A century of Leptospira strain typing

Genetic diversity of pathogenic Leptospira spp. harbored by bats in Japan

Leptospirosis is a zoonotic infectious disease caused by pathogenic Leptospira species. In Japan, human and canine leptospirosis cases are reported annually. Although wild animals, including bats, are known to harbor pathogenic Leptospira spp., infection of bats in this region has never been explored. This study aimed to determine the presence of leptospires and their genetic diversity in five Japanese bat species. Kidney tissue and blood samples were collected from 115 bats captured in the Yamaguchi Prefecture and Hokkaido, Japan. Pathogenic Leptospira spp. were detected in the kidneys by real-time PCR and conventional PCR using primers targeting lipL32 and rrs2. Multilocus sequence typing (MLST) and sequencing of secY gene were performed on PCR-positive DNA samples. Leptospira spp. were detected in 26 of the 115 bats (22.6 %), including Rhinolophus ferrumequinum (5/37, 14 %), Rhinolophus cornutus (2/6, 33 %), Miniopterus schreibersii (6/37, 16 %), Myotis macrodactylus (11/15, 73 %), and Vespertilio sinensis (2/20, 10 %). Phylogenetic analysis based on MLST genes and secY gene revealed detected genes clustered with either L. interrogans, L. borgpetersenii, or L. kirschneri and a relationship between the leptospires identified in the bats in this study and bats in other countries or other host, and PCR with L. borgpetersenii-specific primers revealed co-infection with multiple Leptospira species in individual bats. Our study demonstrated a high carriage rate, genetic diversity of Leptospira spp., and co-infection with multiple Leptospira spp. in Japanese bats.

Identification of virulence genes and clade-specific markers through pan-genomic analysis of Leptospira

Leptospirosis is an emerging zoonotic and neglected disease across the world causing huge loss of life and economy. In this study, we did whole genome sequencing of one Leptospira isolate and a comparative genomic analysis with 69 other species of Leptospira available in RefSeq database provided insight into taxonomic and evolutionary relationship between species. AAI and whole genome based phylogenomic analysis established 3 clusters of Leptospira i.e. pathogenic, intermediate and saprophytic correlating with level of virulence of species. Leptospira has large closed core genome of 1038 genes and an open pan genome with 20,822 genes. The mobilome related genes were found mainly in pan-genome of pathogenic clade. A total of 498 genes have been identified as virulomes, with 329 virulent genes exhibiting presence/absence in various Leptospira species contributing to each species specific virulence profile. The hierarchical clustering of the congregated pathogenic genes yielded five groups, each with a distinct pattern of predominant genes that were either unique or common among clades, indicating lineage uniqueness. Most of the virulent gene pool identified were significantly enriched in COG functional categories of Nucleotide transport and metabolism, Intracellular trafficking, secretion and vesicular transport, cell motility and amino acid transport & metabolism. Pathogenic leptospires exhibit fewer clade-specific genes than non-pathogenic and intermediate leptospires, indicating gene loss and gain events in the evolution of pathogenic leptospires from non-pathogenic. The study's clade-specific and virulent genes can be utilised as markers for defining clade and associated virulence levels in any new Leptospira isolates. Wet-lab validation of virulent genes will help in accurately targeting pathogenic pathways of Leptospira and controlling leptospirosis.

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.

The Challenge of Bacterial Strain Identification: Leptospira interrogans Serovars Australis in a Dog and Long-Term Clinical Follow-Up

Leptospirosis is a widespread disease throughout the world, presenting in severe clinical forms in dogs. The pathogenicity of the different serovars in field infections is not fully documented, and clinical diagnosis is often limited to a combination of serological tests and molecular analyses. The latter, although a fundamental tool, cannot identify the infecting strain without further analysis. This study reports the use of various indirect (microscopic agglutination test, MAT) and direct (microbiological culture, real-time PCR) laboratory techniques, followed by typing protocols (Multi-locus Sequence Typing (MLST), Multiple Loci Variable number tandem repeat Analysis (MLVA), serotyping) that allowed for the identification of the Leptospira serovar Australis in a symptomatic and previously vaccinated dog (vaccine containing heterologous strains). This study reports long-term clinical follow-up (0-640 days) and describes the possible role of the infection in the development of chronic renal failure. This study aims to highlight how a combination of different techniques can be useful to better characterise the environmental circulation of zoonotic agents. Therefore, the identification and isolation of circulating L. strains would facilitate the updating of epidemiological data, enhance the knowledge of pathogenicity and long-term clinical effects, and provide a valuable resource for improving the efficacy of a specific serovar vaccination.

Leptospirosis in the Platypus (Ornithorhynchus anatinus) in Australia: Who Is Infecting Whom?

The platypus (Ornithorhynchus anatinus) is an amphibious, egg-laying mammal of high conservation value that is found only in Australia. The zoonotic bacterium Leptospira interrogans serovar Hardjo was discovered in platypuses in prior studies, but little is known about its epidemiology. Samples in the Platypus Serum Bank were tested in 2023 and the results were combined with historical records. Antibodies against L. interrogans serovar Hardjo were found in 50% of 464 serum samples from 411 platypuses collected from 14 river basins in southeastern Australia between 1981 and 2012; prevalence remained high over three decades in the Shoalhaven River population. Seroprevalence increased with age, suggesting environmental exposure. Individual platypuses had persistent titres, some for six years. Seropositive females lactated, juveniles were recruited into the population, and there were no reports of clinical leptospirosis. Three necropsied platypuses were seropositive and had mild nephritis with leptospires in the renal tubules. The high seroprevalence, persistent titres, lack of disease, mild renal lesions, and renal colonisation suggest the platypus may be a maintenance host. Sympatric cattle had L. interrogans serovar Hardjo titres, but the spatial association with seropositive platypuses was statistically weak. Other mammalian wildlife species and sheep also have L. interrogans serovar Hardjo titres; therefore, a complex ecological network must be considered. A landscape-wide study is recommended to properly assess transmission pathways and confirm who is infecting whom.

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.

Seroprevalence and Risk Factors Associated with Leptospirosis in High-Risk Occupational Groups in the State of Gujarat as Determined by IgM ELISA and MAT Test: A Cross-Sectional Study

Background

Leptospirosis is a reemerging zoonosis affecting humans and animals worldwide in tropical and subtropical countries. The study was conducted to estimate the seroprevalence of leptospirosis in high-risk occupational groups (cattle farm workers, poultry farm workers, and slaughterhouse workers) in the state of Gujarat and to determine related risk factors for leptospirosis.

Methods

Using an interview-guided questionnaire, a cross-sectional study was conducted involving 123 people in high-risk occupational groups (namely, cattle farm workers, poultry farm workers, and slaughterhouse workers) from five districts of the state of Gujarat, India. The participants' serum samples were screened for antileptospiral antibodies by using Immunoglobulin G (IgG) and Immunoglobulin M (IgM) enzyme-linked immunosorbent assays (ELISAs) followed by a microscopic agglutination test (MAT). The Chi-square (χ2) test and odds ratio were calculated using IBM SPSS Statistics for Windows, version 22 (IBM Corp., Armonk, N.Y., USA) to ascertain the associated risk factors.

Results

Regarding demographic information, this study included 104 men and 19 women in high-risk occupational groups. The overall seroprevalence of antileptospiral antibodies in these high-risk workers was 46.3%. The seroprevalence was the highest among poultry farm workers (56.6%), followed by cattle farm workers (54.5%) and slaughterhouse workers (25.6%). The MAT in combination with IgM is adequate for the serological diagnosis of leptospirosis, but we have also employed IgG ELISA to understand the chronic infection in these high-risk occupational groups as exposure was both past and present. Tests were conducted for antibodies against various Leptospira serovars in the major serogroups; frequent serovars included Hurstbridge, Panama, Javanica, Tarassovi, Copenhageni, Pomona, and Weaveri, among others. The significant (P < 0.05) risk factors associated with leptospirosis in these high-risk occupations reported to be living in field areas, the presence of livestock in the neighborhood, working in slaughterhouses, drinking water from natural water resources, contact with animals such as dogs or livestock, and wounds during occupational practice.

Conclusion

Considering the high seroprevalence of leptospirosis, high-risk occupational groups should be regularly screened for potential development of the fatal disease. Hurstbridge was found to be the most prevalent serovar in the studied population, followed by Panama, Javanica, and Tarassovi.

Cross-sectional serosurvey of Leptospira species among slaughter pigs, goats, and sheep in Uganda

INTRODUCTION

Leptospira are a group of bacteria, including pathogenic types that cause leptospirosis. In Uganda, Leptospira exposure has been reported in humans, with domesticated animals being speculated as the source. However, comparable evidence of Leptospira prevalence and circulating serovars/serogroups in animals is only documented for cattle, and dogs. Our study determined Leptospira seroprevalence, associated risk factors and serogroups circulating among slaughtered pigs, goats, and sheep in Uganda.

METHODS

During an 11-month cross-sectional survey in selected slaughter facilities in three regions of Uganda, we collected blood from 926 pigs, 347 goats, and 116 sheep. The age, sex, breed, and origin of each sampled animal were noted. The samples were tested for anti-Leptospira antibodies using the microscopic agglutination test, based on a panel of 12 serovars belonging to 12 serogroups.

RESULTS

Leptospira seroprevalence was 26.67% (247/926, 95%CI 23.92-29.61) among pigs, and 21.81% (101/463, 95%CI 18.29-25.80) in goats and sheep (small ruminants). L. interrogans Australis and L. kirschneri Grippotyphosa were the commonest serovars among pigs, as was L. borgpetersenii Tarassovi in small ruminants. Pigs sourced from the Eastern (Odds Ratio [OR] = 2.82, 95%CI 1.84-4.30) and Northern (OR = 3.56, 95%CI 2.52-5.02) regions were more likely to be seropositive, compared to those from the Central region. For small ruminants, being female (OR 2.74, 95% CI 1.69-4.57) and adult (OR 4.47, 95% CI 1.57-18.80) was significantly more associated with Leptospira seropositivity. Conclusion/significance: Detection of a moderate seroprevalence, and several Leptospira serogroups among pigs, sheep, and goats from all regions of Uganda, supports existing reports in cattle and dogs, and implies widespread Leptospira exposure in domestic animals in Uganda. These findings may inform future programs for the control of leptospirosis in livestock in Uganda.

Relevance of Polymerase Chain Reaction in Early Diagnosis of Leptospirosis

Aim and background

Leptospirosis is common in India, especially in the southern states. Mortality is high among untreated cases. Diagnosis of leptospirosis remains a challenge in India as polymerase chain reaction (PCR), which is more sensitive than Immunoglobulin M (IgM) is not widely available. This study aimed to find out the difference in diagnostic yield with PCR and IgM in early leptospirosis.

Materials and methods

This retrospective, single-center study included 67 adults with laboratory-confirmed leptospirosis (IgM, PCR, or both) who presented within 7 days of symptom onset and were admitted to the intensive care unit (ICU). The difference in the diagnostic yield with PCR and IgM ELISA was studied.

Results

About 77.6% of the patients tested positive by PCR and 55.2% tested positive by IgM. There was a statistically significant difference in the detection of leptospirosis by PCR and IgM (p-value = 0.036). In the subgroup of patients who presented within 3 days of onset of symptoms, PCR positivity was 90.32% whereas IgM positivity was only 25.8%.

Conclusion

Our study showed that the sensitivity of leptospira PCR is significantly higher than IgM in the first week of illness. It also showed that among the subset of patients who died, a majority were detected only by PCR. Since PCR is not widely available, leptospirosis remains underdiagnosed and mortality from the same is underestimated. Polymerase chain reaction, if routinely done along with IgM for all suspected cases of leptospirosis that present within the first week of illness helps in prompt diagnosis and treatment.

How to cite this article

Sreevalsan TV, Chandra R. Relevance of Polymerase Chain Reaction in Early Diagnosis of Leptospirosis. Indian J Crit Care Med 2024;28(3):290-293.

The leptospiral OmpA-like protein (Loa22) is a surface-exposed antigen that elicits bactericidal antibody against heterologous Leptospira

Leptospirosis is the most widespread zoonosis, affecting over 1 million humans each year, with more than 60,000 deaths worldwide. Leptospirosis poses a significant health threat to dogs, horses, cattle, and wildlife. The disease may be self-limiting or progress to a life-threatening multi-system disorder affecting the kidneys, liver, and lungs. Currently, bacterin vaccine formulations that consist of one or more laboratory-cultivated strains are used for prevention. However, the antibody response elicited by these vaccines is directed primarily at lipopolysaccharide and is generally serovar-specific. The development of broadly protective subunit vaccines for veterinary and human applications would be a significant step forward in efforts to combat this emerging and antigenically variable pathogen. This study assessed the properties and potential utility of the Leptospira Loa22 (Leptospira OmpA-like 22 kDa protein) protein as a vaccine antigen. Loa22 is a virulence factor that is predicted to transverse the outer membrane and present its N-terminal domain on the cell surface. This report demonstrates that diverse Leptospira strains express Loa22 in vitro and that the protein is antigenic during infection in dogs. Immunoblot and size exclusion chromatography revealed that Loa22 exists in monomeric and trimeric forms. Immunization of rats with recombinant Loa22 elicited bactericidal antibodies against diverse Leptospira strains. The immunodominant bactericidal epitopes were localized within the N-terminal domain using protein-blocking bactericidal assays. This study supports the utility of Loa22, or subfragments thereof, in developing a multivalent chimeric subunit vaccine to prevent leptospirosis and sheds new light on the cellular localization of Loa22.

Exploration of the potential utility of the luciferase immunoprecipitation system (LIPS) assay for the detection of anti-leptospira antibodies in dogs

Canine leptospirosis represents a diagnostic challenge to veterinarians, due to the variability in presenting clinical signs and interpretation of serology test results in dogs that have been vaccinated previously. None of the commercially available serological assays, including the microscopic agglutination test (MAT), have been verified to be capable of differentiating infected from vaccinated animals (DIVA). Recent work identified that half of primary practice attending dogs were up to date with their leptospirosis vaccination and would be expected to have circulating anti-leptospira antibodies (Taylor et al., 2022), indicating that this is a relevant issue for suspected leptospirosis cases in dogs in the UK. This study aimed to explore the utility of three leptospiral outer membrane proteins (OMPs: LipL32, LipL21 and LipL41) as potential DIVA targets in the luciferase immunoprecipitation system (LIPS) assay. N and C terminal nanoluciferase tagged recombinant proteins were generated for each OMP. Differences in reactivity between serum samples from MAT positive dogs (n = 29) and paired samples (n = 6 dogs) taken pre and 21 days post leptospirosis vaccination were assessed against these six constructs. Reactivity was greater towards the N terminal than the C terminal recombinant proteins for all three OMPs. None of the constructs appeared to demonstrate DIVA capability, although two (pNLF1-N-FLAG/LipL32 and pNLF1-N-FLAG/LipL21) were able to detect vaccine seroconversion. The findings of this work suggest that these particular OMP targets do not offer DIVA ability, however LipL32 and LipL21 may be suitable for use in immunoassays for vaccine trials or for detection of infections in humans, where there is no requirement for DIVA capability.

Influence of landscape structure on previous exposure to Leptospira spp. and Brucella abortus in free-living neotropical primates from southern Brazil

The environments in which neotropical primates live have been undergoing an intense fragmentation process, constituting a major threat to the species' survival and causing resource scarcity, social isolation, and difficulty in dispersal, leaving populations increasingly vulnerable. Moreover, the proximity of wild environments to anthropized landscapes can change the dynamics of pathogens and the parasite-host-environment relationship, creating conditions that favor exposure to different pathogens. To investigate the previous exposure of free-living primates in Rio Grande do Sul State (RS), southern Brazil, to the bacterial agents Leptospira spp. and Brucella abortus, we investigated agglutinating antibodies against 23 serovars of Leptospira spp. using the microscopic agglutination test and B. abortus acidified antigen test in primate serum samples; 101 samples from primates captured between 2002 and 2016 in different forest fragments were used: 63 Alouatta caraya, 36 Alouatta guariba clamitans, and 02 Sapajus nigritus cucullatus. In addition, the forest remnants where the primates were sampled were characterized in a multiscale approach in radii ranging from 200 to 1400 m to investigate the potential relationship of previous exposure to the agent with the elements that make up the landscape structure. The serological investigation indicated the presence of antibodies for at least one of the 23 serovars of Leptospira spp. in 36.6% (37/101) of the samples analyzed, with titers ranging from 100 to 1600. The most observed serovars were Panama (17.8%), Ballum (5.9%), Butembo (5.9%), Canicola (5.9%), Hardjo (4.9%), and Tarassovi (3.9%); no samples were seropositive for Brucella abortus. Decreased forest cover and edge density were the landscape factors that had a significant relationship with Leptospira spp. exposure, indicating that habitat fragmentation may influence contact with the pathogen. The data generated in this study demonstrate the importance of understanding how changes in landscape structure affect exposure to pathogenic microorganisms of zoonotic relevance. Hence, improving epidemiological research and understanding primates' ecological role in these settings can help improve environmental surveillance and conservation strategies for primate populations in different landscapes.

Serological and Molecular Evidence of Pathogenic Leptospira spp. in Stray Dogs and Cats of Sicily (South Italy), 2017-2021

Leptospirosis is a zoonosis of public health concern. Its prevalence in stray animals in the South of Italy is unknown. This study aimed to investigate Leptospira spp. prevalence in 1009 stray animals. Out of them, 749 were alive animals, including 358 dogs (316 from Palermo and 42 from Ragusa) and 391 cats (359 from Palermo and 32 from Ragusa), and 260 were corpses (216 dogs and 44 cats) randomly collected in Sicily. Dogs and cats underwent a serological screening by Microscopic Agglutination Test and a molecular investigation by Real-Time PCR targeting lipL32. Corpses were subjected to Real-Time PCR. Serological analyses showed a prevalence of 1.12% (4/358) for dogs and 0.26% (1/391) for cats, with the only positive cat coming from Palermo. Serogroup Icterohaemorrhagiae serovar Icterohaemorrhagiae or Copenhageni, followed by Canicola and Bratislava, were the most spread among dogs, while the serological positive cat reacted with Hardjo serogroup. Two urine (2/32, 6.25%) and one blood (1/391, 0.26%) samples of cats, all from Ragusa, were positive at Real-Time PCR for pathogenic Leptospira spp. Sequencing analyses showed the presence of L. interrogans serogroup Icterohaemorrhagiae serovar Icterohaemorrhagiae or Copenhageni in one of the positive urine samples and in the positive blood sample. Analyses on corpses showed a prevalence of 1.85% (4/216) in Sicilian dog kidney samples, while all corpses of cats resulted in negative. Genotyping analysis showed a genetic relatedness between cat and human isolates. Results show Leptospira spp. circulation among Sicilian stray animals. The genetic relatedness between cat and human isolates suggests a possible common infection source.

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.

Evaluation of the genetic stability of Leptospira reference strains maintained under two conservation methods

Objective. The genetic stability of Strains of Leptospira spp., maintained under two conservation systems, was evaluated. Methodology. The degree of conservation of the 16S rRNA and ompL1 genes of 10 reference serovars from the Leptospira spp. collection, belonging to the Sistema de Bancos de Germoplasma de la Nación para la Alimentación y la Agricultura (SBGNAA), was determined. Results. It was corroborated that the genes evaluated these have not undergone considerable changes, since similarities greater than 99.69 % were evidenced for 16S rRNA and 99.02% for ompL1, in the paired alignments. Conclusion. The genetic stability and purity of the reference strains of Leptospira spp. were verified. spp., kept in cryopreservation in liquid nitrogen at -196 °C and at room temperature for approximately eight years.

Prevalence of anti-leptospiral IgM and detection of pathogenic Leptospira species DNA in neonates presenting with clinical sepsis in Southwestern Uganda

BACKGROUND

Leptospirosis is an emerging neglected zoonotic disease that presents with nonspecific signs/symptoms and it can be mistaken for other diseases. Owing to limited diagnostic capacity and unawareness, the data on human leptospirosis particularly in neonates are scarce in many sub-Saharan countries. It has been underreported hindering preventive and control measures in place. The study aimed at determining prevalence of leptospirosis as a cause of febrile illness in neonates using IgM ELISA and a quantitative real-time PCR (qPCR).

METHODS

This was a descriptive cross-sectional study that included 103 neonatal sepsis cases whose parents/legal guardians gave informed consent. The data on demographic and clinical characteristics were collected using structured data collection form. EDTA whole blood sample was collected from the neonates by trained study nurses. From the samples, IgM ELISA was done using automated analyzers, DNA extracted and qPCR was performed using primers for LipL32, specific for the pathogenic leptospires.

RESULTS

The prevalence of anti-leptospiral IgM among the neonates as determined by ELISA was 4.3%, where all of them presented with lethargy and poor feeding. No pathogenic Leptospira species DNA was amplified by qPCR.

CONCLUSIONS

Evidence of leptospirosis was demonstrated in neonatal sepsis cases in this study. The findings suggest considerations of leptospirosis in the differential diagnosis of neonates with sepsis. More data are needed on the real epidemiology, clinical features, and burden of leptospirosis in neonates. There is need to include intermediate pathogenic species of Leptospira in the diagnostic qPCR assays.

Serological Investigation and Epidemiological Analysis of Bovine Leptospirosis in Egypt

Bovine leptospirosis is a bacterial zoonotic disease of worldwide distribution. Little information is available regarding the occurrence of the disease in the Nile Delta provinces, Egypt. The present study investigated the seroprevalence of leptospirosis among cattle from Dakahlia province, Northern Egypt, and identified the individual variables factors associated with infection. To this end, a total of 600 serum samples from cattle of small stakeholders with various clinical manifestations possibly associated with leptospirosis were collected from different localities across Dakahlia province, Egypt. Sera were examined serologically via ELISA to investigate the occurrence of the disease among animals. Chi-square test and multivariable logistic regression analyses were applied to determine the association between hypothesized risk factors and the disease. Interestingly, our findings showed that 39.33% of the examined sera were positive for Leptospira antibodies, with significant differences among different localities. In addition, statistical analysis showed significant differences among age groups. Notably, the highest prevalence rate (22%) was observed in those aged between 3 and 5 years (p < 0.0001), whereas the lowest prevalence (2.66%) was reported in cattle <1 year old (p < 0.0001). Moreover, females had a significantly higher prevalence rate (35.33%) than males (4%) (p < 0.0001). Furthermore, our results showed significant differences in the occurrence of infection and reported clinical signs (p < 0.0001). Multivariable logistic regression identified repeated breeder and drop milk yield as the best predictors for prediction of ELISA results and linear discriminant analysis (LDA) model showed that overall classification accuracy of ELISA result using clinical signs and demographic data as predictors was 70.7%. The current study concluded a relative high prevalence of leptospirosis among cows bred in movable herds and households in the studied area and that age, repeated breeder and drop milk yield can be considered major risk factors associated with infection.

Comparative genomic analysis of Leptospira spp. isolated from Rattus norvegicus in Indonesia

Leptospirosis is one of the most prevalent zoonotic diseases caused by pathogenic spirochetes of Leptospira spp. The disease has become a public health concern in urban localities in the tropics, where rats serve as significant reservoir animals for leptospirosis transmission. In Indonesia, the occurrence of leptospirosis is underestimated, and information on the causative Leptospira genotypes and serotypes is limited. This study reports the isolation of Leptospira spp. from rats captured in urban areas of Bogor, Indonesia. Serogroups and genotypes, sequence types (STs), or multiple-locus variable-number tandem repeat analysis (MLVA) types using 11 loci, were determined for the isolates. Furthermore, whole genome sequencing (WGS) was performed on 11 Indonesian isolates and 24 isolates from other Asian countries. Ninety small mammals, including 80 Rattus norvegicus and ten Suncus murinus, were captured and, 25 Leptospira spp. were isolated solely from R. norvegicus (31.3%). The isolates were identified as Leptospira borgpetersenii serogroup Javanica with ST 143 (four strains) and Leptospira interrogans serogroup Bataviae with the same MLVA type as isolates from other Asian countries (19); the serogroup of the two L. interrogans with ST252 could not be identified. The core genome SNP-based phylogenetic tree revealed that Indonesian isolates were genetically related to L. borgpetersenii serogroup Javanica strains widely distributed in Asian countries but formed a different cluster from other strains. The phylogenetic tree of L. interrogans serogroup Bataviae isolates from Indonesia, the Philippines, Taiwan, and Vietnam revealed that isolates were grouped into five clusters based on their geographic locations. This study discovered a high carriage rate of Leptospira spp. among R. norvegicus in Bogor, Indonesia, indicating a potential risk of rat-borne leptospirosis in the area. Besides L. borgpetersenii serogroup Javanica, WGS on L. interrogans serogroup Bataviae illustrated the geographical structuring of genetic diversity in Leptospira spp.

The impact of genetic recombination on pathogenic Leptospira

Leptospirosis is the most common zoonosis worldwide, and is increasingly common in poor urban communities, where there is inadequate sewage disposal and abundance of domestic and peridomestic animals. There are many risk factors associated with the disease, such as contaminated water exposure, close contact with animals, floods, recreational activities related to water, wet agriculture. The symptoms of leptospirosis are common to other infectious diseases and, if not treated, it can lead to meningitis, liver failure, kidney damage and death. Leptospirosis is caused by 38 pathogenic species of Leptospira, which are divided in almost 30 serogroups and more than 300 serovars. The serological classification (serogroups and serovars) is based on the expression of distinct lipopolysaccharide (LPS) antigens. These antigens are also associated to protective immunity; antibodies against a serovar protect from any member of the same serovar. Serologic and phylogenetic analyses are not congruent probably due to genetic recombination of LPS genes among different leptospiral species. To analyze the importance of recombination in leptospiral evolution, we performed a gene-by-gene tree topology comparison on closed genomes available in public databases at two levels: among core genomes of pathogenic species (34 recombinant among 1213 core genes), and among core genomes of L. interrogans isolates (178/798). We found that most recombinant genes code for proteins involved in translation, ribosomal structure and biogenesis, but also for cell wall, membrane and envelope biogenesis. Besides, our final results showed that half of LPS genes are recombinant (18/36). This is relevant because serovar classification and vaccine development are based on these epitopes. The frequent recombination of LPS-associated genes suggests that natural selection is promoting the survival of recombinant lineages. These results may help understanding the factors that make Leptospira a successful pathogen.

Use of machine-learning algorithms to aid in the early detection of leptospirosis in dogs

Leptospirosis is a life-threatening, zoonotic disease with various clinical presentations, including renal injury, hepatic injury, pancreatitis, and pulmonary hemorrhage. With prompt recognition of the disease and treatment, 90% of infected dogs have a positive outcome. Therefore, rapid, early diagnosis of leptospirosis is crucial. Testing for Leptospira-specific serum antibodies using the microscopic agglutination test (MAT) lacks sensitivity early in the disease process, and diagnosis can take >2 wk because of the need to demonstrate a rise in titer. We applied machine-learning algorithms to clinical variables from the first day of hospitalization to create machine-learning prediction models (MLMs). The models incorporated patient signalment, clinicopathologic data (CBC, serum chemistry profile, and urinalysis = blood work [BW] model), with or without a MAT titer obtained at patient intake (=BW + MAT model). The models were trained with data from 91 dogs with confirmed leptospirosis and 322 dogs without leptospirosis. Once trained, the models were tested with a cohort of dogs not included in the model training (9 leptospirosis-positive and 44 leptospirosis-negative dogs), and performance was assessed. Both models predicted leptospirosis in the test set with 100% sensitivity (95% CI: 70.1–100%). Specificity was 90.9% (95% CI: 78.8–96.4%) and 93.2% (95% CI: 81.8–97.7%) for the BW and BW + MAT models, respectively. Our MLMs outperformed traditional acute serologic screening and can provide accurate early screening for the probable diagnosis of leptospirosis in dogs.

Leptospira sp. infection in bats: A systematic review and meta-analysis

Bats are the only flying mammalian animals and are distributed worldwide. Bats are well-known hosts of several zoonotic viruses and bacteria, including Leptospira sp. Here, we performed a systematic review and a meta-analysis of evidence of Leptospira sp. infection in bats by examining studies published between 1964 and 2021. We reported the frequencies of various species and serogroups on all continents, several species and feeding habits of bats, and different diagnostic tools. Together, 33 papers from all continents with seven to 2077 individuals from one to 31 species were included. Molecular detection was conducted in most studies, followed by MAT (Microscopic Agglutination Test) and isolation and identification. Molecular characterization of Leptospira sp. revealed L. borgpetersenii as the most frequent species. Moreover, 179 positive samples for MAT contained the most likely infecting serogroups described, particularly the Australis serogroup. The percentage of positive tests in isolation and identification ranged between zero and 0.5%. The highest frequency of Leptospira infection among the continents was observed in Asia, whereas South America had the lowest percentage. Finally, Nycteridae and Rhinonycteridae were the most frequently infected bat families. Our study provides valuable information about the epidemiology of Leptospira sp. infection in bats. This article is protected by copyright. All rights reserved.

Leptospira in Slaughtered Fattening Pigs in Southern Italy: Serological Survey and Molecular Typing

Simple Summary

In this study, serological and molecular assays in 55 pigs in Sicily were conducted in order to investigate Leptospira spp. prevalence and to carry out strain characterization. A seropositivity rate of 16.4% was determined; 3.64% of kidney samples tested positive for pathogenic Leptospiral DNA. Obtained data showed that Leptospira infection is common among pigs in southern Italy, confirming the importance of Leptospiral infection in pigs and reaffirming the potential role of these animals as a source of infection for humans (occupational risk) and other animals. Our study delivers a comprehensive overview based on up-to-date data to deepen the knowledge of swine leptospiral infections, characterize new potential emerging strains, and reinforce control measures able to reduce the infection risk in swine herds.

Abstract

Leptospirosis is a re-emerging zoonosis of worldwide significance; a wide spectrum of wild and domestic animal species act as natural or accidental hosts. Swine can act as maintenance or accidental hosts of pathogenic Leptospira spp. This study aimed at investigation of Leptospira spp. prevalence and diversity in slaughtered pigs in southern Italy (Sicily). In total, 55 samples of kidneys and blood were collected. Microscopic agglutination test and real-time PCR were performed to detect pathogenic and intermediately pathogenic Leptospira. Partial rpoB gene sequencing and multi-locus sequence typing (MLST) were performed to characterize Leptospira species. The analysis showed a seropositivity rate of 16.4%, with Australis representing the most frequently identified serogroup (63.64%); Pomona and Sejroe were detected with a prevalence of 27.27% and 9.09%, respectively. Pathogenic Leptospiral DNA was detected in 2 kidney samples (3.64%). Leptospira were identified through MLST as L. borgpetersenii serovar Tarassovi (serogroup Tarassovi). Obtained data confirmed the presence of Leptospira infection among pigs in southern Italy, suggesting that management of these animals may be considered an occupational risk for humans.

Laboratory diagnostic, epidemiological, and clinical characteristics of human leptospirosis in Okinawa Prefecture, Japan, 2003-2020

BACKGROUND

Leptospirosis is considered an endemic disease among agricultural workers in Okinawa Prefecture, which is the southernmost part of Japan and has a subtropical climate, but data on the current status and trend of this disease are scarce.

METHODOLOGY/PRINCIPAL FINDINGS

We conducted a retrospective study of clinically suspected leptospirosis patients whose sample and information were sent to the Okinawa Prefectural Institute of Health and Environment from November 2003 to December 2020. Laboratory diagnosis was established using culture, nested polymerase chain reaction (PCR), and/or microscopic agglutination test (MAT) with blood, cerebrospinal fluid, and/or urine samples. Statistical analyses were performed to compare the epidemiological information, clinical features, and sensitivities of diagnostic methods among laboratory-confirmed cases. Serogroups and the species of Leptospira isolates were determined by MAT using 13 antisera and flaB sequencing. A total of 531 clinically suspected patients were recruited, among whom 246 (46.3%) were laboratory confirmed to have leptospirosis. Among the confirmed cases, patients aged 20-29 years (22.4%) and male patients (85.7%) were the most common. The most common estimated sources of infection were recreation (44.5%) and labor (27.8%) in rivers. Approximately half of the isolates were of the L. interrogans serogroup Hebdomadis. The main clinical symptoms were fever (97.1%), myalgia (56.3%), and conjunctival hyperemia (52.2%). Headache occurred significantly more often in patients with Hebdomadis serogroup infections than those with other serogroup infections. The sensitivities of culture and PCR exceeded 65% during the first 6 days, while the sensitivity of MAT surpassed that of culture and PCR in the second week after onset. PCR using blood samples was a preferable method for the early diagnosis of leptospirosis.

CONCLUSIONS/SIGNIFICANCE

The results of this study will support clinicians in the diagnosis and treatment of undifferentiated febrile patients in Okinawa Prefecture as well as patients returning from Okinawa Prefecture.

Protective efficacy of whole-cell inactivated Leptospira vaccines made using virulent or avirulent strains in a hamster model

Whole-cell inactivated vaccines remain the only licensed vaccines used to control human and animal leptospirosis worldwide. Although they are protective against lethal infections, the efficacy of these vaccines has been divergent. The manufacturing process often involves the use of standard bacterial strains subjected to serial in vitro passages, with a risk of loss of virulence, and may affect the immunogenicity and consequently decrease protection. Thus, the objective of this study was to perform a comparative analysis of the efficacy of in-house bacterins produced with standard (avirulent) and virulent strains. Hamsters were immunized with killed bacteria produced using avirulent and virulent strains of L. interrogans serovars Copenhageni and Canicola. Vaccine efficacy was determined in terms of protection against lethal homologous or heterologous challenges. The results showed that immunization with both avirulent and virulent Canicola strains resulted in 100% protection against homologous challenge. Conversely, Copenhageni bacterins produced using an avirulent strain conferred only 25-37.5% protection against homologous challenge (P > 0.05), while virulent Copenhageni bacterin conferred 100% protection (P < 0.001). A single vaccine dose was sufficient to induce protection, and administration of a prime boost significantly reduced the bacterial load in the kidneys and improved the humoral immune response to the virulent Copenhageni strain. These findings suggest that the maintenance of virulent strains in bacterin formulations is essential for improving the immunogenicity and efficacy of leptospirosis vaccines.

High Diversity of Leptospira Species Infecting Bats Captured in the Urabá Region (Antioquia-Colombia)

Leptospirosis is a globally distributed zoonotic disease caused by pathogenic bacteria of the genus Leptospira. This zoonotic disease affects humans, domestic animals and wild animals. Colombia is considered an endemic country for leptospirosis; Antioquia is the second department in Colombia, with the highest number of reported leptospirosis cases. Currently, many studies report bats as reservoirs of Leptospira spp. but the prevalence in these mammals is unknown. The goal of this study was to better understand the role of bats as reservoir hosts of Leptospira species and to evaluate the genetic diversity of circulating Leptospira species in Antioquia-Colombia. We captured 206 bats in the municipalities of Chigorodó (43 bats), Carepa (43 bats), Apartadó (39 bats), Turbo (40 bats), and Necoclí (41 bats) in the Urabá region (Antioquia-Colombia). Twenty bats tested positive for Leptospira spp. infection (20/206—9.70%) and the species of infected bats were Carollia perspicillata, Dermanura rava, Glossophaga soricina, Molossus molossus, Artibeus planirostris, and Uroderma convexum. These species have different feeding strategies such as frugivorous, insectivores, and nectarivores. The infecting Leptospira species identified were Leptospira borgpetersenii (3/20–15%), Leptospira alexanderi (2/20–10%), Leptospira noguchii (6/20–30%), Leptospira interrogans (3/20–15%), and Leptospira kirschneri (6/20–30%). Our results showed the importance of bats in the epidemiology, ecology, and evolution of Leptospira in this host-pathogen association. This is the first step in deciphering the role played by bats in the epidemiology of human leptospirosis in the endemic region of Urabá (Antioquia-Colombia).

Leptospirosis and Coinfection: Should We Be Concerned?

Pathogenic Leptospira is the causative agent of leptospirosis, an emerging zoonotic disease affecting animals and humans worldwide. The risk of host infection following interaction with environmental sources depends on the ability of Leptospira to persist, survive, and infect the new host to continue the transmission chain. Leptospira may coexist with other pathogens, thus providing a suitable condition for the development of other pathogens, resulting in multi-pathogen infection in humans. Therefore, it is important to better understand the dynamics of transmission by these pathogens. We conducted Boolean searches of several databases, including Google Scholar, PubMed, SciELO, and ScienceDirect, to identify relevant published data on Leptospira and coinfection with other pathogenic bacteria. We review the role of the host-microbiota in determining the synanthropic interaction of Leptospira sp. with other bacteria, thus creating a suitable condition for the leptospira to survive and persist successfully. We also discuss the biotic and abiotic factors that amplify the viability of Leptospira in the environment. The coinfection of leptospira with pathogenic bacteria has rarely been reported, potentially contributing to a lack of awareness. Therefore, the occurrence of leptospirosis coinfection may complicate diagnosis, long-lasting examination, and mistreatment that could lead to mortality. Identifying the presence of leptospirosis with other bacteria through metagenomic analysis could reveal possible coinfection. In conclusion, the occurrence of leptospirosis with other diseases should be of concern and may depend on the success of the transmission and severity of individual infections. Medical practitioners may misdiagnose the presence of multiple infections and should be made aware of and receive adequate training on appropriate treatment for leptospirosis patients. Physicians could undertake a more targeted approach for leptospirosis diagnosis by considering other symptoms caused by the coinfected bacteria; thus, more specific treatment could be given.

Regional Prevalence of Intermediate Leptospira spp. in Humans: A Meta-Analysis

Leptospirosis is one of the most widespread bacterial diseases caused by pathogenic Leptospira. There are broad clinical manifestations due to varied pathogenicity of Leptospira spp., which can be classified into three clusters such as pathogenic, intermediate, and saprophytic. Intermediate Leptospira spp. can either be pathogenic or non-pathogenic and they have been reported to cause mild to severe forms of leptospirosis in several studies, contributing to the disease burden. Hence, this study aimed to estimate the global prevalence of intermediate Leptospira spp. in humans using meta-analysis with region-wise stratification. The articles were searched from three databases which include PubMed, Scopus, and ScienceDirect. Seven studies were included consisting of two regions based on United Nations geo-scheme regions, among 469 records identified. Statistical analysis was performed using RevMan software. The overall prevalence estimate of intermediate Leptospira spp. in humans was 86% and the pooled prevalences were 96% and 17% for the American and Asia regions, respectively. The data also revealed that Leptospira wolffii was the most predominantly found compared to the other intermediate species identified from the included studies, which were Leptospira inadai and Leptospira broomii. The estimated prevalence data from this study could be used to develop better control and intervention strategies in combating human leptospirosis.

Seroepidemiological investigation of animal leptospirosis and molecular characterization of the first Leptospira strain isolated from Fernando de Noronha archipelago, Brazil

Leptospirosis has been widely reported in insular environments worldwide, characterizing a major public health threat. Although low-genetic biodiversity is expected in these regions, the introduction of domestic and synanthropic mammals may contribute to the wider diversity of leptospiral strains in insular settings. This study proposes a large-scale seroepidemiological investigation of Leptospira infection in animals from Fernando de Noronha archipelago and describes the characterization of the first leptospiral strain ever isolated from an insular setting in Brazil. A total of 1,265 blood samples from domestic (n = 682), synanthropic (n = 133) and wild (n = 450) animals were collected between 2007 and 2014, totalling 12 species. The presence of anti-Leptospira spp. antibodies was investigated by the microscopic agglutination test (MAT), and kidney samples from 20 synanthropic rodents were collected for the isolation of Leptospira spp. The leptospires recovered were further characterized by serogrouping with polyclonal antibodies, whole-genome sequencing and multilocus sequence typing (MLST). The MAT results revealed the presence of agglutinins in 90 samples (7.1%) and the most frequently found serogroup was Icterohaemorrhagiae (n = 57) in practically all species included. Viable leptospires were recovered from one brown rat, and characterization revealed that the isolate belongs to L. interrogans serogroup Pyrogenes. The results suggest that synanthropic rodents might play an important role in leptospiral infection among wildlife and domestic species in the archipelago.

Quantitative Real-Time PCR Assays for the Detection of Pathogenic Leptospira Species in Urine and Blood Samples in Canine Vaccine Clinical Studies: a Rapid Alternative to Classical Culture Methods

Leptospirosis is a vaccine-preventable bacterial zoonotic disease caused by pathogenic Leptospira species. The efficacy of Leptospira canine vaccines is assessed by challenging vaccinated and control dogs with virulent serovars of Leptospira, followed by detection of Leptospira in blood and urine. We assessed the consistency between results obtained for urine and blood samples from clinical studies with species-specific real-time quantitative PCR (qPCR) targeting the lipL32 gene and those obtained with the reference culture method. The specificity of the qPCR assay was confirmed by negative results for nonpathogenic Leptospira and for several canine viruses, bacteria, and parasites. The results from the two methods were compared using McNemar’s test, kappa coefficient (κ), and percentage of agreement analyses. The results for numbers of positive and negative dogs were similar, with no false-negative results with the qPCR assay. For both blood and urine, there was strong agreement between the culture method and qPCR results (κ = 0.68 [95% confidence interval (CI), 0.62 to 0.74] and κ = 0.65 [95% CI, 0.59 to 0.71], respectively). However, there was a statistically significant difference between blood samples (P < 0.001) and urine samples (P = 0.028). The negative percentage agreements were 97% and 84% and the positive percentage agreements were 68% and 83% for blood and urine samples, respectively. Although the cell culture method is the recommended gold standard, our results show that qPCR assay is a valid alternative method for the rapid and specific detection of pathogenic Leptospira spp. in urine and blood samples during vaccine efficacy studies, without loss of sensitivity.

Molecular and serological epidemiology of Leptospira infection in cats in Okinawa Island, Japan

Leptospirosis is a zoonosis caused by pathogenic Leptospira spp. Cats have been reported to be infected with Leptospira spp. and shed the bacteria in the urine. However, the importance of cats as an infection source for humans remains unclear. In this study, Leptospira infection in cats in Okinawa Prefecture, Japan, where leptospirosis is endemic, was investigated by leptospiral antibody and DNA detection using microscopic agglutination test and nested PCR, respectively. Moreover, multilocus sequence typing (MLST) and whole genome sequencing (WGS) were conducted on the Leptospira borgpetersenii serogroup Javanica isolated from cats, black rats, a mongoose, and humans. Anti-Leptospira antibodies were detected in 16.6% (40/241) of the cats tested, and the predominant reactive serogroup was Javanica. The leptospiral flaB gene was detected in 7.1% (3/42) of cat urine samples, and their sequences were identical and identified as L. borgpetersenii. MLST and WGS revealed the genetic relatedness of L. borgpetersenii serogroup Javanica isolates. This study indicated that most seropositive cats had antibodies against the serogroup Javanica and that cats excreted L. borgpetersenii in the urine after infection. Further, genetic relatedness between cat and human isolates suggests that cats may be a maintenance host for L. borgpetersenii serogroup Javanica and a source for human infection.

Rat trade and leptospirosis: Molecular epidemiology of Leptospira species in rats exported from Cambodia to Vietnam

Rats are an important maintenance host of Leptospira spp., the causative agents of leptospirosis, a zoonotic disease with worldwide distribution. Rats are traded as food in the Mekong Delta, where Cambodia exports tons of rats to Vietnam. Handling wild rats is a potential health risk, but the information on Leptospira spp. carried by rats traded in the region remains limited. In this study, we investigated the carriage of Leptospira spp. in rats exported from Cambodia to Vietnam using bacterial culture, nested PCR and DNA sequencing. Isolates were then assessed using serological analysis and whole-genome sequencing (WGS), and Leptospira DNA detected in rat kidney tissues was also analysed by multilocus sequence typing (MLST). Seventy-two rats (2 Bandicota indica, 57 Rattus argentiventer, 11 R. losea, 1 R. norvegicus and 1 R. rattus) were subjected to bacterial culture, and three L. borgpetersenii serogroup Javanica isolates were obtained from R. argentiventer (5.3%). WGS revealed that although Cambodian isolates were genetically related to L. borgpetersenii serogroup Javanica strains widely distributed in East and South-East Asian countries, they formed a different cluster from other strains. In addition to the three L. borgpetersenii sequences, the flaB sequence of L. interrogans was detected in 18 R. argentiventer and 7 R. losea kidney tissue samples (38.9%) using nested PCR followed by DNA sequencing. The L. interrogans flaB-positive samples were further analysed by MLST, revealing that seven housekeeping genes (glmU, pntA, sucA, tpiA, pfkB, mreA and caiB) contained novel sequences with distinct lineages from other sequence types. This study revealed a high prevalence of Leptospira spp. among rats exported from Cambodia to Vietnam, indicating a potential risk to people engaging in rat trade and demonstrating that a fastidious L. interrogans strain circulates among Cambodian rats.

Exposure to Leptospira spp. and Associated Risk Factors in the Human, Cattle and Dog Populations in Bhutan

Leptospirosis is a neglected worldwide zoonotic bacterial disease with a high prevalence in subtropical and tropical countries. The prevalence of Leptospira spp. in humans, cattle and dogs is unknown in Bhutan. Therefore, we sought to find out whether humans, cattle or dogs had been infected in the past with leptospires by measuring antibodies in the serum. We therefore collected blood from 864 humans ≥13 years of age, 130 bovines and 84 dogs from different rural and urban areas in Bhutan and tested the serum for antibodies specific for leptospires with a screening of enzyme-linked immunosorbent assays (ELISA) and a confirmatory microscopic agglutination test (MAT). In humans, 17.6% were seropositive by ELISA and 1.6% by MAT. The seropositivity was stronger in bovines (36.9%) and dogs (47.6%). "Having had a fever recently" (OR 5.2, p = 0.004), "working for the military" (OR 26.6, p = 0.028) and "being unemployed" (OR 12.9, p = 0.041) (reference category = housemaker) were statistically significantly associated with seropositivity when controlled for the effects of other risk factors. However, due to the small number of positive test results, the findings on risk factors should be interpreted with caution. Based on the serogroups found in the three species, dogs could be a source of infection for humans, or dogs and humans are exposed to the same environmental risk factors Clinical leptospirosis in humans and domestic animals should be investigated by testing blood and urine for the presence of leptospires by molecular methods (qPCR).

Leptospira fainei Detected in Testicles and Epididymis of Wild Boar (Sus scrofa)

Leptospirosis is a re-emerging and worldwide diffused zoonosis. Recently, the high importance of their epidemiology was explained by the intermediate Leptospira strains. Among these strains, Leptospira fainei was the first intermediate strain detected in domestic and wild swine. Wild boars (Sus scrofa) are well known as a reservoir, as well as all swine, for pathogenic Leptospira, but very little information is available concerning intermediate Leptospira infection. The investigation aim was to evaluate if intermediate Leptospira can infect the reproductive systems of wild boars hunted in the Tuscany region (Italy), as previously demonstrated for pathogenic ones. The reproductive system tissue (testicles, epididymides, uteri), and placentas and fetuses, were collected from 200 regularly hunted animals. Bacteriological examination and real-time PCR were performed to detect intermediate Leptospira DNA. Unfortunately, no isolates were obtained. Using real-time PCR, in six (3%) male organs (both testicles and epididymis), intermediate Leptospira DNA was found. The amplification of the 16S rRNA gene identified that all DNA obtained belong to Leptospira fainei. The results of this investigation highlighted for the first time the localization of Leptospira fainei in the male wild boar reproductive system, opening up a new avenue to further investigate.

Urinary shedding of leptospires in palearctic bats

Leptospirosis is a bacterial zoonotic infection of worldwide occurrence. Bats, like other mammalian reservoirs, may be long-term carriers that maintain endemicity of infection and shed viable leptospires in urine. Direct and/or indirect contact with these Leptospira shedders is the main risk factor as regards public health concern. However, knowledge about bat leptospirosis in the Palearctic Region, and in Europe in particular, is poor. We collected urine from 176 specimens of 11 bat species in the Czech Republic, Poland, Republic of Armenia and the Altai Region of Russia between 2014 and 2019. We extracted DNA from the urine samples to detect Leptospira spp. shedders using PCR amplification of the 16S rRNA and LipL32 genes. Four bat species (Barbastella barbastellus n = 1, Myotis bechsteinii n = 1, Myotis myotis n = 24 and Myotis nattereri n = 1) tested positive for Leptospira spp., with detected amplicons showing 100% genetic identity with pathogenic Leptospira interrogans. The site- and species-specific prevalence range was 0%-24.1% and 0%-20%, respectively. All bats sampled in the Republic of Armenia and Russia were negative. Given the circulation of pathogenic leptospires in strictly protected Palearctic bat species and their populations, non-invasive and non-lethal sampling of urine for molecular Leptospira spp. detection is recommended as a suitable surveillance and monitoring strategy. Moreover, our results should raise awareness of this potential disease risk among health professionals, veterinarians, chiropterologists and wildlife rescue workers handling bats, as well as speleologists and persons cleaning premises following bat infestation.

Didelphis albiventris as a carrier of Leptospira sp. in the central nervous tissue in the semiarid region of Northeast, Brazil

Leptospirosis has been investigated in several species of wild animals. The white-eared opossum (Didelphis albiventris) is a mammal common in the brazilian semi-arid, so, this study aimed to investigate its role in the occurrence of the leptospirosis in the region Northeast of Brazil. 12 animals were used, from which samples were collected for the attempt of isolation, molecular detection and serological examination. There was no microbial growth, nor were any anti-Leptospira sp. antibodies found in the serological samples. The PCR detected leptospiric DNA in the central nervous system (CNS) of five animals (41.7 %). The gene in one of the samples was sequenced and showed identity with Leptospira interrogans. The presence of Leptospira sp. in the CNS of Didelphis albiventris does not allow the characterization of the studied animals as reservoirs with potential for transmission of the pathogen in the region, however it represents a site that needs to be further investigated.

Análise espacial da leptospirose no Brasil

RESUMO A leptospirose é um problema de saúde pública mundial. No Brasil, ela é uma doença de notificação compulsória e está relacionada a áreas com precárias condições sanitárias. Foi realizado um estudo ecológico retrospectivo para observar a distribuição espacial e temporal de casos confirmados da leptospirose em escala nacional no período entre 2007 e 2017. A espacialização da leptospirose utilizou técnicas de geoprocessamento por análise de padrões pontuais e por mapas de densidade Kernel. Os resultados revelaram que, no período, foram registrados 42.310 casos confirmados de leptospirose no País, com média anual de 3.846 casos e prevalência de 1,9 a cada 100 mil habitantes. As localidades com mais casos prevalentes foram as regiões Sul e Norte. O Sudeste apresentou taxa de prevalência inferior à taxa nacional em virtude da alta densidade demográfica. O método Kernel se mostrou útil na análise global da situação epidemiológica da leptospirose nas regiões do Brasil.

Crawling Motility on the Host Tissue Surfaces Is Associated With the Pathogenicity of the Zoonotic Spirochete Leptospira

Bacterial motility is crucial for many pathogenic species in the process of invasion and/or dissemination. The spirochete bacteria Leptospira spp. cause symptoms, such as hemorrhage, jaundice, and nephritis, in diverse mammals including humans. Although loss-of-motility attenuate the spirochete's virulence, the mechanism of the motility-dependent pathogenicity is unknown. Here, focusing on that Leptospira spp. swim in liquid and crawl on solid surfaces, we investigated the spirochetal dynamics on the host tissues by infecting cultured kidney cells from various species with pathogenic and non-pathogenic leptospires. We found that, in the case of the pathogenic leptospires, a larger fraction of bacteria attached to the host cells and persistently traveled long distances using the crawling mechanism. Our results associate the kinetics and kinematic features of the spirochetal pathogens with their virulence.

Genetic relatedness of Leptospira interrogans serogroup Autumnalis isolated from humans, dogs, and mice in Japan

OBJECTIVE

Leptospirosis is a zoonotic disease caused by pathogenic spirochetes of Leptospira spp., and peridomiciliary rodents are the most important reservoir animals for human infection. Dogs are known to be the reservoir animal of L. interrogans serovar Canicola, but the importance of dogs in zoonotic transmission of other Leptospira serotypes/genotypes remains unclear. This study reports the isolation of L. interrogans serogroup Autumnalis from two human patients in Japan and describes the genetic comparison between canine and mouse isolates using multiple-locus variable-number tandem repeat analysis (MLVA).

RESULTS

MLVA revealed that 8 out of the 11 loci compared were identical between the two human isolates. The human isolates clustered with the dog but not the mouse isolates. Moreover, the profile of one of the human isolates was identical to that of one of the dog isolates.

Comparative genomic analysis of Leptospira borgpetersenii serogroup Javanica isolated from Rattus species in Southern Japan, Philippines, and Taiwan

Leptospira spp. are the causative agents of leptospirosis, a zoonosis that occurs worldwide, and are maintained by various mammals. Recent molecular typing studies have indicated the existence of a specific Leptospira genotype-host association; however, few studies have shown the colonization of a single genotype in multiple animal genera. To gain further insights into the Leptospira genotype-host association, we conducted whole genome sequencing of 35 strains of L. borgpetersenii serogroup Javanica isolated from various Rattus species in Southern Japan, Philippines, and Taiwan. The SNP-based phylogenetic tree showed that the strains were grouped into five clusters based on their geographic location, indicating geographical structuring of genetic diversity in L. borgpetersenii serogroup Javanica strains. Furthermore, phylogenetic analysis indicated that the L. borgpetersenii serogroup Javanica can infect various animal species, thus making these strains generalist pathogens. This study reports the whole genome comparison of L. borgpetersenii serogroup Javanica strains isolated from Rattus species in East Asian states. The data herein suggest that the serogroup Javanica strains can infect the dominant Rattus species in each region and can be genetically diversified in a geographic manner.

Novel genotypes of Leptospira interrogans serogroup Sejroe isolated from human patients in Okinawa Prefecture, Japan

Leptospirosis is a zoonotic disease caused by pathogenic spirochetes of Leptospira species. It is a public health issue in the tropics, including Okinawa, the southernmost prefecture of Japan. This study reports the first isolation of L. interrogans serogroup Sejroe from two human patients in Japan, and describes its molecular characterization using multilocus sequence typing (MLST) and multiple-locus variable-number tandem repeat analysis (MLVA). MLST on the two isolates, 168036 and 178129, showed that pfkB in 178129 is a novel allele, and that both isolates constitute novel sequence types (STs); ST286 for 168036 and ST287 for 178129. A minimum spanning tree based on seven alleles of L. interrogans indicates that both isolates are genetically close, but are distinct from known L. interrogans serogroup Sejroe strains. MLVA using 11 loci demonstrated that seven of the 11 loci were identical between the two isolates, whereas the identity between the isolates and the seven reference strains of L. interrogans serogroup Sejroe was zero to three loci. These results indicate that the isolates investigated in this study have novel genotypes, and are genetically closest to each other among the known L. interrogans serogroup Sejroe strains.

Genetic diversity of pathogenic leptospires from wild, domestic and captive host species in Portugal

Leptospirosis is a neglected zoonotic disease of worldwide distribution with a significant veterinary and public health impact. It is caused by pathogenic bacteria of the genus Leptospira. The availability of effective tools to accurately identify and type leptospires is of utmost importance for the diagnosis of the disease and for assessing its epidemiology. Several multi-locus sequence typing (MLST) approaches were described for the typing of worldwide isolates of Leptospira but an extensive agreement towards the adoption of a unique consensus scheme for this agent is still lacking. Most genotyped strains originate from Asian and South American countries, with a minority originating from Europe (being most countries represented only by one or a few isolates). The knowledge of the diversity of circulating leptospires is the key to understanding the disease transmission and its zoonotic implications. In this study, we revisited the taxonomy of several isolates of pathogenic Leptospira obtained from domestic, wild and captive animals in Portugal, between 1990 and 2012. A selection of these isolates was genotyped using two previously published MLST schemes. A total of seven distinct sequence types (STs) were detected among the Portuguese isolates with two STs representing L. borgpetersenii (ST149 and ST152), two STs representing L. kirschneri (ST117 and ST100) and three STs representing L. interrogans (ST17, ST24 and ST140). Global widespread (and maybe more virulent) Leptospira genotypes seem to circulate in Portugal, particularly the L. interrogans ST17 isolates which are associated with several outbreaks of leptospirosis among humans and animals in different regions of the world. This study contributes to the enrichment of the global MLST databases with a new set of allele and sequence type information also providing novel data on circulating Leptospira serovars in Portugal.

Leptospira Seroprevalence Among Ugandan Slaughter Cattle: Comparison of Sero-Status With Renal Leptospira Infection

Despite evidence of both human and animal Leptospira exposures in Uganda, the epidemiology of the disease is still not well-investigated. Contact with animals and their environments have been pointed out as potential source of infection with Leptospira species in humans; and cattle may be an important reservoir in Uganda. In this cross-sectional study, we estimated the prevalence of anti-Leptospira antibodies by the standard microscopic agglutination test (MAT); and associated risk factors among slaughtered cattle. We also compared the performance of the MAT used in this study against a lipL32 based real time PCR (qPCR) assay previously conducted on the kidneys and urine of the same slaughter cattle as tested in this reported study. Of 500 cattle sampled, 27.8% (95% CI 23.9-32.0) tested positive (titer ≥ 100) to at least one Leptospira serovar, with the majority of seropositive cattle reacting to serovars Tarassovi (sg Tarassovi) (11.6%), Sejroe (Sg Sejroe) (7.8%), and Australis (Sg Australis) (5.2%). Older animals had 2.8 times (95% CI 1.0-8.2, p-value 0.055) greater odds of being seropositive than younger ones (<1.5 years). The sensitivity and specificity of the MAT over the qPCR were 65.9% (95% CI 50.1-79.5) and 75.9% (95% CI 71.7-79.7), respectively; with a negative predictive value of 95.8% and positive predictive value of 20.9%. In conclusion, slaughter cattle in this study were significantly exposed to pathogenic Leptospira species of mainly the Tarassovi, Sejroe, and Australis serogroups, with seroprevalence being higher among older cattle. The high specificity and negative predictive value of MAT as used in this study when compared to the qPCR assay may imply a rather strong association between seronegativity and absence of renal Leptospira infection. However, MAT predictability for renal Leptospira infection may be interpreted cautiously since predictive values of diagnostic tests are dependent on prevalence.

Leptospira spp., a genus in the stage of diversity and genomic data expansion

Leptospirosis is a widespread global zoonotic bacterial disease with a noteworthy human-animal-ecosystem interface. The disease presents different clinical manifestations and a high mortality and morbidity rates in humans and animals throughout the world. Characterization and correct classification of Leptospira isolates is essential for a better understanding the epidemiological properties of the disease. In the last ten years, molecular typing tools have been developed and applied to this field. These methods together with the availability of hundreds of new whole genome sequences that belong to known and new described species are shaping the understanding and structure of the entire genus.

Seroprevalence and associated risk factors of leptospirosis in slaughter pigs; a neglected public health risk, western Kenya

BACKGROUND

Leptospirosis is a neglected zoonosis of public health importance transmitted through contact with contaminated soil, water or urine of infected animals. In pigs the disease is characterized by abortion, still births and weak piglets. A cross-sectional study was conducted in May to July 2018 to estimate the sero-prevalence of leptospirosis and factors associated with seropositivity in slaughter pigs. A questionnaire was used to collect information on animal demographics. Serum was tested for anti-leptospiral antibodies using microscopic agglutination test (MAT) with a panel of 8 serovars. Sera were considered positive for sero-reactivity at a MAT titre ≥1:40 against at least one serovar. Chi-square tests were used to measure the strength of association between the MAT test result and exploratory variables.

RESULTS

A total of 252 pig serum samples from seven slaughterhouses were tested for Leptospira antibodies by MAT. Of the 252 pigs sampled, 88.8% (244/252) were indigenous breeds; 55.6% (140/252) were female and 88.7% (220/252) were reared in extensive production systems. Eighty-three (32.9%; 83/252) sera samples tested positive on MAT against at least one serovar. Of the 8 serovars, the highest prevalence was recorded for serovar Lora 21.4% followed by Kenya 5.2%, Sokoine 3.6% and Grippotyphosa at 3.2%. Risk factors for leptospirosis seropositivity in pigs were: originating from farms with other types of livestock (OR 2.3; 95% CI 1.0-4.5) and mature pigs (OR 1.9; 95% CI 1.1-3.3).

CONCLUSION

This study demonstrates that there is a high prevalence of leptospirosis positive pigs at slaughter in a small-holder livestock keeping region of the Lake Victoria basin. The potential for cross species transmission of pathogenic serovars is highlighted as well as the potential for occupational exposure to slaughterhouse personnel. Improvements in husbandry practices (confinement and rodent control) and public health education among slaughterhouse workers and other high-risk groups is recommended.

Leptospirosis, one neglected disease in rural Senegal

A serological study was carried out in two Senegalese villages located in the Sine-Saloum region in order to estimate the presence of anti-leptospiral antibodies in humans and animals, and to identify the predominant serogroups. Seven hundred and forty-nine serum samples were collected from humans (n = 545), dogs (n = 33), donkeys (n = 20), goats (n = 52), sheep (n = 43) and N'Dama cattle (n = 56), all originated from Dielmo and Ndiop villages. All samples were tested for different serovars of pathogenic Leptospira species by the microscopic agglutination test. Considering titres ≥ 1:100, 7.7% [CI 95:5.5 to 9.9] on the 545 human blood samples tested and 42.2% [CI95 :35.4 to 48.9] on the 204 animal blood samples tested were found to be positive to one or more serovars. The results obtained indicate that the Australis serogroup is the most prevalent serogroup in human (67.3%) and cattle (27.3%). Serogroup Icterohaemorhagiae is the most frequent serogroup in goat (55.6%) and donkey (37.5%). Canicola (23.4%), Icterohaemorhagiae (21.1%) and Australis (12.5%) serogroups are the most prevalent serogroups in dogs. This study shows that diverse Leptospira serovars occur in a wide range of wild and domestic mammal species, as well as in humans in Senegal. However, further studies are needed to better understand the complexity of Leptospira epidemiology in Africa, identify the reservoirs of different serogroups and estimate its impact on livestock. Understanding the multi-host epidemiology of leptospirosis is essential to control and prevent the disease.

Molecular characterization and phylogenetic analysis of human pathogenic Leptospira species circulating in a tertiary care hospital of Western Uttar Pradesh in India

Leptospirosis is identified as an important reemerging zoonotic disease distributed worldwide, caused by Leptospira. This study was carried out to explore the genetic characterization and its phylogenetic analysis of circulating Leptospira species, among the Aligarh region of western Uttar Pradesh in India, utilizing secY gene-based nucleotide sequence. A total of 190 human samples were included in the study. Positive samples were identified by ELISA, MAT and PCR. MAT was carried out utilizing local circulating Leptospira serovars. Four positive samples including two MAT positive samples were subjected to DNA sequencing for further confirmation and phylogenetic tree was constructed. Out of the total of 190 samples, 24 patients were found positive by ELISA and 29 by PCR. Two samples were found reactive in MAT with L. interrogans serovars like hebdomadis and copenhageni. Phylogenetic analysis of four isolates based on partial secY gene nucleotide sequences revealed that species obtained from the Aligarh region clustered with the several published pathogenic Leptospira interrogans, while some of our isolates nucleotide sequences also clustered with the published sequence of intermediate and saprophytic Leptospira serovars like Leptospira inadai and Leptospira meyeri. This pilot study will help us to decipher the present scenario of circulating serovars of leptospira as well as to identify the nucleotide changes in secY gene, in this region.

Bovine leptospirosis in abattoirs in Uganda: Molecular detection and risk of exposure among workers

Leptospirosis is a zoonotic bacterial disease reported worldwide. In Uganda, seropositivity has been reported in both humans and domesticated animals, including cattle. However, it remains unknown whether cattle are shedding leptospires and thus acting as potential source for human leptospirosis. We conducted this cross-sectional study in two cattle abattoirs in Kampala, Uganda between June and July 2017. Kidney and urine samples from 500 cattle sourced from across the country were analysed by real-time PCR to establish the prevalence of Leptospira-positive cattle and risk of exposure to abattoir workers. The species of infecting Leptospira was determined by amplification of secY gene and compared to reference sequences published in GenBank. Of 500 cattle tested, 36 (7.2%) had Leptospira DNA in their kidneys (carriers), 29 (5.8%) in their urine (shedders); with an overall prevalence (kidney and/or urine) of 8.8%. Leptospira borgpetersenii was confirmed as the infecting species in three cattle and Leptospira kirschneri in one animal. Male versus female cattle (OR = 3, p-value 0.003), exotic versus local breeds (OR = 21.3, p-value 0.002) or cattle from Western Uganda (OR = 4.4, p-value 0.001) and from regions across the border (OR = 3.3, p-value 0.032) versus from the central region were more likely to be Leptospira-positive. The daily risk of exposure of abattoir workers to ≥1 (kidney and/or urine) positive carcass ranged from 27% (95% credibility interval 18.6-52.3) to 100% (95% CI 91.0-100.0), with halal butchers and pluck inspectors being at highest risk. In conclusion, cattle slaughtered at abattoirs in Uganda carry and shed pathogenic Leptospira species; and this may pose occupation-related risk of exposure among workers in these abattoirs, with workers who handle larger numbers of animals being at higher risk.

Prevalence of Leptospira Infection in Rodents from Bangladesh

Worldwide, Leptospira infection poses an increasing public health problem. In 2008, leptospirosis was recognised as a re-emerging zoonosis of global importance with South-East Asia being one of the most significant centres of the disease. Rodents are thought to be the most important host for a variety of Leptospira serovars. Because Bangladesh offers a suitable humid climate for the survival of these pathogenic bacteria, the presence of rodents could be a serious risk for human infection, especially in peri-urban areas or locations where food is stored. In order to gain more understanding of the multi-host epidemiology, a prevalence study was conducted in Comilla, Bangladesh to determine the presence of pathogenic Leptospira species in rodents. Real-time Polymerase Chain Reaction (qPCR) and sequencing showed that 13.1% (61/465) of the trapped rodents were infected with pathogenic Leptospira. Sequencing of the qPCR products identified the presence of three species: Leptospira interrogans, Leptospira borgpetersenii, and Leptospira kirschneri. Rodents of the genus, Bandicota, were significantly more likely to be positive than those of the genus, Rattus and Mus. Our results confirm the importance of rodents as hosts of pathogenic Leptospira and indicate that human exposure to pathogenic Leptospira may be considerable, also in places where food (rice) is stored for longer times. This study emphasizes the need to improve rodent management at such locations and to further quantify the public health impacts of this neglected emerging zoonosis in Bangladesh.

Seroprevalence of Leptospira spp. Infection in Cattle from Central and Northern Madagascar

Leptospirosis is a zoonotic disease of global importance, especially in tropical countries. The current Leptospira spp. seroprevalence in cattle from central and northern Madagascar is unknown. Thus, the aim of this study was to determine the seroprevalence resulting from infections with pathogenic Leptospira spp. in zebu cattle from these areas. Serum samples from 194 animals were tested by microscopic agglutination test (MAT) using a panel of 12 serovars as antigens. Samples with a titer of ≥1:100 were considered positive. The overall seroprevalence was 59.3% (95% CI; 52.0–66.2%) with titers ranging from 1:100 to 1:1600. Among the seropositive animals, the most frequent antibody reactions were against serovar L. Tarassovi (serogroup L. Tarassovi) with 40.2% (33.3–47.5%), followed by L. Hardjo (L. Sejroe) with 13.9% (9.5–19.8%), L. Grippotyphosa (L. Grippotyphosa) with 9.8% (6.2–15.1%), L. Pomona (L. Pomona) with 7.7% (4.5–12.7%) and L. Autumnalis (L. Autumnalis) with 5.2% (2.6–9.5%). Less than 5% of the samples reacted positively against the remaining serovars. These results indicate a very high exposure of Malagasy cattle to Leptospira spp. which, consequently, poses a definite risk for people working with cattle acquiring this zoonotic infection.