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

A New Licensed Quadrivalent Antileptospiral Canine Vaccine Prevents Mortality, Clinical Signs, Infection, Bacterial Excretion, Renal Carriage and Renal Lesions Caused by Leptospira Australis Experimental Challenge

BACKGROUND

L. Australis is one of the most prevalent Leptospira strains infecting dogs, leading, in natural conditions, to severe life-threatening cases.

OBJECTIVE

The objective was to evaluate the onset and duration of immunity (OOI and DOI) induced by a new licensed quadrivalent antileptospiral vaccine (EURICAN® L4) including four Leptospira components (Canicola, Icterohaemorrhagiae, Grippotyphosa and Australis) against L. Australis. To this end, a severe L. Australis challenge model was developed, using a canine strain recently isolated from the field.

MATERIAL AND METHODS

Seven- to ten-week-old puppies received two doses of the vaccine four weeks apart and were challenged with an L. Australis isolate two weeks (OOI) and 12 months (DOI) later. Mortality, clinical signs, leptospiremia, leptospiruria, renal carriage, and renal lesions were assessed after challenge.

RESULTS

The challenge induced multiple severe clinical signs in controls, leading to the death or euthanasia of 83% of puppies and 57% of adults. In controls, leptospiremia was detected in all dogs, leptospiruria in 67% of puppies and 86% of adults, kidneys tested positive for Leptospira in 83% of puppies and 71% of adults, and kidney lesions were observed in 100% of puppies and 86% of adults. In addition, thrombocytopenia associated with increased concentrations of urea, creatinine, and aspartate aminotransferase was recorded in controls displaying severe clinical signs. In both OOI and DOI studies, none of the vaccinates had clinical signs, no Leptospira was detected in blood, urine, and kidney samples, and no kidney lesions were observed in vaccinates. No significant changes in hematological and biochemical parameters in vaccinates were recorded.

CONCLUSION

EURICAN® L4 was shown to induce quick and long-lasting protection against a severe L. Australis infectious challenge, preventing mortality, clinical signs, infection, bacterial excretion, renal lesions, and renal carriage.

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.

Serological evidence of exposure of healthy dogs to Leptospira in Sydney, New South Wales, Australia

In 2017, highly fatal canine leptospirosis emerged in Sydney, Australia. Based on results of microscopic agglutination testing (MAT), serovar Copenhageni appeared to be the most common causative serovar. Prior to this, no clinical cases had been reported since 1976. In a serosurvey of healthy dogs in Australian shelters in 2004, 2.4% of 431 New South Wales dogs had serological evidence of exposure to Copenhageni, the most prevalent serovar. The aim of this study was to estimate the current prevalence of Leptospira exposure and associated serovars in healthy Sydney dogs, previously unvaccinated against Leptospira. Serum samples from 411 healthy dogs in leptospirosis hotspots and neighbouring suburbs were collected before vaccination. MAT for 23 serovars was performed at the WHO Leptospirosis Reference Laboratory in Queensland, Australia. The overall seroprevalence was 4.1% (17/411) with low titres (1/50-1/200) detected. Eleven dogs were from known leptospirosis hotspots. Eight dogs were known to hunt rodents. One dog had been in contact with a leptospirosis positive dog 1 year prior. Serovar Topaz was the most prevalent serovar (n = 5) followed by serovars Australis (n = 4), Copenhageni (n = 4), Djasiman (n = 2), Cynopteri (n = 1), Javanica (n = 1), Medanensis (n = 1), and Pomona (n = 1). In conclusion, serological evidence of exposure of dogs in Sydney to Leptospira is low, but apparently has increased since 2004. Positive titres to serovars not previously reported to cause disease in dogs could be due to low virulence of those serovars or cross-reactivity with other serovars.

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.

Spatial Owner-Dog Seroprevalence of Leptospira spp. Antibodies in Oceanic Islands and Costal Mainland of Southern Brazil

Leptospirosis has been described as a disease neglected worldwide. Affecting humans and animals, the disease is often related to poor environmental conditions such as lack of sanitation and presence of synanthropic rodents. Despite being considered as a One Health issue, no study has focused on comparing owner-dog seroprevalence between islands and seashore mainland. Accordingly, the present study assessed anti-Leptospira spp. antibodies by applying microscopic agglutination test (MAT) methods to Leptospira and assessing associated risk factors via univariate and multivariate logistic regression analysis of owners and their dogs in islands and seashore mainland of southern Brazil. No anti-Leptospira spp. Seropositivity was found in 330 owner serum samples, while dogs presented an overall seroprevalence of 5.9%. All seropositive dogs reacted to serogroups of Leptospira interrogans, including 66.7% of Pyrogenes, 44.4% Canicola, 22.2% Icterohaemorrhagiae, 16.7% Australis; six reacted to more than one serogroup. No association was found among seropositivity and epidemiological variables, except that neighborhood dogs were less likely to be seropositive. Although no seropositivity was observed in owners, seropositivity in dogs had the potential to indicate such species as being sentinels for environmental exposure and potential human risk of infection.

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.

Seroprevalence of pathogenic Leptospira spp. in domestic dogs from southern Chile and risk factors associated with different environments

Leptospirosis is a neglected and severe zoonotic bacterial disease that affects canine populations worldwide, and it is present in animals from different settings, such as urban and rural environments. Therefore, a cross-sectional study was conducted on owned domestic dogs from urban and rural origins in southern Chile. The study aimed: 1) to estimate the true prevalence of pathogenic Leptospira in dogs from urban and rural environments in southern Chile, 2) to determine the serovars circulating in an endemic area of Chile, 3) to assess potential risk factors associated with seropositivity in dogs from urban and rural environments. Blood samples from 706 canines were collected, and the serum was tested with Micro-Agglutination-Test (MAT), using a panel of 13 serovars. A Bayesian approach was applied to estimate True prevalence (TP). In addition, dog owners answered a questionnaire that had prompts regarding dog characteristics and potential risk factors. The effect of these factors on the risk of being infected was analysed using a logistic regression model. The TP for urban dogs was 9.4% and 9.1% for rural animals. However, seroprevalence was higher in dogs with different individual, lifestyle, and habitat characteristics regarding their origin. For example, in urban animals, those living in places with rodents roaming near houses and dogs with rodent hunting habits had decreased risk for the seropositivity in MAT. On the other hand, in rural dogs, those of a recognized breed, with contact with cattle and sheep, living with more than one cat at home and living in places close to natural water sources have more risk to seropositivity in MAT. The presence of anti-Leptospira antibodies is widespread in pet dogs in urban and rural environments in southern Chile, and individual, lifestyle and habitat characteristics of the animals, according to the origin, are associated with the seropositivity in MAT. Therefore, the adoption of preventive measures is urgent, in addition to increase the awareness either in public health institutions, practitioners and companion animals' owners, considering the zoonotic potential of Leptospira infection and the close contact between people and their pets.

Leptospira infection among human-close-contact animals in different geographical areas in Vietnam

Leptospirosis is a neglected disease in Vietnam. Only a few studies have evaluated the status of Leptospira infection in both humans and animals. To our knowledge, this is the first serological survey of Leptospira in both domestic and wild animals, which may act as reservoirs of this agent. This study aimed to evaluate the seroprevalence of Leptospira in animals that are in close contact with humans in different geographical areas in Vietnam. Sera were collected from 1205 individual animals of six species, including buffaloes, cattle, cats, dogs, swine, and rats. The microscopic agglutination test (MAT) against 25 serovars of Leptospira spp. has been employed to detect serovars of Leptospira among the studied population. Overall, 44.2% of buffaloes, 24.9% of cattle, 10.2% of swine, 32.9% of dogs, 12.2% of cats, and 16% of rats were seropositive. A total of 17 different serovars were detected, of which serovars Hebdomadis and Canicola circulated in all the studied animal species. Variability of the predominant serovars circulating in animal species and in different geographical areas of Vietnam has been noted. We conclude that this study showed a high prevalence of Leptospira circulating in animals that are in close contact with humans, raising an alert of the important sources of pathogenic leptospires transmission to humans in Vietnam. These findings prove an imperative need for effective measures for disease prevention.

High seroprevalence of anti-Leptospira spp. antibodies in domestic and wild mammals from a mixed use rescue center in Ecuador: Lessons for "One Health" based conservation strategies

Leptospirosis is a zoonotic disease of worldwide distribution that affects humans, domestic and wild animals. This study evaluates the frequency of anti- Leptospira spp. antibodies in companion, livestock and wild mammals from a mixed use rescue center on Guayaquil, the main city of Ecuador. Sera were collected from 23 domestic and 6 wild mammals. All animals tested were seropositive for Leptospira spp. using Microscopic Agglutination Test (MAT), most of them for multiple serovars. Leptospira interrogans serovars Canicola, Hardjo and Icterohaemorrhagiae were the most frequent ones. We conclude that the presence of domestic animals at this mixed use rescue center may cause the exposure of wild animals, considering the high frequency of Leptospira spp. seropositivity already reported for livestock and companion animals in Ecuador. This is the first serological survey for leptospirosis including wild animals rescued from illegal traffic in Ecuador and point out the urgent need of exclusive rescue and conservation units for wild species and the potential role as Leptospira spp. reservoir for wild mammals.

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.