Leptospirosis: Increasing importance in developing countries

Changing epidemiology of leptospirosis in China from 1955 to 2022

BACKGROUND

Leptospirosis, a zoonotic disease caused by pathogenic species of the genus Leptospira, is an important public health concern globally. Leptospirosis has been notifiable under statute in China since 1955, and its epidemiological characteristics have evolved during near 70 years. This study aimed to describe the spatial and temporal patterns and demographic characteristics of leptospirosis from 1955 to 2022 in China, and explore the possible factors that influence leptospirosis transmission risk.

METHODS

Wavelet time series analysis, global Moran's I coefficients, space-time scanning statistics, and so on were used to analyze temporal, seasonal, geographic, and demographic trends in leptospirosis using reported national surveillance data from Chinese mainland from 1955 to 2022. Additionally, a Bayesian spatiotemporal model was used in a preliminary analysis to explore potential factors associated with leptospirosis occurrence.

RESULTS

Between 1955 and 2022, China reported 25,236,601 leptospirosis cases, with 91% occurring from July to October. The annual incidence rate peaked at 38.28/100,000 during outbreaks in the 1960s-1980s but stabilized at a low level (0.07/100,000) between 2005 and 2022, with over 99% of cases in southern China. Clustering increased over time, being greatest during the period 2015-2022 (Moran's I = 0.41, P < 0.01). Space-time cluster analysis indicated that the most likely clusters were in northern provincial-level administrative divisions (PLADs) from 1955 to 1984, in southern PLADs from 1985 to 2022. The main identified risk factors of leptospirosis occurrence were annual average precipitation (3.68, 95% CI: 2.50 to 5.12), GDP per capita (-3.70, 95% CI: - 5.97 to - 1.41), and the total power of agricultural machinery (- 2.51, 95% CI: - 3.85 to - 1.17).

CONCLUSIONS

Over past 70 years, leptospirosis in China has occurred as significant outbreaks but has ultimately declined to stable, low levels of occurrence. However, a clear north-south disparity persists, with tropical and subtropical regions in southern China remaining high-risk areas. The nearly 70-year dataset underscores the complex interplay of climate and socioeconomic factors influencing the disease's occurrence. Targeted prevention and control measures are critical to prevent outbreaks, especially in regions prone to extreme climatic events like heavy rainfall and floods, which may signal the resurgence of leptospirosis.

Current antibiotics for leptospirosis: Are still effective?

Leptospirosis is a recurring zoonotic disease of global significance. Leptospirosis is curable, and antibiotics are available for its treatment. However, little is known about the effectiveness of the currently used antibiotics against different Leptospira species, serovars, and strains. This review aimed to give insight into the anti-leptospiral activities of the currently available antibiotics towards Leptospira strains and their effectiveness in treating and preventing leptospirosis. Anti-leptospiral activities from natural resources were also reviewed. The literature search was conducted using several databases. The majority of Leptospira strains were sensitive to the current antibiotics. Antibiotics can accelerate the defervescence and reduced the occurrence of leptospirosis cases, nevertheless, there is no affirmative evidence on the beneficial effects of the antibiotics compared to placebo in preventing death. Adverse reactions like Jarisch-Herxheimer reactions (JHR) in patients treated with the current antibiotics were also reported. Plants, marine actinobacteria and propolis are shown as potential sources of new anti-leptospiral compounds. Although leptospirosis can still be adequately treated with current antibiotics, continuous susceptibility testing and the development of novel antibiotics especially from natural resources are highly encouraged.

Epitopes mapping for identification of potential cross-reactive peptide against leptospirosis

Leptospira, the pathogenic helical spirochetes that cause leptospirosis, is an emerging zoonotic disease with effective dissemination tactics in the host and can infect humans and animals with moderate or severe illnesses. Thus, peptide-based vaccines may be the most effective strategy to manage the immune response against Leptospira to close these gaps. In the current investigation, highly immunogenic proteins from the proteome of Leptospira interorgan serogroup Icterohaemorrhagie serovar Lai strain 56601 were identified using immunoinformatic methods. It was discovered that the conserved and most immunogenic outer membrane Lepin protein was both antigenic and non-allergenic by testing 15 linear B-cells and the ten best T-cell (Helper-lymphocyte (HTL) with the most significant number of HLA-DR binding alleles and the eight cytotoxic T lymphocyte (CTL)) epitopes. Furthermore, a 3D structural model of CTL epitopes was created using the Pep-Fold3 platform. Using the Autodock 4.2 docking server, research was conducted to determine how well the top-ranked CTL peptide models attach to HLA-A*0201 (PDB ID: 4U6Y). With HLA-A*0201, the epitope SSGTGNLHV binds with a binding energy of -1.29 kcal/mol. Utilizing molecular dynamics modeling, the projected epitope-allele docked complex structure was optimized, and the stability of the complex system was assessed. Therefore, this epitope can trigger an immunological response and produce effective Leptospira vaccine candidates. Overall, this study offers a unique vaccination candidate and may encourage additional research into leptospirosis vaccines.Communicated by Ramaswamy H. Sarma.

Spatio-temporal risk prediction of leptospirosis: A machine-learning-based approach

BACKGROUND

Leptospirosis is a neglected zoonotic disease prevalent worldwide, particularly in tropical regions experiencing frequent rainfall and severe cyclones, which are further aggravated by climate change. This bacterial zoonosis, caused by the Leptospira genus, can be transmitted through contaminated water and soil. The Pacific islands bear a high burden of leptospirosis, making it crucial to identify key factors influencing its distribution. Understanding these factors is vital for developing targeted policy decisions to mitigate the spread of Leptospira.

METHODOLOGY/PRINCIPAL FINDINGS

This study aims to establish a precise spatio-temporal risk map of leptospirosis at a national scale, using binarized incidence rates as the variable to predict. The spatial analysis was conducted at a finer resolution than the city level, while the temporal analysis was performed on a monthly basis from 2011 to 2022. Our approach utilized a comprehensive strategy combining machine learning models trained on binarized incidences, along with descriptive techniques for identifying key factors. The analysis encompasses a broad spectrum of variables, including meteorological, topographic, and socio-demographic factors. The strategy achieved a concordance metric of 83.29%, indicating a strong ability to predict the presence of contamination risk, with a sensitivity of 83.93%. Key findings included the identification of seasonal patterns, such as the impact of the El Niño Southern Oscillation, and the determination that rainfall and humidity with a one-month lag are significant contributors to Leptospira contamination. Conversely, soil types rich in organic matter may reduce bacterial presence and survival.

CONCLUSIONS/SIGNIFICANCE

The study highlights the significant influence of environmental factors on the seasonal spread of Leptospira, particularly in tropical and subtropical regions. These findings are crucial for public health planning, providing insights for targeted policies to reduce leptospirosis, while advanced machine learning models serve as a robust tool for improving disease surveillance, and risk assessment, which ultimately supports the development of an early warning system.

A systematic survey of environmental DNA in Palau's lakes and waterfalls reveals an increase in Leptospira levels after flooding

Objective

Leptospirosis is an important bacterial zoonosis which is widespread in tropical and subtropical islands and influences human and animal health which has secondary economic effects. Although leptospirosis is endemic in Palau, an Oceanian Pacific Island country, few systematic surveys of potential risk factors for Leptospira infection, such as weather and host animals, have been conducted in the natural environment. We used environmental DNA metabarcoding to assess the distribution, species diversity, and abundance of pathogenic Leptospira in this endemic region to investigate the potential environmental risks.

Methods

Forty-two paired water samples, representing fine and rainy weather conditions, were collected from four representative waterfalls and lakes on Babeldaob Island, the largest island in Palau. High-throughput sequencing analysis was conducted for polymerase chain reaction products of leptospiral 16S rRNA and vertebrate animal mitochondrial 12S rRNA genes.

Results

We revealed greater Leptospira diversity and abundance in samples collected after continuous rain, particularly in the presence of flooding, compared with samples collected under typhoon, monsoon, or fine weather conditions. From same samples, six mammalian species including cats (Felis catus), mice (Mus musculus), Yap flying fox (Pteropus yapensis), rats (Rattus spp.), and pigs (Sus scrofa) were repeatedly detected. These may be candidates of host animals of Leptospira in Palau; however, their detection was not clearly correlated with that of Leptospira.

Conclusion

We repeatedly detected several species of pathogenic Leptospira from water samples of a wide region of Babeldaob Island. We confirmed that Leptospira contamination in freshwater environments increased under rainy conditions, particularly in the presence of flooding. This information could be used to improve public health control measures in this region.

Frequency of Leptospira in the Blood of Patients with Fever of Unknown Origin in Sinaloa, Mexico

Background: Leptospira is a genus of bacteria that causes the zoonotic disease known as leptospirosis, which mainly affects countries with tropical and subtropical climates. Its prevalence may be underestimated because the initial stage of the infection is characterized by presenting a febrile condition that is easily confused with other diseases, such as dengue. This work reports the frequency of leptospirosis in the blood of patients with febrile symptoms of unknown origin. Materials and Methods: A total of 218 peripheral blood samples were analyzed from volunteer participants from Culiacan Sinaloa in June 2019, one half corresponded to patients with undiagnosed febrile symptoms and the other half to asymptomatic volunteers. Data collected included the age and sex of the participants. Leptospira was detected by qPCR using a fragment of the lipL32 gene from the bacteria's genome as a target. Fisher's exact test was used as a statistical method to estimate the relationship between the infection and the data collected. Results: The study group comprised 134 female and 84 male patients ranging from ages 1 to 92 years, averaging 41 years. In this study, Leptospira infection was identified in the blood of 22/218 participating volunteers (10.09%), of which 20/109 (18.34%) presented febrile symptoms, whereas 2/109 (1.83%) were asymptomatic. The most affected participants were women with ages between 27 and 59 years. However, the analysis of the relationship between infection and the variables studied did not show statistical significance. Conclusions: Leptospirosis was detected in blood samples from patients with undiagnosed febrile illness and asymptomatic symptoms in Sinaloa. The lipL32 gene is useful as a target in identifying Leptospira in human blood in the acute phase of the disease.

Drivers of human Leptospira infection in the Pacific Islands: A systematic review

Leptospirosis is a bacterial zoonosis that poses an increasing global public health risk. Pacific Island communities are highly vulnerable to leptospirosis outbreaks, yet the local drivers of infection remain poorly understood. We conducted a systematic review to identify the drivers of human Leptospira infection in the Pacific Islands. There were 42 included studies from which findings were synthesized descriptively. In tropical Pacific Islands, infections were a product of sociodemographic factors such as male gender/sex, age 20 to 60 years, Indigenous ethnicity, and poverty; lifestyle factors such as swimming, gardening, and open skin wounds; and environmental factors, including seasonality, heavy rainfall, and exposure to rodents, cattle, and pigs. Possible mitigation strategies in these islands include strengthening disease reporting standards at a regional level; improving water security, rodent control, and piggery management at a community level; and information campaigns to target individual-level drivers of infection. By contrast, in New Zealand, exposures were predominantly occupational, with infections occurring in meat and farm workers. Accordingly, interventions could include adjustments to occupational practices and promoting the uptake of animal vaccinations. Given the complexity of disease transmission and future challenges posed by climate change, further action is required for leptospirosis control in the Pacific Islands.

Metagenomic next-generation sequencing for diagnosing severe leptospirosis in a patient suspected COVID-19: A case report

Leptospirosis is a zoonotic and neglected waterborne disease caused by the pathogenic helical spirochetes. Early diagnosis of leptospirosis remains challenging due to non-specific symptoms and the limited availability of rapid point-of-care diagnostic tests. Herein, we present a case where a patient suspected of having COVID-19 was diagnosed with leptospirosis using metagenomic next-generation sequencing (mNGS). This case highlights the potential of mNGS to diagnose leptospirosis in the context of the COVID-19 pandemic.

Pooled lagged effect of runoff on leptospirosis cases in Colombia

Leptospirosis is a global zoonotic disease caused by spirochete bacteria of the genus Leptospira. The disease exhibits a notable incidence in tropical and developing countries, and in Colombia, environmental, economic, social, and cultural conditions favor disease transmission, directly impacting both mortality and morbidity rates. Our objective was to establish the pooled lagged effect of runoff on leptospirosis cases in Colombia. For our study, we included the top 20 Colombian municipalities with the highest number of leptospirosis cases. Monthly cases of leptospirosis, confirmed by laboratory tests and spanning from 2007 to 2022, were obtained from the National Public Health Surveillance System. Additionally, we collected monthly runoff and atmospheric and oceanic data from remote sensors. Multidimensional poverty index values for each municipality were sourced from the Terridata repository. We employed causal inference and distributed lag nonlinear models to estimate the lagged effect of runoff on leptospirosis cases. Municipality-specific estimates were combined through meta-analysis to derive a single estimate for all municipalities under study. The pooled results for the 20 municipalities suggest a lagged effect for the 0 to 2, and 0-3 months of runoff on leptospirosis when the runoff is < 120 g/m2. No effect was identified for longer lagged periods (0-1, 0 to 4, 0 to 5, and 0-6 months) or higher runoff values. Incorporation of the multidimensional poverty index into the meta-analysis of runoff contributed to the models for the lagged periods of 0-3, and 0-4 months.

The Role of Transplacental Infection in Leptospira spp. Epidemiology in Cattle in Caatinga Biome, Brazil

Leptospirosis is an infectious disease that affects domestic animals, wild animals, and humans. It represents a public health problem and has an important economic impact on livestock. This study aims to investigate the importance of genital and transplacental infection in the epidemiology of leptospirosis in cows maintained in Caatinga biome conditions, Northeastern Brazil, as well as reporting organs colonized by Leptospira spp. in embryos and fetuses. Blood, urinary tract (urine, bladder, and kidney), and reproductive tract (vaginal fluid, uterus, uterine tube, ovary, and placenta) samples were collected from 15 slaughtered pregnant cows. Two embryos and 13 fetuses were sampled. Central nervous system and choroid ovoid samples were collected from embryos. Blood, central nervous system, lung, peritoneal liquid, abomasal content, liver, spleen, urine, bladder, kidney, and reproductive system samples were collected from fetuses. Diagnostic methods included the microscopic agglutination test (MAT) using a collection of 24 serovars belonging to 17 different pathogenic serogroups of five species as antigens, as well as polymerase chain reaction (PCR). Anti-Leptospira spp. antibodies were found in 9 cows (60%), while 13 cows (86.67%) had at least one organ or urine with leptospiral DNA. No fetus was seroreactive. Among the embryos and fetuses, 13 (86.67%) presented leptospiral DNA, proving a high frequency of transplacental infection (100%). For cows, the most frequent biological materials regarding Leptospira spp. DNA detection were placenta (13 out of 15 samples; 86.7%), uterus (10 out of 15 samples; 66.7%), and vaginal fluid (5 out of 15 samples; 33.3%), while, for fetuses/embryos, the most frequent PCR-positive samples were choroid ovoid (1/2; 50%), spleen (6/13; 46.2%), kidney (5/13; 38.5%), and central nervous system (5/15; 33.3%). Sequenced samples based on the LipL32 gene presented 99% similarity with L. borgpetersenii. The results indicate that transplacental infection is an efficient way of spreading Leptospira spp. in cows maintained in Caatinga biome conditions. Therefore, prevention and control strategies must include actions that interrupt transmission through this alternative route.

Efficacy and safety of antibiotics for treatment of leptospirosis: a systematic review and network meta-analysis

BACKGROUND

Leptospirosis, an important zoonotic bacterial disease, commonly affects resource-poor populations and results in significant morbidity and mortality worldwide. The value of antibiotics in leptospirosis remains unclear, as evidenced by the conflicting opinions published.

METHODS

We conducted a search in the PubMed, Web of Science, and Cochrane Library databases for studies. These studies included clinical trials and retrospective studies that evaluated the efficacy or safety of antibiotics for leptospirosis treatment. The primary outcomes assessed were defervescence time, mortality rate, and hospital stays. Subgroup analyses were performed based on whether there were cases involving children and whether there were cases of severe jaundice. Safety was defined as the prevalence of adverse events associated with the use of antibiotics. p scores were utilized to rank the efficacy of the antibiotics.

RESULTS

There are included 9 randomized controlled trials (RCTs), 1 control trial (CT), and 3 retrospective studies (RS) involving 920 patients and 8 antibiotics. Six antibiotics resulted in significantly shorter defervescence times compared to the control, namely cefotaxime (MD, - 1.88; 95% CI =  - 2.60 to - 1.15), azithromycin (MD, - 1.74; 95% CI =  - 2.52 to - 0.95), doxycycline (MD, - 1.53; 95% CI =  - 2.05 to - 1.00), ceftriaxone (MD, - 1.22; 95% CI =  - 1.89 to - 0.55), penicillin (MD, - 1.22; 95% CI =  - 1.80 to - 0.64), and penicillin or ampicillin (MD, - 0.08; 95% CI =  - 1.01 to - 0.59). The antibiotics were not effective in reducing the mortality and hospital stays. Common adverse reactions to antibiotics included Jarisch-Herxheimer reaction, rash, headache, and digestive reactions (nausea, vomiting, diarrhea, abdominal pain, and others).

CONCLUSIONS

Findings recommend that leptospirosis patients be treated with antibiotics, which significantly reduced the leptospirosis defervescence time. Cephalosporins, doxycycline, and penicillin are suggested, and azithromycin may be a suitable alternative for drug-resistant cases.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42022354938.

Prevalence, genetic diversity and eco-epidemiology of pathogenic Leptospira species in small mammal communities in urban parks Lyon city, France

Rodents are recognized as the main reservoirs of Leptospira spp. Rats, in particular, serve as hosts for the widely predominant Leptospira interrogans serovar Icterohaemorrhagiae, found worldwide. Several studies have shown the importance of other reservoirs, such as mice or hedgehogs, which harbor other leptospires' serovars. Nevertheless, our knowledge of circulating Leptospira spp. in reservoirs other than rats remains limited. In this context, we proposed an eco-health approach to assess the health hazard associated with leptospires in urban green spaces, where contacts between human/small mammals and domestic animals are likely. We studied the prevalence, the diversity of circulating strains, and epidemiology of pathogenic Leptospira species in small terrestrial mammal communities (rodents and shrews), between 2020-2022, in two parks in Lyon metropolis, France. Our study showed a significant carriage of Leptospira spp. in small terrestrial mammals in these parks and unveiled a global prevalence rate of 11.4%. Significant variations of prevalence were observed among the small mammal species (from 0 to 26.1%), with Rattus norvegicus exhibiting the highest infection levels (26.1%). We also observed strong spatio-temporal variations in Leptospira spp. circulation in its reservoirs. Prevalence seems to be higher in the peri-urban park and in autumn in 2021 and 2022. This is potentially due to differences in landscape, abiotic conditions and small mammal communities' composition. Our study suggests an important public health relevance of rats and in a lesser extent of other rodents (Apodemus spp., Clethrionomys glareolus and Mus musculus) as reservoirs of L. interrogans, with rodent species carrying specific serogroups/serovars. We also emphasize the potential hazard associated between the shrew Crocidura russula and L. kirschneri. Altogether, these results improve our knowledge about the prevalence of leptospirosis in an urban environment, which is an essential prerequisite for the implementation of prevention of associated risks.

Domestic dogs in indigenous Amazonian communities: Key players in Leptospira cycling and transmission?

BACKGROUND

Leptospirosis is the world's most common zoonotic disease. Mitigation and control rely on pathogen identification and understanding the roles of potential reservoirs in cycling and transmission. Underreporting and misdiagnosis obscure the magnitude of the problem and confound efforts to understand key epidemiological components. Difficulties in culturing hamper the use of serological diagnostics and delay the development of DNA detection methods. As a result, especially in complex ecosystems, we know very little about the importance of different mammalian host species in cycling and transmission to humans.

METHODOLOGY/PRINCIPAL FINDINGS

We sampled dogs from five indigenous Kichwa communities living in the Yasuní National Park in the Ecuadorian Amazon basin. Blood and urine samples from domestic dogs were collected to assess the exposure of these animals to Leptospira and to identify the circulating species. Microscopic Agglutination Tests with a panel of 22 different serovars showed anti-leptospira antibodies in 36 sampled dogs (75%), and 7 serogroups were detected. Two DNA-based detection assays revealed pathogenic Leptospira DNA in 18 of 19 dog urine samples (94.7%). Amplicon sequencing and phylogenetic analysis of 16S rRNA and SecY genes from 15 urine samples revealed genetic diversity within two of three different Leptospira species: noguchii (n = 7), santarosai (n = 7), and interrogans (n = 1).

CONCLUSIONS/SIGNIFICANCE

The high prevalence of antibodies and Leptospira DNA provides strong evidence for high rates of past and current infections. Such high prevalence has not been previously reported for dogs. These dogs live in the peridomestic environment in close contact with humans, yet they are free-ranging animals that interact with wildlife. This complex web of interactions may explain the diverse types of pathogenic Leptospira observed in this study. Our results suggest that domestic dogs are likely to play an important role in the cycling and transmission of Leptospira. Future studies in areas with complex ecoepidemiology will enable better parsing of the significance of genotypic, environmental, and host characteristics.

Molecular Diagnosis as an Alternative for Public Health Surveillance of Leptospirosis in Colombia

Leptospirosis represents a public health problem in Colombia. However, the underreporting of the disease is an unfortunate reality, with a clear trend towards a decrease in cases since 2019, when the guidelines for its confirmatory diagnosis changed with the requirement of two paired samples. The purpose of this review is to highlight the importance of leptospirosis. While the access to rapid diagnosis is available at practically all levels of care for dengue and malaria, leptospirosis-a doubly neglected disease-deserves recognition as a serious public health problem in Colombia. In this manner, it is proposed that molecular tests are a viable diagnostic alternative that can improve the targeted treatment of the patient and the timeliness of data and case reporting to SIVIGILA, and reduce the underreporting of the disease. Taking advantage of the strengthened technological infrastructure derived from the SARS-CoV-2 pandemic for molecular diagnosis in Colombia, with a network of 227 laboratories distributed throughout the national territory, with an installed capacity for PCR testing, it is proposed that molecular diagnosis can be used as an alternative for early diagnosis. This would allow case confirmation through the public health network in Colombia, and, together with the microagglutination (MAT) technique, the epidemiological surveillance of this disease in this country would be strengthened.

Leptospirosis in the Air: A Case Review Series During Air Medical Transport in Haiti

Leptospirosis is an infectious illness encountered mostly in tropical climates and has been of particular concern in Haiti after natural disasters. Heavy rainfalls and natural disasters in combination with scarce resources to control and identify clusters of infections make certain populations and countries vulnerable. In some cases, patients who contract this disease may need air medical transport to hospitals that have a higher level of care. In this case report, a trio of cases is highlighted from an outbreak that required air transport to transfer patients to a facility with the availability of an intensive care unit. The goal of highlighting these cases is to increase the awareness of physicians and air transport providers to the manifestation and treatment of this disease and to provide pearls to stabilize patients during transport.

A Canine Leptospirosis Clinical Case Due to Leptospira interrogans (Serogroup Icterohaemorrhagiae) in a Dog Kennel in Castelvetrano (Western Sicily, South Italy)

Leptospirosis is a worldwide widespread zoonosis caused by Leptospira genus. We report an acute leptospirosis case in a puppy housed at a municipal kennel and the subsequent diagnostic investigations carried out on all dogs housed in the kennel. Laboratory investigation included mainly a microagglutination test, real-time PCR, and multi-locus sequence typing (MLST) for Leptospira genus. Other agents of infection were excluded. The puppy resulted positive for Leptospira interrogans Icterohaemorrhagiae both with serological and molecular assays. All of the other 66 dogs in the kennel underwent clinical and laboratory investigations twice, 15 days apart. No other dog showed leptospirosis clinical signs. At the first sampling, eight dogs (12%) showed antibodies against Leptospira interrogans serogroup Icterohaemorragiae serovar Copenhageni. Real-time PCR on urine samples of seropositive dogs detected Leptospira spp. DNA in one sample, then identified as Leptospira interrogans serogroup Icterohaemorragiae by MLST. Fifteen days after, four of the previous seropositive dogs still showed antibodies against Leptospira spp. All urine samples collected from seropositive dogs were negative at real-time PCR. The study allowed the early confirmation of a Leptospirosis case and the identification of at least one asymptomatic carrier of pathogenic Leptospira spp. The prompt activation of all appropriate management measures allowed limiting and extinguishing the infection.

Leptospiral uveitis- "Transition 'from epidemic to endemic form" difficulties in laboratory confirmations

Purpose

Leptospirosis is a waterborne zoonotic disease that primarily causes systemic illness, followed by uveitis. After heavy flooding in Madurai district, an epidemic outbreak of systemic and ocular leptospirosis occurred in 1994. Our data shows a transition to endemicity after each epidemic.

Aim

The aim of this study is to report the clinical signs, epidemic outbreaks, and persistent endemicity of leptospiral uveitis, as well as the diagnostic dilemmas associated with it.

Methods

A retrospective analysis of clinical signs was conducted using medical records of leptospiral uveitis patients over a period of 27 years (1994-2020) in a tertiary care eye hospital. The clinical workup of uveitis included a detailed clinical history, systemic, and ophthalmic examination. Microagglutination tests (MATs) was done at the Centers for Disease Control and Prevention (CDC) in Atlanta and later in our regional laboratory. Serum samples were collected from human systemic leptospirosis cases and a small group of animals in and around Madurai.

Results

The first epidemic outbreak resulted in 200 seropositive patients. Subsequent epidemic outbreaks occurred in 1997, 1998, 2001, 2005, and 2012, with Madurai experiencing multiple outbreaks. However, the disease remained endemic, with 25-50 patients being observed per year in between the peaks. Ocular examination revealed acute non-granulomatous uveitis (94.9%), pan uveitis (59.8%), vitreous inflammatory reaction (55.4%), retinal vasculitis (29.5%), disc hyperemia (20.9%), and hypopyon. (16.2%). New serovars emerged every year, resulting in decreased sensitivity of the MAT. Over time, the MAT started to miss diagnoses.

Conclusion

The persistent endemicity of leptospiral uveitis emphasizes the need for accessible diagnostic tests. The low performance of the MAT can be attributable to the use of an older panel. The incorporation of new isolates in the MAT by a national laboratory will improve the accuracy of diagnosis.

Demographic and clinical risk factors associated with severity of lab-confirmed human leptospirosis in Colombia, 2015-2020

BACKGROUND

Leptospirosis is a common zoonoses and is a major global public health threat. Most cases are mild, typically presenting as a non-specific acute febrile illness. However, leptospirosis can have life-threatening manifestations, including pulmonary hemorrhage syndrome, and acute kidney injury. In Colombia, notification and lab-confirmation of suspected human cases are mandatory. However, little is known about the demographic and clinical factors associated with severe leptospirosis, which could help to reduce clinical complications and mortality. Our aim was to identify risk factors associated with severe leptospirosis, intensive care unit (ICU) admission, and mortality in lab-confirmed cases in Colombia, 2015-2020.

METHODS AND FINDINGS

We analyzed 201 lab-confirmed human leptospirosis cases by microagglutination test. We used a logistic regression to identify the demographic and clinical risk factors associated with severe leptospirosis, admission to ICU, and death. Most leptospirosis confirmed cases occurred in men (85.6%); the mean age was 36.7 years. We classified severe cases (43.3%) by clinical manifestations as renal (29.9%) and liver (27.4%) failure, multiple-organ failure (24.4%), septic shock (24.4%), Weil syndrome (18.4%), pulmonary hemorrhage (18.4%), and meningitis (2.5%), admitted to the ICU (30.3%), and fatal (8.5%). Clinical conditions associated with severe leptospirosis were dyspnea (OR: 5.54; 95% CI: 1.46 to 20.98), tachycardia (OR:9.69; 95% CI: 15.96 to 58.8), and rash (OR: 10.25; 95% CI: 25.01 to 42.08).

CONCLUSIONS

We identified demographic characteristics and clinical symptoms associated with severe leptospirosis in Colombia. We hope these results can support clinicians in providing timely treatment to leptospirosis patients to avoid preventable medical complications or deaths.

Co-Infection by Leptospira montravelensis and Leptospira interrogans Serovar Pomona in Urine Samples of Donkeys and Pigs in Sardinia, Italy

Saprophytic leptospires are spirochetes enclosed within the non-pathogenic clade of the genus Leptospira, which in turn is subdivided into two subclades S1 and S2. To date, the microorganisms included in these subclades have been isolated from the environment in various parts of the world, and are believed to have no known animal reservoirs. After a case of Leptospira interrogans serovar Pomona was notified to the owner of a farm in Sardinia, all of the farm animals (11 pigs and 3 donkeys) were examined for the presence of Leptospira. Sera of all tested animals resulted positive for antibodies to Leptospira using a microscopic agglutination test (MAT). Moreover, nine (82%) kidney samples from pigs and three urine samples collected from donkeys (100%) tested positive for Leptospira DNA after qPCR. Results obtained after MLST analysis and sequencing of rrs, rpoB, and secY genes, performed on six Leptospira strains isolated in culture, revealed the presence of the genomospecies L. interrogans serovar Pomona in the kidney samples. Conversely, whole-genome sequencing combined with mean nucleotide identity revealed the presence of the saprophytic L. montravelensis in the urine samples. Our results report, for the first time, the isolation of a saprophytic species from mammalian urine, suggesting a new ecological specialization for these bacteria, with a possible transition from free-living to a symbiotic lifestyle. Further studies will have to be conducted to understand the evolution of virulence of these bacteria, potential infectivity, and possible public health implications.

Bovine Leptospirosis in Caatinga Biome, Brazil: New Insights into Diagnosis and Epidemiology

Bovine leptospirosis causes economic losses and raises public health concerns. It is possible that there are peculiarities in the epidemiology of leptospirosis in regions with a semiarid climate, such as the Caatinga biome in Brazil, where the climate is hot and dry, and the etiological agent require alternative routes of transmission. This study aimed to close knowledge gaps to the diagnosis and epidemiology of Leptospira spp. infection in cows from the Caatinga biome, Brazil. Samples of the blood, urinary tract (urine, bladder and kidney) and reproductive tract (vaginal fluid, uterus, uterine tube, ovary and placenta) were collected from 42 slaughtered cows. Diagnostic tests included were the microscopic agglutination test (MAT), polymerase chain reaction (PCR) and bacterial isolation. Anti-Leptospira spp. antibodies were found in 27 (64.3%) of the animals analyzed using MAT at a 1:50 dilution (cut-off 50), while 31 (73.8%) animals had at least one organ/fluid where the presence of Leptospira spp. DNA was identified, and 29 animals (69%) were positive at bacteriological culture. The highest sensitivity values for MAT were obtained at the cut-off point of 50. In conclusion, even under hot and dry climate conditions, it is possible that Leptospira spp. can spread through alternative routes such as venereal transmission; moreover, a cut-off of 50 is recommended for the serological diagnosis of cattle from the Caatinga biome.

Leptospirosis modelling using hydrometeorological indices and random forest machine learning

Leptospirosis is a zoonosis that has been linked to hydrometeorological variability. Hydrometeorological averages and extremes have been used before as drivers in the statistical prediction of disease. However, their importance and predictive capacity are still little known. In this study, the use of a random forest classifier was explored to analyze the relative importance of hydrometeorological indices in developing the leptospirosis model and to evaluate the performance of models based on the type of indices used, using case data from three districts in Kelantan, Malaysia, that experience annual monsoonal rainfall and flooding. First, hydrometeorological data including rainfall, streamflow, water level, relative humidity, and temperature were transformed into 164 weekly average and extreme indices in accordance with the Expert Team on Climate Change Detection and Indices (ETCCDI). Then, weekly case occurrences were classified into binary classes "high" and "low" based on an average threshold. Seventeen models based on "average," "extreme," and "mixed" indices were trained by optimizing the feature subsets based on the model computed mean decrease Gini (MDG) scores. The variable importance was assessed through cross-correlation analysis and the MDG score. The average and extreme models showed similar prediction accuracy ranges (61.5-76.1% and 72.3-77.0%) while the mixed models showed an improvement (71.7-82.6% prediction accuracy). An extreme model was the most sensitive while an average model was the most specific. The time lag associated with the driving indices agreed with the seasonality of the monsoon. The rainfall variable (extreme) was the most important in classifying the leptospirosis occurrence while streamflow was the least important despite showing higher correlations with leptospirosis.

One Health challenges and actions: Integration of gender considerations to reduce risks at the human-animal-environmental interface

The human-animal-environment interface is where the emergence of new infectious diseases can occur as a result of many complex reasons, including its alteration due to intensive farming and agriculture, increased human encroachment into wildlife habitats, international travel networks, and urbanization. The One Health approach to zoonoses is a holistic approach that considers environmental sustainability, animal health, and human health together. Gender-specific social and domestic roles can modulate (increase or decrease) an individual's risk of exposure to various hazards, including infectious diseases and zoonoses. The two scenarios presented here, one on avian influenza and the other on leptospirosis, clearly highlight the influence of gender, demonstrating that women's roles at the human-animal-environment interface are not the same as men's. Integrating the gender aspect into cross-sectoral interventions defined according to the One Health perspective could help reduce the risks of exposure to infections for humans and animals and the possible consequent economic losses. We suggest supplementing the One Health perspective with a gender analysis to study the influence of social norms, activities and risk behavior on exposure to infections, chemical pollution and the consequences of climate change.

Leptospirosis: A Potential Culprit for Chronic Kidney Disease of Uncertain Etiology

PURPOSE

Chronic kidney disease of uncertain etiology (CKDu) is an environmental nephropathy in which the etiological factors are yet uncertain. Leptospirosis, a spirochetal infection that is common among agricultural communities, has been identified as a potential etiology for CKDu beyond environmental nephropathy. Although CKDu is a chronic kidney disease, in endemic regions, an increasing number of cases are reported with features suggestive of acute interstitial nephritis without any known reason (AINu), with or without background CKD. The study hypothesizes that exposure to pathogenic leptospires is one of the causative factors for the occurrence of AINu.

METHOD

This study was carried out using 59 clinically diagnosed AINu patients, 72 healthy controls from CKDu endemic region (endemic controls [ECs]), and 71 healthy controls from CKDu non-endemic region (non-endemic controls [NECs]).

RESULTS

The seroprevalence of 18.6, 6.9, and 7.0% was observed in the AIN (or AINu), EC, and NEC groups, respectively, from the rapid IgM test. Among 19 serovars tested, the highest seroprevalence was observed at 72.9, 38.9, and 21.1% in the AIN (AINu), EC, and NEC groups, respectively, by microscopic agglutination test (MAT), particularly for serovar Leptospira santarosai serovar Shermani. This emphasizes the presence of infection in AINu patients, and this also suggests that Leptospira exposure might play an important role in AINu.

CONCLUSION

These data suggest that exposure to Leptospira infection could be one of the possible causative factors for the occurrence of AINu, which may lead to CKDu in Sri Lanka.

In silico screening and epitope mapping of leptospiral outer membrane protein-Lsa46

Leptospirosis is one of the neglected diseases caused by the spirochete, Leptospira interrogans. Leptospiral surface adhesion (Lsa) proteins are surface exposed outer membrane proteins present in the pathogen. It acts as laminin and plasminogen binding proteins which enable them to infect host cells. The major target for the development of vaccine in the current era focuses on surface exposed outer membrane proteins, as they can induce strong and fast immune response in hosts. Therefore, the present study mapped the potential epitopes of the Leptospiral outer membrane proteins, mainly the surface adhesion proteins. Protein sequence analysis of Lsa proteins was done by in silico methods. The primary protein sequence analysis revealed Lsa46 as a suitable target which can be a potent Leptospiral vaccine candidate. Its structure was modelled by threading based method in I-TASSER server and validated by Ramachandran plot. The predicted epitope's interactions with human IgG, IgM(Fab) and T-cell receptor TCR(αβ) were performed by molecular docking studies using Biovia Discovery studio 2018. One of the predicted B-cell epitopes and the IgG showed desirable binding interactions, while four of the predicted B-cell epitopes and T-cell epitopes showed desirable binding interactions with IgM and TCR respectively. The molecular dynamic simulation studies carried out with the molecular docked complexes gave minimized energies indicating stable interactions. The structural analysis of the entire simulated complex showed a stable nature except for one of the Epitope-IgM complex. Further the binding free energy calculation of eight receptor-ligand complex predicted them energetically stable. The results of the study help in elucidating the structural and functional characterization of Lsa46 for epitope-based vaccine design.Communicated by Ramaswamy H. Sarma.

Utility evaluation of two molecular methods for Leptospira spp. typing in human serum samples

Most of the available genotyping methods were applied and evaluated in Leptospira isolates and only few of them in a relevant sample size of blood specimens but not of sera. The objective of this study was to evaluate the utility of one partial 16S rRNA gene sequencing assay (16S rRNA) and an optimized. Multilocus sequence typing scheme (MLST) for Leptospira typing directly in serum samples. Confirmed leptospirosis patients (n = 228) from Argentina (2005-2016) were randomly included. Septicemic-phase serum samples (n = 228) were studied by two genotyping methods. Available immune-phase serum samples of the included patients (n = 159) were studied by MAT to compare serological and molecular results. In culture-proven cases (n = 8), genotyping results between clinical samples and isolates were compared. Typing success rate (TSR) was 21.9% for 16S rRNA and 11.4% for MLST (full allelic profile) and a positive trend in both TSR during the study period was observed. Two species (L. interrogans and L. borgpertesenii) were identified by both methods and MLST assigned 8 different STs. The probable serogroups identified by MLST were coincident with the presumptive infecting serogroups identified by MAT, but with different frequencies. The three serogroups (Canicola, Sejroe and Icterohaemorrhagiae) most frequently identified by MAT were also genotyped by MLST. Typing results via 16S rRNA and MLST in clinical samples and isolates of culture-proven cases, were consistent except for one case. Performance of partial 16S rRNA gene sequencing assay and the optimized MLST scheme directly in sera may increase and improve the knowledge about species and serogroups causing human leptospirosis, especially in countries with low rates of culture sample collection or Leptospira isolation.

Distribution, frequency and clinical presentation of leptospirosis and coinfections: a systematic review protocol

INTRODUCTION

Leptospirosis is a zoonotic disease with high prevalence in low-income and middle-income countries and tropical and subtropical regions. The clinical symptoms of the disease are similar to symptoms presented by other endemic infectious diseases that could be present simultaneously. Thus, leptospirosis could be masked by similar infections like dengue, malaria, hantavirus, melioidosis and borreliosis, among others. Therefore, leptospirosis could present itself as an under-reported infection or as a coinfection with another pathogen, as has been reported in the literature. However, there is a lack of documented evidence about the specific risk factors of leptospirosis infection, the symptoms, the coinfection's mortality and the frequency of coinfection. Additionally, leptospirosis coinfections have not been considered a neglected public health concern. Therefore, this systematic review aims to evaluate published articles that show the risk factors associated with leptospirosis infection and coinfection with other pathogens.

METHODS AND ANALYSIS

The search process to identify eligible studies will be conducted including the LILACS, ProQuest, PubMed and Scopus databases with no restriction in terms of publication date. Also, grey literature will be included in the research. Authors will independently screen the title and abstracts of the articles identified from the search using Rayyan free software. Eligibility criteria include peer-reviewed research articles written in English or Spanish, including observational studies, cohorts, case-control, cross-sectional, ecological studies and report cases. The systematic review will include studies that report descriptions of leptospirosis cases with coinfection or co-occurrence. The search will be accomplished by articles from 1950 to May 2022. The data will be extracted in a standard extraction form using an Excel format.

ETHICS AND DISSEMINATION

Results will be published in a peer-reviewed journal. Also, findings will be disseminated through scientific meetings. Ethical approval will not be required as this is a systematic review and primary data will be not collected or included.

PROSPERO REGISTRATION NUMBER

CRD42021234754.

Leptospiral sphingomyelinase Sph2 as a potential biomarker for diagnosis of leptospirosis

Leptospirosis is an underestimated infectious tropical disease caused by the spirochetes belonging to the genus Leptospira. Leptospirosis is grossly underdiagnosed due to its myriad symptoms, varying from mild febrile illness to severe haemorrhage. Laboratory tests for leptospirosis is an extremely important and potent way for disease diagnosis, as the clinical manifestations are very similar to other febrile diseases. Currently available diagnostic techniques are time-consuming, require expertise and sophisticated instruments, and cannot identify the disease at an early phase of infection. Early diagnosis of leptospirosis is the need of the hour while considering the severe complications after the infection and the rate of mortality after misdiagnosis. Secretion of Leptospira-specific sphingomyelinases in leptospirosis patient's urine within a few days of the onset of infection is quite common and is a virulence factor present only in pathogenic Leptospira species. Herein, the structural and functional importance of leptospiral sphingomyelinase Sph2 in leptospirosis pathogenesis, as well as the potential of screening urinary Sph2 for diagnosis and the scope for developing a rapid and easily affordable point-of-care test for urinary leptospiral sphingomyelinase Sph2 as an alternative to current diagnostic methods are discussed.

Monitoring of Leptospira species diversity in freshwater bathing area and in rats in Paris, France

Leptospirosis is a neglected zoonotic disease with a worldwide distribution caused by bacterial pathogenic Leptospira. Rodents are considered as the main reservoir of Leptospira and transmission usually occurs through exposure to urine-contaminated environment. However, interactions between environment, rodent reservoir and human leptospirosis remain poorly studied. Here, we evaluated the concentration of Leptospira in surface water and captured rats in the city of Paris (France) from 2018 to 2020 using an integrity qPCR (Quantitative Polymerase Chain Reaction). All environmental samples (n = 1031) were positive for saprophytic Leptospira but pathogenic Leptospira P1 group were only found in 40% (n = 363; 2018) to 0% (n = 264; 2020) of samples. In the same time, analysis of 200 brown rat corpses trapped in the city, showed about 15% of positivity for Leptospira but the different method used for rats conservation (based on presence or absence of conservative agent) showed important variations in the Leptospira prevalence. Metagenomic analysis, based on rrs gene sequencing, was also carried out to evaluate the distribution of Leptospira in samples. Results could indicate that some species of Leptospira are found in surface waters as well as rats, but further study is needed to accurately describe the nature of the link between these two reservoirs. Quantification of Leptospira and pathogenic species description circulating inside animal reservoir living in the vicinity of freshwater in urban areas, will be helpful to understand the eco-epidemiology of leptospirosis and to establish prevention and intervention strategies, especially in the context of organization of recreative activity events in these urban areas.

The COVID-19 Mirage: A Young Biologist With an Atypical Presentation of a Zoonotic Disease During the COVID-19 Pandemic

COVID-19 has become one of the main causes of febrile illness among emergency department patients and is always a differential diagnosis to keep in mind. Nonetheless, some patients with a history of exposure, persistent fever, and suspicion of COVID-19 end up having entirely different etiologies. Here, we present the case of a 29-year-old male biologist with an uncommon presentation of a zoonotic disease, characterized by unspecific signs and symptoms, which led to a delayed diagnosis, causing significant emotional distress in the patient. We also coin the term “COVID-19 Mirage," to serve as a constant reminder for clinicians of the effect that COVID-19 has caused on the differential diagnosis of fever of unknown etiology.

Etiological spectrum of persistent fever in the tropics and predictors of ubiquitous infections: a prospective four-country study with pooled analysis

BACKGROUND

Persistent fever, defined as fever lasting for 7 days or more at first medical evaluation, has been hardly investigated as a separate clinical entity in the tropics. This study aimed at exploring the frequencies and diagnostic predictors of the ubiquitous priority (i.e., severe and treatable) infections causing persistent fever in the tropics.

METHODS

In six different health settings across four countries in Africa and Asia (Sudan, Democratic Republic of Congo [DRC], Nepal, and Cambodia), consecutive patients aged 5 years or older with persistent fever were prospectively recruited from January 2013 to October 2014. Participants underwent a reference diagnostic workup targeting a pre-established list of 12 epidemiologically relevant priority infections (i.e., malaria, tuberculosis, HIV, enteric fever, leptospirosis, rickettsiosis, brucellosis, melioidosis, relapsing fever, visceral leishmaniasis, human African trypanosomiasis, amebic liver abscess). The likelihood ratios (LRs) of clinical and basic laboratory features were determined by pooling all cases of each identified ubiquitous infection (i.e., found in all countries). In addition, we assessed the diagnostic accuracy of five antibody-based rapid diagnostic tests (RDTs): Typhidot Rapid IgM, Test-it^TM Typhoid IgM Lateral Flow Assay, and SD Bioline Salmonella typhi IgG/IgM for Salmonella Typhi infection, and Test-it^TM Leptospira IgM Lateral Flow Assay and SD Bioline Leptospira IgG/IgM for leptospirosis.

RESULTS

A total of 1922 patients (median age: 35 years; female: 51%) were enrolled (Sudan, n = 667; DRC, n = 300; Nepal, n = 577; Cambodia, n = 378). Ubiquitous priority infections were diagnosed in 452 (23.5%) participants and included malaria 8.0% (n = 154), tuberculosis 6.7% (n = 129), leptospirosis 4.0% (n = 77), rickettsiosis 2.3% (n = 44), enteric fever 1.8% (n = 34), and new HIV diagnosis 0.7% (n = 14). The other priority infections were limited to one or two countries. The only features with a positive LR ≥ 3 were diarrhea for enteric fever and elevated alanine aminotransferase level for enteric fever and rickettsiosis. Sensitivities ranged from 29 to 67% for the three RDTs targeting S. Typhi and were 9% and 16% for the two RDTs targeting leptospirosis. Specificities ranged from 86 to 99% for S. Typhi detecting RDTs and were 96% and 97% for leptospirosis RDTs.

CONCLUSIONS

Leptospirosis, rickettsiosis, and enteric fever accounted each for a substantial proportion of the persistent fever caseload across all tropical areas, in addition to malaria, tuberculosis, and HIV. Very few discriminative features were however identified, and RDTs for leptospirosis and Salmonella Typhi infection performed poorly. Improved field diagnostics are urgently needed for these challenging infections.

TRIAL REGISTRATION

NCT01766830 at ClinicalTrials.gov.

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.

Dissemination of Leptospira into the intestinal tract resulting in fecal excretion in a hamster model of subcutaneous infection with Leptospirainterrogans

Leptospirosis, caused by pathogenic Leptospira, is one of the most common zoonotic diseases in the world. It is transmitted to humans through the skin and mucous membranes by contact with water or soil contaminated with urine excreted from infected animals. In human infections, gastrointestinal symptoms such as abdominal pain, vomiting, and diarrhea have been frequently observed, but there have been no reports analyzing gastrointestinal lesions in leptospirosis, and the pathological mechanism of gastrointestinal symptoms in leptospirosis remains unclear. In this study, we investigated the pathological changes and the distribution of leptospires in the intestinal wall, and the presence of leptospires in the intestinal contents and feces, of hamsters subcutaneously infected with Leptospira interrogans. Results showed that infected hamsters had macroscopic redness in the jejunum and ileum. Submucosal hemorrhage was observed histologically, and there was no infiltration of inflammatory cells such as neutrophils. There were no obvious changes in the colon, either macroscopically or histologically, and the feces were normal (solid stools). Leptospira was isolated from all the intestinal walls from the small intestine to the colon, the intestinal contents, and the feces. These findings suggest that the invasion of leptospires into the intestinal wall and the associated submucosal hemorrhage may be the cause of the gastrointestinal symptoms observed in leptospirosis. Furthermore, not only the urine of infected animals but also the feces could be a source of infection.

Assessment of the Current Surveillance System for Human Leptospirosis in Ecuador by Decision Analytic Modeling

Leptospirosis is a globally disseminated zoonotic disease with no national surveillance systems. On the other hand, surveillance is crucial for improving population health, and surveillance systems produce data that motivates action. Unfortunately, like many other countries, Ecuador put in place a monitoring system that has never been tested. The goal of this study was to use scenario tree modeling to assess the sensitivity of Ecuador's current national surveillance system to human leptospirosis as the basis for an economic assessment of the system. We created a decision-tree model to analyze the current system's sensitivity. The inputs were described as probabilities distributions, and the model assessed the program's sensitivity as an output. The model also considers the geographical and weather variations across Ecuador's three continental regions: Andean, Amazonia, and the Coast. Several data sources were used to create the model, including leptospirosis records from Ecuador's Ministry of Public Health, national and international literature, and expert elicitation, all of which were incorporated in a Bayesian framework. We were able to determine the most critical parameters influencing each scenario's output (CSU) sensitivity through sensitivity analysis. The Coast region had the best sensitivity scenario, with a median of 0.85% (IC 95% 0.41-0.99), followed by the Amazonia with a median of 0.54% (CI 95% 0.18-0.99) and the Andes with a median of 0.29% (CI 95% 0.02-0.89). As per the sensitivity study, the most influential criteria on the system's sensitivity were "Attendance or probability of going to a health center" and "probability of having symptoms," notably for the Coast and Amazonia Regions.

Rapid diagnostic test (Leptocheck-WB) for detection of acute leptospirosis: a meta-analysis of diagnostic accuracy

The majority of leptospirosis is subclinical or mild self-limiting systemic illness. A rapid and accurate diagnostic test for the detection of leptospirosis is essential to prevent disease progression from acute non-severe illness to potentially fatal infection. Rapid diagnostic tests (RDTs) recognized as point-of-care (PoC) tests may support clinical decision-making in resource-poor settings. We aimed to assess the accuracy of PoC (Leptocheck-WB) for the detection of acute leptospirosis by meta-analysis of data from eligible studies. This study adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis for Diagnostic Test Accuracy (PRISMA-DTA) guideline. The pooling of data was done only when there were two or more studies that used a particular type of reference test. A total of ten studies (n = 5369) were identified. The majority (70%) were from the Asian region. Using microscopic agglutination test (MAT) as reference test, the pooled sensitivity (0.75, 95% CI: 0.64 to 0.84, 10 studies, I²: 85.9%) and specificity (0.87, 95% CI: 0.77 to 0.94, 10 studies, I²: 97.37%) of Leptocheck-WB in the detection of leptospirosis were moderate. With the use of enzyme-linked immunosorbent assay (ELISA) reference test, the pooled sensitivity 0.85 (95% CI: 0.79 to 0.9, 4 studies, I²: 27.49%) and specificity 0.79 (95% CI: 0.71 to 0.85, 4 studies, I²: 58.9%) of Leptocheck-WB were also moderate. Diagnostic odds ratio of Leptocheck-WB with MAT (21, 95% CI: 10-44) or with ELISA as reference test (21, 95% CI: 9-46) showed an acceptable level of accuracy. Meta-regression analysis showed methodological quality of studies (p: 0.06) and study design (p: 0.09) were potential factors that affected the accuracy of Leptocheck-WB test. Findings suggest that Leptocheck-WB has a moderate level of acceptance for detection of acute leptospirosis. Further confirmation with large-sampled, prospectively designed studies using the same samples for evaluating test accuracy is recommended.

The role of small ruminants in the epidemiology of leptospirosis

Leptospirosis is a common global zoonotic disease of man and all farm animals. Although most leptospiral infections in sheep and goats are asymptomatic, they may play a role in the epidemiology of the disease by the spread of Leptospira through the urine. This study was carried out to evaluate the role of sheep and goats in the epidemiology of leptospirosis. Blood and urine samples were taken from 210 goats and 246 sheep. To detect antibodies, sera samples were tested with 8 live serovars of L. interrogans (Hardjo, Pomona, Grippotyphosa, Canicola, Ballum, Icterhemorrhagiae, Tarasovi, and Australis) by MAT. Then, urine samples were tested by Nested PCR targeting 16S rRNA gene for detection of pathogenic Leptospira. Results of MAT showed that 10.95% of goats and 8.53% of sheep had antibodies against at least one examined serovars. In both species, the highest reacting was L. i. Pomona with a rate of 68.18% and 56% in sheep and goats, respectively. Moreover, in PCR, 2 (0.95%) urine samples of goat and 12 (4.87%) urine samples of sheep were positive. All of the MAT positive studied animals were PCR negative and, statistical analysis showed that there was no relationship and agreement between the results of PCR and MAT in sheep (kappa = − 0.07, p > 0.05) and goats (kappa = − 0.02, p > 0.05). Finally, it is concluded that sheep and goats can excrete L. interrogans in the urine and thus transmit them to other animals and humans.

Integrated Lateral Flow Electrochemical Strip for Leptospirosis Diagnosis

LipL32 is an outer membrane protein present only on pathogenic Leptospira species, which is the causative agent of leptospirosis. Leptospirosis symptoms are often misdiagnosed with other febrile illnesses as the clinical manifestations are non-specific. Therefore, an accurate diagnostic tool for leptospirosis is indeed critical for proper and prompt treatment. Typical diagnosis via serological assays is generally performed to assess the antibodies produced against Leptospira. However, their delayed antibody response and complicated procedure undoubtedly limit the practical utilization especially in a primary care setting. Here, we demonstrate for the first time an early-stage detection of LipL32 by an integrated lateral-flow immunoassay with an electrochemical readout (eLFIA). A ferrocene trace tag was monitored via differential pulse voltammetry operated on a smartphone-based device, thus allowing for on-field testing. A superior performance in terms of the lowest detectable limit of detection of 8.53 pg/mL and broad linear dynamic range (5 orders of magnitude) among other sensors available thus far was established. Additionally, the developed test strip provided a straightforward yet sensitive approach for diagnosis of leptospirosis using the collected human sera from patients, in which the results were comparable to the real-time polymerase chain reaction technique.

Rapid and sensitive point-of-care detection of Leptospira by RPA-CRISPR/Cas12a targeting lipL32

Background

One of the key barriers preventing rapid diagnosis of leptospirosis is the lack of available sensitive point-of-care testing. This study aimed to develop and validate a clustered regularly-interspaced short palindromic repeat (CRISPR)/CRISPR-associated protein 12a (CRISPR/Cas12a) platform combined with isothermal amplification to detect leptospires from extracted patient DNA samples.

Methodology/Principal findings

A Recombinase Polymerase Amplification (RPA)-CRISPR/Cas12a-fluorescence assay was designed to detect the lipL32 gene of pathogenic Leptospira spp. The assays demonstrated a limit of detection (LOD) of 100 cells/mL, with no cross-reactivity against several other acute febrile illnesses. The clinical performance of the assay was validated with DNA extracted from 110 clinical specimens and then compared to results from qPCR detection of Leptospira spp. The RPA-CRISPR/Cas12a assay showed 85.2% sensitivity, 100% specificity, and 92.7% accuracy. The sensitivity increased on days 4–6 after the fever onset and decreased after day 7. The specificity was consistent for several days after the onset of fever. The overall performance of the RPA-CRISPR/Cas12a platform was better than the commercial rapid diagnostic test (RDT). We also developed a lateral flow detection assay (LFDA) combined with RPA-CRISPR/Cas12a to make the test more accessible and easier to interpret. The combined LFDA showed a similar LOD of 100 cells/mL and could correctly distinguish between known positive and negative clinical samples in a pilot study.

Conclusions/Significance

The RPA-CRISPR/Cas12 targeting the lipL32 gene demonstrated acceptable sensitivity and excellent specificity for detection of leptospires. This assay might be an appropriate test for acute leptospirosis screening in limited-resource settings.

Clinical signs and symptoms of leptospirosis are similar to those of other infectious diseases such as dengue, sepsis, and malaria, making it difficult to diagnose. In this study, we developed an RPA-CRISPR/Cas12a -based detection platform to identify the lipL32 gene of pathogenic Leptospira spp. The results showed that the limit of detection (LOD) was approximately 10² cells/mL without cross-reactivity against other infectious diseases. The platform was validated using 110 patients from 15 hospitals in Sisaket province, Thailand. The sensitivity, specificity, and accuracy was found to be 85.2%, 100% and 92.7%, respectively, for the diagnosis of leptospirosis. Assay sensitivity increased at 4–6 d post-onset of fever, with a consistent specificity every day after the onset of fever. We also developed a lateral flow detection assay combined with RPA-CRISPR/Cas12a, which also had a LOD of 10² cells/mL and could correctly distinguish known positive and negative clinical samples in a pilot study. Findings from this study demonstrate the potential effectiveness of the RPA-CRISPR/Cas12a platform in improving speed and accuracy of leptospirosis diagnosis especially in limited-resource settings.

Leptospirosis is an emerging infectious disease of pig-hunting dogs and humans in North Queensland

BACKGROUND

Leptospirosis is a zoonotic disease with a worldwide distribution, caused by pathogenic serovars in the genus Leptospira. Feral pigs are known carriers of Leptospira species and pig hunting using dogs is a common recreational activity in Queensland, Australia.

METHODOLOGY AND PRINCIPAL FINDINGS

This study aimed to determine the seroprevalence of Leptospira spp. serovars in pig-hunting dogs above the Tropic of Capricorn in Queensland and by establishing the geographic distribution, serovars and incidence of human cases of leptospirosis in Queensland, identify potential overlap between human and canine exposure. We also explored the knowledge and risk-taking behaviours of pig-hunting dog owners towards zoonotic diseases. Ninety-eight pig-hunting dogs deemed healthy by physical examination and owned by 41 people from Queensland had serum submitted for Microscopic Agglutination Testing (MAT) to determine antibody titres against Leptospira serovars, while 40/41 dog owners completed a survey on their knowledge of diseases relating to pig hunting. Human leptospirosis cases (n = 330) notified to Queensland Health between 2015-2018 were analysed. Approximately one quarter (23/87; 26%) of unvaccinated pig-hunting dogs were seropositive to Leptospira spp. Although harder to interpret, 8/11 (73%) vaccinated dogs were seropositive to Leptospira spp. Pig hunters may be more likely to contract leptospirosis compared with the general Queensland population, based on responses from surveyed hunters. The highest concentration of human leptospirosis was in the wet tropics region of Far North Queensland. There was little overlap between the serovars dogs were exposed to and those infecting humans. The dominant serovar identified in unvaccinated dogs was Australis (13/23; 57%), with serovar Arborea (36/330; 10.9%) responsible for the highest number of human leptospirosis cases. Topaz was the second most common serovar in both humans and dogs and was previously unrecorded in Australian dogs. Most hunters surveyed used hand washing as a zoonotic disease risk reduction technique.

CONCLUSIONS

Leptospirosis is an emerging disease of growing significance. The infection requires a 'one health' approach to understand its epidemiology. With shifting climatic patterns influencing human-animal-environment interactions, ongoing monitoring of diseases like leptospirosis is critical to helping prevent infection of individuals and disease outbreaks.

Leptospirosis

Leptospirosis is a blood infection caused by the bacterium Leptospira. Signs and symptoms can range from none to mild (headaches, muscle pains, and fevers) to severe (bleeding in the lungs or meningitis). Weil's disease, the acute, severe form of leptospirosis, causes the infected individual to become jaundiced (skin and eyes become yellow), develop kidney failure, and bleed. Pulmonary hemorrhage in association with leptospirosis is known as "severe pulmonary haemorrhage syndrome". More than ten genetic types of Leptospira, which are a type of a spirochaete, cause disease in humans. Both wild and domestic animals can spread the disease, most commonly rodents. The bacteria are spread to humans through animal urine, or water and soil contaminated with animal urine, coming into contact with the eyes, mouth, nose or breaks in the skin. In developing countries, the disease occurs most commonly in farmers and low-income people who live in areas with poor sanitation. In developed countries, it occurs during heavy downpours and can affect those involved in outdoor activities in warm and wet areas. Diagnosis is typically by testing for antibodies against the bacteria or finding bacterial DNA in the blood. Efforts to prevent the disease include protective equipment to block contact when working with potentially infected animals, washing after contact, and reducing rodents in areas where people live and work. The antibiotic doxycycline is effective in preventing leptospirosis infection. Human vaccines are of limited usefulness; vaccines for other animals are more widely available. Treatment when infected is with antibiotics such as doxycycline, penicillin, or ceftriaxone. The overall risk of death is 5–10%. However, when the lungs are involved, the risk of death increases to the range of 50–70%. It is estimated that one million people worldwide are infected by leptospirosis every year, causing approximately 58,900 deaths. The disease is most common in tropical areas of the world but may occur anywhere. Outbreaks may arise after heavy rainfall. The disease was first described by physician Adolf Weil in 1886 in Germany. Infected animals may have no, mild or severe symptoms. These may vary by the type of animal. In some animals Leptospira live in the reproductive tract, leading to transmission during mating.

Spectrofluorimetric-based approach to screen urine contamination in drinking water: A step toward the development of screening method for leptospirosis

Hygiene hypothesis and sanitization are two important pivots of modern civilization. The drinking water should be free from urine and stool contamination. Coliform test is popular for understanding feces contamination. However, understanding urine contamination in drinking water is a difficult task. On the other hand, urine contamination can cause disease like leptospirosis. It occurs mainly in animals and infects humans through contaminated water, food, and soil and causes serious consequences. Rat urine is the most common source of such disease outbreaks. Further, sophisticated laboratories with high-end technologies may not be present at the site of disease outbreaks. In this context, we have proposed a spectrofluorimetric approach to screen urine contamination in water. The screening method can sense up to 156 nl/ml of rat urine.

Comparison of ELISA using recombinant LipL32 and sonicated antigen of leptospira for detecting bovine leptospirosis

Leptospirosis is one of the most widely distributed zoonosis in the world. Bovine leptospirosis is a serious problem in bovine production, causing reproductive losses. The aim of this work was to compare recombinant LipL32 with sonicated antigen for detecting anti-Leptospira IgG antibodies in bovine serum using ELISA. The Microscopic Agglutination Test (MAT) is used as the gold standard. Sonicated antigen from cultures of Leptospira interrogans serogroup Icterohaemorrhagiae serovar copenhageni (strain M20) was used for the eELISA and rLipL32 for the rELISA. The performance of these assays was evaluated using serum samples from 166 bovines, 69 MAT positive and 97 MAT negative. At the optimal cut-off point recommended by the receiver operating characteristic (ROC) curve analysis, the sensitivity and specificity values were 98.6% and 97.9%, respectively, for eELISA, and 85.5% and 86.6% respectively, for rELISA. The value for the area under the ROC curve was 0.998 (0.994-1.0) (CI 95%) for eELISA and 0.929 (0.891-0.968) (CI 95%) for rELISA. The ROC curves for rLipL32 and sonicated antigen showed statistically significant differences (z = -3.826; p = 0.000). A three-way comparison showed statistically significant differences in the sensitivity and specificity of rELISA and eELISA. Our results showed that eELISA was more specific and sensitive than rELISA. The difference in performance (eELISA-rELISA) was 13.4% (4.03-23.28) (CI 95%) for sensitivity and 11.34 % (4.07-19.56) (CI 95%) for specificity. Our results show that the eELISA has a better diagnostic performance than rELISA for the detection of anti-Leptospira IgG antibodies in bovine serum.

Absence of serological or molecular evidence of Leptospira infection in farmed swine in the Hong Kong Special Administrative Region

Leptospirosis is an important zoonotic disease with several maintenance host species including swine. A cross sectional survey was undertaken between January to October 2020 to investigate the prevalence of leptospirosis in farmed swine in the Hong Kong Special Administrative Region (HKSAR) of China. Serum samples were collected from swine on seven farms (15 swine per farm; ten multiparous sows and five twelve-week-old weaners), while kidney samples were collected from 64 swine submitted for routine post-mortem (26 farms; average 2.4 swine per farm, range 1-6). Microscopic agglutination tests (MAT) to a panel of 24 Leptospira antigens did not reveal any evidence of seroconversion at a titre of 1:100. Polymerase chain reaction (PCR) testing of the kidney samples for Leptospira DNA did not detect any evidence of infection. Bayesian methods were used to compute the probability that the leptospirosis prevalence in farmed swine in the HKSAR was <3%, given none of the 105 swine sampled were positive on the MAT. The results of this study demonstrate no serological or molecular evidence of leptospirosis in farmed swine in the HKSAR. Subsequent statistical analysis supports the conclusion that the prevalence of leptospirosis in farmed swine in the HKSAR is negligible at present.

Seroprevalence and risk factors of Leptospira sp. among different groups in the Jordanian population: first study

BACKGROUND

Leptospirosis is re-emerging as a major public health problem worldwide. However, there are limited data on the disease from the Middle East, including from Jordan, despite recent outbreaks occurring in Jordan's neighbouring countries.

METHODS

Sera samples from 809 participants in 11 governorates were tested for Leptospira sp. seropositivity to determine the seroprevalence and risk factors of Leptospira sp. in Jordan.

RESULTS

Overall, 3.3% (95% confidence interval [CI] 2.2 to 4.8) of individuals tested were seropositive for Leptospira antibodies. Individuals who drink surface water (spring or rain water) had 5.69 (95% CI 2.57 to 12.60) higher odds of seropositivity compared with individuals who used municipal or filtered water, after controlling for age and practicing horticulture.

CONCLUSIONS

This is the first seroprevalence study of Leptospira sp. in Jordan and included important data on environmental and animal exposures.