Molecular and serological characterization of the first Leptospira santarosai strain isolated from a dog

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

BACKGROUND

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

METHODOLOGY/PRINCIPAL FINDINGS

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

CONCLUSIONS/SIGNIFICANCE

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

Phylogenomics of Leptospira santarosai, a prevalent pathogenic species in the Americas

BACKGROUND

Leptospirosis is a complex zoonotic disease mostly caused by a group of eight pathogenic species (L. interrogans, L. borgpetersenii, L. kirschneri, L. mayottensis, L. noguchii, L. santarosai, L. weilii, L. alexanderi), with a wide spectrum of animal reservoirs and patient outcomes. Leptospira interrogans is considered as the leading causative agent of leptospirosis worldwide and it is the most studied species. However, the genomic features and phylogeography of other Leptospira pathogenic species remain to be determined.

METHODOLOGY/PRINCIPAL FINDINGS

Here we investigated the genome diversity of the main pathogenic Leptospira species based on a collection of 914 genomes from strains isolated around the world. Genome analyses revealed species-specific genome size and GC content, and an open pangenome in the pathogenic species, except for L. mayottensis. Taking advantage of a new set of genomes of L. santarosai strains isolated from patients in Costa Rica, we took a closer look at this species. L. santarosai strains are largely distributed in America, including the Caribbean islands, with over 96% of the available genomes originating from this continent. Phylogenetic analysis showed high genetic diversity within L. santarosai, and the clonal groups identified by cgMLST were strongly associated with geographical areas. Serotype identification based on serogrouping and/or analysis of the O-antigen biosynthesis gene loci further confirmed the great diversity of strains within the species.

CONCLUSIONS/SIGNIFICANCE

In conclusion, we report a comprehensive genome analysis of pathogenic Leptospira species with a focus on L. santarosai. Our study sheds new light onto the genomic diversity, evolutionary history, and epidemiology of leptospirosis in America and globally. Our findings also expand our knowledge of the genes driving O-antigen diversity. In addition, our work provides a framework for understanding the virulence and spread of L. santarosai and for improving its surveillance in both humans and animals.

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

Background

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

Methodology/Principal Findings

We sampled five indigenous Kichwa communities living in the Yasuní National Park in the Ecuadorian Amazon basin. Blood and urine samples from domestic dogs were collected to assess the exposure of these animals to Leptospira, and to identify the circulating species. Microscopic Agglutination Tests with a panel of 22 different serovars showed anti-leptospira antibodies in 36 sampled dogs (75%), and 10 serotypes were detected. Two DNA-based detection assays revealed pathogenic Leptospira DNA in 18 of 19 dog urine samples (94.7%). Amplicon sequencing and phylogenetic analysis of 16s rDNA and SecY genes from 15 urine samples revealed genetic diversity within two of three different Leptospira species: noguchii (n=7), santarosai (n=7), and interrogans (n=1).

Conclusions/Significance

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

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

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

Time for change? A systematic review with meta-analysis of leptospires infecting dogs to assess vaccine compatibility in Brazil

Dogs are thought to be highly exposed to environmental pathogenic leptospires, possibly acting as potential sources of infection for zoonotic transmission. Vaccination stands as the cornerstone strategy to prevent disease and urinary shedding in dogs, yet the success of vaccination is highly dependent on the correspondence of leptospires circulating locally with those used in vaccine compositions. To provide evidence for vaccine compatibility, and to assess whether there are regional differences on serogroup distribution, we conducted a systematic review with meta-analysis on serological data, characterization of leptospiral isolates and risk factors for seropositivity in dogs from Brazil. Studies reporting canine leptospirosis within the Brazilian territory were eligible for inclusion, and methodology was validated by PROSPERO under registration CRD42020204187. Six electronic databases were searched, and data regarding population, methods, and outcomes were extracted. Sixty-one studies were included to access serogroup distribution and risk factors, with a pooled positivity rate of 19.7% in dog population. Serological evidence indicates that Canicola, Icterohaemorrhagiae and Autumnalis are the most frequently found serogroups. Twenty-eight records were included to access leptospiral strains isolated in Brazil, with n = 56 strains characterized as serogroups Canicola, n = 37 as Icterohaemorrhagiae, n = 2 as Pomona, and n = 1 strain as Australis and Sejroe each. Risk factor analysis revealed that stray dogs, puppies or elderly dogs, male dogs and dogs kept by tutors with poor social and economic conditions are at high risk for infection. The present study revealed overall good compatibility of leptospiral strains circulating locally with those used in vaccines against canine leptospirosis in Brazil. The circulation of serovars Pomona and Grippotyphosa has not been consistently demonstrated, and the inclusion of these serovars in local vaccines cannot be supported by our results. The results also provided serological evidence for the circulation of Serogroup Autumnalis among the studied populations.

Canine Leptospirosis in a Northwestern Region of Colombia: Serological, Molecular and Epidemiological Factors

Canine leptospirosis is a zoonosis of epidemiological importance. Dogs are recognized as primary reservoirs of Leptospira interrogans serogroup Canicola and a source of infection to the environment through urine. This study aimed to determine the presence of antibodies against Leptospira in canines from 49 municipalities in the Department of Antioquia, Colombia. We performed a cross-sectional study of dogs included in a neutering control program. We collected 1335 sera samples, assayed by a microagglutination test (MAT), and performed PCR detection in 21 urine samples. We also surveyed 903 dog owners. We found a seroreactivity of 11.2% (150/1335) in Antioquia with titers ≥1:50. Municipalities with the highest number of cases were Belmira (46.1%), Turbo (34.5%), and Concepción (31.0%). L. santarosai was identified by phylogenetic analysis in one urine sample from the municipality of Granada. The most important factor associated with a positive result was the lack of vaccination against leptospirosis (PR 3.3, p ≤ 0.014). Environmental factors such as water presence and bare soil around the household were also associated with Leptospira seroreactivity in the Department of Antioquia. We reviewed a national epidemiological surveillance database for human cases in those municipalities. We found a correlation between the high number of cases in canines and humans, especially in the Uraba. Serological and molecular results showed the circulation of Leptospira. Future public health efforts in the municipalities with the highest numbers of seroreactivity should be directed towards vaccination to prevent animal disease and decrease the probability of transmission of Leptospira. Dogs actively participate in the Leptospira cycle in Antioquia and encourage the implementation of vaccination protocols and coverage.

Detection of Leptospira in a forest fragmentation area in eastern Amazon: A unique health approach

The objective of this study was to detect the presence of anti-Leptospira spp. in samples of humans and domestic animals of forest fragmentation areas in the Brazilian Amazon. A total of 208 samples from dogs, cats, and humans were collected during two expeditions within the same fragment. Detection of anti-Leptospira spp. antibodies was performed by the Microscopic Agglutination Test (MAT) using live antigens from 19 Leptospira spp. serogroups and DNA detection of Leptospira 16S rRNA gene was done using Polymerase Chain Reaction. After the analysis, we observed 24.03% (50/208) of reactive serum samples, where the most prevalent serogroups circulating in the human and animal population were Canicola, Djasiman, Cynopteri, and Serjoe. Leptospira DNA was detected only in the samples of 13 dogs, which demonstrated 100% identity with L. interrogans DNA deposited in the GenBank. We concluded that there is a circulation of Leptospira spp. in the studied fragment.

Detection and characterization of Leptospira spp. in dogs diagnosed with kidney and/or liver disease in Selangor, Malaysia

Leptospirosis is a serious bacterial disease that affects both humans and animals. A wide range of symptoms have been described in humans; the disease in dogs is commonly associated with kidney and/or liver disease. In Malaysia, information about the common serovars infecting dogs is limited. Therefore, we investigated the occurrences of leptospirosis in 124 pet dogs diagnosed with kidney and/or liver disease. Blood, urine, abdominal effusion, and/or kidney and liver were collected from the dogs. Based on microscopic agglutination testing, 53 of 124 (42.7%) dogs were seropositive for leptospiral exposure. Sera were frequently positive to serovars Bataviae (n = 12), Javanica (n = 10), and Icterohaemorrhagiae (n = 10). Direct detection using PCR showed that 42 of 124 (33.9%) of the whole blood and 36 of 113 (31.9%) urine samples were positive for pathogenic Leptospira spp. By PCR, 2 of 23 (9.1%) kidney and 2 of 23 (9.1%) liver were positive for pathogenic Leptospira spp. Abdominal effusion from 4 dogs were PCR-positive for pathogenic Leptospira spp. The species detected were L. interrogans, L. borgpetersenii, L. kirschneri, and L. kmetyi by partial 16S rRNA sequencing. We further identified and characterized 11 Leptospira spp. isolates from 8 dogs as serovars Bataviae, Javanica, and Australis. The mortality rate of the Leptospira-infected dogs was high (18 of 53; 34%).

Multidisciplinary approach in the diagnosis of acute leptospirosis in dogs naturally infected by Leptospira interrogans serogroup Icterohaemorrhagiae: A prospective study

Leptospirosis, a zoonotic disease with worldwide distribution, is caused by spirochetes of the genus Leptospira. In dogs, this disease is frequently misdiagnosed. Few studies have attempted to associate the detection of Leptospira spp. infection with clinicopathological and renal histopathological findings using a multidisciplinary approach. The present study isolated and characterized Leptospira spp. obtained from naturally infected dogs and described relevant clinical and histopathological findings. Blood and urine were collected from 57 dogs with clinical symptomatology suggestive of leptospirosis; 38 cases were confirmed by PCR in urine or by culture or microscopic agglutination testing (titers ≥800). A total of 12 strains of pathogenic Leptospira were isolated from the studied dogs (seven in blood, four in urine and one in both blood and urine samples). All isolates were characterized as Leptospira interrogans serogroup Icterohaemorrhagiae. Of the confirmed cases, almost one-third of the animals had been vaccinated. Our analysis of laboratory testing revealed that azotemia and proteinuria were statistically significant predictors of infection. The main histopathological findings seen in kidney tissues were necrosis, degeneration, tubular regeneration, mononuclear inflammatory infiltrate and congestion. A multidisciplinary approach involving clinicopathological and histopathological characterization of renal involvement can aid in the identification of acute leptospirosis infection.

Potentially Pathogenic Leptospira in the Environment of an Elephant Camp in Thailand

Leptospira is the causative agent of leptospirosis, a globally emerging zoonotic disease. The infection is commonly acquired through contact with the contaminated environment. To extend the knowledge on environmental source of leptospirosis, we investigated the presence of Leptospira in an elephant camp setting where the interaction between humans, animals, and the shared environment occur particularly when engaging in recreational activities. In this study, a total of 24 environmental samples were collected from an elephant camp area in western Thailand. All samples were processed for Leptospira isolation using the EMJH medium. The identification of Leptospira species was carried out by partial 16S rRNA and secY gene sequencing. Of those 24 samples, 18 samples (75%) were culture-positive for Leptospira. The recovered leptospires were mostly derived from water and soil sampled from a river and a mud pond, the main areas for recreational activities. The majority of the isolates were classified into “Pathogens” clade (89%, 16/18) and more than half of the isolates (61%, 11/18) contained species of the “Saprophytes” clade. Notably, two soil isolates from the river beach sampling area were found to contain leptospiral DNA with high similarity to the pathogenic L. interrogans and L. santarosai. The evidence of diverse Leptospira species, particularly those belonging to the “Pathogens” clade, suggest that the shared environments of an elephant camp can serve as potential infection source and may pose a risk to the elephant camp tourists and workers.

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.

Identification of Pathogenic Leptospira Species in the Urogenital Tract of Water Buffaloes (Bubalus bubalis) From the Amazon River Delta Region, Brazil

In the current context of deforestation and fire in the Amazon, buffaloes could be a cost-effective and sustainable alternative for cattle production in the region, as they can convert low-quality foods and be raised in floodplain areas. However, little is known about the reproductive diseases that affect these animals; thus, the purpose of this study was to perform the molecular characterization of Leptospira spp. in the urogenital tract of water buffaloes (Bubalus bubalis) raised in the Amazon River Delta region in Brazil. Samples were collected from 114 kidneys, 204 ovaries, and 160 uterine swabs of slaughtered buffaloes in the Macapá microregion of Amapá State (Brazil) and were subjected to PCR to detect bacterial DNA. Positive amplicons were sequenced to identify Leptospira species. Among the total samples, 11/473 were PCR positive (2.3%), including 10 kidney samples and one uterine swab sample. DNA sequencing identified two pathogenic species from the kidney samples: L. interrogans, accounting for 60.0% (6/10) of these samples, and L. borgpetersenii, accounting for 20.0% (2/10), while 20.0% (2/10) were identified only at the genus level. The bacterium in the uterine swab sample was identified as L. interrogans with genetic proximity to strains belonging to the serovar Hardjo. This is the first report of leptospires species identified in buffaloes from the Amazon River Delta region and revealed that these animals may be carriers of different pathogenic Leptospira species, similar to bovines, including showing genital colonization.

First report of human Leptospira santarosai infection in French Guiana

Leptospirosis is a zoonotic disease with worldwide distribution. In French Guiana, a French overseas department of South America, this bacterial infection is endemic with the increase of human cases since the last 5 years. Nevertheless, the epidemiological data on the circulating infecting strain remains scarce due to the lack of specific symptoms and the used diagnostic approaches. We report a severe case of leptospirosis in a 52-years-old male, working as a street cleaner, hospitalized at the Intensive Care Unit of city capital hospital of French Guiana because of hemodynamic, neurological, renal, and respiratory failure. At ICU admission, the patient was comatose, his temperature was 37.3°C, heart rate 104 beats per minute, blood pressure 84/45mmHg, and oxygen saturation 95% while under mechanical ventilation. Retrospective exploration using molecular and serological approaches from the samples allowed reporting an infection by Leptospira santarosai serogroup Sejroe serovar Hardjo. To our knowledge, this is the first human case infected with this species in French Guiana. Through these analyses, this report provides new epidemiological information about the Leptospira strains circulating in French Guiana. In particular, this emphasizes the importance of accurate diagnosis to characterize with more precision the circulating Leptospira strains in this department.

Recommendations on vaccination for Latin American small animal practitioners: a report of the WSAVA Vaccination Guidelines Group

The World Small Animal Veterinary Association Vaccination Guidelines Group has produced global guidelines for small companion animal practitioners on best practice in canine and feline vaccination. Recognising that there are unique aspects of veterinary practice in certain geographical regions of the world, the Vaccination Guidelines Group undertook a regional project in Latin America between 2016 and 2019, culminating in the present document. The Vaccination Guidelines Group gathered scientific and demographic data during visits to Argentina, Brazil and Mexico, by discussion with national key opinion leaders, visiting veterinary practices and review of the scientific literature. A questionnaire survey was completed by 1390 veterinarians in five Latin American countries and the Vaccination Guidelines Group delivered continuing education at seven events attended by over 3500 veterinarians.

The Vaccination Guidelines Group recognised numerous challenges in Latin America, for example: (1) lack of national oversight of the veterinary profession, (2) extraordinary growth in private veterinary schools of undetermined quality, (3) socioeconomic constraints on client engagement with preventive health care, (4) high regional prevalence of some key infectious diseases (e.g. feline leukaemia virus infection, canine visceral leishmaniosis), (5) almost complete lack of minimal antigen vaccine products as available in other markets, (6) relative lack of vaccine products with extended duration of immunity as available in other markets, (7) availability of vaccine products withdrawn from other markets (e.g. Giardia vaccine) or unique to Latin America (e.g. some Leishmania vaccines), (8) accessibility of vaccines directly by pet owners or breeders such that vaccination is not delivered under veterinary supervision, (9) limited availability of continuing education in veterinary vaccinology and lack of compulsion for continuing professional development and (10) limited peer‐reviewed published scientific data on small companion animal infectious diseases (with the exception of leishmaniosis) and lack of support for such academic research.

In this document, the Vaccination Guidelines Group summarises the findings of this project and assesses in evidence‐based fashion the scientific literature pertaining to companion animal vaccine‐preventable diseases in Latin America. The Vaccination Guidelines Group makes some recommendations on undergraduate and postgraduate education and academic research. Recognising that current product availability in Latin America does not permit veterinarians in these countries to vaccinate according to the global World Small Animal Veterinary Association guidelines, the Vaccination Guidelines Group makes a series of “pragmatic” recommendations as to what might be currently achievable, and a series of “aspirational” recommendations as to what might be desirable for the future. The concept of “vaccine husbandry” is addressed via some simple guidelines for the management of vaccine products in the practice. Finally, the Vaccination Guidelines Group emphasises the global trend towards delivery of vaccination as one part of an “annual health check” or “health care plan” that reviews holistically the preventive health care needs of the individual pet animal. Latin American practitioners should transition towards these important new practices that are now well embedded in more developed veterinary markets.

The document also includes 70 frequently asked questions and their answers; these were posed to the Vaccination Guidelines Group during our continuing education events and small group discussions and should address many of the issues surrounding delivery of vaccination in the Latin American countries. Spanish and Portuguese translations of this document will be made freely available from the on‐line resource pages of the Vaccination Guidelines Group.

Leptospiral shedding and seropositivity in shelter dogs in the Cumberland Gap Region of Southeastern Appalachia

BACKGROUND

Leptospirosis, caused by pathogenic Leptospira spp., is a zoonotic infection that affects humans, dogs and many other mammalian species. Virtually any mammalian species can act as asymptomatic reservoir, characterized by chronic renal carriage and shedding of a host-adapted leptospiral serovar. Environmental contamination by chronic shedders results in acquisition of infection by humans and susceptible animals.

METHODS

In this study, we investigated if clinically normal shelter dogs and cats harbor leptospires in their kidneys by screening urine samples for the presence of leptospiral DNA by a TaqMan based-quantitative PCR (qPCR) that targets pathogen-associated lipl32 gene. To identify the infecting leptospiral species, a fragment of leptospiral rpoB gene was PCR amplified and sequenced. Additionally, we measured Leptospira-specific serum antibodies using the microscopic agglutination test (MAT), a gold standard in leptospiral serology.

RESULTS

A total of 269 shelter animals (219 dogs and 50 cats) from seven shelters located in the tri-state area of western Virginia, eastern Tennessee, and southeastern Kentucky were included in this study. All cats tested negative by both qPCR and MAT. Of the 219 dogs tested in the study, 26/198 (13.1%, 95% CI: 8.4-17.8%) were positive for leptospiral DNA in urine by qPCR and 38/211 (18.0%, 95% CI: 12.8-23.2%) were seropositive by MAT. Twelve dogs were positive for both qPCR and MAT. Fourteen dogs were positive by qPCR but not by MAT. Additionally, leptospiral rpoB gene sequencing from a sub-set of qPCR-positive urine samples (n = 21) revealed L. interrogans to be the leptospiral species shed by dogs.

CONCLUSIONS

These findings have significant implications regarding animal and public health in the Cumberland Gap Region and possibly outside where these animals may be adopted.

Frequency of anti-Leptospira spp. antibodies in dogs and wild small mammals from rural properties and conservation units in southern Brazil

Leptospirosis is a disease of worldwide distribution that affects man and several animal species. Domestic and wild animals can behave as reservoirs of the agent. The aim of this study was to evaluate the frequency of anti-Leptospira spp. antibodies in dogs and wild small mammals from rural properties and conservation units of three municipalities of Rio Grande do Sul State, Brazil. Sera were collected from 192 domestic dogs and 132 small mammals, namely rodents of the Cricetidae and Caviidae families and marsupials of the Didelphidae family. The study used Microscopic Agglutination Test (MAT) against 23 serovars of Leptospira spp. Overall, 9.90% (19/192) dogs, and 1.51% (2/132) small mammals were seropositive. Leptospira interrogans serovar Australis was the most frequent serovar in dogs and antibodies against L. interrogans serovar Pomona were detected in a dog and a small mammal belonging to the same municipality. We conclude that in the regions studied the frequency of seropositivity in dogs is low, and leptospires do not seem to be circulating in small mammals, yet, further research is necessary to assess the real role that these animals may have for leptospirosis in the studied areas. This is the first serological survey in small mammals, including wild rodents, in the area that encompasses conservation units of great importance to Rio Grande do Sul state.

Novel MLST sequence types of pathogenic Leptospira spp.: Opening the black box of animal leptospirosis in Brazil

In the current context of the emergence of certain infectious diseases and discussion of the One Health concept for many of these, the study of leptospirosis - both in domestic and wild hosts - cannot be neglected. The study of animal leptospirosis has evolved in recent years. It has been demonstrated that the human-animal-environment interface is more important than previously thought. In the present study, 35 strains of five pathogenic Leptospira species were isolated from different animal species in Brazil and characterized by rrs, secY, and Multilocus Sequence Typing (MLST) sequencing. Phylogenetic inferences were performed and the molecular diversity of the populations (intra- and inter-population levels) was evaluated. Among the five studied species, 18 different sequence types (STs) were found (22 new alleles and 11 new STs). eBURST analysis revealed two clonal complexes (CCs) and seven singletons. A high genetic diversity was demonstrated (H = 0.954 ± 0.017), mainly for the L. santarosai population (H = 0.942 ± 0.034, n = 20). The same strain was identified in different host species, as well as strains with zoonotic potential circulating in the country. Although the difficulty of culturing Leptospira strains is well known, the high variability of the strains found in Brazil highlights the importance of animals in maintaining the biological cycle of the bacterium in nature. Moreover, the selection of autochthonous strains for the development of vaccines becomes a challenge.

Diagnosis of acute canine leptospirosis using multiple laboratory tests and characterization of the isolated strains

BACKGROUND

Dogs presenting with acute leptospirosis may present non-specific clinical and laboratory findings, and the definitive diagnosis may require additional confirmatory tests, including bacterial culture, for the direct or indirect identification of the pathogen. The present study describes the diagnosis of leptospirosis in suspected dogs based on the use of multiple diagnostic tests, including serological, molecular and bacteriological tests, along with the characterization of the recovered leptospiral strains.

RESULTS

Urine, serum and blood samples were collected from 33 dogs with suspected clinical leptospirosis treated at the University of São Paulo Veterinary Hospital Service (Hovet FMVZ-USP) between 2013 and 2016. Only dogs with high blood urea nitrogen and creatinine levels in association with multiple clinical manifestations of the disease were included. Leptospiral culture, PCR and serology (Microscopic agglutination test - MAT) were performed in blood and urine samples taken from all suspected dogs at clinical presentation, and an additional prospective MAT titration was performed in seven dogs. Infection could be identified exclusively by PCR in 10 dogs (30.3%), exclusively by MAT in four dogs (12.1%) and by both tests in four dogs, totaling 18 dogs (54.5-95%CI: 37.6-71.5). Six out of eight MAT-confirmed cases presented with the highest titers against the Icterohaemorrhagiae serogroup. Leptospires were recovered from urine samples from two PCR-positive dogs, and both strains could be characterized by Multilocus Sequence Analysis and serogrouping as L. interrogans serogroup Icterohaemorrhagiae. Both isolates were shown to be pathogenic in the hamster model.

CONCLUSIONS

The simultaneous use of MAT and PCR was able to increase the diagnosis of leptospirosis in clinically suspected cases. Despite the increasing incidence of new serovars affecting dogs being reported in different locations, our results suggest that leptospiral strains belonging to the Icterohaemorrhagiae serogroup are still a major causative agent of canine leptospirosis in São Paulo, Brazil.

Prospective study of canine leptospirosis in shelter and stray dog populations: Identification of chronic carriers and different Leptospira species infecting dogs

Dogs are highly susceptible to the leptospiral infection, notably stray and sheltered dogs. Unsanitary conditions often observed in dog shelters may predispose the introduction and spread of leptospires among sheltered populations, potentially increasing the chances for the inadvertent adoption of asymptomatically infected animals. The present work describes a longitudinal study using a multidisciplinary approach for the identification of chronically infected dogs and the characterization of potentially pathogenic strains circulating among stray and sheltered dog populations in São Paulo, Brazil. A total of 123 dogs from three populations were included. The initial evaluation consisted of blood and urine quantitative PCR testing (qPCR), the detection of specific antibodies by microscopic agglutination test (MAT), physical examination and hematological and serum biochemistry analyses. The qPCR-positive dogs were prospectively examined, and reevaluations also included culture from urine samples. Positive qPCR samples were subjected to 16S rRNA and secY gene phylogenetic analysis. The recovered strains were characterized by Multilocus Sequence Typing, polyclonal serogroup identification and virulence determination. Leptospiruria was detected in all populations studied (13/123), and phylogenetic analysis revealed that 10 dogs had L. interrogans infection. Three dogs (3/13) had L. santarosai infection. The secY phylogenetic analysis revealed that the L. santarosai sequences clustered separately from those obtained from other hosts. Ten leptospiruric dogs were reevaluated, and three dogs presented persistent leptospiruria, allowing culturing from two dogs. The strains were characterized as L. interrogans serogroup Canicola (virulent) and L. santarosai serogroup Sejroe (not virulent). Serum samples were retested by MAT using the DU92 and DU114 strains as antigens, and no increased seroreactivity was detected. Asymptomatic L. santarosai infection was observed in all populations studied, suggesting a possible role of dogs in the chain of transmission of this leptospiral species. The results suggest a genetic distinction between lineages of Brazilian L. santarosai maintained by dogs and other animal hosts. Our findings revealed that dogs could act as maintenance hosts for distinct pathogenic Leptospira, highlighting also that asymptomatically infected dogs can be inadvertently admitted and adopted in dog shelters, potentially increasing the risks of zoonotic transmission.

Leptospira reservoirs among wildlife in Brazil: Beyond rodents

Leptospirosis is a disease of great importance in tropical regions. Infection occurs mainly through contact with water contaminated with the urine of infected animals, especially that of rodents. Despite the diversity and abundance of wild fauna in Brazil, little is known about the role of other wild species in the epidemiology of leptospirosis. This study aimed to investigate new reservoirs of Leptospira among wildlife in Brazil, using serological and molecular diagnoses in a large-sized sample. Biological samples were collected from 309 free-ranging mammals, belonging to 16 species. The majority of the animals included were opossums (Didelphis albiventris) and coatis (Nasua nasua). Blood and urine samples were subjected to the microscopic agglutination test (MAT) and real-time PCR, respectively. Genetic characterization of genomospecies was performed using PCR amplicons. Statistical analysis was applied to test associations between positive diagnoses and age, sex, season and type of environment. The prevalence of infection found via MAT and PCR was 11% and 5.5%, respectively. If these tests are taken to be complementary, the overall prevalence was 16%. The most common serogroups were Djasiman and Australis, while L. santarosai was the prevalent genomospecies. Significant differences in prevalence between animal species were observed. Greater risk of infection was detected among adult opossums than among young ones. The influence of each serogroup and genomospecies was tested for the same variables, and this revealed higher risk of infection by L. santarosai among male opossums than among females. The present study highlights the exposure and carrier status of several wild species in Brazil and it indicates that coatis and other carnivores are priorities for further investigations.

Development and validation of a modified TaqMan based real-time PCR assay targeting the lipl32 gene for detection of pathogenic Leptospira in canine urine samples

A modified TaqMan real-time polymerase chain reaction targeting a 138bp fragment within the lipl32 gene was developed to identify exclusively pathogenic Leptospira spp. in dog urine samples. Thirty-five samples from dogs with suspected clinical leptospirosis and 116 samples from apparently healthy dogs were tested for presence of leptospiral DNA using the TaqMan-based assay. The results were compared with those from a well-established conventional PCR targeting the 16S RNA encoding gene associated with nucleotide sequencing analysis. The overall agreement between the assays was 94.8% (confidence interval [CI] 95% 88-100%). The newly developed assay presented 91.6% (CI 95% 71.5-98.5%) relative sensitivity (22[+] lipl32 PCR/24[+] 16S RNA and sequencing), 100% (CI 95% 96.3-100%) relative specificity and 98.7% accuracy (CI 95% 94.8-100%). The lipl32 assay was able to detect and quantify at least 10 genome equivalents/reaction. DNA extracted from 17 pathogenic Leptospira spp., 8 intermediate/saprophytic strains and 21 different pathogenic microorganisms were also tested using the lipl32 assay, resulting in amplification exclusively for pathogenic leptospiral strains. The results also demonstrated high intra and inter-assay reproducibility (coefficient of variation 1.50 and 1.12, respectively), thereby qualifying the newly developed assay as a highly sensitive, specific and reliable diagnostic tool for leptospiral infection in dogs using urine specimens.

Plurality of Leptospira strains on slaughtered animals suggest a broader concept of adaptability of leptospires to cattle

Leptospirosis in bovines is in majority determined by the host-adapted serovars, mainly Hardjo (types Hardjoprajitno and Hardjobovis), that belong to the serogroup Sejroe. Members of other serogroups as Pomona and Tarassovi have been eventually reported, mainly when outbreaks occurs. Nevertheless, the real role of other strains (non-Hardjo) on determining disease or being transmitted by cattle free of apparent clinical signs of acute infection remains to be elucidated. In that context, the aim of the present study was to investigate the hypothesis that strains of serovars/serogroups other than Hardjo may also be maintained and shed by cattle free of clinical signs. Samples of urine and/or vaginal fluid were collected from 697 bovines from a slaughterhouse located close to Rio de Janeiro, Brazil. Culturing yielded 19 isolates what represents the largest number ever obtained in Brazil on similar studies. These strains were serogrouped and genetically characterized. Fifteen of those were described in other papers and four are first described on the present study. Isolates belong to three different species (Leptospira santarosai, L. alstonii and L. interrogans) and five serogroups (Sarmin, Tarassovi, Shermani, Grippotyphosa and Sejroe). The majority (84.2%) of the isolates belongs to the species L. santarosai, the most prevalent species on cattle in the studied region. Non-Hardjo (non-Sejroe) strains represent 57.9% of the isolates, what indicates an unexpected high diversity of serogroups obtained from these cattle. This suggest that non-Hardjo (non-Sejroe) strains may also be maintained and shed by cattle and that finding must be considered in the epidemiology and control of the disease.