presentation in leptospirosis. The relationship between GIT symptoms and crowded housing areas with poor sanitation was also significant. Multivariable logistic regression showed that crowded housing areas with poor sanitation (odds ratio [OR] = 3.570, p < 0.001) and age between 20 and 40 years old (OR = 2.056, p = 0.014) were more likely to have GIT symptoms. Conclusions: Information regarding the clinical features of leptospirosis to the public is necessary, while targeted prevention by educational outreach among 20-40 year olds especially those participating in outdoor water activities are crucial to decrease the incidence and complications of leptospirosis.