Leptospira: the dawn of the molecular genetics era for an emerging zoonotic pathogen

Proteolytic activity of secreted proteases from pathogenic leptospires and effects on phagocytosis by murine macrophages

Leptospirosis is a zoonosis caused by spirochete Leptospira. Pathogenic leptospires evade the Complement System, enabling their survival upon contact with normal human serum in vitro. In a previous study, we demonstrated that proteases secreted by pathogenic leptospires cleave several Complement proteins, including C3 and the opsonins C3b and iC3b. We hypothesize that these Leptospira proteases, such as thermolysin and leptolysin, may decrease the phagocytic activity of murine peritoneal macrophages. We observed decreased amounts of CR3 and CR4 using flow cytometry when these cells were treated with supernatant from the culture of pathogenic leptospires (SPL) for 24 h. Through confocal microscopy, we observed a reduction in TLR2, CD11b, and CD206 (mannose receptor) levels when these cells were treated with SPL or recombinant thermolysin for 24 h. Furthermore, opsonins such as C3b/iC3b deposited on the surface of pathogenic leptospires were clearly degraded in the presence of recombinant thermolysin or recombinant leptolysin. Consequently, when opsonized bacteria and macrophages were previously incubated with these proteases, phagocytic activity was diminished. These observations lead us to suggest that proteases secreted by pathogenic leptospires could degrade opsonins present in normal serum or deposited on the bacterial membrane, as well as cleave or inhibit macrophage surface molecules. Therefore, these proteases could interfere with the recognition and internalization by murine macrophages, favoring the spread of leptospires in the host.

Serological and molecular investigation of Leptospira spp. In bats (Chiroptera, Mammalia) from Brazil

Bats play a crucial role in the ecosystem, yet concerns have arisen regarding their potential as carriers of zoonotic bacteria, including Leptospira spp. Due to the lack of knowledge about the carrier state of bats in Brazil, this study aimed to evaluate the presence of antibodies against Leptospira spp. and its DNA in bats from four Brazilian States (São Paulo, Paraíba, Pernambuco, and Ceará). Bats were captured using mist nets and categorized by sex, age, and species. Antibodies were searched in 22 bats via the microscopic agglutination test (MAT). Additionally, 168 kidney and nine urine samples were subjected to PCR for Leptospira spp. Out of 177 samples tested, two (1.13 %) were positive in PCR, while none showed reactivity in MAT. These results suggest a low prevalence of Leptospira spp. infection in bats, indicating a limited role in transmitting leptospirosis to humans, domestic animals, and wildlife in the studied region.

Urinary leptospiral sphingomyelinases as diagnostic markers of leptospirosis in dengue patients co-infected with leptospirosis

The study aims to evaluate the diagnostic potential of pathogen-specific leptospiral sphingomyelinases, LipL32, LipL41, and HbpA in human patients with dengue-leptospirosis coinfection. Patients (n-86), upon clinical evaluation, were categorized into Group I (n-37; leptospirosis), Group II (n-39; dengue-leptospirosis coinfection), and Group III (n-10; negative for both dengue and leptospirosis). ELISA identified significant levels of the four leptospiral antigens in the urine of Group I and II, but not in Group III patients. Immunoblot analysis of the urinary proteins with specific antibodies identified the tissue-damaging true sphingomyelinases Sph2 and pore-forming SphH. Urinary leptospiral antigens identified patients with leptospirosis and with dengue-leptospirosis coinfection. Patients with renal damage and proteinuria showed high urinary excretion of anti-leptospiral antibodies, with markedly low values in the serum. Proteinuria resulted in the loss of the circulating proteins, reflected by the low levels of anti-leptospiral antibodies in serum, with urine showing albumin and high levels of anti-leptospiral antibodies. IMPORTANCE: The study highlights the diagnostic potential of all four leptospiral antigens. Since early detection of urinary sphingomyelinases is possible, their diagnostic and prognostic potential can be evaluated on a larger sample size. Non-invasive, point-of-care diagnostic devices can be developed for use in endemic regions, particularly during monsoon seasons.

Comparison of clinical and laboratory data between hantavirus infection and leptospirosis: a retrospective case series study in southern Taiwan

BACKGROUND

Leptospirosis (LS) and hantavirus (HV) are rodent-borne diseases and share similar clinical manifestations, posing diagnostic challenges.

METHODS

This retrospective study compared clinical characteristics, laboratory data, complications and outcomes of 33 LS and nine HV cases in Kaohsiung, Taiwan, from 2006 to 2021.

RESULTS

Both LS and HV diseases had high rates of acute kidney injury (84.8% vs 66.7%) and hepatitis (65.6% vs 88.9%); LS showed more hyperbilirubinemia (70% vs 12.5% in HV, p=0.005), higher initial creatinine levels (2.9 vs 1.37, p=0.018) and elevated initial C-reactive protein (218.3 vs 28.6 mg/dl, p<0.001), but lower initial lymphocyte percentage (6.63% vs 14.2%, p=0.005) and platelets (138.7/mm3 vs 68.9, p=0.016) compared with HV. Microscopic hematuria was significantly more prevalent in LS (80% vs 28.65% in HV, p=0.016). Notably, the LS and HV groups exhibited statistically significant differences in thrombocytopenia (57.5% vs 100%, p=0.019), hyperbilirubinemia (70% vs 12.5%, p=0.005), shock (45.5% vs 0%, p=0.016) and hematuria (80% vs 28.6%, p=0.016). Neither group experienced fatalities.

CONCLUSIONS

Fever, thrombocytopenia and acute kidney injury alert physicians to consider LS and HV for differential diagnosis. Elevated bilirubin, along with hematuria or shock, suggests a preferred diagnosis for LS.

Herd and animal level seroprevalence and associated risk factors of Leptospira interrogans sensu lato serovar Hardjo in cattle in southwest Ethiopia

Leptospirosis is a significant zoonotic disease that causes high economic losses in cattle production due to its association with abortions, stillbirths, infertility, and reduced milk yields. However, the epidemiology of bovine leptospirosis in Ethiopia is poorly understood. From October 2020 to October 2021, a cross-sectional study was conducted to investigate the seroprevalence of serovar Hardjo in cattle in southwest Ethiopia, as well as the associated risk factors. To test for the existence of L. Hardjo antibodies, blood samples were taken from 461 cattle. Indirect ELISA was used to identify the presence of antibodies against L. Hardjo in sera samples. We conducted a multivariable random-effect logistic regression analysis to identify potential risk factors associated with L. Hardjo seropositivity. An overall L. Hardjo seroprevalence of 24.7% (95% CI: 20.2-48.8) and 53.5% (95% CI: 45.7-90.5) was recorded at the animal level and the herd level, respectively, in the study areas. This study revealed six factors influencing L. Hardjo seropositivity in cattle herds. Large herds had twice the odds of seropositivity (OR = 2.0, 95% CI: 1.1-3.8) compared to small herds. Co-grazing cattle exhibited higher odds (OR = 2.2, 95% CI: 1.2-4.1) of seropositivity. Extensive management systems significantly increased the odds (OR = 10.3, 95% CI: 1.7-61.8) compared to semi-intensive systems. Highland cattle had higher odds (OR = 3.7, 95% CI: 1.4-10.3) than lowland cattle. Older cattle (OR = 4.6, 95% CI: 2.4-8.9) were more likely to be seropositive. At the herd level, extensive management (OR = 2.8, 95% CI: 1.3-5.8) and large herds (OR = 2.5, 95% CI: 1.3-4.7) increased the risk of seropositivity. Herds with sheep/goats (OR = 2.3, 95% CI: 1.3-4.1) were also at higher risk, highlighting significant L. Hardjo seropositivity risk factors in cattle herds. The study findings showed that leptospirosis was highly prevalent across the study areas. As a result, use proper management, raise zoonotic awareness for leptospirosis, and conduct molecular bovine leptospirosis research in study areas were recommended.

Grenadian cats as potential reservoir for Leptospira

Leptospirosis is a spirochetal disease caused by Leptospira spp. bacteria with global distribution affecting multiple mammalian species, including humans. The disease is endemic in many geographic areas and is of particular concern in tropical regions with abundant rainfall, such as the Caribbean. Currently, there are no published reports on Leptospira exposure or infection in Grenadian cat populations, and the role of cats in the epidemiology of the disease is unknown. Our hypothesis is that Grenadian cat population may be a reservoir host for zoonotic Leptospira on the island. During 2019-2021, 160 feral cats were captured from three parishes in Grenada, and their urine and blood were tested for Leptospira. Urine from 4 of 148 (2.7%) cat samples tested PCR-positive for Leptospira. Serum from 6 of 136 (4.4%) cat samples tested PCR-positive for Leptospira. Sequence analysis of the Leptospira rpoB gene showed 86-100% similarity to known or presumed pathogenic Leptospira species. The findings of this study suggest that Grenadian cat populations are infected with and are shedding Leptospira genotypes that are phylogenetically related to known pathogenic Leptospira, including known zoonotic strains. These observations support the hypothesis that Grenadian cat populations may be a reservoir host for zoonotic Leptospira on the Island.

Insights into Leptospira spp. infection in pet cats in Croatia: Clinical, serological and molecular findings with emphasis on the potential important role of serogroup Pomona

Leptospirosis, a globally re-emerging zoonosis caused by pathogenic Leptospira spp., poses a significant threat to public health. Leptospirosis in cats is often neglected due to its high underdiagnosis. Therefore, the role of cats in disease transmission and bacterial maintenance in the environment remains unclear. For this study, 54 serum samples, 54 urine samples and 27 EDTA-anticoagulated blood samples from pet cats presenting to the Veterinary Teaching Hospital due to health problems were used. The serum samples were tested for antibodies against 12 pathogenic serovars of Leptospira spp. using the microscopic agglutination test (MAT). EDTA-anticoagulated blood and urine samples were tested for the lipL32 gene of pathogenic Leptospira spp. by conventional (PCR) and real-time (qPCR) polymerase chain reaction. Agglutinating antibodies were detected in 18.52% (10/54) of the sera with a titre range of 1:50 to 1:12800. The most common serogroup was Pomona, followed by Sejroe, Icterohaemorrhagiae, Australis and Javanica. Leptospira spp. DNA was found in 1.85% (1/54) of the urine samples, while all EDTA-anticoagulated blood samples were negative. A statistically significant difference in seropositivity regarding lifestyle was found between outdoor/indoor and indoor-only cats, while the presence of another cat in the household significantly increased the likelihood of seropositivity. Cats with immunocompromising conditions showed a significantly increased risk of seropositivity, especially those undergoing immunosuppressive treatment. In addition, respiratory signs and changes in lung structure associated with the presence of leptospiral antibodies, and these cats were more likely to be infected with the Pomona serogroup. Moreover, cats with anaemia, leucocytosis, and thrombocytopenia were significantly more likely to have antibodies against Leptospira spp., while seropositive cats had significantly lower urine-specific gravity compared to seronegative cats. The results underline the importance of raising awareness of feline leptospirosis in veterinary care and recognising pet cats as potential carriers of leptospires. Further research is needed to clarify the specific role of the Pomona serogroup as a potentially highly evolutionary drifting serogroup in terms of pathogenicity and to clarify the zoonotic potential of infected cats, which is crucial for the implementation of effective public health measures and veterinary interventions.

The Relationship Between the Spatial Occurrence of Leptospira Exposed Animals and the Characteristics of the Peridomiciles They Inhabit in a Locality of Southeastern Mexico

The occurrence of Leptospira in mammals is an indicator for assessing potential health risks, particularly in tropical regions. Understanding their hosts' habitat characteristics and spatial occurrence is essential to surveil them. This study aimed to determine the characteristics of the peridomiciles associated with the spatial occurrence of Leptospira hosts. We inventoried the characteristics of the peridomiciles. Blood serum was gathered from dogs, opossums, and rodents for a microagglutination essay to detect exposure to several serogroups of Leptospira. A generalized linear model with binomial distribution helped estimate risk ratios and 95% confidence intervals between a seropositive animal's occurrence and the peridomiciles' characteristics. For estimates with the occurrence of one or more seropositive animals, a multinomial model was fitted. The seroprevalence in rodents was 81.8%; in opossums 31.2%; and 56.5% for dogs. The most frequent serogroup in dogs and rodents was Canicola. In opossums, the seroreaction was against Tarassovi, Ballum, Sejroe, and Cynopteri. The results showed that the peridomicile area (m2), the geographic polygon, and the accumulation of plastic containers (PET) were characteristics related to the occurrence of seropositive animals. The results revealed that the peridomicile's characteristics and spatial distribution in the locality help explain the occurrence of Leptospira hosts.

Exposure to live saprophytic Leptospira before challenge with a pathogenic serovar prevents severe leptospirosis and promotes kidney homeostasis

Previous studies demonstrated that Leptospira biflexa, a saprophytic species, triggers innate immune responses in the host during early infection. This raised the question of whether these responses could suppress a subsequent challenge with pathogenic Leptospira. We inoculated C3H/HeJ mice with a single or a double dose of L. biflexa before challenge with a pathogenic serovar, Leptospira interrogans serovar Copenhageni FioCruz (LIC). Pre-challenge exposure to L. biflexa did not prevent LIC dissemination and colonization of the kidney. However, it rescued weight loss and mouse survival thereby mitigating disease severity. Unexpectedly, there was correlation between rescue of overall health (weight gain, higher survival, lower kidney fibrosis marker ColA1) and higher shedding of LIC in urine. This stood in contrast to the L. biflexa unexposed LIC challenged control. Immune responses were dominated by increased frequency of effector T helper (CD4+) cells in spleen, as well as significant increases in serologic IgG2a. Our findings suggest that exposure to live saprophytic Leptospira primes the host to develop Th1 biased immune responses that prevent severe disease induced by a subsequent challenge with a pathogenic species. Thus, mice exposed to live saprophytic Leptospira before facing a pathogenic serovar may withstand infection with far better outcomes. Furthermore, a status of homeostasis may have been reached after kidney colonization that helps LIC complete its enzootic cycle.

Innovative Strategies to Study the Pathogenesis of Elusive Spirochetes and Difficulties Managing the Chronic Infections They Cause

The major human spirochetal pathogens (Leptospira, Borrelia, and Treponema) are difficult to diagnose and lack vaccines to prevent infections. Infection by these spirochetes does not generate general protective immunity, allowing reinfection by different strains to occur. These stealth pathogens have uncommon physiology, pathogenesis, and clinical presentations and possess unique immune evasion mechanisms to facilitate their host adaptation and persistence. Collectively, host-spirochete interactions orchestrate systemic infections in a manner distinct from organ- and tissue-specific diseases caused by many bacterial pathogens. Difficulties in growing and genetic manipulation of infectious spirochetes have hindered the full understanding of their virulence factors despite decades to centuries of research. This article highlights the current understanding of the intricacies of spirochetal pathogenesis and diseases. Our comprehensive review of the progress versus gaps in knowledge lays a foundation for researchers to direct their studies toward the development of effective diagnostics and vaccines to protect patients from serious, chronic spirochetal diseases.

Ketone body oxidation and susceptibility to ethyl acetoacetate in a novel hemolytic multidrug-resistant strain Leptospira interrogans KeTo originated from sewage water

Terrestrial and aquatic environments contaminated with animal urine may contribute to the transmission of Leptospira, a causative agent of leptospirosis in humans and wild/domesticated animals. Although enormous amounts of work have been done decoding the ecophysiology, the factors governing the cell growth and virulence in Leptospires derived from environmental samples still remain elusive. Here, we show oxidation of a wide array of organic acids including acetoacetate by a new strain of Leptospira interrogans designated as KeTo, isolated from a sewage sample originating from a wildlife enclosure located at Mangalore, India. We further demonstrate the susceptibility of KeTo to ethyl ester of acetoacetate (ethyl acetoacetate, EA). A 4.7 Mbp genome of KeTo shared the highest relatedness to pathogenic L. interrogans RGAT (99.3%), followed by L. kirschneri 3522CT (91.3%) and other related species of Leptospira (80.8‒74.3%), and harbored genes encoding acetoacetyl-CoA synthetase and acetoacetate decarboxylase respectively involved in the acetoacetate utilization and acetone formation. In line with this, strain KeTo oxidized acetoacetate when supplied as a sole carbon. Aqueous EA suppressed biofilm formation (p < 0.0001) of KeTo in basal Ellinghausen-McCullough-Johnson-Harris (EMJH) medium. Similarly, significant inhibition in the growth/biofilm of Leptospira was recorded in semisolid EMJH with/without blood supplementation when exposed to volatile EA. The extent of ketone body oxidation and susceptibility to EA was found to vary with strain as evident through the analysis of L. interrogans serogroup Australis sv. Australis strain Ballico and L. interrogans serogroup Icterohaemorrhagiae sv. Lai Like strain AF61. In conclusion, our study demonstrated the ketone body metabolic ability and susceptibility to an esterified derivative of a major ketone body in the tested strains of L. interrogans. Molecular aspects governing EA-driven growth inhibition warrant further investigations to develop optimal therapeutics for leptospirosis.

Disentangling the influence of reservoir abundance and pathogen shedding on zoonotic spillover of the Leptospira agent in urban informal settlements

Rats are major reservoirs for pathogenic Leptospira, the bacteria causing leptospirosis, particularly in urban informal settlements. However, the impact of variation in rat abundance and pathogen shedding rates on spillover transmission to humans remains unclear. This study aimed to investigate how spatial variation in reservoir abundance and pathogen pressure affect Leptospira spillover transmission to humans in a Brazilian urban informal settlement. A longitudinal eco-epidemiological study was conducted from 2013 to 2014 to characterize the spatial distribution of rat abundance and Leptospira shedding rates in rats and determine the association with human infection risk in a cohort of 2,206 community residents. Tracking plates and live-trapping were used to measure rat abundance and quantify rat shedding status and load. In parallel, four sequential biannual serosurveys were used to identify human Leptospira infections. To evaluate the role of shedding on human risk, we built three statistical models for: (1) the relative abundance of rats, (2) the shedding rate by individual rats, and (3) human Leptospira infection, in which "total shedding", obtained by multiplying the predictions from those two models, was used as a risk factor. We found that Leptospira shedding was associated with older and sexually mature rats and varied spatially and temporally-higher at valley bottoms and with seasonal rainfall (December to March). The point estimate for "total shedding" by rat populations was positive, i.e., Leptospira infection risk increased with total shedding, but the association was not significant [odds ratio (OR) = 1.1; 95% confidence interval (CI): 0.9, 1.4]. This positive trend was mainly driven by rat abundance, rather than individual rat shedding (OR = 1.8; 95% CI: 0.6, 5.4 vs. OR = 1.0; 95% CI: 0.7, 1.4]. Infection risk was higher in areas with more vegetative land cover (OR = 2.4; 95% CI: 1.2, 4.8), and when floodwater entered the house (OR = 2.4; 95% CI: 1.6, 3.4). Our findings indicate that environmental and hydrological factors play a more significant role in Leptospira spillover than rat associated factors. Furthermore, we developed a novel approach combining several models to elucidate complex links between animal reservoir abundance, pathogen shedding and environmental factors on zoonotic spillover in humans that can be extended to other environmentally transmitted diseases.

Genomic Analysis of Human-infecting Leptospira borgpetersenii isolates in Sri Lanka: expanded PF07598 gene family repertoire, less overall genome reduction than bovine isolates

Leptospira borgpetersenii commonly causes human leptospirosis, including severe disease. The first published analysis of L. borgpetersenii, performed on two strains of serovar Hardjo (L550 and JB197), concluded that the L. borgpetersenii genome is in the process of genome decay with functional consequences leading to a more obligately host-dependent life cycle. Yet whole genome analysis has only been carried out on few strains of L. borgpetersenii, with limited closed genomes and comprehensive analysis. Herein we report the complete, circularized genomes of seven non-Hardjo Leptospira borgpetersenii isolates from human leptospirosis patients in Sri Lanka. These isolates (all ST144) were found to be nearly identical by whole genome analysis; serotyping showed they are a novel serovar. We show that the L. borgpetersenii isolated from humans in Sri Lanka are less genomically decayed than previously reported isolates: fewer pseudogenes (N=141) and Insertion Sequence (IS) elements (N=46) compared to N=248, N=270, and N=400 pseudogenes, and N=121 and N=116 IS elements in published L. borgpetersenii Hardjo genomes (L550, JB197 and TC112). Compared to previously published L. borgpetersenii whole genome analyses showing two to three VM proteins in L. borgpetersenii isolates from cattle, rats and humans, we found that all of the human L. borgpetersenii isolates from Sri Lanka, including previously reported serovar Piyasena, have 4 encoded VM proteins, one ortholog of L. interrogans Copenhageni LIC12339 and 3 orthologs of LIC12844. Our findings of fewer pseudogenes, IS elements and expansion of the LIC12844 homologs of the PF07598 family in these human isolates suggests that this newly identified L. borgpetersenii serovar from Sri Lanka has unique pathogenicity. Comparative genome analysis and experimental studies of these L. borgpetersenii isolates will enable deeper insights into the molecular and cellular mechanisms of leptospirosis pathogenesis.

A Comprehensive Review on the Importance of Sustainable Synthesized Coinage Metal Nanomaterials and Their Diverse Biomedical Applications

From a historical perspective, coinage metals (CMNMs) are most renowned for their monetary, ornamental, and metallurgical merits; nevertheless, as nanotechnology's potential has only just come to light, their metal nanostructures and uses may be viewed as products of modern science. Notable characteristics of CMNMs include visual, electrical, chemical, and catalytic qualities that depend on shape and size. Due diligence on the creation and synthesis of CMNMs and their possible uses has been greatly promoted by these characteristics. This review focuses on solution-based methods and provides an overview of the latest developments in CMNMs and their bimetallic nanostructures. It discusses a range of synthetic techniques, including conventional procedures and more modern approaches used to enhance functionality by successfully manipulating the CMNMs nanostructure's size, shape, and composition. To help with the design of new nanostructures with improved capabilities in the future, this study offers a brief assessment of the difficulties and potential future directions of these intriguing metal nanostructures. This review focuses on mechanisms and factors influencing the synthesis process, green synthesis, and sustainable synthesis methods. It also discusses the wide range of biological domains in which CMNMs are applied, including antibacterial, antifungal, and anticancer. Researchers will therefore find the appropriateness of both synthesizing and using CMNMS keeping in mind the different levels of environmental effects.

Enhancement of clinical signs in C3H/HeJ mice vaccinated with a highly immunogenic Leptospira methyl-accepting chemotaxis protein following challenge

Leptospirosis is the most widespread zoonosis and a life-threatening disease in humans and animals. Licensed killed whole-cell vaccines are available for animals; however, they do not offer heterologous protection, do not induce long-term protection, or prevent renal colonization. In this study, we characterized an immunogenic Leptospira methyl-accepting chemotaxis protein (MCP) identified through a reverse vaccinology approach, predicted its structure, and tested the protective efficacy of a recombinant MCP fragment in the C3H/HeJ mice model. The predicted structure of the full-length MCP revealed an architecture typical for topology class I MCPs. A single dose of MCP vaccine elicited a significant IgG antibody response in immunized mice compared to controls (P < 0.0001), especially the IgG1 and IgG2a subclasses. The vaccination with MCP, despite eliciting a robust immune response, did not protect mice from disease and renal colonization. However, survival curves significantly differed between groups, and the MCP-vaccinated group developed clinical signs faster than the control group. There were differences in gross and histopathological changes between the MCP-vaccinated and control groups. The factors leading to enhanced disease process in vaccinated animals need further investigation. We speculate that anti-MCP antibodies may block the MCP signaling cascade and may limit chemotaxis, preventing Leptospira from reaching its destination, but facilitating its maintenance and replication in the blood stream. Such a phenomenon may exist in endemic areas where humans are highly exposed to Leptospira antigens, and the presence of antibodies might lead to disease enhancement. The role of this protein in Leptospira pathogenesis should be further evaluated to comprehend the lack of protection and potential exacerbation of the disease process. The absence of immune correlates of protection from Leptospira infection is still a major limitation of this field and efforts to gather this knowledge are needed.

Immunoinformatic approaches for ErpY-LemA chimeric protein design for use in leptospirosis control

AIMS

Currently, immunoinformatic approaches have shown promise in rapidly and cost-effectively identifying new antigens from the Leptospira proteome. Chimeric multiepitope proteins offer a strategy with significant potential for implementation in diagnosis and vaccines development.

METHODS AND RESULTS

In this study, we detail the immunoinformatic analyses and design of a new recombinant chimeric protein constructed with epitopes identified from the sequences of ErpY-like and LemA proteins, previously identified as potential antigens for controlling leptospirosis. We expressed the chimeric protein using Escherichia coli heterologous systems, evaluated its antigenicity using serum from naturally infected patients, and its immunogenicity in mice as an animal model, with Freund as an adjuvant. The resulting recombinant chimeric protein, named rErpY-LemA, was successfully expressed and purified using a prokaryotic system, with an expected mass of 35 kDa. Serologic assays using serum samples from naturally infected patients demonstrated recognition of the chimera protein by antibodies present in sera. Animals immunized with the chimera exhibited a significant IgG antibody response from the 7th day (P < 0.001), persisting until day 49 of experimentation, with a titer of 1:12,800 (P < 0.05). Notably, significant production of IgA, IgM, and IgG subclasses was observed in animals immunized with the chimera.

CONCLUSIONS

These results highlight the promising role of immunoinformatics in rapidly identifying antigens and the potential of chimeric multiepitope proteins in developing effective strategies for leptospirosis control.

Epidemiological Features of Leptospirosis and Identification of Leptospira wolffii as a Persistently Prevailing Species in North-Central Bangladesh

Leptospirosis is considered to be the most widespread, yet neglected, re-emerging zoonotic disease caused by infection with a pathogenic species of the genus Leptospira. Although this disease is prevalent in Bangladesh, the recent epidemiological status has not yet been well documented. In this study, we aimed to determine the prevalence of leptospirosis among febrile patients using different diagnostic methods and to characterize the epidemiological features and species of Leptospira in Mymensingh, north-central Bangladesh. Among the blood samples of 186 patients with suspected leptospirosis who met the inclusion criteria, including having a fever for more than 5 days (November 2021-June 2022), 88 samples (47%) were Leptospira-positive according to IgM LAT, IgM ELISA, or nested PCR (positivity rates: 38%, 37%, and 42%, respectively). Nested PCR showed a significantly higher positivity rate (54%) in patients with a short fever (5-10 day) than the other methods did, with lower rates among those with a longer fever. Leptospirosis cases were more common in males (68%), those 16-45 years of age (70%), residents of rural areas (81%), and farmers (41%). In addition to a fever, myalgia and jaundice were found in more than 70% of the patients, while variable symptoms were observed. The 16S rRNA sequencing analysis revealed that the Leptospira species in all the 22 samples tested were L. wolffii, belonging to the pathogenic subclade P2. This study showed the recent epidemiological features of leptospirosis in Bangladesh, indicating the presumptive predominance of L. wolffii since 2019.

Leptospiral LipL45 lipoprotein undergoes processing and shares structural similarities with bacterial sigma regulators

Leptospirosis is a widespread zoonotic infectious disease of human and veterinary concern caused by pathogenic spirochetes of the genus Leptospira. To date, little progress towards understanding leptospiral pathogenesis and identification of virulence factors has been made, which is the main bottleneck for developing effective measures against the disease. Some leptospiral proteins, including LipL32, Lig proteins, LipL45, and LipL21, are being considered as potential virulence factors or vaccine candidates. However, their function remains to be established. LipL45 is the most expressed membrane lipoprotein in leptospires, upregulated when the bacteria are transferred to temperatures resembling the host, expressed during infection, suppressed after culture attenuation, and known to suffer processing in vivo and in vitro, generating fragments. Based on body of evidence, we hypothesized that the LipL45 processing might occur by an auto-cleavage event, deriving two fragments. The results presented here, based on bioinformatics, structure modeling analysis, and experimental data, corroborate that LipL45 processing probably includes a self-catalyzed non-proteolytic event and suggest the participation of LipL45 in cell-surface signaling pathways, as the protein shares structural similarities with bacterial sigma regulators. Our data indicate that LipL45 might play an important role in response to environmental conditions, with possible function in the adaptation to the host.

Molecular Detection of Viral and Bacterial Pathogens in Red Foxes (Vulpes vulpes) from Italy

Animals, including wildlife, are part of One-Health concept since many infectious diseases can affect both humans and animals. In this study, 126 red foxes (Vulpes vulpes) from Northern Italy in 2022-2023 were tested by molecular assays for Protoparvovirus carnivoran 1 (PPVC-1), Canine adenovirus type 1 and 2 (CAdV-1 and CAdV-2), Circovirus canine (CanineCV), Canine distemper virus (CDV), and Leptospira spp. A total of 39 of 126 (30.9%) red foxes were infected with at least one pathogen and five of these were coinfected: 20/126 (15.9%) red foxes tested positive for PPVC-1, 3/126 (2.4%) for CAdV, 20/126 (15.9%) for CanineCV, and 2/126 (1.6%) for Leptospira spp. DNA. No foxes tested positive for CDV RNA. The pathogens identified were genetically analysed. New findings were reported such as a fox with multiple feline panleukopenia virus (FPV) and canine parvovirus type 2b (CPV-2b) infection associated with quasispecies dynamics, typical genetic characteristics of the identified CanineCV, and the first detection in red foxes of Leptospira ST198 related to L. interrogans serogroup Australis. Further studies are necessary to investigate the transmission between domestic animals and wildlife and to understand the role of red foxes in the maintenance of these pathogens not only in the wild but also in urban and peri-urban environments.

Molecular surveillance of zoonotic pathogens from wild rodents in the Republic of Korea

BACKGROUND

Rodents are recognized as major reservoirs of numerous zoonotic pathogens and are involved in the transmission and maintenance of infectious diseases. Furthermore, despite their importance, diseases transmitted by rodents have been neglected. To date, there have been limited epidemiological studies on rodents, and information regarding their involvement in infectious diseases in the Republic of Korea (ROK) is still scarce.

METHODOLOGY/PRINCIPAL FINDINGS

We investigated rodent-borne pathogens using nested PCR/RT-PCR from 156 rodents including 151 Apodemus agrarius and 5 Rattus norvegicus from 27 regions in eight provinces across the ROK between March 2019 and November 2020. Spleen, kidney, and blood samples were used to detect Anaplasma phagocytophilum, Bartonella spp., Borrelia burgdorferi sensu lato group, Coxiella burnetii, Leptospira interrogans, and severe fever with thrombocytopenia syndrome virus (SFTSV). Of the 156 rodents, 73 (46.8%) were infected with Bartonella spp., 25 (16.0%) with C. burnetii, 24 (15.4%) with L. interrogans, 21 (13.5%) with A. phagocytophilum, 9 (5.8%) with SFTSV, and 5 (3.2%) with Borrelia afzelii. Co-infections with two and three pathogens were detected in 33 (21.1%) and 11 rodents (7.1%), respectively. A. phagocytophilum was detected in all regions, showing a widespread occurrence in the ROK. The infection rates of Bartonella spp. were 83.3% for B. grahamii and 16.7% for B. taylorii.

CONCLUSIONS/SIGNIFICANCE

To the best of our knowledge, this is the first report of C. burnetii and SFTSV infections in rodents in the ROK. This study also provides the first description of various rodent-borne pathogens through an extensive epidemiological survey in the ROK. These results suggest that rodents harbor various pathogens that pose a potential threat to public health in the ROK. Our findings provide useful information on the occurrence and distribution of zoonotic pathogens disseminated among rodents and emphasize the urgent need for rapid diagnosis, prevention, and control strategies for these zoonotic diseases.

Exposure to live saprophytic Leptospira before challenge with a pathogenic serovar prevents severe leptospirosis and promotes kidney homeostasis

Previous studies demonstrated that Leptospira biflexa, a saprophytic species, triggers innate immune responses in the host during early infection. This raised the question of whether these responses could suppress a subsequent challenge with pathogenic Leptospira. We inoculated C3H/HeJ mice with a single or a double dose of L. biflexa before challenge with a pathogenic serovar, L. interrogans serovar Copenhageni FioCruz (LIC). Pre-challenge exposure to L. biflexa did not prevent LIC dissemination and colonization of the kidney. However, it rescued weight loss and mouse survival thereby mitigating disease severity. Unexpectedly, there was correlation between rescue of overall health (weight gain, higher survival, lower kidney fibrosis marker ColA1) and higher shedding of LIC in urine. This stood in contrast to the L. biflexa unexposed LIC challenged control. Immune responses were dominated by increased frequency of effector T helper (CD4+) cells in spleen, as well as significant increases in serologic IgG2a. Our findings suggest that exposure to live saprophytic Leptospira primes the host to develop Th1 biased immune responses that prevent severe disease induced by a subsequent challenge with a pathogenic species. Thus, mice exposed to live saprophytic Leptospira before facing a pathogenic serovar may withstand infection with far better outcomes. Furthermore, a status of homeostasis may have been reached after kidney colonization that helps LIC complete its enzootic cycle.

Surveillance of human leptospirosis infections in Ukraine between 2018 and 2023

Leptospirosis is a bacterial disease that affects both humans and animals worldwide. Currently, a positional war is ongoing in Ukraine, and the military is encountering a significant number of rodents in trenches and dugouts, which are known reservoirs for Leptospira, the causative agent of leptospirosis-a potentially dangerous infectious disease with a high mortality rate. The civilian population is also at potential risk of leptospirosis. The destruction of the Kakhovka Dam on June 6, 2023, has led to widespread devastation and human suffering. In the short term, there is a significant risk of rodent-borne diseases such as leptospirosis. We utilized data from the Ukrainian Centre for Disease Prevention Control and observed a substantial increase in prevalence in 2023. The notification rate in Ukraine in 2023 was 1.06 per 100,000 persons, which is higher than that of other countries in the European Union. Particular attention is being given to Zakarpattia Oblast, located on the western border of Ukraine, which shares boundaries with Romania, Hungary, Poland, and Slovakia, with an extremely high incidence rate of 12.08 per 100,000 persons. Based on these findings, we recommend education and awareness campaigns, vaccination, personal protective measures, and improved surveillance to address the increasing incidence of leptospirosis in Ukraine.

Genetic structure and diversity of the rfb locus of pathogenic species of the genus Leptospira

Leptospirosis is caused by pathogenic strains of the genus Leptospira and is considered the most widespread zoonotic bacterial disease. The genus is characterized by the large number of serology variants, which challenges developing effective serotyping methods and vaccines with a broad spectrum. Because knowledge on the genetic basis of the serological diversity among leptospires is still limited, we aimed to explore the genetic structure and patterns of the rfb locus, which is involved in the biosynthesis of lipopolysaccharides, the major surface antigen that defines the serovar in leptospires. Here, we used genomic data of 722 pathogenic samples and compared the gene composition of their rfb locus by hierarchical clustering. Clustering analysis showed that the rfb locus gene composition is species-independent and strongly associated with the serological classification. The samples were grouped into four well-defined classes, which cluster together samples either belonging to the same serogroup or from different serogroups but sharing serological affinity. Our findings can assist in the development of new strategies based on molecular methods, which can lead to better tools for serological identification in this zoonosis.

Leptospirosis-Associated Acute Respiratory Distress Syndrome (ARDS) in Pregnancy: A Rare Presentation

Leptospirosis, a zoonotic disease caused by spirochetes of the genus Leptospira, poses unique challenges in pregnancy due to its varied clinical presentation and potential adverse outcomes for both mother and fetus. We present a case of a 24-year-old primigravida at 35 weeks of gestation who presented with fever, dyspnea, and abdominal pain, and was ultimately diagnosed with leptospirosis complicated by acute respiratory distress syndrome (ARDS). Prompt initiation of antibiotic therapy, supportive care, and timely delivery via emergency cesarean section led to favorable maternal and neonatal outcomes. This case report underscores the importance of considering leptospirosis in pregnant patients presenting with similar symptoms, particularly in endemic regions, and highlights the critical role of multidisciplinary management in optimizing outcomes.

ELISA for leptospiral 3-hydroxyacyl-CoA dehydrogenase in urine is a promising screening tool for acute leptospirosis

Introduction. Leptospirosis is a zoonotic disease that is prevalent worldwide. Leptospiral 3-hydroxyacyl-CoA dehydrogenase (3-HADH) is excreted in the urine of infected individuals. However, the potential use of 3-HADH as a biomarker for the diagnosis of leptospirosis using enzyme-linked immunosorbent assay (ELISA) has not been investigated. A technique that identifies Leptospira in a patient in urine sample will be valuable in regular diagnostics and epidemic scenarios, as opposed to existing serological approaches. This study aimed to develop and evaluate an ELISA that can detect 3-HADH in the urine of patients with confirmed acute leptospirosis and to assess its potential as a screening test for leptospirosis. Methods. Laboratory confirmation of acute leptospirosis was done by flaB-nested polymerase chain reaction (PCR) of plasma samples from suspected patients. ELISA-based determination of the presence of 3-HADH in the urine of PCR-positive patients versus PCR-negative patients matched for fever date was performed by coating ELISA plates with urine supernatants and using rabbit anti-3-HADH as the primary antibody. Receiver operating characteristic curve analysis was used to determine the cutoff values for the ELISA. The diagnostic measures between the PCR-positive and PCR-negative patients were compared using the Mann-Whitney U test. Results. In total, 158 febrile patients were assessed, of whom 121 (76.6 %) were male. Of the 15 flaB-nested PCR-positive patients, 12 were in the acute phase of the febrile illness. The best cutoff was an average optical density (ODav) value of 0.2200 for febrile patients. Sensitivity and specificity were 83.33% [95 % confidence interval (CI), 51.59-97.91 %) and 83.33 % (95 % CI, 76.05-89.13 %), respectively. The ODav values for PCR-positive patients in the acute phase of the disease (≤7 days of fever) were significantly higher than those for PCR-negative patients (P<0.001, U=114.0, z=-4.946). Conclusion. Detection of 3-HADH in urine by ELISA appears to be promising for the screening of acute leptospirosis in suspected patients.

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

BACKGROUND

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

METHODS/PRINCIPAL FINDINGS

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

CONCLUSIONS/SIGNIFICANCE

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

Evaluation of protective efficacy, serological responses, and cytokine modulation induced by polyvalent Leptospira vaccines in hamsters

Whole-cell inactivated vaccines (bacterins) are the only licensed vaccines available for leptospirosis prevention and control, especially in domestic and farm animals. However, despite their widespread use, inconsistencies in their efficacy have been reported. Because immunity induced by bacterins is mainly mediated by antibodies against leptospiral lipopolysaccharides, the involvement of cellular responses is not well-known. The aim of this study was to investigate the efficacy and characterize the humoral and cellular immune responses induced by whole-cell inactivated leptospirosis bacterin formulations containing serovars Bratislava, Canicola, Copenhageni, Grippotyphosa, Hardjoprajitno, and Pomona. For the potency test, hamsters were immunized with one dose of polyvalent bacterins (either commercial or experimental) and then challenged with a virulent Pomona strain. Serological (MAT and IgM and IgG-ELISA) and cellular (cytokine transcription in blood evaluated by RT-qPCR) analyses were performed. The results revealed that vaccination with either bacterin formulation was able to protect 90-100% of the hamsters infected with the Pomona serovar, although most of the surviving animals remained as renal carriers. Specific agglutinating antibodies and significant levels of IgM, IgG, and IgG2 (P < 0.05) that were able to react with the six serovars present in the vaccine formulations were produced, indicating that the vaccines can potentially provide immunity against all strains. The protective immunity of these vaccines was mainly mediated by balanced a Th1/Th2 response, characterized by increased IFN-γ, IL-10 and IL-α transcription. These data support the importance of characterizing immunological responses involved in bacterin efficacy and investing in the improvement of these vaccine formulations.

Global proteome of the saprophytic strain Leptospira biflexa and comparative analysis with pathogenic strain Leptospira interrogans uncover new pathogenesis mechanisms

Leptospira is a genus of bacteria that includes free-living saprophytic species found in water or soil, and pathogenic species, which are the etiologic agents of leptospirosis. Besides all the efforts, there are only a few proteins described as virulence factors in the pathogenic strain L. interrogans. This work aims to perform L. biflexa serovar Patoc1 strain Paris global proteome and to compare with the proteome database of pathogenic L. interrogans serovar Copenhageni strain Fiocruz L1-130. We identified a total of 2327 expressed proteins of L. biflexa by mass spectrometry. Using the Get Homologues software with the global proteome of L. biflexa and L. interrogans, we found orthologous proteins classified into conserved, low conserved, and specific proteins. Comparative bioinformatic analyses were performed to understand the biological functions of the proteins, subcellular localization, the presence of signal peptide, structural domains, and motifs using public softwares. These results lead to the selection of 182 low conserved within the saprophyte, and 176 specific proteins of L. interrogans. It is anticipated that these findings will indicate further studies to uncover virulence factors in the pathogenic strain. This work presents for the first time the global proteome of saprophytic strain L. biflexa serovar Patoc, strain Patoc1. SIGNIFICANCE: The comparative analysis established an array of specific proteins in pathogenic strain that will narrow down the identification of immune protective proteins that will help fight leptospirosis.

The Presence of a Virulent Clone of Leptospira interrogans Serovar Canicola in Confirmed Cases of Asymptomatic Dog Carriers in Mexico

Leptospirosis is a neglected zoonotic disease that commonly affects cattle, pigs, horses, and dogs in many countries. Infection in dogs is usually subclinical, but acute cases of leptospirosis may occur along with systemic failure, which may become fatal. After recovery from an acute infection, dogs may become asymptomatic carriers and shed pathogenic leptospires through urine for long periods of time. Here, a study of ten different cases of leptospirosis is presented, showing the relevance of dogs as asymptomatic carriers of pathogenic Leptospira. The diagnosis was confirmed via isolation and further serological and genetic identification. Four Leptospira isolates (LOCaS28, 31, 34, and 46) were obtained from the kidneys and urine samples of 58 dogs destined for destruction (6.89%) at a Canine Control Center in Mexico City. No spirochetes were observed in the urine samples of those Leptospira-positive dogs examined under dark-field microscopy, and no clinical signs of disease were observed either. Six additional isolates were obtained: two came from asymptomatic carrier dogs (CEL60 and UADY22); another isolate came from an asymptomatic dog that was a pack companion of a clinically ill dog with fatal leptospirosis (AGFA24); and finally, three isolates were taken from dogs that died of leptospirosis (LOCaS59, Citlalli, and Nayar1). Nine out of the ten isolates were identified as being from the serogroup Canicola via cross-absorption MAT using reference strains and specific antisera, and their identity was genetically confirmed as Canicola ST34 via multi-locus sequencing typing (MLST). In contrast, the isolate Nayar1 was identified as serovar Copenhageni ST2. Interestingly, the asymptomatic dogs from which Leptospira isolates were recovered consistently showed high antibody titers in the microscopic agglutination test (MAT), revealing values of at least 1:3200 against serogroup Canicola and lower titer values against other serogroups. Isolates showed different virulence levels in the hamster model. Taken as a whole, all these findings confirmed that dogs may act as asymptomatic carriers of pathogenic leptospires and possibly spread them out to the environment, thus representing an active public health risk. The results also showed that the Canicola ST34 clone is the most prevalent Leptospira serovar in dogs in Mexico, and finally that the old-fashioned MAT is a good alternative for the detection of presumptive Leptospira asymptomatic carrier dogs.

Leptospiral lipopolysaccharide dampens inflammation through upregulation of autophagy adaptor p62 and NRF2 signaling in macrophages

Leptospira interrogans are pathogenic bacteria responsible for leptospirosis, a worldwide zoonosis. All vertebrates can be infected, and some species like humans are susceptible to the disease whereas rodents such as mice are resistant and become asymptomatic renal carriers. Leptospires are stealth bacteria that are known to escape several immune recognition pathways and resist killing mechanisms. We recently published that leptospires may survive intracellularly in and exit macrophages, avoiding xenophagy, a pathogen-targeting form of autophagy. Interestingly, the latter is one of the antimicrobial mechanisms often highjacked by bacteria to evade the host immune response. In this study we explored whether leptospires subvert the key molecular players of autophagy to facilitate infection. We showed in macrophages that leptospires triggered a specific accumulation of autophagy-adaptor p62 in puncta-like structures, without altering autophagic flux. We demonstrated that Leptospira-induced p62 accumulation is a passive mechanism depending on the leptospiral virulence factor LPS signaling via TLR4/TLR2. p62 is a central pleiotropic protein, also mediating cell stress and death, via the translocation of transcription factors. We demonstrated that Leptospira-driven accumulation of p62 induced the translocation of transcription factor NRF2, a key player in the anti-oxidant response. However, NRF2 translocation upon Leptospira infection did not result as expected in antioxydant response, but dampened the production of inflammatory mediators such as iNOS/NO, TNF and IL6. Overall, these findings highlight a novel passive bacterial mechanism linked to LPS and p62/NRF2 signaling that decreases inflammation and contributes to the stealthiness of leptospires.

Exploring the complex interplay: gut microbiome, stress, and leptospirosis

Leptospirosis, a re-emerging zoonotic disease, remains a significant global health concern, especially amid floods and disasters such as the Kakhovka Dam destruction. As is known, the stress that occurs in the conditions of military conflicts among civilian and military personnel significantly affects susceptibility to infectious diseases and possibly even influences their course. This review aims to explore how the gut microbiome and stress mediators (such as catecholamines and corticosteroids) might impact the leptospirosis disease course. The review opens new horizons for research by elucidating the connections between the gut microbiome, stress, and leptospirosis.

Detection of Antibodies for Pathogenic Leptospira in Wild Mammals and Birds from Southern Chile-First Record of Seropositivity in a Guiña (Leopardus guigna)

Leptospirosis is a neglected bacterial zoonotic disease of worldwide distribution that is present in different animal species. This epidemiological study determined the seroprevalence of pathogenic Leptospira spp. in animals at a wildlife rehabilitation center in Puerto Montt, southern Chile, by sampling 60 animals belonging to three classes (birds, mammals, and reptiles). Diagnosis was performed using the microscopic agglutination test with a panel of eight serovars and serogroups. The results showed that 15 animals had anti-Leptospira antibodies, obtaining a seroprevalence of 25.00%, with Leptospira borgpetersenii serogroup Tarassovi presenting reactivity in 13 of the seropositive animals. Among the classes of mammals, chilla foxes (Lycalopex griseus) and pudus (Pudu puda) were seropositive. A guiña (Leopardus guigna) was also seropositive, which was described for the first time in mammals. Among the classes of birds, choroy parrots (Enicognathus leptorhynchus), bandurrias (Theristicus melanopis), and Magellanic penguins (Spheniscus magellanicus) were seropositive. Routine examinations to diagnose leptospirosis, perform epidemiological surveillance, and apply prevention and control measures are necessary, and additional research focusing on the One Health approach to explore the epidemiological role of different wild animal species in the maintenance and transmission of leptospirosis at the local and global levels are recommended.

Unraveling the leptospirosis epidemic: tales from the Philippine outbreak - a short communication

Leptospirosis, also known as Weil's disease, is an emerging zoonotic infection that occurs worldwide but is particularly common in the tropics. There has been an increasing trend of leptospirosis in the Philippines since the outbreak occurred in 2020. The number of reported cases was 182 in 2020, 1661 in 2021, and 2794 in 2022. This present article aimed to access previously published studies on the prevalence, implications, and efforts to combat leptospirosis worldwide, with a particular focus on the Philippines from 2001 to 2023. In writing this article, we conducted a thorough search of databases such as PubMed, Researchgate, Web of Science, Scopus, and Google Scholar within 20 years. This present article found that more than 810 cases were reported from 1 January to 4 March 2023. The Cagayan Valley Region has 103 cases, the Zamboanga Peninsula has 77 cases, and the Western Visayas Region has 176 cases, making them the worst-hit areas. The increase in leptospirosis cases in the Philippines is primarily attributed to several factors. Firstly, the country is prone to natural disasters such as typhoons, floods, and landslides, which increase the risk of water sources and the environment being contaminated with Leptospira bacteria. To address the menace of leptospirosis in the Philippines, we urge the Philippine government to focus on improving healthcare infrastructure, providing swift, reliable, and effective treatments, implementing safety regulations, supplying personal protective equipment to medical authorities, and taking strict actions to improve water sanitation.

Environmental and Occupational Factors Associated with Leptospirosis: A Systematic Review

Background

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

Objective

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

Methods

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

Results

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

Conclusion

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

Enhancing leptospirosis control with nanosensing technology: A critical analysis

Leptospirosis is a serious health problem in tropical areas; thus, animals shed leptospires in the environment. Humans are accidental hosts infected through exposure to contaminating bacteria in the environment. One health strategy can be applied to protect and eliminate leptospirosis because this cooperates and coordinates activities between doctors, veterinarians, and ecologists. However, conventional methods still have limitations. Therefore, the main challenges of leptospirosis control are the high sensing of detection methods to screen and control the pathogens. Interestingly, nano sensing combined with a leptospirosis detection approach can increase the sensitivity and eliminate some limitations. This article reviews nanomaterial development for an advanced leptospirosis detection method, e.g., latex beads-based agglutination test, magnetic nanoparticles enrichment, and gold-nanoparticles-based immunochromatographic assay. Thus, nanomaterials can be functionalized with biomolecules or sensing molecules utilized in various mechanisms such as biosensors. Over the last decade, many biosensors have been developed for Leptospira spp. pathogen and others. The evolution of biosensors for leptospirosis detection was designed for high efficiency and might be an alternative tool. In addition, the high-sensing fabrications are useful for leptospires screening in very low levels, for example, soil or water from the environment.

Leptospira Lipid A Is a Potent Adjuvant That Induces Sterilizing Immunity against Leptospirosis

Leptospirosis is a globally significant zoonotic disease. The current inactivated vaccine offers protection against specific serovars but does not provide complete immunity. Various surface antigens, such as Leptospira immunoglobulin-like proteins (LigA and LigB), have been identified as potential subunit vaccine candidates. However, these antigens require potent adjuvants for effectiveness. Bacterial lipopolysaccharides (LPSs), including lipid A, are a well-known immunostimulant, and clinical adjuvants often contain monophosphoryl lipid A (MPLA). Being less endotoxic, we investigated the adjuvant properties of lipid A isolated from L. interrogans serovar Pomona (PLA) in activating innate immunity and enhancing antigen-specific adaptive immune responses. PLA activated macrophages to a similar degree as MPLA, albeit at a higher dose, suggesting that it is less potent in stimulation than MPLA. Mice immunized with a variable portion of LigA (LAV) combined with alum and PLA (LAV-alum-PLA) exhibited significantly higher levels of LAV-specific humoral and cellular immune responses compared to alum alone but similar to those induced by alum-MPLA. The adjuvant activity of PLA resembles that of MPLA and is primarily achieved through the increased recruitment, activation, and uptake of antigens by innate immune cells. Furthermore, like MPLA, PLA formulation establishes a long-lasting memory response. Notably, PLA demonstrated superior potency than MPLA formulation and provided sterilizing immunity against the leptospirosis in a hamster model. Overall, our study sheds light on the adjuvant properties of Leptospira lipid A and offers promising avenues for developing LPS-based vaccines against this devastating zoonotic disease.

Identification of the most effective serovars to be included in the MAT antigen panel to optimize the serodiagnosis of Leptospira infection in Northern Italy

The microscopic agglutination test (MAT) assay is adopted as a world-wide reference test for the serodiagnosis of leptospirosis in humans and animals. One of the main limitations of MAT is the lack of sensitivity and serodiagnostic antigens should be periodically updated with locally circulating serovars in order to optimise its performance. The aim of this study was to determine the need to implement the antigen panel currently adopted in Northern Italy for the diagnosis of Leptospira infection in dogs. For this purpose, a group of 288 dogs with and without clinical signs potentially consistent with Leptospira infection or found to have an increased C-reactive protein (CRP) serum concentration, sampled in 2013-2016 in Northern Italy, were tested by MAT comparing the results obtained with a nine antigens panel (Australis-Bratislava, Ballum-Ballum, Canicola-Canicola, Grippotyphosa-Grippotyphosa, Icterohaemorrhagiae-Copenhageni, Icterohaemorrhagiae-Icterohaemorrhagiae, Sejroe-Hardjo, Pomona-Pomona and Tarassovi-Tarassovi serovars) routinely adopted and a panel expanded to 27 antigens. In general, the antigen panel currently adopted in Northern Italy for the routine MAT assay resulted adequate for the diagnosis of Leptospira infection in dogs. The main exception concerns the Sejroe serogroup, with the Saxkoebing and Sejroe serovars that were more effective than Hardjo for diagnosis in dogs and whose inclusion in the antigen panel is recommended. Among other antigens evaluated in this study, Cynopteri serovar was detected with high frequency but its pathogenic role in dogs and as public health threat deserve further investigation.

Leptospirosis-associated meningitis in a patient with sjögren's syndrome: a case report

BACKGROUND

Leptospirosis is a zoonotic disease that afflicts both humans and animals. It progresses from flu-like symptoms to more severe hepatic and renal failure, and may also lead to aseptic meningitis. Individuals with autoimmune diseases (ADs) are potentially more susceptible to Leptospirosis. Thus far, limited data has documented the association between Leptospirosis and autoimmune disorders.

CASE PRESENTATION

The patient had a definitive pathological diagnosis of Sjögren's syndrome (SS). Due to recurrent headaches, the patient sought consultation with a neurologist. Lumbar puncture revealed elevated white blood cells and protein levels in the cerebrospinal fluid, along with decreased glucose. Tuberculous meningitis was suspected. Radiographic imaging exhibited meningeal enhancement, ventricular enlargement, and hydrocephalus. The patient commenced treatment with anti-tuberculosis therapy and corticosteroids. Subsequently, high-throughput sequencing (HTS) of cerebrospinal fluid identified the presence of Leptospira interrogans. The patient was ultimately diagnosed with Leptospiral meningitis, and underwent antimicrobial and immunosuppressive therapy, resulting in stabilization of the condition and gradual symptom recovery.

CONCLUSIONS

The case highlights the challenges in diagnosing and managing leptospirosis-related meningitis in the presence of ADs and emphasizes the importance of utilizing HTS for accurate pathogen detection. The potential correlation between leptospirosis and SS warrants further investigation, as does the need for multidisciplinary involvement in treatment strategies for such complex cases.

Updated ACVIM consensus statement on leptospirosis in dogs

Since publication of the last consensus statement on leptospirosis in dogs, there has been revision of leptospiral taxonomy and advancements in typing methods, widespread use of new diagnostic tests and vaccines, and improved understanding of the epidemiology and pathophysiology of the disease. Leptospirosis continues to be prevalent in dogs, including in small breed dogs from urban areas, puppies as young as 11 weeks of age, geriatric dogs, dogs in rural areas, and dogs that have been inadequately vaccinated for leptospirosis (including dogs vaccinated with 2-serovar Leptospira vaccines in some regions). In 2021, the American College of Veterinary Internal Medicine (ACVIM) Board of Regents voted to approve the topic for a revised Consensus Statement. After identification of core panelists, a multidisciplinary group of 6 experts from the fields of veterinary medicine, human medicine, and public health was assembled to vote on the recommendations using the Delphi method. A draft was presented at the 2023 ACVIM Forum, and a written draft posted on the ACVIM website for comment by the membership before submission to the editors of the Journal of Veterinary Internal Medicine. This revised document provides guidance for veterinary practitioners on disease in dogs as well as cats. The level of agreement among the 12 voting members (including core panelists) is provided in association with each recommendation. A denominator lower than 12 reflects abstention of ≥1 panelists either because they considered the recommendation to be outside their scope of expertise or because there was a perceived conflict of interest.

Differential modulation of innate immune response by lipopolysaccharide of Leptospira

Leptospirosis is a worldwide zoonosis caused by pathogenic Leptospira spp. having more than 300 serovars. These serovars can infect a variety of hosts, some being asymptomatic carriers and others showing varied symptoms of mild to severe infection. Since lipopolysaccharide (LPS) is the major antigen which defines serovar specificity, this different course of infection may be attributed to a differential innate response against this antigen. Previous studies have shown that Leptospira LPS is less endotoxic. However, it is unclear whether there is a difference in the ability of LPS isolated from different serovars to modulate the innate response. In this study, we purified LPS from three widely prevalent pathogenic serovars, i.e. Icterohaemorrhagiae strain RGA, Pomona, Hardjo, and from non-pathogenic L. biflexa serovar semeranga strain Potac 1 collectively termed as L-LPS and tested their ability to modulate innate response in macrophages from both resistant (mice) and susceptible (human and bovine) hosts. L-LPS induced differential response being more proinflammatory in mouse and less proinflammatory in human and bovine macrophages but overall less immunostimulatory than E. coli LPS (E-LPS). Irrespective of serovar, this response was TLR2-dependent in humans, whereas TLR4-dependent/CD14-independent in mouse using MyD88 adapter and signalling through P38 and ERK-dependent MAP kinase pathway. L-LPS-activated macrophages were able to phagocytose Leptospira and this effect was significantly higher or more pronounced when the macrophages were stimulated with L-LPS from the corresponding serovar. L-LPS activated both canonical and non-canonical inflammasome, producing IL-1β without inducing pyroptosis. Further, L-LPS induced both TNF-mediated early and NO-mediated late apoptosis. Altogether, these results indicate that L-LPS induces a differential innate response that is quite distinct from that induced by E-LPS and may be attributed to the structural differences and its atypical nature.

Weil's Disease in an HIV-Infected Patient: A Case Report and Literature Review

Weil's disease, an icterohemorrhagic infection, is the most severe and fatal form of leptospirosis and is characterized by jaundice, renal dysfunction, and hemorrhagic predisposition. Weil's disease with HIV infection has rarely been reported. A 68-year-old male with HIV infection presented to our hospital with fever and dyspnea that progressed to severe hemoptysis and systemic multiple organ failure, necessitating a tracheal intubation ventilator. A diagnosis of Weil's disease was made after Leptospira interrogans was identified via metagenomic next-generation sequencing (mNGS) in bronchoalveolar lavage fluid (BALF). After immediately receiving supportive therapy and targeted antimicrobial agents, the patient achieved complete recovery upon discharge. The co-infection of HIV infection and leptospirosis resulting in systemic multi-organ failure is rare, but awareness should be raised of the differential diagnosis. mNGS can help identify pathogens and facilitate the use of targeted and efficacious antimicrobial therapy in unusual clinical environments.

Electrochemical aptasensor detection of electron transfer flavoprotein subunit beta for leptospirosis diagnosis

Electron transfer flavoprotein subunit beta (ETFB) of Leptospira interrogans is a biomarker for diagnosing leptospiral infection. Thus, the ETFB-specific nuclease-resistant RNA aptamer ETFB3-63 was developed and used in an electrochemical aptasensor to assay ETFB. Although the majority of reported biosensors detect various genes and antibodies of L. interrogans, this is the first attempt to construct an electrochemical biosensor to detect ETFB protein for the diagnosis of leptospiral infection. The ETFB protein can be detected without any extraction phase. In this assay, a single-stranded DNA probe complementary to the ETFB3-63 sequence was immobilized on a screen-printed carbon electrode (SPCE). The aptamer was then incubated and hybridized with the antisense probe on the SPCE. In the presence of ETFB, the aptamer dissociates from the aptamer/probe complex on the SPCE to bind with the protein. Methylene blue was then added to intercalate with the remaining hybridized aptamers, and its signal was measured using differential pulse voltammetry. The signal arising from the intercalated methylene blue decreased with increasing concentration of ETFB, showing a linear response in the range of 50-500 nM of ETFB and 10 to 109 leptospira cells per mL, respectively. The aptasensor signal was also specific to L. interrogans but not to 12 related bacteria tested. In addition, the aptasensor showed similar performance in detecting ETFB spiked in human serum to that in buffer, indicating that proteins in the serum do not interfere with the assay. Therefore, this assay has great potential to develop into a point-of-care electrochemical device that is accurate, cost-effective, and user-friendly for leptospirosis diagnosis.

LipL41 and LigA/LigB Gene Silencing on a LipL32 Knockout Leptospira interrogans Reveals the Impact of Multiple Mutations on Virulence

Leptospirosis is a global zoonosis caused by pathogenic bacteria of the genus Leptospira. The application of the CRISPR/Cas9 system has facilitated the generation of mutants and subsequent evaluation of phenotypes. Since DNA breaks induced by RNA-guided Cas9 nuclease are lethal to Leptospira, different methodologies were implemented to overcome this limitation. Initially, CRISPR interference (CRISPRi) was employed to create knockdown mutants, utilizing a catalytically inactive Cas9 (dCas9). Subsequently, the co-expression of CRISPR/Cas9 and a DNA repair system from Mycobacterium smegmatis enabled the generation of scarless knockout mutants. We eliminated plasmids from the lipL32 knockout L. interrogans strain and further achieved multiple gene mutations via gene silencing in this knockout background. Strains lacking both LipL41 and LipL32 and LigA, LigB, and LipL32, were evaluated. The absence of proteins LipL32 and LipL41 had no effect on leptospiral virulence. On the other hand, mutants lacking LigA, LigB, and LipL32 were unable to cause acute disease. The expanded apparatus for genetic manipulation of pathogenic leptospires via the CRISPR/Cas9 system has allowed the evaluation of multiple mutations upon leptospiral virulence. This work shows that LipL32 and LipL41 are not required for acute disease and consolidates LigA and LigB proteins as virulence factors.

Protective role of stratum corneum in percutaneous Leptospira infection in a hamster model

Leptospira enters humans and animals through injured skin or mucous membranes by direct or indirect contact with urine excreted from infected reservoirs. Individuals with cut or scratched skin are at high risk of infection and are recommended to be protected from contact with Leptospira, but the risk of infection via skin without apparent wounds is unknown. We hypothesized that the stratum corneum of the epidermis might prevent percutaneous invasion of leptospires. We established a stratum corneum deficient model of hamsters using the tape stripping method. The mortality rate of hamsters lacking stratum corneum that were exposed to Leptospira was higher than that of controls with shaved skin, and was not significantly different from an epidermal wound group. These results indicated that the stratum corneum plays a critical role in protecting the host against leptospiral entry. We also examined the migration of leptospires through the monolayer of HaCaT cells (human keratinocyte cell line) using Transwell. The number of pathogenic leptospires penetrating the HaCaT cell monolayers was higher than that of non-pathogenic leptospires. Furthermore, scanning and transmission electron microscopic observations revealed that the bacteria penetrated the cell monolayers through both intracellular and intercellular routes. This suggested that pathogenic Leptospira can migrate easily through keratinocyte layers and is associated with virulence. Our study further highlights the importance of the stratum corneum as a critical barrier against the invasion of Leptospira found in contaminated soil and water. Hence, preventative measures against contact infection should be taken, even without visible skin wounds.

Pathogenic Leptospira are widespread in the urban wildlife of southern California

Leptospirosis, the most widespread zoonotic disease in the world, is broadly understudied in multi-host wildlife systems. Knowledge gaps regarding Leptospira circulation in wildlife, particularly in densely populated areas, contribute to frequent misdiagnoses in humans and domestic animals. We assessed Leptospira prevalence levels and risk factors in five target wildlife species across the greater Los Angeles region: striped skunks (Mephitis mephitis), raccoons (Procyon lotor), coyotes (Canis latrans), Virginia opossums (Didelphis virginiana), and fox squirrels (Sciurus niger). We sampled more than 960 individual animals, including over 700 from target species in the greater Los Angeles region, and an additional 266 sampled opportunistically from other California regions and species. In the five target species seroprevalences ranged from 5 to 60%, and infection prevalences ranged from 0.8 to 15.2% in all except fox squirrels (0%). Leptospira phylogenomics and patterns of serologic reactivity suggest that mainland terrestrial wildlife, particularly mesocarnivores, could be the source of repeated observed introductions of Leptospira into local marine and island ecosystems. Overall, we found evidence of widespread Leptospira exposure in wildlife across Los Angeles and surrounding regions. This indicates exposure risk for humans and domestic animals and highlights that this pathogen can circulate endemically in many wildlife species even in densely populated urban areas.

Molecular Epidemiology of Pathogenic Leptospira spp. Infecting Dogs in Latin America

Canine leptospirosis is a bacterial disease caused by spirochetes of the genus Leptospira. Infections can vary from asymptomatic and chronic infections to clinical acute diseases. The disease is endemic in tropical areas, such as Latin American countries, but a broad understanding of the dynamics of circulation of strains, based on molecular data, has not yet been performed. Based on in silico analyses, the present study aims to analyze the genetic diversity and circulation patterns of haplotypes from pathogenic leptospires infecting dogs in Latin America. DNA sequences were obtained from GenBank platform, curated, and aligned. Genetic distances were calculated, and a maximum likelihood tree and haplotype network were constructed. According to the inclusion criteria adopted, a total of 148 sequences were identified. Most of the records were from Brazil, including sequences from L. interrogans serogroup Icterohaemorrhagiae. Phylogenetic analysis showed a genetically closely related cluster, consisting of a larger haplogroup that includes the reference strain Fiocruz L1-130, known to be the major circulating strain in humans. Moreover, no genetic variations were observed according to clinical history and/or geographical localization. We described the molecular epidemiology of leptospires circulating among dogs in Latin America and demonstrated a very genetically homogeneous group, elucidating its ubiquitous circulation pattern and drawing attention to the important role of dogs in the One Health transmission dynamics of leptospirosis.

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.

MPL36, a major plasminogen (PLG) receptor in pathogenic Leptospira, has an essential role during infection

Leptospirosis, a zoonosis with worldwide distribution, is caused by pathogenic spirochetes belonging to the genus Leptospira. Bacterial outer membrane proteins (OMPs), particularly those with surface-exposed regions, play crucial roles in pathogen dissemination and virulence mechanisms. Here we characterized the leptospiral Membrane Protein L36 (MPL36), a rare lipoprotein A (RlpA) homolog with a C-terminal Sporulation related (SPOR) domain, as an important virulence factor in pathogenic Leptospira. Our results confirmed that MPL36 is surface exposed and expressed during infection. Using recombinant MPL36 (rMPL36) we also confirmed previous findings of its high plasminogen (PLG)-binding ability determined by lysine residues of the C-terminal region of the protein, with ability to convert bound-PLG to active plasmin. Using Koch's molecular postulates, we determined that a mutant of mpl36 has a reduced PLG-binding ability, leading to a decreased capacity to adhere and translocate MDCK cell monolayers. Using recombinant protein and mutant strains, we determined that the MPL36-bound plasmin (PLA) can degrade fibrinogen. Finally, our mpl36 mutant had a significant attenuated phenotype in the hamster model for acute leptospirosis. Our data indicates that MPL36 is the major PLG binding protein in pathogenic Leptospira, and crucial to the pathogen's ability to attach and interact with host tissues during infection. The MPL36 characterization contributes to the expanding field of bacterial pathogens that explore PLG for their virulence, advancing the goal to close the knowledge gap regarding leptospiral pathogenesis while offering a novel potential candidate to improve diagnostic and prevention of this important zoonotic neglected disease.

Evaluation of Leptospira interrogans knockdown mutants for LipL32, LipL41, LipL21, and OmpL1 proteins

Introduction

Leptospirosis is a worldwide zoonosis caused by pathogenic and virulent species of the genus Leptospira, whose pathophysiology and virulence factors remain widely unexplored. Recently, the application of CRISPR interference (CRISPRi) has allowed the specific and rapid gene silencing of major leptospiral proteins, favoring the elucidation of their role in bacterial basic biology, host-pathogen interaction and virulence. Episomally expressed dead Cas9 from the Streptococcus pyogenes CRISPR/Cas system (dCas9) and single-guide RNA recognize and block transcription of the target gene by base pairing, dictated by the sequence contained in the 5' 20-nt sequence of the sgRNA.

Methods

In this work, we tailored plasmids for silencing the major proteins of L. interrogans serovar Copenhageni strain Fiocruz L1-130, namely LipL32, LipL41, LipL21 and OmpL1. Double- and triple-gene silencing by in tandem sgRNA cassettes were also achieved, despite plasmid instability.

Results

OmpL1 silencing resulted in a lethal phenotype, in both L. interrogans and saprophyte L. biflexa, suggesting its essential role in leptospiral biology. Mutants were confirmed and evaluated regarding interaction with host molecules, including extracellular matrix (ECM) and plasma components, and despite the dominant abundance of the studied proteins in the leptospiral membrane, protein silencing mostly resulted in unaltered interactions, either because they intrinsically display low affinity to the molecules assayed or by a compensation mechanism, where other proteins could be upregulated to fill the niche left by protein silencing, a feature previously described for the LipL32 mutant. Evaluation of the mutants in the hamster model confirms the augmented virulence of the LipL32 mutant, as hinted previously. The essential role of LipL21 in acute disease was demonstrated, since the LipL21 knockdown mutants were avirulent in the animal model, and even though mutants could still colonize the kidneys, they were found in markedly lower numbers in the animals' liver. Taking advantage of higher bacterial burden in LipL32 mutant-infected organs, protein silencing was demonstrated in vivo directly in leptospires present in organ homogenates.

Discussion

CRISPRi is now a well-established, attractive genetic tool that can be applied for exploring leptospiral virulence factors, leading to the rational for designing more effective subunit or even chimeric recombinant vaccines.

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

INTRODUCTION

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

METHODS AND ANALYSIS

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

ETHICS AND DISSEMINATION

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

TRIAL REGISTRATION NUMBER

Brazilian Clinical Trials Registry (RBR-8cjjpgm).