Serological Survey and Molecular Typing Reveal New Leptospira Serogroup Pomona Strains among Pigs of Northern Italy

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.

Infectious Agents Associated with Abortion Outbreaks in Italian Pig Farms from 2011 to 2021

The present study retrospectively analyzed the infectious agents associated with 829 abortion outbreaks occurring from 2011 to 2021 in northern Italy. Foetuses were subjected to necropsies, and organ samples were analyzed by direct PCR to screen for six swine pathogens. In 42.0% of the examined outbreaks, at least one infectious agent was found. Porcine reproductive and respiratory syndrome virus (PRRSV) (24.9%) and porcine circovirus-2 (PCV2) (11.5%) were the most frequently detected among the known abortion-inducing pathogens. Chlamydia spp. (5.6%), porcine parvovirus (PPV) (4.0%), and Leptospira spp. (2.6%) were less common. Although its role in swine reproductive disorders is still unclear, PCV3 was detected in 19.6% of the cases. Coinfections were detected in 25.0% of positive outbreaks, and the most frequent coinfection was represented by PRRSV and PCV2 (32.2%), followed by PRRSV and PCV3 (23%). PCV2 prevalence showed a slight but consistent reduction during the study period, while PCV3 increased in frequency. Our data suggest an overall reduction in abortion outbreaks during the study period. PRRSV was confirmed as the main abortion agent detected in the examined area, while PCV2 prevalence showed a decline. Conversely, PCV3 detection has been increasing, supporting its potential role as an abortion agent. Our results highlight the importance of implementing a consistent and standardized sampling procedure, as well as a thorough diagnostic protocol, to reduce the incidence of inconclusive diagnoses.

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.

Genotyping of Leptospira spp. in wild rats leads to first time detection of L. kirshneri serovar Mozdok in Serbia

Introduction

This study aimed to investigate the prevalence and molecular characterization of Leptospira species in Belgrade, Serbia, an area where this disease is underexplored. Specifically, the study sought to employ molecular and multilocus sequence typing analyses to fill the gap in understanding the diversity and distribution of Leptospira species within the region.

Methods

A comprehensive molecular analysis was conducted on kidney samples obtained from Norway rats (Rattus norvegicus) in the urban environment. The study utilized molecular diagnostic techniques including real-time PCR targeting the lipL32 gene and performing sequence-based typing schemes utilizing adk, icdA, lipL32, lipL41, rrs2, and secY genes. These methodologies were applied to ascertain the presence and characterize different Leptospira species and serovars, respectively.

Results

The findings revealed the presence of two Leptospira species and three separate serovars in the Belgrade area. This study identified the presence of L. kirschneri serovar Mozdok in Serbia for the first time, a significant discovery previously undocumented in the region. This pioneering investigation sheds light on the molecular diversity and prevalence of Leptospira species in Serbia.

Discussion

The study underscores the importance of employing molecular typing methods to gain insights into the epidemiology and characterization of Leptospira species. These findings significantly contribute to both local and global perspectives on leptospirosis epidemiology, providing vital insights for the development of effective control strategies and interventions.

Summary

In our recent study, we explored the presence and performed molecular typing of the Leptospira species, the bacteria responsible for leptospirosis, in wild rats in Serbia. This was the first time such a study was conducted in the region. Leptospirosis is a serious disease that affects both animals and humans, often transmitted through contact with water contaminated by infected animals. Our focus was on understanding which types of Leptospira were present in these animals. Excitingly, we discovered a particular strain of Leptospira, known as L. kirshneri serovar Mozdok, for the first time in Serbia. This finding is significant because it sheds light on the presence and spread of different Leptospira serovars in Serbia. It also raises awareness about the potential health risks associated with this serovar, which was previously unknown in the area. Our work fits into a broader context of disease surveillance and public health. By identifying the types of Leptospira present in a specific region, we can better understand the risks to public health and take steps to prevent and control the spread of leptospirosis. This discovery is not just important for scientists studying infectious diseases; it has real implications for public health officials, veterinarians, and anyone concerned with preventing and treating leptospirosis. Our findings highlight the need for ongoing monitoring of Leptospira in wildlife and synanthropic fauna, to protect both animal and human health.

Prevalence and Risk Factors of Leptospira spp. Infection in Backyard Pigs in the State of Paraná, Brazil

Leptospirosis is a zoonotic disease that poses a significant threat to human and animal health worldwide. Among different animal species, pigs are known to play a crucial role in the transmission of the pathogenic Leptospira spp. This study aimed to investigate the prevalence of Leptospira spp. infection and associated risk factors in backyard pigs in the state of Paraná, Brazil. A set of 1393 blood samples were collected from pigs on 188 subsistence properties from 136 different municipalities of the Paraná state and tested using the microscopic agglutination test (MAT) to detect antibodies against 24 different Leptospira spp. serovars. The results revealed an overall seroprevalence of 15.87% (221/1393; 95% CI: 13.95-17.78%) for Leptospira spp. antibodies, with Icterohaemorrhagiae, Butembo, and Pomona being the most commonly detected in serovar levels. The lack of rodent control (OR 1.12, 95% CI: 0.63-1.98, p = 0.02) was the only variable associated with disease incidence and was identified as a significant risk factor for Leptospira spp. infection in this context. These findings highlight the urgent need to implement effective control measures, such as improved housing conditions, rodent control, and veterinary assistance, to prevent the spread of this zoonotic disease in backyard pigs in Paraná, Brazil.

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

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

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

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

Synanthropic and Wild Animals as Sentinels of Zoonotic Agents: A Study of Leptospira Genotypes Circulating in Northeastern Italy

Leptospirosis is an infectious disease widely reported in veterinary practice and a worldwide zoonosis. In Northeastern Italy, different serogroups and genotypes of Leptospira have been described in ill dogs, the most commonly detected being Icterohaemorragiae (ICT) ST 17, Australis (AUS) ST 24 and ST 198, Pomona (POM) ST 117 and ST 289, and Sejroe (SEJ) ST 155. However, there is little information available on the environmental exposure to Leptospira of wild and synanthropic animals. The aim of this study was to identify the circulating genotypes in potential reservoirs to fill this gap of knowledge. Between 2015 and 2022, 681 animal carcasses collected by the Public Veterinary Service were analyzed for Leptospira with a real-time PCR-based screening test, while positive samples were genotyped by multi-locus sequence typing analysis. To carry out our study, we tested 330 hedgehogs, 105 red foxes, 108 Norway rats, 79 mice, 22 coypus, 10 bank voles, 13 grey wolves, 5 common shrews and 9 greater mouse-eared bats. Five sequence types (STs) common in dogs were also found in wild animals: ST 24, ST 198, ST 17 and ST 155 in hedgehogs, ST 17 and ST 24 in foxes, ST 17 in rats, ST 17 and ST 155 in mice, and ST 117 in a wolf. In addition, to the best of the authors' knowledge, this is the first Italian report of SEJ ST 197 in a bank vole. Furthermore, this study described a previous survey conducted in 2009 on coypus (30 animals from the province of Trento and 41 from the province of Padua), referring to a serological positivity (L. Bratislava) without any molecular detection of Leptospira. This study on Leptospira in synanthropic and wild animals highlighted the importance of increasing our epidemiological knowledge of leptospirosis and its zoonotic risks.

Identification of Pathogenic Leptospira kirschneri Serogroup Grippotyphosa in Water Voles (Arvicola terrestris) from Ruminant Pastures in Puy-de-Dôme, Central France

Rodents are the primary reservoirs for pathogenic Leptospira species, which cause leptospirosis. Among the key potential carriers are water voles, whose population outbreaks can consequently pose a major threat to human and animal health. We studied the prevalence, prominence, and epidemiology of pathogenic Leptospira species in water voles in central France. First, 46 voles were captured, and DNA was extracted from kidney, lung, liver, blood, and urine and tested for the presence of Leptospira using three molecular methods: PCR, O-antigen typing, and variable number tandem repeat (VNTR) typing. We also attempted to culture leptospires from kidney and urine samples. In addition, we investigated leptospiral antibodies in serum samples from 60 sheep using microscopic agglutination testing. These animals co-occurred with the voles, so we sought to assess their degree of exposure and involvement in pathogen dynamics. The overall prevalence of infection was 76.1% (CI_95% [61.2%, 87.4%]). The only strain found was L. kirschneri serogroup Grippotyphosa and a similar VNTR profile was acquired. Leptospires were successfully cultured from kidney and urine samples for four voles. Three sheep had low antibody titers against the Leptospira serogroup Grippotyphosa. Taken together, our results suggest the exclusive carriage of L. kirschneri serogroup Grippotyphosa among water voles in central France. Nevertheless, their ability to act as reservoir hosts that transmit the pathogen to co-occurring livestock remains unclear and merits further research.

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.

Leptospira spp. Prevalence in Cats from Southern Italy with Evaluation of Risk Factors for Exposure and Clinical Findings in Infected Cats

Leptospirosis is a worldwide zoonotic disease, but feline leptospirosis is rarely reported. This study aimed at investigating Leptospira spp. prevalence in cats from southern Italy, evaluating risk factors, clinical findings and laboratory data associated with infection. The serum of 112 cats was investigated by microscopic agglutination test (MAT), detecting anti-Leptospira antibodies against 14 pathogenic serovars. Blood and urine samples were tested by a real-time polymerase chain reaction targeting the lipL32 gene of pathogenic Leptospira. Antibodies against serovars Poi, Bratislava, Arborea, Ballum, Pomona and Lora were detected in 15.3% (17/111) of cats (titers range: 20-320). Leptospira spp. DNA was found in 3% (4/109) of blood and 9% (10/111) of urine samples. The spring season was the only risk factor for urinary Leptospira DNA shedding. Laboratory abnormalities significantly associated and/or correlated with Leptospira spp. positivity were anemia, monocytosis, neutrophilia, eosinopenia, increased alanine aminotransferase activity, hypoalbuminemia and hyperglobulinemia. In the investigated areas, cats are frequently infected by Leptospira spp. and can represent an additional reservoir or sentinel for a risk of infection. Moreover, some laboratory changes could be compatible with a pathogenic effect of Leptospira spp. in the feline host.

First detection of Leptospira santarosai in the reproductive track of a boar: A potential threat to swine production and public health

BACKGROUND

Leptospirosis causes significant economic losses and is an occupational risk in the swine industry, especially in developing tropical regions where social and geoclimatic conditions are favorable for the transmission of this disease. Although vaccination can reduce infection risk, efficacy is diminished if local genetic and antigenic variants of the pathogen are not accounted for in the vaccine. Identifying and characterizing strains hosts, and potential mechanisms of transmission is therefore critical for public health mitigation practices.

METHODOLOGY/PRINCIPAL FINDINGS

Our study was conducted on a rural breeding farm in Ecuador, where we used a PCR assay that targets lipL32 to detect Leptospira spp. and targeted gene sequencing to identify Leptospira santarosai in the kidneys, testicles, and ejaculate of a vaccinated boar. MAT results showed low titers against serovars found in the vaccine, but the MAT panel did not include serovars of L. santarosai. The boar showed no symptoms of leptospirosis but did show blood in the semen. However, no postmortem histopathological lesions were observed tissue samples. Vaccinated sows that were artificially inseminated with the semen from this boar had reproductive problems, suggesting that transmission had occurred. This is the first documented case of Leptospira santarosai in the reproductive tract of a boar.

CONCLUSIONS/SIGNIFICANCE

As L. santarosai is pathogenic in other livestock species and humans, our finding highlights the need to evaluate the prevalence and epidemiological significance of this pathogen in livestock and consider the possibility of venereal transmission. In addition, further studies are needed to identify and characterize local serovars that may impact diagnosis and vaccination programs to better control leptospirosis in livestock and spillover into the human population.

Alive Pathogenic and Saprophytic Leptospires Enter and Exit Human and Mouse Macrophages With No Intracellular Replication

Leptospira interrogans are pathogenic bacteria responsible for leptospirosis, a zoonosis impacting 1 million people per year worldwide. Leptospires can infect all vertebrates, but not all hosts develop similar symptoms. Human and cattle may suffer from mild to acute illnesses and are therefore considered as sensitive to leptospirosis. In contrast, mice and rats remain asymptomatic upon infection, although they get chronically colonized in their kidneys. Upon infection, leptospires are stealth pathogens that partially escape the recognition by the host innate immune system. Although leptospires are mainly extracellular bacteria, it was suggested that they could also replicate within macrophages. However, contradictory data in the current literature led us to reevaluate these findings. Using a gentamicin-protection assay coupled to high-content (HC) microscopy, we observed that leptospires were internalized in vivo upon peritoneal infection of C57BL/6J mice. Additionally, three different serotypes of pathogenic L. interrogans and the saprophytic L. biflexa actively infected both human (PMA differentiated) THP1 and mouse RAW264.7 macrophage cell lines. Next, we assessed the intracellular fate of leptospires using bioluminescent strains, and we observed a drastic reduction in the leptospiral intracellular load between 3 h and 6 h post-infection, suggesting that leptospires do not replicate within these cells. Surprisingly, the classical macrophage microbicidal mechanisms (phagocytosis, autophagy, TLR-mediated ROS, and RNS production) were not responsible for the observed decrease. Finally, we demonstrated that the reduction in the intracellular load was associated with an increase of the bacteria in the supernatant, suggesting that leptospires exit both human and murine macrophages. Overall, our study reevaluated the intracellular fate of leptospires and favors an active entrance followed by a rapid exit, suggesting that leptospires do not have an intracellular lifestyle in macrophages.

Outbreak of Leptospira borgpetersenii Serogroup Sejroe Infection in Kennel: The Role of Dogs as Sentinel in Specific Environments

Kennels may represent high-risk environments for the diffusion of Leptospira infection in dogs and consequently a threat to public health. This study describes an outbreak of Leptospira infection in a kennel in Italy in 2020, both with clinically ill and asymptomatic dogs. Fifty-nine dogs, including three ill dogs, were tested for Leptospira spp. infection by the microscopic agglutination test (MAT) and real-time qPCR. Multi-locus sequence typing (MLST) analysis was used to genotype the identified leptospires. Thirty of the fifty-nine (50.9%) dogs had MAT titer and/or molecular positivity indicative of Leptospira infection. Twenty-two of the fifty-nine (37.3%) dogs exhibited seropositivity against at least one serovar belonging to the Sejroe serogroup, and MLST analysis identified L. borgpetersenii serogroup Sejroe (Leptospira ST155) as responsible for the outbreak. Up to now, Sejroe serogroup infection was sporadically reported in dogs. The extension of the MAT antigen panel to several serovars belonging to the serogroup Sejroe could be useful in the diagnosis of canine leptospirosis. Dogs may serve as sentinel of leptospires in specific environments, and surveillance of Leptospira infection in kennels is strongly recommended even when the correct vaccine prophylaxis is administered, because the vaccines currently available are not able to protect from all of the serogroups.

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.

Leptospira interrogans Serogroup Pomona in a Dairy Cattle Farm in a Multi-Host Zootechnical System

Bovine leptospirosis is an infectious zoonotic disease causing reproductive problems and economic losses in livestock. This work reports, for the first time in Sicily (South Italy), an outbreak of Leptospira interrogans serogroup Pomona that occurred in cattle farms within the Nebrodi Park and was mainly characterized by full-term abortion. Blood and urine samples were collected at different time points from animals of six different farms (Farms A–F) sharing the same grazing area. Research of antibodies against pathogenic Leptospira species in serum samples was carried out via Micro Agglutination Test (MAT). Urine samples were subjected to pathogen isolation and molecular analyses via TaqMan Real Time-PCR. Genotyping of Leptospira species was obtained by Multi-locus sequence typing. MAT detected antibodies against Leptospira interrogans serogroup Pomona in serum samples of all the farms. Pathogenic Leptospira spp. DNA and culture isolation was obtained from urine samples. Genotyping confirmed the excretion of L. interrogans serogroup Pomona. This study describes clinical manifestations, diagnostic implications and epidemiological characteristics of an outbreak in cattle due to L. interrogans Pomona in a protected multi-host area, where domestic and wild animals share the same habitat, suggesting a role of wild species in transmission and persistence of Pomona serogroup among cattle.

Serological prevalence of Leptospira serovars among pigs in Ukraine during the period of 2001-2019

Leptospirosis is a widespread infection among pigs throughout the world. In most cases in Ukraine, only the microscopic agglutination test (MAT) is used for the diagnosis of leptospirosis in animals. In general, during the period of 2001-2019, 2 381 163 samples of blood sera from swine were tested in our country and 85 338 positive reactions were received, which is 3.58% [binomial confidence intervals (BCI), 3.56-3.61%]. It was established that the serovars copenhageni - 33.91% (BCI, 33.59-34.23%), bratislava - 14.14% (BCI, 13.90-14.37%), pomona - 8.58% (BCI, 8.39-8.77%), and tarassovi - 7.12% (BCI, 6.95-7.30%) play a leading role in the aetiological structure of swine leptospirosis. A large number of positive reactions to several serovars was observed - 29.78% (BCI, 29.47-30.09%) of the total number of positive cases. In addition, the article presents data according to a retrospective analysis of the eight serovars circulating among pigs in Ukraine. Thus, during the nineteen year period, there was a decrease in the number of positive reactions to bratislava, pomona, and tarassovi and an increase in the number of positive reactions to copenhageni, polonica, and kabura. Mapping Ukraine's territory for leptospirosis among pigs was carried out. This allows one to identify zones with a risk of leptospirosis infections among swine. The maps show that the highest incidence rates were identified in the eastern and central parts of Ukraine.

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

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

Immunoinformatic Study of Recombinant LigA/BCon1-5 Antigen and Evaluation of Its Diagnostic Potential in Primary and Secondary Binding Tests for Serodiagnosis of Porcine Leptospirosis

Leptospirosis is responsible for hampering the productivity of swine husbandry worldwide. The aim of this study was to assess the efficacy of bioinformatics tools in predicting the three-dimensional structure and immunogenicity of recombinant LigBCon1-5 (rLigBCon1-5) antigen. A battery of bioinformatics tools such as I-TASSER, ProSA and SAVES v6.0 were used for the prediction and assessment of the predicted structure of rLigBCon1-5 antigen. Bepipred-2.0, DiscoTope v2.0 and ElliPro servers were used to predict linear and conformational epitopes while T-cell epitopes were predicted using NetMHCpan 4.1 and IEDB recommended 2.22 method for MHC Class I and II peptides respectively. The results obtained using various in silico methods were then compared with wet lab experiments comprising of both primary (IgG Dot ELISA Dipstick test) and secondary-binding assays (Latex Agglutination Test [LAT]) to screen 1153 porcine serum samples. The three-dimensional structure of rLigA/BCon1-5 protein as predicted by I-TASSER was found to be reliable by Ramachandran Plot and ProSA. The ElliPro server suggested 10 and three potential linear and conformational B-cell-epitopes, respectively, on the peptide backbone of the rLigA/BCon1-5 protein. The DiscoTope prediction server suggested 47 amino acid residues to be part of B-cell antigen. Ten of the most efficient peptides for MHC-I and II grooves were predicted by NetMHCpan 4.1 and IEDB recommended 2.22 method, respectively. Of these, three peptides can serve dual functions as it can fit both MHC I and II grooves, thereby eliciting both humoral-and cell-mediated immune responses. The prediction of these computational approaches proved to be reliable since rLigBCon1-5 antigen-based IgG Dot ELISA Dipstick test and LAT gave results in concordance to gold standard test, the Microscopic Agglutination Test (MAT), for serodiagnosis of leptospirosis. Both the IgG Dot ELISA Dipstick test and LAT were serodiagnostic assays ideally suited for peripheral level of animal health care system as "point of care" tests for the detection of porcine leptospirosis.

Wild Small Mammals and Ticks in Zoos-Reservoir of Agents with Zoonotic Potential?

Wild small mammals and ticks play an important role in maintaining and spreading zoonoses in nature, as well as in captive animals. The aim of this study was to monitor selected agents with zoonotic potential in their reservoirs and vectors in a zoo, and to draw attention to the risk of possible contact with these pathogens. In total, 117 wild small mammals (rodents) and 166 ticks were collected in the area of Brno Zoo. Antibodies to the bacteria Coxiella burnetii, Francisella tularensis, and Borrelia burgdorferi s.l. were detected by a modified enzyme-linked immunosorbent assay in 19% (19/99), 4% (4/99), and 15% (15/99) of rodents, respectively. Antibodies to Leptospira spp. bacteria were detected by the microscopic agglutination test in 6% (4/63) of rodents. Coinfection (antibodies to more than two agents) were proved in 14.5% (15/97) of animals. The prevalence of C. burnetii statistically differed according to the years of trapping (p = 0.0241). The DNAs of B. burgdorferi s.l., Rickettsia sp., and Anaplasma phagocytophilum were detected by PCR in 16%, 6%, and 1% of ticks, respectively, without coinfection and without effect of life stage and sex of ticks on positivity. Sequencing showed homology with R. helvetica and A. phagocytophilum in four and one positive samples, respectively. The results of our study show that wild small mammals and ticks in a zoo could serve as reservoirs and vectors of infectious agents with zoonotic potential and thus present a risk of infection to zoo animals and also to keepers and visitors to a zoo.

New Insights on Leptospira Infections in a Canine Population from North Sardinia, Italy: A Sero-Epidemiological Study

Leptospirosis is a widespread zoonosis recognized as a re-emerging infectious disease in a wide variety of animal species, including humans and dogs. No data exist regarding the presence of Leptospira species in the canine population of Sardinia Island. This study reports the first sero-survey for leptospirosis in kennel and owned dogs from six areas of the north of Sardinia. Sera from 1296 dogs were tested by microscopic agglutination test (MAT) specific for nine different serovars that are known to be well widespread in the Mediterranean environment. Moreover, kidney homogenates from rodents collected from the study area were also analyzed by LipL32 real-time PCR and multi-locus sequence type (MLST) on the basis of the analysis of seven concatenated loci. A total of 13% of the examined sera (95%CI: 11-15) tested positive for one or more serovars of Leptospira MAT detected; antibodies for serogroup Icterohaemorrhagiae (57%; 95%CI: 49-65) were the most common, followed by serovars Bratislava (22%; 95%CI: 16-28), Canicola (14%; 95%CI: 9-19), and Grippotyphosa (7%; 95%CI: 3-11). MLST analyses on isolates from rodents identified L. interrogans and L. borgpetersenii genomospecies. Different serovars belonging to pathogenic Leptospira serogroups are circulating in dogs from the island. Moreover, data obtained from rodents, indicated that rodents likely act as reservoir of spirochetes. Further sero-epidemiological studies are needed in order to obtain data from other collection sites in Sardinia and to increase the information on Leptospira species circulating in this area.

Molecular Typing of Pathogenic Leptospira Species Isolated from Wild Mammal Reservoirs in Sardinia

Simple Summary

Leptospirosis is caused by pathogenic spirochaetes of the genus Leptospira. Humans can become infected with these bacteria through direct contact with urine from infected animals or indirectly through interaction with a urine contaminated environment. Among wildlife species, rodents are considered the primary reservoir hosts for leptospirosis in rural and urban environments. Epidemiological data, regarding leptospirosis in various wild species in Europe, suggest that these animals play a different role in leptospiral persistence. Unfortunately, studies on the presence and typing of Leptospira species in wild mammals are lacking in Sardinia. The aim of the present study was to investigate the prevalence of Leptospira species in wild mammals. Kidneys collected from carcasses were analyzed by culture and molecular testing. Greater positivity was found in hedgehogs, followed by weasels and rodents. The results obtained suggest that Sardinian fauna may play a possible sentinel role in the transmission cycle of leptospirosis to humans. Gathering this information in different wildlife species is crucial for better understanding of the epidemiology of leptospirosis and for the development of appropriate prevention measures.

Abstract

Leptospirosis is a global zoonosis caused by pathogenic species of Leptospira that infect a large spectrum of domestic and wild animals. This study is the first molecular identification, characterization, and phylogeny of Leptospira strains with veterinary and zoonotic impact in Sardinian wild hosts. All samples collected were cultured and analyzed by multiplex real time polymerase chain reaction (qPCR). Sequencing, phylogenetic analyses (based on rrs and secY sequences), and Multilocus Sequence Typing (MLST) based on the analysis of seven concatenated loci were also performed. Results revealed the detection of Leptospira DNA and cultured isolates in 21% and 4% of the samples examined, respectively. Sequence analysis of Leptospira positive samples highlighted the presence of the interrogans and borgpetersenii genospecies that grouped in strongly supported monophyletic clades. MLST analyses identified six different Sequence Types (ST) that clustered in two monophyletic groups specific for Leptospirainterrogans, and L. borgpetersenii. This study provided about the prevalence of leptospires in wild mammals in Sardinia, and increased our knowledge of this pathogen on the island. Monitoring Leptospira strains circulating in Sardinia will help clinicians and veterinarians develop strategic plans for the prevention and control of leptospiral infections.

Environmental Exposure of Wild Carnivores to Zoonotic Pathogens: Leptospira Infection in the First Free Living Wolf (Canis lupus Linnaeus, 1758) Found Dead in the Friuli Venezia Giulia Region

Leptospirosis is a worldwide-spread zoonosis causing disease and death in dogs and in humans. A Leptospiral infection has been recorded in several wild carnivore species in Europe, but tissue pathological changes were not commonly described. The Grey wolf (Canis lupus) has been expanding its distribution range in north-eastern Italy during the last decade. A young wolf, representing the first individual handled in the region, was found road-killed and then submitted to necropsy. Pathological changes included erosive lesions of gingival mucosa, mild liver enlargement, and multifocal degenerative-necrotic areas along with hyperemic reactive lesions; multifocal interstitial nephritis and multifocal lung hemorrhages were observed. A Polymerase Chain Reaction (PCR) able to detect pathogenic species of Leptospira performed on a kidney sample was positive. Serological reactions for serogroup Gryppotyphosa (1:6400), Pomona (1:800), and Icterohaemorrhagiae (1:200) were evidenced by MAT. Genotyping by Multilocus Sequence Typing (MLST) performed on detected Leptospira characterized it as belonging to Sequence Type (ST) 117, which refers to L. kirschneri, serogroup Pomona, serovar Mozdok. Regardless of the role of Leptospira infection as an eventual predisposing factor to the road killing of this wolf, to the best of the authors’ knowledge, this is the first report of Leptospira-induced pathology in a wolf in Europe. Surveys on Leptospira infection in free-ranging wildlife species should be pursued in order to achieve further epidemiological knowledge on the circulation of the Leptospira strain.

Leptospira Infections in Domestic and Wild Animals

Leptospirosis is a worldwide-distributed, re-emerging zoonosis due to the large variety of wild and domestic animal species that can play the role of natural or accidental host. Currently, specific animal species play an important role as the reservoir for particular Leptospira serovars, although recent investigations have highlighted new host–pathogen interactions involved in Leptospira epidemiology. Furthermore, the constant modification of ecosystems and wildlife habitats and the constantly increasing number of animal species moving towards urban or peri-urban areas are increasing the possibility of direct or indirect contacts between wildlife and domestic animals; furthermore, the constant modification of animal leptospirosis also causes problems for human health. The studies published in this Special Issue have evidenced and confirmed the hidden role of a large variety of animal species, domestic and wild, in the leptospirosis epidemiology. They highlighted the necessity for continuous monitoring and large-scale surveillance studies to better understand this neglected and re-emerging zoonosis.

Detection of New Leptospira Genotypes Infecting Symptomatic Dogs: Is a New Vaccine Formulation Needed?

Leptospirosis in dogs has been largely described worldwide, and epidemiological studies have been mainly based on serological data. This study aims to detect and genotype leptospires affecting symptomatic dogs in Northeast Italy between 2013 and 2019. Overall, 1631 dogs were tested using real-time PCR, and leptospires from 193 dogs were subjected to Multilocus Sequence Typing and a Multiple Loci Variable-number Tandem Repeat Analysis. Leptospires were successfully isolated from 15 symptomatic dogs. Six distinct Sequence Types (STs) were found for 135 leptospires, with 3 STs characterizing Leptospira interrogans (ST17, ST198 and ST24), 2 STs characterizing Leptospira kirschneri (ST117 and ST289) and 1 ST characterizing Leptospira borgpetersenii (ST155), revealing the circulation of the serogroups Icterohaemorrhagiae, Australis, Sejroe and Pomona. The Multiple Loci Variable-number Tandem Repeat Analysis of 17 samples did not result in any additional discrimination. Genotypes were compared with those of strains present in the historical internal database, and possible transmission chains were identified from rat, mouse, hedgehog and pig. This work highlights the importance of molecular methods in revealing and identifying circulating Leptospira strains, and it also encourages the evaluation of the ability of commercially available vaccines to reduce the disease burden among dogs.