Key Takeaways from the Zoomies Online Vet Conference Lecture by Dr. Jane Sykes
1. Complex Taxonomy and Multiple Transmission Routes
a. Serovar Diversity and Classification
- Over 200 pathogenic Leptospira serovars exist, grouped into antigenic serogroups.
- Modern typing increasingly relies on multi-locus sequence typing.
b. Reservoir Hosts and Spill-over
- Maintenance hosts (rodents, livestock, wildlife) shed Leptospires chronically in urine.
- Incidental hosts (dogs, humans) develop acute disease and shorter shedding periods.
c. Direct and Indirect Transmission
- Direct contact: infectious urine, aborted foetuses, or infected tissues/organs.
- Indirect contact: contaminated water, soil, or bedding.
- Organisms survive best in moist, neutral-to-alkaline environments at 0–25 °C, but can survive freezing.
d. Seasonal and Geographic Factors
- Rainfall, flooding, and warm climates increase environmental load.
- Urban outbreaks are linked to poor sanitation and rodent infestations in backyard settings.
e. Occupational and Zoonotic Risk
- Veterinary personnel, shelter workers, and pet owners face increased risk.
- Simple barrier precautions (gloves and eye protection) reduce transmission.
f. One Health Implications
- Surveillance in animal, human, and environmental samples is essential for early detection and control of emerging serovars.
2. Multisystemic Pathogenesis and Varied Clinical Presentations
a. Initial Septicaemic Phase
- Leptospires invade via mucous membranes or skin abrasions
- Multiplication and dissemination to target organs occurs in blood
b. Renal Involvement
- Tubulointerstitial nephritis
- Symptoms and pathology include polyuria, polydipsia, azotaemia, isosthenuria, electrolyte disturbances
c. Hepatic Involvement
- Cholestatic hepatopathy characterised by icterus, elevated ALP ≫ ALT, hyperbilirubinaemia, hypoalbuminaemia
d. Pulmonary Manifestations
- Leptospiral pulmonary haemorrhage syndrome (LPHS)
- Symptoms and pathology include tachypnoea, dyspnoea, haemoptysis, diffuse alveolar/interstitial patterns on thoracic imaging
e. Haemorrhagic and Vasculitis Signs
- Petechiae, ecchymoses, mucosal bleeding, thrombocytopenia, coagulopathy
f. Other Organ Systems
- Pancreas: acute pancreatitis, abdominal pain, elevated lipase
- Eyes: anterior uveitis, conjunctivitis, retinal haemorrhages
- Heart and Muscle: myocarditis with arrhythmias, myositis with elevated CK
3. Diagnostic Strategy: Combining Complementary Tests
a. Serology (MAT)
- Paired acute and convalescent titres demonstrating a four-fold rise remain the reference standard – but single high acute titres have a 50% sensitivity for disease detection. MAT titres may also be elevated following vaccination, resulting in false-positive disease diagnosis.
b. Rapid In-Clinic Assays
- IgM/IgG lateral-flow tests (e.g. SNAP Lepto, WITNESS Lepto) yield qualitative results within minutes.
- False negatives can occur – so a negative test in a patient in early disease warrants repeat testing.
c. Molecular Detection (PCR)
- PCR on blood (first 7–10 days) and urine (from ~10 days onward) improves sensitivity
- Beware false negatives after antimicrobials or intermittent shedding.
d. Culture and Dark field Microscopy
- Culture is definitive for serovar identification but is slow and technically demanding.
- Dark field microscopy is no longer recommended as a sole diagnostic modality.
e. Interpretation in Context
- Integrate test results with clinical suspicion, exposure history and local serovar prevalence
- Repeat or combine diagnostic tests when initial results are inconclusive.
f. Advanced Imaging and Biomarkers
- Thoracic radiographs, abdominal ultrasound and biomarkers (e.g. SDMA, troponin) guide assessment of organ-specific damage.
4. Clinical Disease Syndromes
Leptospirosis in dogs presents along a continuum from non-specific febrile illness to distinct organ-system syndromes. Key clinical syndromes include:
a. Febrile, Non-Specific Phase
- Acute onset of fever, lethargy, anorexia, vomiting, polyuria and polydipsia
- Usually occurs before biochemical evidence of organ dysfunction is evident
b. Renal Syndrome (Acute Tubulointerstitial Nephritis)
- Clinical Signs: vomiting, dehydration, abdominal pain, polyuria/oliguria progressing to anuria
- Diagnosis: azotaemia, isosthenuria, electrolyte disturbances, casts on urinalysis.
c. Cholestatic Hepatopathy
- Clinical Signs: icterus, vomiting, lethargy
- Diagnosis: elevated ALP > ALT (consistent with cholestasis), hyperbilirubinaemia, hypoalbuminaemia.
d. Leptospiral Pulmonary Haemorrhage Syndrome (LPHS)
- Clinical Signs: tachypnoea, cough, haemoptysis, respiratory distress
- Diagnosis: diffuse or patchy alveolar/interstitial patterns on thoracic imaging, hypoxaemia.
e. Haemorrhagic and Vasculitis Syndromes
- Clinical Signs: petechiae, ecchymoses, epistaxis, melena, coagulopathy
- Diagnosis: thrombocytopenia, hyperfibrinogenaemia, anaemia, prolonged coagulation times
f. Miscellaneous Manifestations
- Ocular: uveitis, conjunctivitis, retinal haemorrhage
- Pancreatitis: abdominal pain, elevated canine pancreatic-specific lipase
- Myocarditis: arrhythmias, elevated troponin
- Enteritis/Myositis: diarrhoea, reluctance to move, increased CK activity
5. Prompt Antimicrobial Therapy and Organ Support
a. Early Empirical Treatment
- Begin penicillin-class antibiotics (e.g. ampicillin 20 mg/kg IV q6–8 h) immediately to clear leptospiraemia
- Do not await confirmatory test results before commencement of treatment
b. Carrier Clearance
- Penicillin therapy should be followed with doxycycline (5 mg/kg PO q12 h for 14 days) to reduce urinary tract shedding.
c. Fluid and Electrolyte Management
- Isotonic crystalloid therapy tailored to hydration status and cardiovascular stability
- Avoid fluid overload, especially in patients with respiratory symptoms associated with Leptospira infection.
d. Supportive Therapies
- Antiemetics, gastric protectants
- Nutritional support
e. Renal Replacement Therapy
- Intermittent haemodialysis or continuous renal replacement therapy (CRRT) indicated in severe AKI unresponsive to medical management.
f. Advanced Critical Care
- Oxygen supplementation or mechanical ventilation for LPHS
- Blood products or plasma exchange for refractory coagulopathies.
6. Prevention: Vaccination and Workplace Precautions
a. Vaccination Protocols
- Annual quadrivalent bacterin (Canicola, Icterohaemorrhagiae, Pomona, Grippotyphosa/Australis) from ≥ 12 weeks of age
- Vaccination boosters confer ≥ 12 months of immunity.
b. Limitations and Serovar Coverage
- Vaccines do not cover all circulating serovars
- Regional surveillance should inform vaccine selection where available.
c. Adverse Reactions
- Low risk of transient lethargy, fever or injection-site swelling following vaccination
- Severe reactions are rare.
d. Environmental Control
- Rodent control, drainage of stagnant water
- Regular disinfection of kennels and equipment
e. Occupational Safety
- Standard barrier precautions in clinics and shelters (PPE)
- Quarantine and signage for infected or shedding dogs.
f. Community and One Health
- Coordinated reporting of animal and human cases to public health authorities
- Owner education on personal hygiene and pet-environment management
References:
- Sykes JE, Francey T, Schuller S, Stoddard RA, Cowgill LD, Moore GE. Updated ACVIM consensus statement on leptospirosis in dogs. Journal of Veterinary Internal Medicine. 2023 Nov;37(6):1966-82.
- Reagan KL, Deng S, Sheng J, Sebastian J, Wang Z, Huebner SN, Wenke LA, Michalak SR, Strohmer T, Sykes JE. Use of machine-learning algorithms to aid in the early detection of leptospirosis in dogs. Journal of Veterinary Diagnostic Investigation. 2022 Jul;34(4):612-21.
- Taylor C, O’Neill DG, Catchpole B, Brodbelt DC. Incidence and demographic risk factors for leptospirosis in dogs in the UK. Veterinary Record. 2022 Mar;190(6): e512.
- Costa AC, Colocho RA, Pereira CR, Lage AP, Heinemann MB, Dorneles EM. Canine leptospirosis in stray and sheltered dogs: a systematic review. Animal Health Research Reviews. 2022 Jun;23(1):39-58.
- Ricardo T, Previtali MA, Signorini M. Meta-analysis of risk factors for canine leptospirosis. Preventive Veterinary Medicine. 2020 Aug 1; 181:105037.
- Francey T, Schweighauser A, Reber A, Schuller S. Evaluation of changes in the epidemiology of leptospirosis in dogs after introduction of a quadrivalent antileptospiral vaccine in a highly endemic area. Journal of veterinary internal medicine. 2020 Nov;34(6):2405-17.
- Griebsch C, Kirkwood N, Ward MP, So W, Weerakoon L, Donahoe S, Norris JM. Emerging leptospirosis in urban Sydney dogs: a case series (2017–2020). Australian Veterinary Journal. 2022 May;100(5):190-200.
