Recent advances in canine leptospirosis: focus on vaccine development

Efficacy and safety of antibiotics for treatment of leptospirosis: a systematic review and network meta-analysis

BACKGROUND

Leptospirosis, an important zoonotic bacterial disease, commonly affects resource-poor populations and results in significant morbidity and mortality worldwide. The value of antibiotics in leptospirosis remains unclear, as evidenced by the conflicting opinions published.

METHODS

We conducted a search in the PubMed, Web of Science, and Cochrane Library databases for studies. These studies included clinical trials and retrospective studies that evaluated the efficacy or safety of antibiotics for leptospirosis treatment. The primary outcomes assessed were defervescence time, mortality rate, and hospital stays. Subgroup analyses were performed based on whether there were cases involving children and whether there were cases of severe jaundice. Safety was defined as the prevalence of adverse events associated with the use of antibiotics. p scores were utilized to rank the efficacy of the antibiotics.

RESULTS

There are included 9 randomized controlled trials (RCTs), 1 control trial (CT), and 3 retrospective studies (RS) involving 920 patients and 8 antibiotics. Six antibiotics resulted in significantly shorter defervescence times compared to the control, namely cefotaxime (MD, - 1.88; 95% CI =  - 2.60 to - 1.15), azithromycin (MD, - 1.74; 95% CI =  - 2.52 to - 0.95), doxycycline (MD, - 1.53; 95% CI =  - 2.05 to - 1.00), ceftriaxone (MD, - 1.22; 95% CI =  - 1.89 to - 0.55), penicillin (MD, - 1.22; 95% CI =  - 1.80 to - 0.64), and penicillin or ampicillin (MD, - 0.08; 95% CI =  - 1.01 to - 0.59). The antibiotics were not effective in reducing the mortality and hospital stays. Common adverse reactions to antibiotics included Jarisch-Herxheimer reaction, rash, headache, and digestive reactions (nausea, vomiting, diarrhea, abdominal pain, and others).

CONCLUSIONS

Findings recommend that leptospirosis patients be treated with antibiotics, which significantly reduced the leptospirosis defervescence time. Cephalosporins, doxycycline, and penicillin are suggested, and azithromycin may be a suitable alternative for drug-resistant cases.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42022354938.

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.

Activation of Canine, Mouse and Human TLR2 and TLR4 by Inactivated Leptospira Vaccine Strains

Canine Leptospira vaccines contain inactivated strains of pathogenic Leptospira, the causative agents of leptospirosis. For an effective response to vaccination, activation of the innate immune system via pattern recognition receptors such as TLRs is crucial. However, it is not known which TLRs are activated by Leptospira in dogs. To investigate the involvement of canine TLR2, TLR4, and TLR5 in the recognition of Leptospira, we stimulated canine moDC and reporter cells expressing canine TLR2 with either whole-inactivated bacteria or purified LPS of Leptospira strains, representing the serogroups generally used in canine leptospirosis vaccines. Using the endotoxin neutralizing reagent polymyxin B and TLR4 antagonist RS-LPS, we demonstrate that Leptospira LPS and canine TLR4 are involved in IL-1β production as well as in the uptake of inactivated Leptospira in canine moDC. Furthermore, polymyxin B only partially inhibited IL-1β production induced by inactivated Leptospira, suggesting that next to TLR4, also other TLRs may be involved. The observed activation of canine TLR2-expressing reporter cells by inactivated Leptospira strains indicates that TLR2 could be one of these TLRs. Next, we analyzed TLR2 and TLR4 activating capabilities by the same Leptospira strains using human and mouse TLR-expressing reporter cells. Inactivated Leptospira and leptospiral LPS activated not only mouse, but also human TLR4 and this activation was shown to be LPS dependent in both cases. Additionally, inactivated Leptospira activated mouse and human TLR2-expressing reporter cell lines. In our study, we could not identify significant species differences in the recognition of Leptospira by TLR2 and TLR4 between dog, human and mouse. Lastly, we show that these inactivated Leptospira strains are recognized by both mouse and human TLR5 reporter cells only after exposure to additional heat-treatment. Unfortunately, we were not able to confirm this in the canine system. Our data show that TLR2 and TLR4 are involved in the recognition of Leptospira strains used in the production of canine Leptospira vaccines. This study contributes to the understanding of Leptospira-induced innate immune responses in dogs, humans, and mice. Future studies are needed to further explore the role of canine TLR2, TLR4 and TLR5 in the induction of vaccine-mediated immunity against Leptospira.

Integrated Lateral Flow Electrochemical Strip for Leptospirosis Diagnosis

LipL32 is an outer membrane protein present only on pathogenic Leptospira species, which is the causative agent of leptospirosis. Leptospirosis symptoms are often misdiagnosed with other febrile illnesses as the clinical manifestations are non-specific. Therefore, an accurate diagnostic tool for leptospirosis is indeed critical for proper and prompt treatment. Typical diagnosis via serological assays is generally performed to assess the antibodies produced against Leptospira. However, their delayed antibody response and complicated procedure undoubtedly limit the practical utilization especially in a primary care setting. Here, we demonstrate for the first time an early-stage detection of LipL32 by an integrated lateral-flow immunoassay with an electrochemical readout (eLFIA). A ferrocene trace tag was monitored via differential pulse voltammetry operated on a smartphone-based device, thus allowing for on-field testing. A superior performance in terms of the lowest detectable limit of detection of 8.53 pg/mL and broad linear dynamic range (5 orders of magnitude) among other sensors available thus far was established. Additionally, the developed test strip provided a straightforward yet sensitive approach for diagnosis of leptospirosis using the collected human sera from patients, in which the results were comparable to the real-time polymerase chain reaction technique.

Next Generation Sequencing for Diagnosis of Leptospirosis Combined With Multiple Organ Failure: A Case Report and Literature Review

Introduction

Leptospirosis poses a major threat to human life. The disease spectrum ranges from a nearly undetectable presentation to severe multi-organ dysfunction and death. Leptospirosis is difficult to diagnose by traditional antibody and culture tests. We here present a case of multiple organ failure associated with leptospirosis.

Material and Methods

A 64-year-old woman presented with fatigue and arthralgia, which developed rapidly into multiple organ injuries, and she eventually died of cerebral hemorrhage. Serum antibody test and cultures of blood, sputum, urine, and feces samples were all negative. The patient was diagnosed with leptospirosis by the next-generation sequencing (NGS).

Conclusion

We conclude that leptospirosis is a neglected zoonosis caused by pathogenic Leptospira species. New techniques such as NGS are highlighted for early diagnosis. Surveillance for pathogens during diagnosis can provide guidance for clinical treatment and improves prognosis.

Practices and perceptions of British dog owners related to pet-associated zoonoses

OBJECTIVES

To investigate husbandry practices, animal health provision and perceptions of British dog owners related to the risk of exposure to zoonoses.

MATERIALS AND METHODS

Using an online survey, we collected data on pet and owner's demographics and husbandry practices, and perceptions of zoonotic risks. Univariable and multivariable logistic regression was performed to investigate if respondents' characteristics were associated with their practices and perceptions.

RESULTS

Overall, 335 dog owners participated in this survey. The odds of engaging in practices associated with a risk of zoonotic exposure and having misconceptions about zoonoses were greater in older than in younger respondents. The same association was observed in respondents without a veterinary background and with a lower level of education compared to those with a veterinary background and with a higher education, respectively. The odds of feeding raw meat-based diets (odds ratio: 4.0, 95% confidence interval: 2.0 to 7.9) were greater in respondents without a veterinary background than in those with a veterinary background. The odds of vaccinating their dogs (OR: 2.7, 1.1 to 6.3) were greater in respondents with an undergraduate qualification than in respondents with lower qualifications. The odds of following recommended dosing when administering both ectoparasitic (OR: 0.09, 0.02 to 0.4) and endoparasitic (OR: 0.08, 0.02 to 0.4) treatments were lower in respondents aged 60 and above than in younger respondents.

CLINICAL SIGNIFICANCE

This study highlights opportunities for targeted client communication and education by veterinarians to reduce risks of pet-associated zoonoses moving forward.

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.

Unusual case of pyogranulomatous hepatitis of suspected infectious etiology in a 3-year-old Labrador retriever dog

A 3-year-old spayed female Labrador retriever dog was presented with clinical signs of lethargy, vomiting, hyporexia, and increased respiratory effort. An exploratory laparotomy was conducted and a liver biopsy submitted for histopathologic evaluation revealed moderate multifocal coalescing pyogranulomatous hepatitis. Clinical signs, hematological parameters, and liver histopathology suggested an infectious etiology, such as leptospirosis, mycobacteriosis, or fungal infection. Polymerase chain reaction (PCR) and immunohistochemistry (IHC) for leptospirosis were negative. The infectious etiology was not identified, but leptospirosis may have played a role in the disease.

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.

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.