Canine leptospirosis

Seroprevalence of leptospirosis among stray dogs in Bosnia and Herzegovina

Leptospirosis is a (re) emerging zoonosis that occurs worldwide. This study aimed to assess seroprevalence of leptospirosis and to identify the most common reactive serovars and risk factors for seropositivity in apparently healthy stray dogs of unknown vaccination status in the Sarajevo region of Bosnia and Herzegovina. Positive microscopic agglutination test titres (≥ 1:25) were detected in 3.87% (156/4028) of samples and most of the sera reacted against one serovar (85.9%). Dogs were most commonly reactive to Canicola (40.4%) and Hardjo (33.3%), followed by Pomona (15.4%) Tarassovi (14.7%), Icterohaemorrhagiae (8.3%), Grippotyphosa (5.8%), Bratislava (1.3%) and Saxkoebing (0.6%). Dogs older than one year had higher odds of seropositivity compared to younger dogs. The seropositivity was higher in spring and autumn than in summer. These results advocate for the need of a control strategy for this zoonosis in the country, which should include sero-surveillance, monitoring, and the inclusion of additional serovars in the testing.

Seroprevalence of pathogenic Leptospira serogroups in asymptomatic domestic dogs and cats: systematic review and meta-analysis

Leptospirosis is a neglected zoonotic disease transmitted by contact with the urine of animals infected with pathogenic species of the bacteria Leptospira or by contact with environments contaminated with the bacteria. Domestic dogs and cats may act as reservoirs or as sentinels of environmental contamination with leptospires, posing a public health concern. There is a great diversity of leptospires, and one common way to classify them is into serogroups that provide some information on the host species they are associated with. The aims of this study were: (1) to quantitatively summarize the overall prevalence and serogroup-specific prevalence of antibodies against pathogenic leptospires in asymptomatic dogs and cats and (2) to identify environmental and host characteristics that may affect the prevalence. Three electronic databases and the reference lists of eligible articles were screened, for epidemiological studies conducted between the years 2012-2022. We estimated overall and serogroup-specific prevalence using three-level meta-analysis models and assessed potential sources of heterogeneity by moderator analysis and meta-regression. Eighty-four studies met the inclusion criteria (dog studies 66.7%, cat studies 26.2%, and both species 7.1%). There were significant differences between dogs and cats in the overall prevalence model (P < 0.001), but not in the serogroup-specific model (P>0.05). In dogs, the prevalence of Leptospira interrogans serogroup Canicola was significantly higher than the other pathogenic serogroups (P < 0.001), while in cats there were no significant differences among serogroups (P = 0.373). Moderator analysis showed that the prevalence of L. kirschneri serogroup Grippotyphosa was significantly higher in stray/sheltered dogs than in domiciled dogs (P = 0.028). These results suggest that pathogenic serogroups associated with small mammals are circulating among asymptomatic pets and should be taken into account in the transmission cycle of leptospires, as well as in the standard MAT panel for diagnosis in dogs and cats. It also highlights the importance of including both dogs and cats as potential reservoirs when conducting eco-epidemiological studies in different geographical and ecological areas.

Acute human leptospirosis in a Caribbean region of Colombia: From classic to emerging risk factors

BACKGROUND

Leptospirosis is a zoonosis of worldwide incidence, with a broad spectrum of health risk factors.

AIM

The objective was to determine risk factors associated with acute human leptospirosis and to explore predictive variables of risk to human leptospirosis.

METHODS

The study was carried out in the Department of Córdoba, in the north of Colombia. We conducted a longitudinal prospective descriptive study with non-probabilistic sampling, which included 339 patients suspected of leptospirosis. Positive cases were confirmed by MAT and PCR. The determination of social and environmental risk factors was done with a survey on epidemiological and environmental variables to establish an association between cases of leptospirosis and risk factors as well as predictive variables.

RESULTS

We found 19.8% (67/339) cases of acute leptospirosis, and the seroprevalence was 27.1% (92/339). The most frequent serogroups were Sejroe, Australis, Pomona, Batavie, Pyrogenes and Grippotyphosa. We identified the following risk factors: age between 10 and 19 years (OR = 2.571; 95% CI); pig ownership (OR = 2.019; 95% CI); bathing or recreational activities in lake/lagoon (OR = 3.85; 95% CI) and in dams (OR = 3.0; 95% CI); floodings 30 days before the onset of symptoms (OR = 2.019; 95% CI), and a mean temperature of 28°C (p 0.044; 95%CI). As significant predictor variables, we identified age (10-19 years), bathing or recreational activities in the lake/lagoon, and flooding 30 days before symptoms were again evidenced. This region presents classic risk factors (pig ownership) and emerging environmental risk factors (recreational practice or bathing in a lake/lagoon and flooding 30 days before the onset of symptoms), and demographic factors such as young age (10-19 years).

CONCLUSIONS

These factors are also predictors of human cases of acute leptospirosis and provide contextual information on environmental and public health that should be considered for epidemiological surveillance in this endemic area.

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.

Seroepidemiological Analysis of Canine Leptospira Species Infections in Changchun, China

Leptospirosis is a significant worldwide zoonotic infectious disease that infects a wide range of animals and humans. Leptospira will colonize the animal's urinary and reproductive systems and be excreted with urine, potentially causing a wide range of infections. Dogs are an essential host for Leptospira, and epidemiological investigation studies of leptospirosis must be conducted to clarify the prevalence of leptospirosis and to reduce the risk of transmission to humans. This study aimed to investigate the seroepidemiology of leptospiral infection in dogs from Changchun, China, using Microscopic Agglutination Test (MAT). A total of 1053 canine blood samples were collected and tested by MAT. The positive rate of MAT was approximately 19.1%. The main prevalent Leptospira serogroups were L. Icterohaemorrhagiae (8.1%), L. Canicola (7.6%), L. Australis (5.3%), L. Ballum (4.7%) and L. Pyrogenes (4.2%). No statistically significant difference among different varieties, sexes and sampling seasons (p > 0.05), except the age (p < 0.05). The seropositive rate was much higher in adult and aged dogs than in juvenile dogs. Our results showed the seroprevalence and the prevalent serogroup of Canine leptospirosis in Changchun, China.

Microscopic detection of Leptospira bacterial organisms in urine sediment from a young dog with leptospirosis and a review of the pathobiology and diagnosis of canine leptospirosis

Samples collected from an 11-month-old Dachshund-mix dog with a history of acute azotemia, fever, and enlarged and irregular kidneys were received at the Colorado State Veterinary Diagnostic Laboratory (CSU VDL). The submitting veterinarians were concerned about lymphoma versus acute nephritis/pyelonephritis. The CSU clinical pathology laboratory received urine for urinalysis and kidney aspirates for cytologic evaluation. Urine had also been submitted for aerobic culture and Leptospirosis PCR, and serum was submitted for Lepto-5 microscopic agglutination testing (MAT). Upon examination of a wet mount of the urine sediment, technical staff noted "vibrating" clumps of granular-appearing material throughout the slide, which prompted the preparation of a stained sediment slide for pathologist review. Very small, faintly staining organisms were observed, and an attempt was made to picture-match these with published reports of Leptospira in dog urine, but none could be found. In addition, some references claimed that Leptospira organisms are not seen in urine with light microscopy. The suspicion that these organisms were Leptospira sp. was supported by the MAT results and later confirmed by PCR. The organisms subsequently exhibited strong positive immunolabeling for the Leptospira antigen. This case report provides a searchable record of Leptospira organisms visualized by routine light microscopy in dog urine during natural infection and a review of canine leptospirosis pathobiology and diagnosis.

Leptospiral infection in domestic cats: Systematic review with meta-analysis

The role of domestic cats in the transmission of Leptospira is controversial, being considered either as a protective factor or a potential source of infection for humans. The aims of this study were to obtain an integrated estimate of the prevalence of leptospiral infection in domestic cats, and to characterize those individuals most susceptible to infection. For this systematic review and meta-analysis, five electronic databases, as well as the reference lists of eligible reports were screened for observational studies published during 1979-2022. The overall prevalence of leptospiral antibodies and of pathogenic Leptospira in kidney/urine was estimated using three-level meta-analysis models. To investigate potential sources of heterogeneity, moderator analyses was performed using the sampling year, health status, living environment, and origin of the cats. The odds-ratio (OR) of potential risk factors was estimated using random-effects meta-analysis models for binary outcomes. The literature search identified 61 eligible publications, containing 114 effect estimates. The overall seroprevalence was 11.7 % (95 % CI: 9.3-14.6 %), the prevalence of leptospires in urine was 3.7 % (95 % CI: 1.7-8.1 %), and the prevalence of leptospires in kidney tissue was 12.8 % (95 % CI: 3.2-39.9 %). There were no significant differences in the estimated prevalence after removing articles with medium risk of bias. Seroprevalence was higher in Europe when compared to Latin America and the Caribbean (P = 0.047) and showed a mild decrease over time (P = 0.023). Outdoor cats had almost three times greater probabilities of infection with Leptospira (OR: 2.74, 95 % CI: 1.10-6.84). No other significant effect was detected among the tested moderators or potential risk factors (P > 0.05). Results suggest that feline leptospirosis should receive particular attention in veterinary care, as exposure to leptospires can occur in approximately 1 in every 10 cats, and more frequently in cats with street access. Domestic cats should be considered as potential Leptospira carriers when designing public health strategies for the control and prevention of leptospirosis. Further investigation is required to improve knowledge of the role of these animals in the environmental transmission cycle.

Leptospiral Leucine-Rich Repeat Protein-Based Lateral Flow for Assessment of Canine Leptospiral Immunoglobulin G

The recombinant, modified leucine-rich repeat protein rhKU_Sej_LRR_2271 has been suggested as a candidate for leptospiral vaccine development since it was predicted to be a transmembrane protein containing leucine-rich repeat motifs and immunogenic epitopes. The immunogenic epitopes showed binding affinities with lower IC₅₀ values than peptides of known antigenic proteins, e.g., LipL32. Moreover, this protein was immunoreactive with hyperimmune sera against several serovars. In this study, we aimed to develop a lateral flow strip test using the rhKU_Sej_LRR_2271 protein for the detection of anti-leptospiral IgG in dogs. The lateral flow assay was performed with 184 dog plasma samples and evaluated with a culture method, 16S ribosomal RNA gene (rss) analysis real-time PCR, and LipL32 ELISA. The culture method failed to detect leptospires in the dog blood samples. Six of nine symptomatic dogs gave positive results with the real-time PCR assay. The lateral flow assay and LipL32 ELISA gave positive results with 59 and 50 dogs, respectively. The sensitivity, specificity, and accuracy of the rhKU_Sej_LRR_2271 lateral flow strip test were 70.00, 82.09, and 78.80%, respectively, when compared with LipL32 ELISA. There was a significant association between the LipL32 ELISA and the rhKU_Sej_LRR_2271 lateral flow assay. The rhKU_Sej_LRR_2271 lateral flow strip test has therefore demonstrated a good potential to detect anti-leptospiral IgG in dogs.

Leptospirosis with multiple organ dysfunction in a mongoose-scat-detection dog infected with Leptospira interrogans serogroup Hebdomadis, Okinawa, Japan

A 2-year-old male mongoose-scat-detection dog was diagnosed with leptospirosis by urine PCR. The patient developed acute renal failure, hepatic dysfunction, and disseminated intravascular coagulation. Treatment with antibiotics was administered, including ampicillin and doxycycline, and supportive care management was provided. Seroconversion against serogroup Hebdomadis was observed on day 8. The leptospiral gene flaB was detected only in urine collected on day 1, from which Leptospira interrogans ST329 was identified by multilocus sequence typing using seven housekeeping genes. L. interrogans serogroup Hebdomadis ST329 has been isolated from mongooses and humans in Okinawa, Japan. This patient received early treatment with antibiotics, which may have contributed to the early recovery of renal function and removal of L. interrogans from kidney tissue.

Transcriptome and proteome analysis of innate immune responses to inactivated Leptospira and bivalent Leptospira vaccines in canine 030-D cells

Mandatory potency testing of Leptospira vaccine batches relies partially on in vivo procedures, requiring large numbers of laboratory animals. Cell-based assays could replace in vivo tests for vaccine quality control if biomarkers indicative of Leptospira vaccine potency are identified. We investigated innate immune responsiveness induced by inactivated L. interrogans serogroups Canicola and Icterohaemorrhagiae, and two bivalent, non-adjuvanted canine Leptospira vaccines containing the same serogroups. First, the transcriptome and proteome analysis of a canine monocyte/macrophage 030-D cell line stimulated with Leptospira strains, and vaccine B revealed more than 900 DEGs and 23 DEPs in common to these three stimuli. Second, comparison of responses induced by vaccine B and vaccine D revealed a large overlap in DEGs and DEPs as well, suggesting potential to identify biomarkers indicative of Leptospira vaccine quality. Because not many common DEPs were identified, we selected seven molecules from the identified DEGs, associated with pathways related to innate immunity, of which CXCL-10, IL-1β, SAA, and complement C3 showed increased secretion upon stimulation with both Leptospira vaccines. These molecules could be interesting targets for development of biomarker-based assays for Leptospira vaccine quality control in the future. Additionally, this study contributes to the understanding of the mechanisms by which Leptospira vaccines induce innate immune responses in the dog.

The Evaluation of the Diagnostic Value of a PCR Assay When Compared to a Serologic Micro-Agglutination Test for Canine Leptospirosis

Objective

To evaluate PCR assay sensitivity and specificity compared to that of microscopic agglutination test (MAT) for diagnosis of canine leptospirosis. Electronic records search was performed to identify dogs with results for both PCR and MAT testing for leptospirosis.

Methods

All dogs were clinically ill. Diagnosis of leptospirosis was defined as an unvaccinated dog with a positive MAT titer of ≥1:800 or a vaccinated dog or dog with an unknown vaccination status with a positive MAT titer of ≥1:1,600. Diagnosis of leptospirosis was excluded based on MAT titer <1:800 on both the initial and convalescent samples or an initial MAT titer <1:800 and an alternative definitive diagnosis.

Results

Forty-nine samples (urine, n = 39; blood, n = 10) were evaluated. Leptospirosis was diagnosed in 17 dogs and excluded in 26 dogs. Urine PCR assay demonstrated sensitivity of 69.2%, specificity of 100%, positive predictive value of 100%, and negative predictive value of 86.6%. Blood PCR assay demonstrated sensitivity of 25%, specificity of 100%, positive predictive value of 100%, and negative predictive value of 25%. Overall PCR sensitivity was 52.4%, specificity was 100%, positive predictive value was 100%, and negative predictive value was 73.7%.

Conclusions

PCR assay performed on urine or blood has high specificity and positive predictive value when compared to MAT for diagnosis of clinical canine leptospirosis. Sensitivity and negative predictive value are moderate to low, so PCR testing should be performed in conjunction with paired MAT testing for canine leptospirosis. Prior antibiotic therapy does not preclude the use of the PCR test.

Risk and Predictive Factors of Leptospirosis in Dogs Diagnosed with Kidney and/or Liver Disease in Selangor, Malaysia

Simple Summary

Canine leptospirosis is commonly associated with kidney and/or liver disease. The current study identified the potential risk and predictive factors of dogs diagnosed with kidney and/or liver disease due to leptospirosis. A total of 124 client-owned dogs were recruited and the samples collected were directly tested using polymerase chain reaction (PCR) and subsequently inoculated for bacterial isolation. Statistical analyses were descriptively analyzed, and risk analyses were performed using Pearson chi-square tests and logistic regression. The different breeds of dog with history of exposure to rats and those managed outdoors had a greater risk of leptospirosis (p < 0.05). The significant predictors for the dogs’ positivity were presence of rats and acute clinical illness (p < 0.05). Administration of antibiotics and detection of clinical illness at an early stage of the disease improved the survivability of the dogs (p < 0.05).

Abstract

Canine leptospirosis is commonly associated with kidney and/or liver disease. It has been widely reported and causes public health concerns due to its zoonotic potential and its re-emergence, resulting from close contact between humans and dogs. The current study identified potential risk and predictive factors for dogs diagnosed with kidney and/or liver disease due to leptospirosis. A total of 124 client-owned dogs were recruited, and information such as signalment, medical history, management, and clinical findings were documented. Samples collected from the recruited dogs were directly tested using polymerase chain reaction (PCR) and subsequently inoculated for bacterial isolation. Statistical analyses were descriptively analyzed, and risk analyses were performed using Pearson chi-square tests and logistic regression. A total of 53 dogs (42.7%) were positive for leptospiral infection based on PCR, and 10 leptospiral isolates were successfully recovered from eight dogs. The mortality rate of infected dogs was 34.0% (18/53). Medium and large dog breeds, with a history of exposure to rats, and managed outdoors had a greater risk for leptospirosis (p < 0.05). The significant predictors for the dogs’ positivity were the presence of rats and acute clinical illness (p < 0.05). Administration of antibiotics and the detection of clinical illness at an early stage of the disease improved the survivability of the dogs (p < 0.05). Identifying the profile of dogs that are at risk to leptospirosis could be useful in the design of diagnostic and treatment strategies, as well as to increase awareness for prevention of the disease.

Molecular and serological characterization of pathogenic Leptospira spp. isolated from symptomatic dogs in a highly endemic area, Brazil

Abstract

Background

Leptospirosis is an endemic zoonosis in Brazil, with a great impact on human and animal health. Although dogs are frequently infected by pathogenic Leptospira, the current epidemiological understanding of canine leptospirosis is mainly based on serological tests that predict the infecting serogroup/serovar. Thus, the present study aimed at identifying the causative agent for severe cases of canine leptospirosis in a highly endemic area through the isolation and characterization of the isolated strains.

Results

Urine, serum and blood samples were collected from 31 dogs with suspected acute leptospirosis treated at the Veterinary Hospital Service of Santo Amaro University between 2018 and 2019. Acute infection was confirmed in 17 dogs (54.8%) by the associated use of Polymerase Chain Reaction (PCR), Microscopic Agglutination (MAT) and bacteriological culture. Eleven dogs (35.5%) had titers ≥800, with the most frequent serogroups being Autumnalis and Icterohaemorrhagiae (n = 4 each) and Canicola (n = 2). Leptospires were recovered from four dogs, and Multilocus Sequence Analysis (MLSA) revealed infection caused by L. interrogans, which were further characterized as serogroups Canicola (n = 1) and Icterohaemorrhagiae (n = 3).

Conclusion

The identity of the isolates and serological pattern of MAT suggest that dogs are highly exposed to the serogroup Icterohaemorrhagiae and Canicola, also indicating possible circulation of serogroups not yet isolated in Brazil, notably serogroup Autumnalis. Our findings also reinforce the usefulness of using multiple diagnostic approaches to confirm acute canine leptospirosis.

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.

Incidence and demographic risk factors for leptospirosis in dogs in the UK

OBJECTIVES

To estimate the annual incidence risk of leptospirosis diagnosis in practice-attending dogs in the UK during 2016 and identify risk factors for diagnosis.

METHODS

Incidence of leptospirosis diagnosis in dogs during 2016 was estimated from dogs in primary-care practices from the VetCompass Programme (n = 905,543). A case-control study of laboratory cases (n = 362) versus VetCompass controls explored factors (age, sex, neutering, breed, Kennel Club group, urban-rural location, indices of deprivation) associated with leptospirosis diagnosis through multivariable logistic regression.

RESULTS

Annual incidence risk of leptospirosis in the VetCompass population was 0.8 cases per 100,000 dogs (0.0008%, 95% CI 9.1 × 10^-8 -5.2 × 10^-5 ). Adult dogs, especially 1- < 5 years olds (odds ratio [OR] = 0.38, 95% CI 0.27-0.54), and dogs attending urban clinics (OR = 0.26, 95% CI 0.19-0.35) had reduced odds of leptospirosis versus dogs < 1 year old and rural dogs, respectively. Dogs attending clinics in less deprived areas had increased odds of diagnosis (OR = 3.63, 95% CI 2.28-5.78) compared to crossbreds, Cocker Spaniels (OR = 4.25, 95% CI 2.65-6.84), Collies (OR = 3.53, 95% CI 2.22-5.62) and Lurchers (OR = 3.49, 95% CI 1.50-8.11) had increased odds of diagnosis.

DISCUSSION

Leptospirosis is rarely diagnosed in clinical practice, suggesting that many true cases may be missed. Demographic risk factors identified here may inform the index of suspicion and encourage increased use of confirmatory diagnostic testing.

Molecular epidemiology of Leptospira spp. among wild mammals and a dog in Amami Oshima Island, Japan

Leptospirosis is a worldwide zoonosis caused by the pathogenic Leptospira spp. Canine and human leptospirosis sometimes occur on Amami Oshima Island, located in the Nansei Archipelago, southwestern Japan; however, information on the causative Leptospira spp. on this island is quite limited. This study aimed to investigate the molecular and serological characteristics of Leptospira spp. isolated from wild animals and a dog in Amami Oshima Island. We obtained seven Leptospira strains by culturing kidney tissues of wild animals, such as black rats (2), wild boars (3), and rabbit (1) as well as blood from a symptomatic dog. Using flaB sequencing and microscopic agglutination test with antisera for 18 serovars, the isolates were identified as Leptospira borgpetersenii serogroups Javanica (black rat), L. interrogans serogroup Australis (black rat and dog), and L. interrogans serogroup Hebdomadis (wild boar and rabbit). The sequence type (ST) of L. borgpetersenii serogroup Javanica was determined to be ST143 via multilocus sequence typing (MLST) using seven housekeeping genes. For L. interrogans, MLST and multiple-locus variable-tandem repeat analysis (MLVA) revealed identical ST and MLVA types in rat and canine isolates, whereas two STs and MLVA types were identified in wild boar isolates. The STs and MLVA types of rabbit and one of the wild boars were identical. Bacterial culture and flaB-nested polymerase chain reaction demonstrated a high rate of Leptospira infection in wild boars (58.3%, 7/12), whereas Leptospira spp. were detected in 4.8% of black rats (2/42). This study revealed diverse Leptospira genotype and serotype maintenance in wild mammals on Amami Oshima Island. MLST and MLVA indicated that black rats were a source of canine infection. Wild boars carry L. interrogans and are considered an important maintenance host because antibodies against serogroup Hebdomadis were detected in human and canine leptospirosis patients on this island.

Clinical, diagnostic, and epidemiological features of a community-wide outbreak of canine leptospirosis in a low-prevalence region (Maricopa County, Arizona)

OBJECTIVE

To describe clinical, diagnostic, and epidemiological features of an outbreak of leptospirosis in dogs in Maricopa County, Ariz, from January 2016 through June 2017.

ANIMALS

71 case and 281 control dogs.

PROCEDURES

Cases were classified as confirmed, probable, suspect, or not a case on the basis of medical record data that fulfilled clinical, diagnostic, and epidemiological criteria. Potential exposures were assessed by owner survey. For the case-control investigation, control dogs were recruited through owner completion of a July 2017 survey. Summary statistics and ORs for case dog lifestyle factors were reported.

RESULTS

54 dogs were classified as confirmed and 17 as probable cases. For 4 dogs of a household cluster (5 confirmed and 3 probable), the highest microscopic agglutination titer was for serovar Djasiman (Leptospira kirschneri detected by PCR assay), and for 13 dogs of a community outbreak (49 confirmed and 14 probable cases), the highest titer was for serovar Canicola (Leptospira interrogans detected by PCR assay). The 44 case dogs included in the case-control investigation were 7.7 (95% CI, 3.5 to 16.7) and 2.9 times (95% CI, 1.3 to 6.6) as likely as control dogs to have visited dog daycare or to have been kenneled overnight at a boarding facility, respectively, 30 days prior to the onset of clinical signs or diagnosis.

CONCLUSIONS AND CLINICAL RELEVANCE

Diagnostic and epidemiological findings indicated 2 outbreaks. Transmission where dogs congregated likely propagated the community outbreak. Outbreaks of leptospiral infections can occur in regions of low prevalence, and a dog's exposure to areas where dogs congregate should be considered when making Leptospira vaccination recommendations.

Unusual case of polyarthritis and hepatorenal syndrome associated with Leptospira interrogans infection in a dog: A case report

Leptospirosis is a zoonotic disease caused by spirochetal bacterial of the genus Leptospira affecting virtually all mammals. The infection has a broad range of effects, from mild clinical manifestation to multiple organ failure, and ultimately death. A 5-months-old male unvaccinated dog was admitted to the University Veterinary Teaching Hospital presenting dullness, dehydration, jaundiced mucous, bloody diarrhea, vomiting, and hyporexia. Microscopic agglutination test (MAT) detected serological titers of 1:1.600 for serogroup Canicola. After five days of monitoring by the medical team he developed fever and swelling of carpal and tarsal joints, accompanied by functional limitation. Initial antimicrobial treatment was instituted for leptospirosis. Polyarthritis responsiveness to glucocorticoid therapy was observed through decreasing signs of inflammation of the affected joints. The diagnosis of leptospirosis was further confirmed by molecular investigation for Leptospira spp. on blood and synovial fluid samples. Amplification and sequencing of the secY partial gene characterized the infective bacterial as Leptospira interrogans. From the 7th day the respiratory condition worsened and on Day 14 the patient evolved to death, when necropsy and histological evaluation were performed. Prominent anatomopathological findings included: fibrinous polyarthritis, bronchointerstitial pneumonia, intense hepatocyte dissociation, cholestasis, and periportal multifocal hepatitis, diffuse acute tubular necrosis, and significant dystrophic mineralization in the renal parenchyma, lungs, and atrial endocardium. Here, we present a case report of systemic clinical manifestations polyarthritis associated with the presence of leptospiras in the synovial fluid. We highlight the need for richer knowledge about the different clinical manifestations of leptospirosis.

Leptospirosis in cats: Current literature review to guide diagnosis and management

GLOBAL IMPORTANCE

Leptospirosis is the most widespread zoonosis worldwide. Mammals (eg, rats, horses, cows, pigs, dogs, cats and aquatic species, such as sea lions and northern elephant seals) can all be infected by leptospires. Infection in animals occurs through contact with urine or water contaminated with the bacteria. In people, the disease is acquired mainly from animal sources or through recreational activities in contaminated water.

PRACTICAL RELEVANCE

Literature on the clinical presentation of leptospirosis in cats is scarce, although it has been demonstrated that cats are susceptible to infection and are capable of developing antibodies. The prevalence of antileptospiral antibodies in cats varies from 4% to 33.3% depending on the geographical location. Urinary shedding of leptospires in naturally infected cats has been reported, with a prevalence of up to 68%. Infection in cats has been associated with the consumption of infected prey, especially rodents. Thus, outdoor cats have a higher risk of becoming infected.

CLINICAL CHALLENGES

Clinical presentation of this disease in cats is rare and it is not known what role cats have in the transmission of leptospirosis. Ongoing work is needed to characterise feline leptospirosis.

AUDIENCE

This review is aimed at all veterinarians, both general practitioners who deal with cats on a daily basis in private practice, as well as feline practitioners, since both groups face the challenge of diagnosing and treating infectious and zoonotic diseases.

EVIDENCE BASE

The current literature on leptospirosis in cats is reviewed. To date, few case reports have been published in the field, and information has mostly been extrapolated from infections in people and dogs. This review is expected to serve as a guide for the diagnosis and management of the disease in cats.

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.

Frequency of Animal Leptospirosis in the Southern United States and the Implications for Human Health

Leptospirosis is a zoonotic disease with symptoms in humans and animals, ranging from subclinical to serious and fatal. The disease occurs worldwide, but there is limited recognition of the public and animal health risks it poses in the southern United States. A systematic review of the frequency of animal leptospirosis in 17 states and jurisdictions covering the southern continental United States was performed to advance our understanding of the pathogen's distribution and identify transmission patterns that could be targeted for prevention efforts. Fifty-two articles, spanning >100 years, met the analysis criteria. A wide range of techniques were used to measure seroprevalence and isolate the bacteria. The assessment identified exposure to Leptospira spp and Leptospira spp infection among a diverse range of species, spanning 22 animal families within 14 states, suggesting that the pathogen is distributed throughout the southern region. Disease frequency trends were assessed among animals in various habitats (all habitats, nonwild habitats, and wild habitats). The frequency of Leptospira spp detection in animals in wild habitats increased slightly over time (<0.2%/year). We identified reports of 11 human leptospirosis illness clusters and outbreaks in the southern United States. Exposure to potentially contaminated surface waters were documented for at least seven of the events, and interactions with infected or likely infected animals were documented for at least six of the events. This analysis highlights the need for stronger partnerships across the public and animal health fields to enhance diagnostics, surveillance, and reporting. The early identification of leptospirosis in animals may serve as an indicator of environmental contamination and trigger prevention measures, such as vaccinating companion animals and livestock, use of potable water, and the wearing of waterproof protective clothing near water that may be contaminated.

Meta-analysis of risk factors for canine leptospirosis

Leptospirosis is one of the most widespread zoonotic diseases, with more than one million human cases reported worldwide every year. Dogs could develop infections that range from asymptomatic to severe, and shed leptospires with their urine. Given their close contact with humans, dogs may act both as epidemiological links or as sentinels of pathogenic leptospires in the environment. The aims of our study were to quantitatively summarize the overall prevalence of leptospiral antibodies and to identify factors associated with the probabilities of infection. We searched the electronic databases Scopus, PubMed, PMC and ScienceDirect for observational studies on canine leptospirosis published between 1989 and December 2019 and written in English, Spanish or Portuguese. We fitted a series of multilevel random effects meta-analysis models to estimate the prevalence of antibodies against Leptospira for different types of dogs, health statuses, diagnostic tests, geographic regions and income categories of the countries. We also fitted a number of random effects meta-analysis models to estimate the pooled odds-ratio of factors associated with canine leptospirosis. After removing duplicates and articles not meeting selection criteria, a total of 130 studies in 91 articles were included in this work. We found lower seroprevalence estimates in North America countries (P<0.001) and other high income countries (P<0.001). We also found higher probabilities of leptospiral infection in adult (P=0.017), male dogs with access to the streets (P<0.001). Identifying the profile of dogs that are more exposed to leptospirosis could be useful in the design of public health strategies for the prevention and control of leptospirosis.

Leptospirosis and immune-mediated hemolytic anemia: A lethal association

Immune-mediated hemolytic anemia (IMHA) is a common cause of anemia in dogs. The immune aggression towards erythrocytes can be triggered by many pathological conditions such as infection, inflammatory disease or neoplasia. Upon ruling out any eliciting conditions, a diagnosis of the primary immune-mediated disease can be made. In this particular case of severe anemia (tested positive for circulating antibodies against red blood cells with flow cytometry), vector-borne diseases (which are a common cause of immunopathology in Mediterranean countries) were excluded, leptospirosis was not. This resulted in an unsuccessful immunosuppressive therapy with prednisone, two whole blood transfusions and ultimately death of the patient. Leptospirosis (confirmed positive in two tests, micro-agglutination test for antibodies and PCR for microbial DNA in urine), can mimic a primary IMHA and must be considered in its differential list of causes. A liver involvement, that included elevated serum activity of liver enzymes and increased serum bile acid was observed at the admission and suggested an etiopathogenesis other than a primary IMHA.

Development of antibody ELISA specific of Leptospira interrogans serovar Grippotyphosa, Canicola, and Icterohaemorrhagiae to monitor vaccine immunogenicity

The antibody response after primary vaccination and annual revaccination with a multivalent DAPPi-L vaccine was assessed respectively in SPF dogs and in client owned dogs against the Grippotyphosa (Lg), Canicola (Lc) and Icterohaemorrhagiae (Li) Leptospira serovars. To overcome limitations of the microscopic agglutination test (MAT), we developed serovar-specific and sensitive blocking ELISA assays. Serovar-specific antibodies against Lg, Lc and Li were detected in 100%, 45% and 91% of dogs, respectively, after the first dose of vaccine, and in 100% of dogs for all serovars after the second dose. In addition, mean ELISA antibody titers increased 14 days after annual revaccination with most dogs remaining ELISA antibody positive against Lg (85.3%), Lc (90%) and Li (100%). Parallel testing of sera from the annual revaccination study in the MAT and ELISA assays resulted in an overall agreement of 72%, 67%, 77% of samples for Lg, Lc and Li serovars, respectively. More sera tested positive by ELISA than by MAT, suggesting that the ELISA assay is more sensitive than the MAT. These three new antibody-based assays are the first suitable and reliable ELISA assays for the assessment of the canine antibody response following vaccination and an attractive alternative to the MAT.

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.

Risk Factors and Prediction of Leptospiral Seropositivity Among Dogs and Dog Handlers in Malaysia

This study determined the potential risk factors that may contribute to seropositivity among dogs and dog handlers from working dog and dog shelter institutions. Data was collected from dogs (n = 266) and dog handlers (n = 161) using a standardised guided questionnaire. Serum obtained from the dogs and dog handlers was tested using the microscopic agglutination test (MAT). A logistic regression analysis was used to predict leptospiral seropositivity of dogs and dog handlers based on potential risk factors. A total of 22.2% of dogs and 21.7% of dog handlers were seropositive. The significant predictors for the dogs' seropositivity were presence of rats (OR = 4.61 (95% CI: 1.05, 20.33), p = 0.043) and shared common area (OR = 5.12 (95% CI: 1.94, 13.46), p = 0.001) within the organisation. Significant predictor for dog handler seropositivity was contact time with the dogs of more than six hours/day (OR = 3.28 (95% CI: 1.28, 8.40), p = 0.013) after controlling for the effect of other risk factors such as small mammal contact, rat infestation at home, flooding at housing area (within three months) and urban locality. The exposure to various disease sources identified poses risk to dogs and dog handlers. Risk could be reduced with adequate application of protection at work while handling dogs and thus limiting contact with these sources and reducing exposure to infection.

Diagnosis of Canine Leptospirosis

Several diagnostic tests are available to aid veterinarians in diagnosis of leptospirosis. Understanding the course of infection is imperative to determining which diagnostic test to order and sample to submit. Diagnostic tests for dogs suspected of having leptospirosis include antibody-based tests and polymerase chain reaction (PCR). Paired acute and convalescent microscopic agglutination test (MAT) are diagnostic for leptospirosis. PCR performed on blood and/or urine can be a valuable tool to aid in diagnosis of leptospirosis. Commercially available rapid point-of-care diagnostics have been validated in dogs and have value early in the course of illness before MAT and PCR results are available.

Hepatic leptospiral infections in dogs without obvious renal involvement

Background

Reports of chronic hepatitis in dogs caused by Leptospira spp. are confined to small case series. Fluorescence in situ hybridization (FISH) allows the identification of spirochetes in liver samples. Consequently, this technique may help elucidate the role of Leptospira spp. in cases of chronic hepatitis.

Objectives

To describe cases of hepatic leptospirosis in dogs diagnosed by FISH and subsequent polymerase chain reaction (PCR) speciation, with the absence of clinically relevant renal involvement.

Animals

Ten client‐owned dogs.

Methods

Retrospective case series from the University of Cambridge presented between 2013 and 2016 or cases consulted by telephone advice during this time period. Cases were selected based on histopathologically confirmed granulomatous hepatitis and leptospiral organisms identified by FISH and PCR speciation (Leptospira interrogans/kirschneri).

Results

All cases had increased liver enzyme activities, and FISH in combination with PCR speciation‐confirmed infection with L. interrogans/kirschneri. Four dogs underwent repeat liver biopsy, FISH and PCR speciation 4‐15 months after initial presentation and doxycycline treatment with 1 dog undergoing repeat sampling at necropsy. Three dogs that underwent repeat biopsy remained positive for L. interrogans/kirschneri infection. Six dogs were alive at the time of manuscript preparation and 4 dogs were euthanized as a result of progressive liver disease.

Conclusions and Clinical Importance

The presence of hepatic leptospiral organisms may be associated with chronic granulomatous hepatitis without clinical evidence of renal involvement. Further studies are necessary to elucidate the etiological role of these organisms in the disease.

MAT cross-reactions or vaccine cross-protection: retrospective study of 863 leptospirosis canine cases

Dogs are naturally exposed to numerous pathogenic serogroups. Leptospirosis vaccines are claimed to afford a clinical protection restricted to the serogroups of which they are composed.

Objectives

Dogs exhibiting liver and kidney injury were suspected of having leptospirosis. The purpose of this study was to compare the microscopic agglutination test (MAT) results in naive and vaccinated dogs experiencing leptospirosis outcomes. Only MAT-positive animals were included in the study.

Methods

Over five years, 3 512 dogs were suspected of having leptospirosis. For each case, biochemical parameter results were recorded. Leptospirosis involvement was investigated by MAT performed against 6 major serogroups (Icterohaemorrhagiae, Canicola, Australis, Autumnalis, Grippotyphosa and Sejroë). MAT-positive results confirmed leptospirosis cases in 147 naïve dogs and in 580 fully vaccinated dogs. Serological titres of agglutinating antibodies were related to the severity of liver and kidney failure.

Results

The most prevalent outcome of leptospirosis in unvaccinated dogs was liver failure (57.8%) compared to 51.7% for kidney disease, but the most severe onset (90.8%) was found among the cases of acute kidney injury compared to the severe (42.3%) hepatitis cases. In dogs vaccinated by bivalent Icterohaemorrhagiae and Canicola bacterins, hepatitis decreased from 57.8 to 46.5% and acute kidney injury from 51.7 to 21.6%. The decrease was shown in leptospirosis cases induced by field strains belonging to the six most prevalent serogroups, including the 4 serogroups heterologous to the vaccine.

Conclusion

Common vaccination was efficient in decreasing hepatitis and kidney failure induced by field Leptospira spp infection regardless of the MAT-prominent serogroup and limited the disease severity in the remaining cases.

Evaluation of 3 Serological Tests for Early Detection Of Leptospira-specific Antibodies in Experimentally Infected Dogs

BACKGROUND

Leptospirosis in dogs is a disease of global importance. Early detection and appropriate therapeutic intervention are necessary to resolve infection and prevent zoonotic transmission. However, its diagnosis is hindered by nonspecific clinical signs and lack of rapid diagnostic tests of early infection. Recently, 2 rapid point-of-care tests (WITNESS Lepto [WITNESS Lepto, Zoetis LLC, Kalamazoo, MI, USA] and SNAP Lepto [SNAP Lepto, IDEXX Laboratories, Westbrook, ME, USA]) for detection of Leptospira-specific antibodies in canine sera were developed.

HYPOTHESIS

Immunoglobulin M-based WITNESS Lepto containing multiple detection antigens can detect Leptospira-specific antibodies to common leptospiral serovars earlier in the course of infection as compared to microscopic agglutination test (MAT) and SNAP Lepto.

ANIMALS

Four groups of 8 6- to 8-month-old male Beagle dogs were used.

METHODS

Thirty-two healthy seronegative dogs were inoculated experimentally with serovars Canicola, Grippotyphosa, Icterohaemorrhagiae, and Pomona (8 dogs/serovar). Acute-phase sera were collected at regular intervals and monitored for Leptospira-specific antibodies by WITNESS Lepto, MAT, and SNAP Lepto.

RESULTS

Seroconversion was detected in all dogs by day 10 by WITNESS Lepto and in 30 of 32 dogs by day 14 by MAT. The SNAP Lepto test detected seroconversion in 3 dogs during the 2 weeks postchallenge.

CONCLUSIONS

Immunoglobulin M-based WITNESS Lepto detected immune responses specific to multiple leptospiral serovars early in the course of infection and identified seroconversion in all animals earlier than did the gold standard MAT. The SNAP Lepto test displayed considerably lower and inconsistent performance during the study period. At the point-of-care, WITNESS Lepto should be the test of choice for rapid and reliable screening of acutely ill dogs suspected to have leptospirosis.

Seroprevalence of Leptospirosis in Working Dogs

Working dogs are canine animals that have been trained to assist human beings in carrying out various tasks. They help in guarding property, performing rescues, assisting the visually impaired or physically handicapped, searching for drugs, explosives, and others. Leptospirosis is one of the most widespread zoonotic diseases in the world and a commonly occurring disease of the tropics and subtropics. In Malaysia, all working dogs are normally vaccinated with serovars, Pomona, Icterohaemorrhagiae, Canicola, and Grippotyphosa based on protocols recommended from other countries. The duration of immunity in vaccinated dogs for Leptospira can last up to 13 months; however, there is no full crossprotection between the different serovars. Five representative canine units from different government agencies in Malaysia (n = 96 dogs) were recruited in this study. For detection, the microscopic agglutination test was performed by incubating the serum from dogs with various serovars of leptospires, namely, Icterohaemorrhagiae, Canicola, Pomona, Grippotyphosa, Australis, Bataviae, Javanica, Tarassovi, Hebdomadis, Lai, and Pyrogenes. The plasma obtained was used for polymerase chain reaction (PCR) analysis, for the detection of 16S rRNA, and lipL 32 genes of Leptospira. Out of the 96 dogs sampled, only 3 dogs were positive toward serovars, Australis, Bataviae, and Javanica, based on the cutoff point at 1:80. The seroprevalence of canine leptospirosis in this population was 3.1% (n = 3/96). However, all 96 blood samples of working dogs tested negative for both pathogenic and nonpathogenic Leptospira genes. The results revealed that, by vaccination alone, working dogs were not fully protected against leptospirosis and could pose a risk to dog handlers. A preventative and control protocol for leptospirosis is warranted, and its implementation should be monitored and improved accordingly from time to time, in order to maintain a healthy condition in both working dogs and their handlers.

Meta-analysis to estimate the load of Leptospira excreted in urine: beyond rats as important sources of transmission in low-income rural communities

BACKGROUND

Leptospirosis is a major zoonotic disease with widespread distribution and a large impact on human health. Carrier animals excrete pathogenic Leptospira primarily in their urine. Infection occurs when the pathogen enters a host through mucosa or small skin abrasions. Humans and other animals are exposed to the pathogen by direct contact with urine, contaminated soil or water. While many factors influence environmental cycling and the transmission of Leptospira to humans, the load of pathogenic Leptospira in the environment is likely to play a major role. Peridomestic rats are often implicated as a potential source of human disease; however exposure to other animals is a risk factor as well. The aim of this report is to highlight the importance of various carrier animals in terms of the quantity of Leptospira shed into the environment. For this, we performed a systematic literature review and a meta-analysis of the amount of pathogen that various animal species shed in their urine.

RESULTS

The quantity of pathogen has been reported for cows, deer, dogs, humans, mice, and rats, in a total of 14 research articles. We estimated the average Leptospira per unit volume shed by each animal species, and the daily environmental contribution by considering the total volume of urine excreted by each carrier animal. Rats excrete the highest quantity of Leptospira per millilitre of urine (median = 5.7 × 10⁶ cells), but large mammals excrete much more urine and thus shed significantly more Leptospira per day (5.1 × 10⁸ to 1.3 × 10⁹ cells).

CONCLUSIONS

Here we illustrate how, in a low-income rural Ecuadorian community, host population demographics, and prevalence of Leptospira infection can be integrated with estimates of shed Leptospira to suggest that peridomestic cattle may be more important than rats in environmental cycling and ultimately, transmission to humans.

Meta-Analyses of Factors Associated with Leptospirosis in Domestic Dogs

Factors related with leptospirosis in domestic dogs have been reported worldwide. The aims of this study were to identify factors associated with this disease described in different observational studies and to combine the coinciding factors in at least four studies using meta-analyses, to obtain a pooled odds ratio (OR) as measure of infection risk. A literature search was performed in electronic databases, electronic databases of specific journals and search engines to find studies published in English, Spanish and Portuguese available from January 1960 to January 2015. Two hundred and eighteen factors were identified in 31 publications including cross-sectional and case-control studies. Finally, independent meta-analyses were performed with six different variables, which included between 4 and 8 articles. The pooled OR indicated that the variables 'mixed-breed dogs', 'flooding occurrence in the habitat of the dog' and 'working dogs' were risk factors for leptospirosis, while 'being a dog less than 1 year old' was a protective factor; however, all these associations were not statistically significant. Otherwise, the variables 'male dog' and 'urban dog' were statistically significant risk factors for infection. This study highlights the need for more formal studies on the epidemiology of canine leptospirosis. Nevertheless, the study revealed that some risk factors for infection coincided in different observational studies. These factors could be considered to raise suspicion about the disease, especially when there is a history of exposure to the bacteria.

Evaluation of three 5' exonuclease-based real-time polymerase chain reaction assays for detection of pathogenic Leptospira species in canine urine

Leptospirosis is caused by several pathogenic Leptospira species, and is an important infectious disease of dogs. Early detection of infection is crucial for an effective antibiotic treatment of the disease. Though different polymerase chain reaction (PCR) assays have been developed for detection of pathogenic Leptospira spp., thorough evaluation of the performance of these assays using dog urine samples has not been carried out. In the current study, the performance of 3 real-time PCR (qPCR) assays was assessed, 1 targeting the 16S ribosomal RNA (rRNA) gene and the other 2 targeting the lipL32 gene, a gene for the LipL32 outer membrane protein. With DNA extracted from laboratory-cultured pathogenic Leptospira spp., all 3 qPCR assays showed 100% specificity and had identical lower limits of detection. Compared to a conventional, gel-based PCR assay, all 3 qPCR assays were 100-fold more sensitive. There was a 100% agreement in the results of the 3 assays when tested on urine samples collected aseptically from 30 dogs suspected for leptospirosis. However, when tested on 30 urine samples that were collected by the free-catch method, the 16S rRNA-based assay falsely detected 13.3% of the samples as positive for pathogenic Leptospira spp. Nucleotide sequence analysis of the amplified DNA fragments showed that the assay resulted in false positives because of unrelated bacteria. All urine samples collected from 100 apparently healthy dogs at a local animal shelter tested negative for pathogenic Leptospira spp. These results highlight the importance of sample-specific validation of PCR-based diagnostic assays and the application of appropriately validated assays for more reliable pathogen detection.

Phenotypic and Molecular Characterization of Leptospira interrogans Isolated from Canis familiaris in Southern Brazil

Leptospirosis is a zoonotic disease caused by pathogenic spirochetes from the genus Leptospira, which includes 20 species and more than 300 serovars. Canines are important hosts of pathogenic leptospires and can transmit the pathogen to humans via infected urine. Here, we report the phenotypic and molecular characterization of Leptospira interrogans isolated from Canis familiaris in Southern Brazil. The isolated strain was characterized by variable-number tandem-repeats analysis as L. interrogans, serogroup Icterohaemorrhagiae. In addition, the isolate was recognized by antibodies from human and canine serum samples previously tested by microscopic agglutination test. Ultimately, the expression of membrane-associated antigens (LipL32 and leptospiral immunoglobulin-like proteins) from pathogenic leptospires using monoclonal antibodies was detected by indirect immunofluorescence assay. In conclusion, identification of new strains of Leptospira can help in the diagnosis and control of leptospirosis.

Recent advances in canine leptospirosis: focus on vaccine development

Leptospirosis is a global infection of humans and animals caused by pathogenic Leptospira spp. Leptospirosis is a major zoonosis, with infection acquired from wild and domestic animals. It is also a significant cause of morbidity, mortality, and economic loss in production and companion animals. Leptospirosis in dogs is prevalent worldwide and as well as a cause of canine disease, it presents a zoonotic risk to human contacts. Canine leptospirosis does not differ greatly from the syndromes seen in other animal species, with hepatic, renal, and pulmonary involvement being the main manifestations. While the pathogenesis of disease is well documented at the whole animal level, the cellular and molecular basis remains obscure. Killed, whole-cell bacterin vaccines are licensed worldwide and have not changed greatly over the past several decades. Vaccine-induced immunity is restricted to serologically related serovars and is generally short-lived, necessitating annual revaccination. The appearance of new serovars as causes of canine leptospirosis requires constant epidemiological surveillance and tailoring of vaccines to cover emerging serovars. At the present time, there is no realistic prospect of alternative, non-bacterin vaccines in the foreseeable future.

Multiple-locus variable-number tandem repeat analysis and clinical characterization of Leptospira interrogans canine isolates

Canine leptospirosis occurs worldwide; however, information on the relationship between Leptospira serotypes/genotypes and virulence in dogs remains limited. We investigated the molecular characteristics of Leptospira interrogans canine isolates belonging to three serogroups using multiple-locus variable-number tandem repeat analysis (MLVA) and the effects of each serotype/genotype on the clinical characteristics of leptospirosis in dogs. MLVA using 11 loci of the three major L. interrogans serogroups in Japan, Australis (32 strains from 21 dogs), Autumnalis (12; 7) and Hebdomadis (66; 39), revealed more divergent genetic heterogeneity within each serogroup than multilocus sequence typing (MLST), and they formed two, three and five clusters (CLs), respectively. Lethal infections were caused by all Leptospira serogroup isolates (70.3 % with Hebdomadis, 83.3 % with Australis and 100 % with Autumnalis) or Leptospira isolates belonging to all the CLs (57.1-100 %) without any significant differences. A significant difference in hyperaemia and haemorrhage of mucus membrane was observed between serogroups Australis and Autumnalis (P = 0.03). Leptospira isolates of Australis CL2 caused no hyperaemia and haemorrhage from mucus membrane, whereas those of Australis CL1, Autumnalis CL3 and Hebdomadis CL1 and CL3 did (P<0.05). Significant differences in creatinine (Cre) levels were observed between serogroups Australis and Hebdomadis (P = 0.02). In addition, significant differences in blood urea nitrogen levels were observed between serogroups Australis and Hebdomadis (P = 0.004) and Australis and Autumnalis (P = 0.02). Based on MLVA types, a significant difference in Cre levels was observed between Hebdomadis CL1 and CL4 (P = 0.0018). Our results indicated that MLVA had a higher discriminatory power and was more concordant with serotyping than MLST. Although all Leptospira serotypes and genotypes caused lethal infections in dogs, the L. interrogans serogroup Australis strains were more likely to cause severe kidney damage than Autumnalis and Hebdomadis, which may be more critical to the outcome of infected dogs than haemorrhage. Our results also suggest that the virulence mechanisms and target organs in dogs may differ by Leptospira genotype.

Though not reservoirs, dogs might transmit Leptospira in New Caledonia

Leptospira has been a major public health concern in New Caledonia for decades. However, few multidisciplinary studies addressing the zoonotic pattern of this disease were conducted so far. Here, pig, deer and dog samples were collected. Analyses were performed using molecular detection and genotyping. Serological analyses were also performed for dogs. Our results suggest that deer are a reservoir of L. borgpetersenii Hardjobovis and pigs a reservoir of L. interrogans Pomona. Interestingly, 4.4% of dogs were renal carriers of Leptospira. In dog populations, MAT results confirmed the circulation of the same Leptospira serogroups involved in human cases. Even if not reservoirs, dogs might be of significance in human contamination by making an epidemiological link between wild or feral reservoirs and humans. Dogs could bring pathogens back home, shedding Leptospira via their urine and in turn increasing the risk of human contamination. We propose to consider dog as a vector, particularly in rural areas where seroprevalence is significantly higher than urban areas. Our results highlight the importance of animal health in improving leptospirosis prevention in a One Health approach.

Distal renal tubular acidosis associated with concurrent leptospirosis in a dog

A 9 yr old spayed female boxer was presented for evaluation of vomiting, lethargy, anorexia, and weight loss. Initial laboratory evaluation revealed a hyperchloremic normal anion gap metabolic acidosis with alkaline urine that was consistent with a diagnosis of distal renal tubular acidosis (RTA). Targeted therapy was initiated with Na bicarbonate (HCO3) and potassium (K) gluconate. Leptospirosis was subsequently diagnosed with paired microagglutination testing (MAT), and doxycycline was added to the other treatments. Clinical signs resolved, and 6 mo after diagnosis, although the dog remained on alkali therapy (i.e., NaHCO3 and K gluconate) and a mild metabolic acidosis persisted, the dog remained otherwise healthy with a good quality of life. To the authors' knowledge, this is the first report to describe the concomitant association of those two disorders. Leptospirosis should be considered for any case of RTA in dogs.

A new multivalent (DHPPi/L4R) canine combination vaccine prevents infection, shedding and clinical signs following experimental challenge with four Leptospira serovars

Although effective vaccines have been developed against the common Leptospira serovars, they are still reported in clinical cases, while others are increasingly prevalent. The results from four challenge studies following vaccination of dogs with a new combination vaccine (DHPPi/L4R) containing inactivated L. serovars, L. canicola, L. icterohaemorrhagiae, L. bratislava and L. grippotyphosa conducted to satisfy the requirements of the European Pharmacopoeia monograph (01/2008:0447), are reported. Six week old dogs received two vaccinations, three weeks apart, and were challenged 25 days later with different isolates of the L. serovars. Clinical observations were recorded, and blood, urine and tissue samples were collected for analysis. Following challenge, non-vaccinated dogs demonstrated various clinical signs, while no vaccinated dogs were affected; significant differences in mean clinical scores were observed. Measurable antibody titres to each Leptospira antigen were seen in vaccinated dogs 21 days following the first vaccination, with further increases in antibody titres observed following challenge with the respective Leptospira strain. Non-vaccinated dogs remained seronegative until challenge. Leptospira were re-isolated from the blood, urine, kidney and liver of all non-vaccinated dogs following challenge. In contrast no vaccinated dogs had Leptospira re-isolated from the same tissues. Significant differences were seen in number of days with positive isolation (blood and urine) and in number of dogs with positive samples (kidney and liver). In conclusion, vaccination of dogs with the new vaccine induces protective immunity 25 days after second vaccination with protection against infection, renal infection and clinical signs following challenge.