NAVLE Urinary

Canine Leptospirosis Study Guide

📅 March 28, 2026 ⏱ 25 min read

Leptospirosis is a globally important zoonotic bacterial disease caused by pathogenic spirochetes of the genus Leptospira.

Overview and Clinical Importance

Leptospirosis is a globally important zoonotic bacterial disease caused by pathogenic spirochetes of the genus Leptospira. This disease represents one of the most clinically significant infectious causes of acute kidney injury (AKI) in dogs and is a frequently tested topic on the NAVLE due to its clinical complexity, zoonotic potential, and importance in veterinary public health.

The 2023 ACVIM Consensus Statement updated recommendations to include leptospirosis vaccination as a core vaccine for all dogs, regardless of lifestyle, signaling the increased recognition of this disease's widespread occurrence even in urban and suburban environments.

High-YieldOn the NAVLE, leptospirosis should be your top differential for any dog presenting with acute kidney injury, especially if accompanied by hepatic involvement, fever, and thrombocytopenia. Remember: this disease is ZOONOTIC - always consider public health implications!

Serovar	Primary Reservoir	In Vaccine?	Clinical Notes
Icterohaemorrhagiae	Rats	Yes	Classic severe disease; hepatorenal
Canicola	Dogs	Yes	Dogs are maintenance host
Grippotyphosa	Raccoons, voles	Yes	Most common in US currently
Pomona	Pigs, skunks, opossums	Yes	Livestock exposure risk
Bratislava	Pigs, horses, rodents	No (N. America)	Emerging; in European vaccines

Etiology

The Organism

Leptospira species are thin, tightly coiled, motile spirochetes measuring 0.1 micrometers in diameter and 6-20 micrometers in length. Key morphological features include:

Gram-negative cell wall structure
Characteristic hook-shaped or question mark-shaped ends (hence the name 'interrogans')
Two periplasmic flagella enabling corkscrew motility
Best visualized by darkfield microscopy (too thin for routine light microscopy)
Obligate aerobe; grows optimally at 28-30 degrees Celsius

Clinically Important Serovars

NAVLE TipThe 4-serovar vaccine available in North America contains Icterohaemorrhagiae, Canicola, Grippotyphosa, and Pomona. Remember: immunity is serogroup-specific, so dogs can still be infected by non-vaccine serovars!

System	Clinical Signs
Systemic	Fever, lethargy, anorexia, vomiting, abdominal pain, weight loss
Renal (most common)	Polyuria/polydipsia (early), oliguria/anuria (late), azotemia, renomegaly on palpation
Hepatic	Icterus, hepatomegaly, elevated liver enzymes, hyperbilirubinemia
Hemorrhagic	Petechiae, ecchymoses, epistaxis, melena, hematemesis, hematuria
Respiratory	Cough, dyspnea, tachypnea (pulmonary hemorrhage syndrome - poor prognosis)
Musculoskeletal	Muscle pain, stiffness, reluctance to move (myositis/vasculitis)
Ocular	Uveitis, conjunctival hyperemia (less common in dogs than horses)

Transmission and Epidemiology

Routes of Infection

Leptospires enter the host through:

Intact mucous membranes (oral, nasal, conjunctival)
Skin wounds or abrasions
Waterlogged or macerated skin
Less commonly: bite wounds, venereal transmission, transplacental

Environmental Survival

Survives weeks to months in warm, moist soil
Thrives in stagnant or slow-moving water (ponds, puddles, streams)
Optimal conditions: warm temperature, neutral pH (6.9-7.4), high humidity
Killed by desiccation, UV light, and common disinfectants

Risk Factors

Exposure to standing water (ponds, puddles, flooded areas)
Contact with wildlife (raccoons, skunks, rats) or their urine
Periods following heavy rainfall or flooding
Urban/suburban environments with rodent populations
Boarding facilities (dog-to-dog transmission with serovar Canicola)

High-YieldLeptospirosis is NO LONGER just a 'rural dog' disease! Recent outbreaks have occurred in urban areas and boarding facilities. ALL dogs should be considered at risk regardless of lifestyle, breed, size, or age.

Test	Sample	Timing	Advantages	Limitations
MAT	Serum	Acute + convalescent (2-4 wks)	Gold standard; serogroup identification	Delayed results; vaccination interference
PCR	Blood (early), Urine (later)	Any time	Rapid; unaffected by vaccination	False negatives if on antibiotics
SNAP Lepto	Serum	Point-of-care	Rapid (20 min); detects LipL32	Affected by vaccination
WITNESS Lepto	Serum	Point-of-care	Rapid; IgM-based (earlier detection)	Affected by vaccination

Pathophysiology

Disease Phases

Phase 1 - Leptospiremic Phase (Days 1-7): Following entry through mucous membranes or skin, leptospires rapidly disseminate via the bloodstream. Using their corkscrew motility, they efficiently penetrate tissue barriers by binding to vascular endothelial cadherin and disrupting endothelial cell junctions.

Phase 2 - Immune/Organ Phase (Day 7+): The host mounts an antibody response, clearing organisms from the blood. However, leptospires localize to target organs, particularly the kidneys and liver, causing tissue damage through:

Direct nephrotoxicity: LipL32 outer membrane protein binds TLR-2 on renal tubular epithelial cells, triggering inflammatory cascades (TNF-alpha, NF-kappa B activation)
Vasculitis: Endothelial damage leads to hemorrhage, edema, and impaired perfusion
Tubular dysfunction: Proximal tubule damage with Na-K ATPase inhibition and vasopressin resistance
Tubulointerstitial nephritis: Mixed inflammatory infiltrate with potential progression to fibrosis

Key Pathophysiological Concepts for NAVLE

Non-oliguric AKI is classic: Due to tubular dysfunction causing impaired concentrating ability before GFR decline
Hypokalemia common: Tubular potassium wasting precedes azotemia
Glucosuria with normoglycemia: Proximal tubular dysfunction impairs glucose reabsorption
Chronic renal carrier state: Organisms persist in renal tubules, shed intermittently in urine

Phase	Drug	Dose	Notes
First Choice	Doxycycline	5 mg/kg PO q12h x 14 days	Clears renal tubular infection; eliminates carrier state
If vomiting	Ampicillin	20-30 mg/kg IV q6-8h	Until oral doxy tolerated; adjust for azotemia
Alternative	Penicillin G	25,000-40,000 U/kg IV q6-8h	Terminates leptospiremia but does not clear renal infection

Clinical Signs

Clinical presentation ranges from subclinical infection to severe multisystemic disease. The most common presentation in modern practice is acute kidney injury, often with concurrent hepatic involvement.

Clinical Presentations by Organ System

High-YieldThe CLASSIC NAVLE presentation is a young adult dog with acute onset lethargy, vomiting, azotemia, elevated liver enzymes, and thrombocytopenia. The combination of AKI + hepatopathy + thrombocytopenia should immediately trigger leptospirosis in your differential!

Diagnosis

Laboratory Abnormalities

Complete Blood Count (CBC)

Thrombocytopenia (14-73% of cases) - mild to moderate; not severe enough for spontaneous bleeding
Neutrophilia with left shift (27-94% of cases)
Non-regenerative anemia (18-92% of cases) - usually mild to moderate
Lymphopenia, monocytosis

Serum Biochemistry

Azotemia: Elevated BUN (54-100%) and creatinine (55-100%)
Hyperphosphatemia (42-100%)
Hepatic enzymes: Elevated ALP (19-94%), ALT (22-87%), AST (28-69%)
Hyperbilirubinemia (15-94%)
Electrolyte abnormalities: Hyponatremia, hypo- or hyperkalemia

Urinalysis

Isosthenuria (USG 1.008-1.012) - loss of concentrating ability
Glucosuria with normoglycemia (proximal tubular dysfunction)
Proteinuria
Bilirubinuria, granular casts, pyuria

NAVLE TipGLUCOSURIA + NORMOGLYCEMIA is a classic board question clue for proximal renal tubular dysfunction! When you see this combination with AKI, think leptospirosis (or other causes of Fanconi-like syndrome).

Specific Diagnostic Tests

MAT Interpretation

Unvaccinated dog: Single titer greater than or equal to 1:800 is suggestive
Vaccinated dog: Single titer greater than or equal to 1:1600 is suggestive
Definitive diagnosis: 4-fold rise in titer between acute and convalescent samples (2-4 weeks apart)
High confidence: Single titer greater than or equal to 1:6400

Diagnostic Imaging

Abdominal Ultrasound Findings

Renomegaly (60% of cases)
Increased renal cortical echogenicity (100% in some studies)
Medullary band of hyperechogenicity (may be specific for leptospirosis)
Reduced corticomedullary definition
Mild pyelectasia
Perirenal and peritoneal effusion
Hepatomegaly with hypoechoic parenchyma; gallbladder wall thickening

Thoracic Radiographs

Diffuse or caudodorsal interstitial to alveolar pattern
Reticulonodular pulmonary opacities (pulmonary hemorrhage)
Note: Pulmonary involvement indicates poor prognosis (survival drops to 40-50%)

Treatment

CRITICAL: Do NOT delay treatment pending diagnostic confirmation! Progression to irreversible AKI can occur within 24-48 hours.

Antibiotic Therapy

NAVLE TipDOXYCYCLINE is the ONLY antibiotic that reliably clears leptospires from renal tubules! Penicillins terminate leptospiremia but do not eliminate the carrier state. Always complete a FULL 2-WEEK COURSE of doxycycline.

Supportive Care

Fluid therapy: IV crystalloids to correct dehydration and support renal perfusion; CAREFUL monitoring - overhydration risk is HIGH in oliguric patients
Antiemetics: Maropitant (Cerenia), ondansetron
Gastroprotection: H2 blockers, proton pump inhibitors, sucralfate
Nutritional support: Enteral feeding (NG/E-tube) if prolonged anorexia
Urine output monitoring: Closed collection system or frequent body weight measurement
Hemodialysis: Consider early referral for oliguric/anuric patients or progressive azotemia despite appropriate therapy

Prognosis

Overall survival: Approximately 80% with prompt, aggressive treatment
With hemodialysis: Greater than 80% survival in otherwise fatal oliguric/anuric AKI
Pulmonary hemorrhage syndrome: Survival drops to 40-50%
Chronic sequelae: 33-40% of survivors may have residual chronic kidney disease
Without dialysis (anuric): Prognosis is grave

Prevention

Vaccination

Per the 2023 ACVIM Consensus Statement, leptospirosis vaccination is now recommended as a CORE vaccine for ALL dogs, regardless of lifestyle, breed, size, or geographic location.

Vaccine Protocol

Initial series: 2 doses, 3-4 weeks apart, starting at 12 weeks of age
Boosters: Annual revaccination required (bacterin vaccines)
Duration of immunity: At least 12 months (some studies show 15 months)
Serovars covered (N. America): Icterohaemorrhagiae, Canicola, Grippotyphosa, Pomona

Vaccine Safety

Modern vaccines have improved safety profiles
Adverse event rates similar to other common vaccines (less than 53 events per 10,000 doses)
Historical concerns about small breed reactions have been addressed with newer formulations

Zoonotic Considerations

Leptospirosis is the most common zoonotic disease worldwide! Veterinary staff and pet owners are at risk.

Client Education

Avoid direct contact with urine
Wear gloves when cleaning urine accidents
Disinfect contaminated areas with iodine-based products or dilute bleach
Wash hands thoroughly after handling infected pets
Immunocompromised family members should consult their physician
Encourage dog to urinate away from standing water and common areas

Memory Aids

LEPTO-AKI Mnemonic:

Liver involvement (elevated ALP, ALT, bilirubin)
Elevated BUN and creatinine (azotemia)
Platelets low (thrombocytopenia)
Tubular damage (glucosuria, isosthenuria)
O-utbreak potential (ZOONOTIC!)

Treatment Memory Aid - 'DOXY Does it All':

Doxycycline is first choice
Oral route preferred
X-terminates renal carriage (only abx that does!)
Y = 2 weeks (14 days minimum)

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