Agglutinating antibodies against pathogenic Leptospira in healthy dogs and horses indicate common exposure and regular occurrence of subclinical infections

Leptospirosis in horses: Sentinels for a neglected zoonosis? A systematic review

Background and Aim

Leptospirosis is considered a neglected tropical zoonosis in low-income countries due to surveillance system limitations and non-specificity of symptoms. Humans become infected through direct contact with carrier animals or indirectly through Leptospira-contaminated environments. Conventionally, equines have been considered an uncommon source of leptospirosis, but recent publications in Latin America suggest that their role in the maintenance and dispersion of the bacteria could be more relevant than expected, as horses are susceptible to a wide variety of zoonotic Leptospira spp. from domestic and wild animals with which they share the environment. A systematic review of the published literature was conducted to compile the available information on Leptospira spp. in Ecuador, with a special focus on equine leptospirosis, to better understand the epidemiology of the bacterium and identify possible knowledge gaps.

Materials and Methods

A systematic review of the published literature was conducted in PubMed, SciELO and Web of Science databases to compile the available information on Leptospira spp. in Ecuador, with a special focus on equine leptospirosis, to better understand the epidemiology of the bacterium. We used a combination of the terms (Leptospira OR Leptospirosis) AND Ecuador, without restrictions on language or publication date.

Results

Our literature review reveals that published scientific information is very scarce. Eighteen full-text original scientific articles related to Leptospira or leptospirosis cases in Ecuador were included in the systematic review. Most of the studies reported data obtained from one of the four regions (Coast), and specifically from only one of the 24 Provinces of Ecuador (Manabí), which evidence a large information bias at the geographical level. Furthermore, only the studies focused on humans included clinical signs of leptospirosis and there is only one study that analyzes the presence of Leptospira spp. in water or soil as a risk factor for pathogen transmission. Finally, only one study investigated Leptospira in horses.

Conclusion

Since sentinel species can provide useful data on infectious diseases when epidemiologic al information is lacking, and horses could be considered excellent sentinel species to reveal circulating serovars, we propose developing a nationwide surveillance system using horses. This cost-effective epidemiological survey method provides a baseline for implementing specific prevention and control programs in Ecuador and neighboring developing countries.

Spatio-temporal distribution and agroecological factors associated with canine leptospirosis in Great Britain

Leptospirosis is an important global zoonotic disease that affects a wide range of mammalian species. Canine leptospirosis outbreaks have been reported after metereological events such as flooding (eg. in Brazil and the United States of America) suggesting an environmental association, but there has been no such study in Great Britain (GB). The distribution of cases across GB is also unreported. Objectives of this study were to: (1) assess the spatio-temporal variation of leptospirosis test submissions (2) explore associations between agroecological risk factors and distribution of different canine leptospirosis serogroups in GB, and (3) generate probability of presence maps for the different serogroups. Data analysed comprised laboratory submissions (n = 3986) to IDEXX laboratories between 1st January 2009 and 31st December 2018 for PCR or MAT leptospirosis testing. Spatial and seasonal scan statistics were used to investigate spatial and temporal clustering of positive tests, logistic regression was used to identify significant agroecological risk factors for positive tests, and the Maxent algorithm was used to model the environmental niche of four serogroups. There was an increased risk of a positive test result in the West Midlands of England (relative risk = 2.16) and between October and January (relative risk = 1.54). Logistic regression identified season and region to be significantly associated with a positive diagnosis,with higher odds of a positive test in Autumn (OR = 1.86 95 %CI 1.29-2.69) and Winter (OR = 1.51, 95 %CI 1.02-2.23) and in the East (OR = 2.20, 95 %CI = 1.31-3.71) and West Midlands (OR = 2.32, 95 %CI 1.45-3.71). The increased test-positive proportion in Autumn together with the increased odds of a positive diagnosis in Autumn suggests there may be a seasonal pattern to the canine leptospirosis in GB. The most important variable associated with higher leptospirosis presence in all ecological niche models was higher average annual temperature. The importance and retention of other variables differed between serogroups. Overall, a higher probability of leptospirosis presence was predicted in southern England and a low probability in Scotland and northern England. Although leptospirosis vaccine usage provides protection against the majority of serogroups identified here, one is not represented in the currently licensed vaccine formulations and therefore leptospirosis should remain a differential diagnosis in vaccinated dogs demonstrating consistent clinical signs of the disease.

Clinical findings in dogs diagnosed with leptospirosis in England

BACKGROUND

Leptospirosis is a zoonotic disease of worldwide importance. This study describes the clinical findings and outcome of dogs diagnosed with leptospirosis in England.

METHODS

Retrospective review of medical records of dogs diagnosed with leptospirosis from a single referral hospital located in Eastern England.

RESULTS

Thirty-eight dogs met the inclusion criteria. Clinical signs included inappetence (76%), vomiting (68%), lethargy (58%), polydipsia and polyuria (18%) and abdominal pain (16%). Disease manifestations included hepatic and renal involvement (47%), hepatic only (37%), renal only (16%); no dogs were found to have respiratory involvement. Clinicopathological findings at presentation included anaemia (42%), thrombocytopenia (43%), increased alanine transaminase activity (ALT) (66%), hyperbilirubinemia (55%), azotaemia (68%), hypoalbuminaemia (49%) and glucosuria (32%). Seven serovars of Leptospira interrogans or Leptospira kirschneri were detected; the most prevalent was Copenhageni (48%). Seventy-one percent survived to discharge. Dogs in the non-surviving group had a higher creatinine at presentation compared to survivors (p = 0.02).

CONCLUSIONS

Copenhageni was the most prevalent serovar in this population. This supports the use of a vaccine including this serovar, in this region. Renal involvement was associated with reduced survival to discharge. A hepatic only form was common in this population, and leptospirosis should be included as a differential diagnosis for dogs suffering with a hepatopathy. No cases had significant pulmonary involvement, but ongoing clinical vigilance for this disease manifestation is essential.

Equine leptospirosis: Experimental challenge of Leptospira interrogans serovar Bratislava fails to establish infection in naïve horses

BACKGROUND

Little information is available about experimental inoculation of leptospirosis in horses and the pathogenicity of Leptospira interrogans serovar Bratislava in this host.

OBJECTIVES

To determine the serological, clinical, pathological and haematological responses of horses to L. interrogans serovar Bratislava strain PigK151.

STUDY DESIGN

Randomised controlled in vivo experiment.

METHODS

Ten seronegative female foals were divided into 2 groups, control (n = 4) and challenged (n = 6). The challenged group received 1 × 10⁹ leptospires divided equally between topical ocular and intraperitoneal injections. Blood and urine samples were analysed. The temperature was recorded daily for the first 9 days, then weekly. Sera were tested by microscopic agglutination test (MAT). Automated complete blood count, differential and chemistry panel were performed. Histopathological analysis was performed on sections of liver, kidney, urinary bladder, uterine body and pineal gland. Sample culturing was performed from blood, urine, liver, kidney, reproductive tract and vitreous humour.

RESULTS

No pyrexia was noted. PCR and culture were negative from all samples. Differences between groups were found in CBC, differential counts and serum biochemistry panel (or profile), suggesting that leptospiral challenge triggered an inflammatory response. No evidence of leptospirosis was found from histopathological analysis. All challenged foals developed a humoral response. The MAT allowed the confirmation of the infecting serovar at a later stage, but it also revealed cross-reactive results that were further explained by genomic analysis.

MAIN LIMITATIONS

This experimental challenge had two main limitations: (a) the results might have varied if another strain from the same serovar had been used and (b) the use of another route of infection and a higher bacterial dose might have achieved colonisation.

CONCLUSIONS

Based on these findings, it may suggest that L. interrogans serovar Bratislava is neither pathogenic nor host-adapted serovar for horses, although these results might have varied if another strain from the same serovar had been used instead.

Evaluation of new leptospiral antigens for the diagnosis of equine leptospirosis: An approach using pan-genomic analysis, reverse vaccinology and antigenic selection

BACKGROUND

The current gold standard diagnostic test for leptospirosis is the microscopic agglutination test (MAT), which has many drawbacks; therefore, the development of a better and easier serological test for leptospirosis is needed.

OBJECTIVES

To apply reverse vaccinology (RV) and antigenic selection on the assortment of leptospiral targets and evaluate their potential for use as reagents for the diagnosis of equine leptospirosis.

STUDY DESIGN

Cross-sectional study.

METHODS

The antigenic selection parameters were: proteins with antigenicity score ≥0.5 (VaxiJen), at least one B cell epitope and size between 10 and 275 KDa. New leptospiral proteins were cloned, expressed and serologically screened against equine sera (n = 128) on a single analysis and comparative combinations. Sensitivity (Se) and specificity (Sp), accuracy, positive predictive value (PPV) and negative predictive value (NPV) were calculated. A BLAST with nucleotide and protein sequences was used to identify the serovar or species specificity.

MAIN LIMITATIONS

This cross-sectional analysis had three main limitations: (a) The equine sera used in these tests were limited to sera submitted to the Animal Health Diagnosis Center and were only tested against seven serovars; (b) MAT results were considered being 'perfect', and the highest titre presented was considered being the infecting serovar, which may not hold true; (c) The strains used to represent the serovars and the limited number of different serovars and species included in the genetic analysis, which leads to the possibility that these proteins might be present in different species or serovars that perhaps would be seroprevalent in another geographic region.

CONCLUSIONS

The new leptospiral antigens described in this research could increase the sensitivity and specificity of ELISA for detection of Leptospira exposure and the detection of leptospirosis in horses along with support from other clinical signs. Some of these new antigens might be used to improve the detection of infecting serovar.

Leptospira spp. in horses in southern Brazil: Seroprevalence, infection risk factors, and influence on reproduction

Leptospirosis in horses is often associated with reproductive disorders. In the southern states of Brazil, horses are used for various jobs and cultural practices; nevertheless, serological surveillance for Leptospira is rare. Therefore, the objective of this study was to determine the seroprevalence of Leptospira spp. in horses in southern Brazil, as well as to identify the risk factors for infection and its impacts on reproduction. We performed microscopic agglutination tests for 12 serovars that corresponding 9 serogroup (Sejroe, Icterohaemorrhagiae, Australis, Pyrogenes, Pomona, Canicola, Grippotyphosa, Tarassovi and Ballum) in 595 samples from 60 herds. A brief history was obtained to analyze risk factors for reproductive disorders. A total of 45.9% of the tested horses were seropositive, of which the most frequent serogroups were Icterohaemorrhagiae (Icterohaemorrhagiae and Copenhageni serovars) and Ballum (Ballum serovar). Simple infections were found in 45.4% of seropositive animals, while mixed infections occurred in 54.6% of horses. There was a correlation between seropositivity and age and sex, that is, seropositivity was more frequent in animals over 6 years old and in females. There was no correlation between seropositivity and reproductive disorders. We conclude that there is a high seroprevalence of Leptospira spp. in southern Brazil with predominance of Icterohaemorrhagiae serogroup, mainly in older animals. Location, breeds, contact with dogs or other domestic animals are not risk factors, whereas gender is a risk factor. Reproductive disorders are not due to leptospirosis in the study region.

Leptospira sp. vertical transmission in ewes maintained in semiarid conditions

Leptospirosis is a globally distributed disease associated with reproductive failures in livestock; however, its pathogenesis has not been fully elucidated. Results from the present study indicate there is a presence of Leptospira sp. in organs and fluids of fetuses from ewes slaughtered in the semiarid region of Brazil. Twenty-nine fetuses from 23 ewes determined to be Leptospira sp.-positive using PCR were sampled (14 and 15 in dry and rainy seasons, respectively). Fetal samples of blood, central nervous system (CNS), lung, liver, spleen, stomach contents, peritoneal fluid, kidney, bladder, urine and reproductive system were collected. Diagnostic methods included the microscopic agglutination test (MAT), polymerase chain reaction (PCR) and bacterial isolation. Of the 29 fetuses, 24 (82.8 %) had at least one Leptospira sp.-positive organ or fluid, as determined using PCR, and of a total of 209 samples, 62 (29.7 %) contained leptospiral DNA. Of the 99 samples collected during the dry season, 42 (42.4 %) were positive, and of 110 samples collected during the rainy season, 20 (18.2 %) were positive (P = 0.0001). There was deoxyribonucleic acid (DNA) sequencing of three samples of kidney, CNS and liver, and in all of these, there was 99.3 % similarity with Leptospira interrogans. Leptospires were present in cultures of pooled samples from fetuses with deformities. Results indicate there is vertical (maternal-to-fetus) transmission which would represent an alternative transmission route for the spread of Leptospira sp. in ewes, suggesting molecular detection is essential in the investigation of leptospirosis in fetuses to identify animals that have been infected with this bacterium.

Detection of Coxiella burnetii and equine herpesvirus 1, but not Leptospira spp. or Toxoplasma gondii, in cases of equine abortion in Australia - a 25 year retrospective study

Equine abortion is a cause of severe economic loss to the equine industry. Equine herpesvirus 1 is considered a primary cause of infectious abortion in horses, however other infectious agents can also cause abortion. Abortions due to zoonotic pathogens have implications for both human and animal health. We determined the prevalence of Coxiella burnetii, Leptospira spp. and Toxoplasma gondii in 600 aborted equine foetal tissues that were submitted to our diagnostic laboratories at the University of Melbourne from 1994 to 2019. Using qPCR we found that the prevalence of C. burnetii was 4%. The highest annual incidence of C. burnetii was observed between 1997-2003 and 2016-2018. The prevalence of C. burnetii in Victoria and New South Wales was 3% and 6% respectively. All the samples tested negative for Leptospira spp. and Toxoplasma gondii DNA. Equine herpesvirus 1 DNA was detected at a prevalence of 3%. This study has provided evidence for the presence of C. burnetii in equine aborted foetal tissues in Australia, but the role of C. burnetii as potential cause of abortion in Australia requires further investigation. C. burnetii is a zoonotic disease agent that causes the disease 'Q fever' in humans. We recommend that appropriate protective measures should be considered when handling material associated with equine abortions to reduce the risk of becoming infected with C. burnetii.

Crested Porcupine (Hystrix cristata L.): A New Potential Host for Pathogenic Leptospira Among Semi-Fossorial Mammals

Wildlife plays a pivot role in the epidemiology of leptospirosis and rodents have a reservoir function for several Leptospira serogroups. The crested porcupine is the largest rodent of the Italian fauna and shares the same environment with red foxes, badgers, coypus and wild boars that are known to be infected by Leptospira. Between 2018 and 2019 the seroprevalence of Leptospira in crested porcupine was investigated for the first time. Overall 7 out of 14 sera (50 %) were found positive to Leptospira. Icterohaemorrhagiae resulted as the most detected serogroup (57 %) followed by Pomona, Australis and Sejroe. The highest titer (1:1600) was detected for the serogroup Australis. These results indicate that porcupines could be infected by several serogroup of Leptospira and the role of reservoir or accidental host need to be addressed. Further investigations are necessary in order to clarify the leptospirosis - epidemiology - wildlife framework in light of its potential zoonotic source.

Leptospira Seroprevalence in Bardigiano Horses in Northern Italy

A cross-sectional study was carried out in Bardigiano horses in the Province of Parma, Northern Italy, to assess the seroprevalence of Leptospira spp. and to investigate risk factors associated with the infection. A representative sample of 134 horses from 43 farms was selected by stratified systematic randomization. Blood sera were examined by MAT for the presence of antibodies against seven Leptospira serovars. Ninety animals (67.2%; 95% Confidence Interval 63.2-71.1) and 41 farms (95.3%; 95% CI 92.2-98.5%) were found positive to at least one of the serovars. The most frequently detected reactions were against serovar Bratislava (41.8%), followed by Canicola (36.6%), Tarassovi (28.4%), Copenhageni (17.9%), Pomona (10.4%) and Hardjo (2.2%). None of the sera reacted against serovar Grippothyphosa. Forty-eight horses (53.3% of the seropositives) were positive for more than one serovar and 21 (15.7% of the seropositives) had serum titres ≥ 1000. Bratislava was the serovar providing the highest antibody titres. Prevalence was significantly higher between adult horses and in farms lacking rodent control (p = 0.006 and p = 0.025, respectively). No significant gender or housing-related difference in seroprevalence was found. The anamnestic data suggest that the infection in Bardigiano horses is subclinical in most of the cases. The high seroprevalence indicates that Bardigiano horses living in the investigated area are at high risk of exposure and infection by Leptospira spp.

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.

Serological and molecular detection of Leptospira spp in dogs

INTRODUCTION

This study aimed to detect anti-Leptospira spp antibodies and Leptospira DNA in domestic dogs.

METHODS

Blood and urine from 106 dogs were evaluated by microscopic agglutination test (MAT) and polymerase chain reaction (PCR), respectively.

RESULTS

Six (5.7%) and one (1%) animals were positive by MAT and PCR, respectively.

CONCLUSIONS

These results show a low prevalence of infection by Leptospira spp. The absence of positive results for the Icterohaemorrhagiae serogroup indicates the small relevance of these dogs as sources of human leptospirosis.

New host species for Leptospira borgpetersenii and Leptospira interrogans serovar Copenhageni

We investigated the presence of infection by Leptospira spp. in an assembly of Sigmodontinae rodents from the Paraná Delta, Argentina. Rodents were captured in places with natural grassland, implanted forest, with and without raising cattle and in sites prone and not prone to flooding. The DNA was amplified from cultured isolates by PCR and Leptospira spp. strains were genotyped using Multiple - Locus Variable Number Tandem Repeat Analysis (MLVA). We isolated Leptospira interrogans serovar Copenhageni from Oligoryzomys nigripes, Leptospira borgpetersenii from Scapteromys aquaticus and Leptospira interrogans serovar Icterohaemorrhagiae from Akodon azarae. The zoonotic Leptospira isolated and genotyped from O. nigripes and S. aquaticus are the first reports from these species. The geographic range of these rodent species include, in addition to Argentina, the countries of Paraguay, Uruguay and Brazil, suggesting that these rodents might be involved in the transmission of spirochetes in other regions. Human and animal health care professionals should be alert to the potential occurrence of leptospirosis in areas where these rodent species are present.

A systematic review of leptospirosis on dogs, pigs, and horses in Latin America

Leptospirosis is a worldwide zoonosis which can affect many species. Control programs need accurate diagnosis to be successful, and currently, diagnosis relies on serology. It presents three main issues: the sampling, the antigen panel, and the cutoff point. Herein, we propose a systematic review on leptospirosis among dogs, pigs, and horses in Latin America in order to improve the understanding of the seroepidemiology of leptospirosis in these species in the region as well as the temporal development of the research on this topic and, consequently, improve the chances of success on control programs. Internet databases were consulted over 2015. Inclusion criteria included serosurvey using MAT; a relevant number of animals; the presence in the antigen panel of at least one representative of serogroups Icterohaemorrhagiae and Canicola for dogs, Icterohaemorrhagiae, Australis, and Pomona for pigs, and Icterohaemorrhagiae and Australis for horses; and a cutoff point of ≥100. Overall, 240 papers were studied, of which 87 referred to dogs, 66 to pigs, 39 to horses, and 48 to more than one of the studied species. In relation to those that met all the inclusion criteria, it was 45 (66.2%) in dogs, 23 (41.8%) in pigs, and 23 (63.9%) in horses. Leptospirosis is widespread in Latin America. Predominant serogroups are Canicola to dogs and Icterohaemorrhagiae to pigs and horses. Therefore, research on animal leptospirosis should be encouraged in Latin America, in order to reach a greater standardization in studies and then achieve better results on control programs.

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.

Serological and molecular survey of Leptospira spp. among cart horses from an endemic area of human leptospirosis in Curitiba, southern Brazil

Introduction: Cart horses are a re-emerging population employed to carry recyclable material in cities.

Methods: Sixty-two horses were sampled in an endemic area of human leptospirosis. The microscopic agglutination test (MAT) and real-time polymerase chain reaction (qPCR) were performed.

Results: A seropositivity of 75.8% with serovar Icterohaemorrhagiae in 80.8% of the horses was observed. Blood and urine were qPCR negative. MAT showed positive correlations with rainfall (p = 0.02) and flooding (p = 0.03).

Conclusions: Although horses may be constantly exposed to Leptospira spp. in the environment mostly because of rainfall and flooding, no leptospiremia or leptospiruria were observed in this study.

The role of leptospirosis in reproductive disorders in horses

Leptospirosis is a zoonotic disease of global importance and has a worldwide distribution. This infection displays clear seasonal nature in some regions of the tropics, where the rainy season is marked by high temperatures. Household and wild animals carry leptospires and contribute to their dissemination in nature. Transmission mainly occurs by contact with water contaminated with the urine of infected animals, and consequently, it is quite widespread especially in times of rain, since many areas are subject to flooding and have poor sanitation. Serological tests demonstrate that Leptospira sp. infection in horses occurs worldwide and that the predominant serovar may vary depending on the region or infection sources. Besides systemic and ocular manifestations, leptospirosis in horses has been recognized as an important disease of the reproductive system, since it leads to the birth of weak foals, stillbirths or neonatal mortality, and mainly to abortion, usually after the sixth month of pregnancy. In this context, this review aims to gather and discuss information about the role of leptospirosis in reproductive disorders in horses.

Human leptospirosis trends, the Netherlands, 1925-2008

To increase knowledge of leptospirosis in the Netherlands and identify changing trends of this disease over time, we analyzed historical passive surveillance reports for an 84-year period (1925-2008). We found that 2,553 mainly severe leptospirosis cases were diagnosed (average annual incidence rate 0.25 cases/100,000 population). The overall case-fatality rate for patients with reported leptospirosis was 6.5% but decreased over the period, probably because of improved treatment. Ninety percent of reported leptospirosis cases were in male patients. Most autochthonous leptospirosis infections were associated with recreational exposures, but 15.5% of the cases were attributed to accidents that resulted in injury and to concomitant water contact. Since the end of the 1950s, the proportion of imported infections gradually increased, reaching 53.1% of the total during 2005-2008. Most (80.1%) imported infections were associated with sporting and adventurous vacation activities.

A novel tetravalent Leptospira bacterin protects against infection and shedding following challenge in dogs

Recent evidence based on the current epidemiological situation suggests that vaccines against canine leptospirosis in Europe should be directed against infection with Leptospira interrogans (sensu lato) serogroups Canicola, Icterohaemorrhagiae, Grippotyphosa and Australis. In the eight studies presented here, dogs were vaccinated with Nobivac L4 (MSD Animal Health), a new tetravalent inactivated vaccine containing antigen from four strains representing these four serogroups. The dogs were then challenged, together with unvaccinated control dogs, using heterologous strains from the same four serogroups. In four of the studies, pups without agglutinating antibodies against the four serogroups were vaccinated with Nobivac L4 vaccine. In a further four studies, Nobivac L4 vaccine was given 48 hours after administration of antiserum from vaccinated dogs designed to mimic the serological status of pups with maternally derived antibodies against these serogroups. In all eight studies, vaccine efficacy was assessed in terms of antibody response, clinical signs, fever, thrombocyte count, frequency of positive isolation of challenge organisms from blood, urine and kidney and frequency of interstitial nephritis. The results demonstrate that Nobivac L4 vaccine induces sterile immunity against leptospiraemia and renal infection with strains of serogroups Canicola, Icterohaemorrhagiae and Grippotyphosa, and induces sterile immunity against leptospiraemia with a strain of serogroup Australis. Since sterile immunity was achieved in pups pretreated with antiserum as well, it can be concluded that this vaccine is also likely to be efficacious in the face of maternally derived antibodies in pups from the age of six weeks.

Emergence of novel Leptospira serovars: a need for adjusting vaccination policies for dogs?

A total of 855 sera from dogs in Greece were tested for antibodies to strains belonging to the Pomona, Grippotyphosa and Australis serogroups of Leptospira to assess exposure levels to these serogroups, possible associations with clinical disease and to evaluate whether these findings support the inclusion of additional serovars in dog vaccines. Antibodies were detected in 110 (12·9%) dogs. The highest seroprevalence (4·9%) was to the proposed novel serovar Altodouro belonging to the Pomona serogroup. This serovar also showed a statistically significant association with clinical disease. Serovar Bratislava antibodies were found in 3·4% of sera. Consideration should be given to the inclusion of serovars belonging to the Pomona serogroup and serovar Bratislava in future dog vaccines for the Greek market.

The role of horses in the transmission of leptospirosis in an urban tropical area

The objective of this study was to demonstrate the presence of leptospires in equine urine, as evidence for a potential role of horses in transmission of this organism. Thoroughbred horses (aged 2–5 years, n = 276) from Rio de Janeiro, Brazil, were studied. After a severe storm, the premises of the animals remained flooded for 72 h. Blood samples for serology were collected on days 20 and 35 (day of storm = day 0). On day 20, 132 (47·8%) horses were seroreactive (titre ⩾200) and, of these, 23 (31·0%) had increased antibody titres on day 35. Furthermore, 34 urine samples (for PCR and culture) were collected from seroreactive horses on day 35. Copenhageni was the most frequent serovar (88·8% of reactive titres). Although none of the urine samples were culture positive, 12 (35·2%) were PCR positive. This is apparently the first report of evidence of leptospires in urban horses. Furthermore, we suggest that these animals can play a role in the transmission of leptospirosis in urban areas.