Leptospirosis in Dogs: Symptoms, Diagnosis, Treatment, Vaccination, and Zoonotic Risk Guide
This article is reviewed for clinical accuracy. Always consult your veterinarian for diagnosis and treatment.
Key Takeaways
- Leptospirosis is a bacterial infection caused by Leptospira interrogans, a spirochete bacterium transmitted through the urine of infected animals; dogs become infected by ingesting or contacting urine-contaminated water, soil, or vegetation, or through direct contact with infected animals; the bacteria penetrate intact or abraded mucous membranes (mouth, nose, conjunctiva) and broken skin; infection leads to spirochetemia (bacteria circulating in the bloodstream), followed by colonization of the kidneys and liver, where the most significant organ damage occurs; leptospirosis is one of the most important zoonotic infectious diseases in the world (transmissible from animals to humans) and is legally reportable in many US jurisdictions.
- Multiple Leptospira serovars (antigenic variants) can infect dogs, and different serovars are associated with different reservoir host species; the four serovars most commonly causing clinical disease in dogs in North America are Canicola (dogs and pigs as primary reservoirs), Icterohaemorrhagiae (rats), Pomona (cattle, pigs, skunks), and Grippotyphosa (raccoons, skunks, opossums, rodents); Bratislava is another serovar of concern associated with swine and horses; tetravalent vaccines (covering four serovars: Canicola, Icterohaemorrhagiae, Pomona, and Grippotyphosa) provide better protection than older bivalent vaccines (covering only Canicola and Icterohaemorrhagiae), because the Pomona and Grippotyphosa serovars are currently responsible for the majority of clinical cases in dogs in North America.
- The kidneys are the primary target organ in canine leptospirosis; Leptospira bacteria colonize the renal tubular epithelium, causing acute tubular injury and acute kidney injury (AKI); the glomeruli are also affected through immune complex deposition; clinical signs of AKI include sudden onset of lethargy, anorexia, vomiting, increased or decreased urination (polyuria progressing to oliguria or anuria as AKI worsens), oral ulcers, and a hunched painful posture; azotemia (elevated BUN and creatinine), hyperphosphatemia, and electrolyte abnormalities are the characteristic bloodwork findings; the liver is the second most commonly affected organ, producing hepatitis and icterus (jaundice); in the most severe cases, leptospiral pulmonary hemorrhage syndrome (LPHS) develops, producing respiratory distress and diffuse pulmonary hemorrhage with a high fatality rate.
- Diagnosis of leptospirosis requires specific testing because routine bloodwork and urinalysis alone cannot confirm the infection; the microscopic agglutination test (MAT) is the gold standard serological test: it detects antibodies against specific serovars by testing the patient’s serum against live Leptospira cultures; a fourfold rise in MAT titer between an acute sample and a convalescent sample (collected 2 to 4 weeks later) confirms active infection; a single MAT titer of 1:800 or higher is considered presumptive evidence of infection in an unvaccinated dog (recently vaccinated dogs may have MAT titers up to 1:400 from vaccination); urine polymerase chain reaction (PCR) is the most sensitive early diagnostic test (positive in the first week of illness before antibodies develop), but a negative PCR does not rule out leptospirosis; point-of-care ELISA antibody tests (SNAP Lepto) offer rapid in-clinic screening with reasonable sensitivity.
- Treatment of leptospirosis requires antibiotics to eliminate the infection and supportive care for organ dysfunction; doxycycline (5 mg/kg orally or IV every 12 hours for 14 days) is the preferred antibiotic for both treating active infection and eliminating the renal carrier state (the period during which bacteria persist in the kidneys and are shed in urine even after clinical recovery); penicillin-class antibiotics (ampicillin, amoxicillin) are also effective against leptospires and were historically used first in severely ill hospitalized dogs, though doxycycline is now more commonly used throughout; dogs with AKI require aggressive IV fluid therapy, and dogs with severe AKI unresponsive to fluid therapy may require dialysis (hemodialysis or peritoneal dialysis); the overall case fatality rate is approximately 10 to 20 percent in hospitalized dogs, with higher rates in dogs developing pulmonary hemorrhage syndrome.
- Prevention of leptospirosis relies on vaccination with the tetravalent Leptospira vaccine (covering the four most clinically important serovars: Canicola, Icterohaemorrhagiae, Pomona, Grippotyphosa), environmental risk reduction (avoiding stagnant water, wildlife contact, and rodent exposure), and understanding that vaccination does not prevent all serovars; the annual or semiannual booster schedule for the Leptospira vaccine is critical because immunity from the leptospirosis component wanes faster than other vaccine components; the risk-based vaccination guidelines from the American Animal Hospital Association (AAHA) recommend leptospirosis vaccination for any dog with potential exposure to infected water, soil, or wildlife, which in practice includes most dogs outside urban environments; dogs with exposure to standing water, wildlife, farms, or hunting activities should be considered high-risk.
The 4-year-old mixed-breed dog arrived at the emergency clinic on a Thursday evening. The owners described 48 hours of progressive lethargy, refusal to eat, and two episodes of vomiting. On physical examination, the dog was dehydrated, had pale-yellow tinted sclerae, and cried out when the veterinarian palpated the cranial abdomen over the kidneys. The bloodwork showed a BUN of 98 mg/dL and creatinine of 5.4 mg/dL. The dog lived in a suburban neighborhood but had been swimming in a retention pond adjacent to a golf course two weeks earlier. The veterinarian recognized the combination of acute kidney injury, hepatitis, and recent water exposure and immediately ordered a urine PCR for Leptospira and a SNAP Lepto test. The SNAP came back positive. The dog was started on doxycycline and aggressive IV fluid therapy within the hour. The urine PCR confirmed Leptospira infection two days later. The owners were informed that leptospirosis is zoonotic and should see their physician, and were counseled on the vaccination that could have prevented the infection.
What Is Leptospirosis: The Bacterium and How Infection Spreads
Leptospira interrogans is a spirochete: a thin, tightly coiled, motile bacterium that moves with a distinctive corkscrew motion. Unlike most bacteria, Leptospira survive for weeks to months in warm, moist, slightly alkaline environments (optimal pH 7.2 to 7.4) such as stagnant ponds, puddles, rivers, and waterlogged soil. They are killed quickly by drying, direct sunlight, and most disinfectants. Infected animals (reservoir hosts) shed leptospires in their urine continuously or intermittently without becoming ill, contaminating water and soil in their environment. Dogs become infected primarily through:
- Direct contact with contaminated water: swimming in or drinking from ponds, puddles, streams, slow-moving water bodies, or flooded areas
- Contact with contaminated soil or vegetation: walking through wet grass, mud, or soil where infected animals have urinated
- Direct contact with infected animals: bites, ingestion of infected tissues (especially kidneys and urine of prey animals), or contact with an infected dog’s urine
- Transplacental transmission: pregnant dogs infected during pregnancy can transmit leptospires to their fetuses, causing stillbirths or neonatal leptospirosis
The bacteria penetrate through intact mucous membranes (conjunctival, oral, nasal), macerated or abraded skin (particularly between paw pads after prolonged water contact), or minor skin injuries. Once inside the body, leptospires replicate in the bloodstream (leptospiremia or spirochetemia) during the first 4 to 10 days of infection and are then cleared by the immune response from most organs except the kidneys (and sometimes the liver, eyes, and reproductive tract), where they take up residence in tubular epithelial cells.
Reservoir Hosts and Serovar Distribution
| Serovar | Primary Reservoir Hosts | Geographic Pattern | Vaccine Coverage |
|---|---|---|---|
| Canicola | Dogs, pigs | Worldwide; historically the most common serovar in dogs; less common now due to widespread vaccination | Bivalent and tetravalent |
| Icterohaemorrhagiae | Rats, other rodents | Worldwide; urban and suburban areas with rat populations; often associated with the most severe icteric (jaundiced) clinical disease | Bivalent and tetravalent |
| Pomona | Cattle, pigs, skunks, wildlife | Rural and agricultural areas; hunting dogs at increased risk; now one of the most common serovars causing clinical disease in US dogs | Tetravalent only |
| Grippotyphosa | Raccoons, skunks, opossums, voles, squirrels | Suburban and rural areas with wildlife; most common serovar in some US regional surveys; water and wildlife exposure as primary risk factors | Tetravalent only |
| Bratislava | Pigs, horses, hedgehogs | Agricultural areas; associated with chronic renal and reproductive disease; not covered by current commercial vaccines in North America | Not covered in US vaccines |
| Autumnalis, Hardjo, others | Various wildlife and livestock | Variable; regional importance; most not covered by commercial vaccines | Not covered in US vaccines |
Pathophysiology: How Leptospira Damages the Kidneys and Liver
Renal Injury Mechanism
After the initial spirochetemia, leptospires colonize the renal tubular epithelium (particularly the proximal convoluted tubules and the loops of Henle) via specific adhesin proteins that bind to tubular cell surface receptors. Once attached, leptospires evade complement-mediated killing through their outer membrane lipoproteins and replicate within tubular cells, causing direct cytotoxic damage through toxic products including sphingomyelinase, pore-forming proteins, and lipopolysaccharide (LPS). The resulting acute tubular necrosis impairs renal tubular reabsorption of glucose, sodium, potassium, and amino acids (producing glucosuria at normal blood glucose concentrations, which is a classic early finding), and in severe cases leads to oliguric or anuric AKI. Simultaneously, immune complex deposition in the glomeruli produces a glomerulonephritis that compounds the tubular injury. During the early weeks of clinical recovery, leptospires continue replicating in the renal tubules and are shed into the urine (the renal carrier state), which can persist for weeks to months; doxycycline is used specifically to eliminate this carrier state and prevent continued environmental shedding and zoonotic risk from the recovering dog.
Hepatic Injury Mechanism
The liver is the second most commonly affected organ. Leptospires invade hepatocytes directly and cause a centrolobular hepatocellular necrosis pattern, with elevated ALT and AST. Disruption of the bile canaliculi produces intrahepatic cholestasis, elevating alkaline phosphatase (ALP) and causing hyperbilirubinemia and clinical icterus (jaundice, seen as yellowing of the sclerae, skin, and mucous membranes). The combination of AKI and hepatic necrosis in the same patient is sometimes called the icterohaemorrhagiae presentation or Weil’s disease (a term also used in human medicine). Fortunately, leptospiral hepatic injury is often reversible with appropriate treatment, and hepatic function typically normalizes over weeks to months following recovery from the acute illness.
Pulmonary Hemorrhage Syndrome
Leptospiral pulmonary hemorrhage syndrome (LPHS) is the most life-threatening manifestation of leptospirosis, carrying a fatality rate of over 70 percent in affected dogs. It produces diffuse alveolar hemorrhage through direct endothelial injury and immune-mediated mechanisms, not through coagulopathy (coagulation parameters may be normal or only mildly abnormal). Clinical signs include sudden onset of respiratory distress, coughing blood (hemoptysis), and rapid respiratory failure. Radiographs show diffuse bilateral pulmonary infiltrates. Intensive care with oxygen therapy, careful fluid management (avoiding fluid overload which worsens pulmonary hemorrhage), and antibiotic therapy is required, but the prognosis is poor once frank respiratory failure develops.
Clinical Signs by Disease Phase
| Phase | Timing | Clinical Signs |
|---|---|---|
| Leptospiremic (acute) phase | Days 0 to 7 post-infection | Sudden onset fever (103 to 104.5 F), lethargy, anorexia, vomiting, muscle pain (myalgia, reluctance to move), shivering; some dogs show mild transient signs and apparently recover before entering the immune phase |
| Immune (leptospiruric) phase | Days 7 to 21 | AKI signs: polydipsia/polyuria progressing to oliguria/anuria; vomiting; oral ulcers; painful kidneys on palpation; hepatic signs: icterus (jaundice), hepatomegaly; uveitis (ocular leptospirosis) in some cases; coagulopathy (petechiae, epistaxis) in severe disease; pulmonary signs (LPHS) in a subset |
| Peracute/septicemic (rare) | Within first 2 to 5 days | Sudden death or rapid deterioration before clinical AKI develops; most common with highly pathogenic serovars and high inoculum exposure; shock, hypothermia, DIC |
| Chronic/carrier phase | Weeks to months post-recovery | No clinical signs; leptospires persist in renal tubules and continue to be shed in urine; important for zoonotic risk and transmission to other animals; eliminated by completing the doxycycline course |
Diagnosis
Routine Bloodwork Abnormalities
| Test | Finding in Leptospirosis |
|---|---|
| BUN and creatinine | Elevated; severity ranges from mild azotemia to BUN greater than 200 mg/dL and creatinine greater than 10 mg/dL in severe AKI |
| ALT and AST | Moderately to markedly elevated from hepatocellular necrosis; may be 5 to 50x normal |
| ALP (alkaline phosphatase) | Elevated from cholestasis; total bilirubin elevated with icterus |
| CBC | Leukocytosis with left shift (neutrophilia and band cells) in many cases; thrombocytopenia in approximately 50 to 60 percent of cases (from vasculitis and immune-mediated platelet consumption); anemia from hemorrhage in severe LPHS |
| Urinalysis | Glucosuria despite normoglycemia (classic tubular injury finding); proteinuria; cylindruria (granular casts indicating tubular necrosis); isosthenuria (urine specific gravity close to 1.008 to 1.012 in a dehydrated dog indicating impaired concentrating ability); occasionally bilirubinuria |
| Electrolytes | Hyperphosphatemia, hyperkalemia, hyponatremia from AKI; hypokalemia in some cases from renal tubular potassium wasting early in the disease |
| Coagulation panel | Prolonged PT/PTT and low fibrinogen in cases developing DIC; check in any severely ill dog |
| Chest radiographs | Normal in uncomplicated cases; diffuse bilateral alveolar infiltrates or nodular pattern in LPHS |
Specific Diagnostic Tests for Leptospirosis
| Test | Timing | Sensitivity/Specificity | Notes |
|---|---|---|---|
| Microscopic agglutination test (MAT) | Gold standard serology; acute sample first week, convalescent sample 2 to 4 weeks later | High specificity; sensitivity limited in first week before antibody response; fourfold rise in titer between acute and convalescent confirms active infection | Single titer above 1:800 presumptive in unvaccinated dog; vaccinated dogs may have titers up to 1:400; serovar with highest titer suggests (but does not confirm) infecting serovar; requires specialized laboratory |
| Urine PCR | Most sensitive in first 1 to 2 weeks before antibody response develops | Sensitivity 60 to 80% in the first week; specificity very high; negative result does not rule out disease | Collect urine before starting antibiotics when possible; submit to PCR laboratory; positive confirms active renal shedding |
| SNAP Lepto (IDEXX) in-clinic ELISA | Any time after first 5 to 7 days of illness | Sensitivity approximately 85 to 90%; specificity approximately 95%; may be negative early in illness and in recently vaccinated dogs | Rapid in-clinic screening; positive result warrants confirmatory MAT and PCR; negative in the first week of illness does not rule out leptospirosis |
| Blood PCR | Most useful in the leptospiremic phase (first 7 days) | Low sensitivity after day 7 when spirochetemia clears; useful for very early cases | Less commonly available than urine PCR; useful if urine not obtainable |
| Dark field microscopy (urine or blood) | Any time | Low sensitivity; artifacts common; unreliable for diagnosis | Not recommended as primary diagnostic tool despite historical use |
Treatment Protocol
Antibiotic Selection
Doxycycline is the current antibiotic of choice for canine leptospirosis at 5 mg/kg orally or IV every 12 hours for a minimum of 14 days. Doxycycline is preferred because it: (1) is highly effective against Leptospira spirochetes; (2) penetrates into renal tubular cells where leptospires persist; (3) eliminates the renal carrier state, stopping ongoing urine shedding and zoonotic risk; and (4) can be continued at home after discharge. In dogs with severe vomiting that precludes oral administration, IV doxycycline is given during hospitalization and then transitioned to oral once vomiting is controlled. Penicillin-class antibiotics (ampicillin 22 mg/kg IV every 8 hours, or amoxicillin 22 mg/kg orally every 12 hours) are effective against leptospires in the acute phase but do not reliably eliminate the renal carrier state and have historically been used as first-line agents during acute hospitalization before transitioning to doxycycline to complete the carrier-state elimination. Current practice in most referral hospitals is to use doxycycline throughout rather than switching between antibiotic classes.
Supportive Care for AKI
- IV fluid therapy: The cornerstone of treatment; aggressive crystalloid fluid therapy (isotonic saline or balanced electrolyte solutions) to correct dehydration, restore renal perfusion, and promote leptospire elimination via diuresis; urinary catheter placement and urine output monitoring (targeting more than 1 to 2 mL/kg/hour); fluid rates adjusted based on urine output, hydration status, and blood pressure
- Antiemetics: Maropitant (Cerenia), ondansetron, or metoclopramide to control vomiting and maintain enteral fluid and antibiotic absorption
- Phosphate binders: For severe hyperphosphatemia from AKI
- Potassium supplementation: If hypokalemia is present; careful with hyperkalemic dogs (common in anuric AKI)
- Dialysis: Hemodialysis or peritoneal dialysis for dogs with severe anuric or oliguric AKI unresponsive to fluid therapy; available at veterinary specialty centers; substantially improves survival in dogs with dialysis-requiring AKI (survival rates of 50 to 70 percent in dialyzed dogs vs. near 100 percent mortality without dialysis in anuric patients)
- Management of LPHS: Supplemental oxygen, minimize IV fluid volumes to avoid worsening alveolar flooding, intensive monitoring; prognosis poor once frank respiratory failure develops
Zoonotic Risk: Protecting the Human Family
Leptospirosis is one of the most widespread zoonotic diseases globally. In humans, leptospirosis (also called Weil’s disease in its severe form) causes flu-like illness with fever, headache, and myalgias that can progress to AKI, liver failure, pulmonary hemorrhage, and meningitis. The human case fatality rate for severe leptospirosis is approximately 5 to 15 percent. Dogs with confirmed or suspected leptospirosis are a direct infection risk to their owners and to veterinary staff. Key zoonotic precautions when managing a leptospirosis case or caring for a dog recently diagnosed with leptospirosis:
- Wear gloves and eye protection when handling the dog or its urine during the infectious period (until 2 to 4 weeks of doxycycline treatment have been completed)
- Prevent the dog from urinating in areas where people (especially children) walk barefoot; clean urination spots with dilute bleach solution (1:10 dilution)
- Wash hands thoroughly after any contact with the dog or its environment
- Notify all family members, including other pets’ veterinarians if other animals were exposed to the same water source
- Inform the dog’s owner that all human household members with any flu-like illness in the preceding 2 to 4 weeks should inform their physician of potential leptospirosis exposure
- Veterinary staff and household members who are immunocompromised, pregnant, elderly, or have chronic kidney or liver disease are at higher risk for severe disease and should be especially vigilant
- Leptospirosis is a nationally notifiable disease in the US; veterinary cases should be reported to the state veterinarian per local regulations
Vaccination: Bivalent vs. Tetravalent and Who Should Be Vaccinated
| Vaccine Type | Serovars Covered | Examples | Who Should Receive It |
|---|---|---|---|
| Bivalent | Canicola + Icterohaemorrhagiae only | Vanguard L2 | Not recommended as the sole Leptospira vaccine in current practice; most Pomona and Grippotyphosa infections will not be prevented |
| Tetravalent | Canicola + Icterohaemorrhagiae + Pomona + Grippotyphosa | Nobivac Lepto4 (Merck), Vanguard L4 (Zoetis), Recombitek L4 (Boehringer) | All dogs with any potential exposure to wildlife, standing water, soil, other dogs, farms, or outdoor environments; annual or biannual booster required |
| Vaccination schedule | Two doses 2 to 4 weeks apart for initial series; then annual booster | Leptospira immunity wanes faster than most other vaccine components; annual boosting is essential; some high-risk dogs in endemic areas benefit from biannual vaccination | Puppies can receive initial series starting at 12 weeks; vaccine is not recommended before 12 weeks due to maternal antibody interference |
AAHA (American Animal Hospital Association) classifies leptospirosis as a “lifestyle-based” vaccine recommended for dogs with potential exposure rather than a core vaccine for all dogs. However, in practice, the lifestyle criteria are broad: any dog that goes outdoors, contacts standing water, lives in an area with raccoon, skunk, or rodent populations (suburban to rural environments), engages in hunting, swimming, or hiking, or attends dog parks or boarding facilities in endemic areas should receive the tetravalent vaccine. Purely indoor dogs in urban environments may not require it, but this population is small. Vaccination does not prevent all serovars (Bratislava and others are not covered), so environmental risk reduction remains important even in vaccinated dogs.
US Cost Overview for Leptospirosis
| Service | Typical US Cost |
|---|---|
| Initial exam + routine bloodwork (CBC, chemistry, urinalysis) | $200 to $500 |
| SNAP Lepto in-clinic test | $40 to $80 |
| Urine PCR for Leptospira (reference laboratory) | $80 to $150 |
| MAT serology (acute titer) | $80 to $150 (requires specialized laboratory) |
| Hospitalization for AKI (IV fluids, antibiotics, monitoring, 3 to 5 days) | $2,000 to $6,000 |
| Hemodialysis (per session, referral center) | $800 to $1,500 per session; 3 to 10 sessions typical |
| ICU care for LPHS with respiratory support | $3,000 to $10,000+ depending on duration |
| Doxycycline course (14 days, home) | $20 to $60 |
| Tetravalent lepto vaccine (annual) | $25 to $60 per dose at time of annual exam |
Risk Factors: Which Dogs Are Most Vulnerable
High-Risk Lifestyles and Environments
- Swimming in or drinking from natural water bodies (ponds, lakes, streams, rivers, retention ponds, flooded areas)
- Walking through wet grass, mud, or flooded soil in areas frequented by wildlife
- Hunting, retrieving, or field trial activities
- Rural or semi-rural living with exposure to farms (cattle, pigs), wildlife, or rodents
- Suburban areas with high raccoon, skunk, or opossum populations
- Dog parks with standing water or shared water bowls in endemic areas
- Kenneling or boarding in endemic areas during high-risk seasons (late summer and fall in temperate climates; warm wet months in subtropical and tropical regions)
- Dense rat or rodent populations in urban environments
Geographic and Seasonal Patterns
Leptospirosis cases peak in late summer and fall in temperate North America, correlating with warm temperatures (leptospires survive longer in warm water), heavy rainfall events that spread contaminated surface water, and periods of increased outdoor activity. States with the highest reported canine leptospirosis incidence include those in the northeast, mid-Atlantic, Pacific northwest, and Gulf Coast regions. Cases occur year-round in subtropical and tropical regions (Florida, Hawaii, Puerto Rico, coastal Gulf states). Climate trends increasing heavy rainfall events and flooding are expected to expand the geographic range and seasonal window of leptospirosis transmission.
Age-Specific Considerations
Puppies (Under 1 Year)
- Puppies under 12 weeks generally should not receive the leptospirosis vaccine due to risk of maternal antibody interference reducing vaccine immunogenicity; the initial two-dose leptospirosis series should begin at 12 weeks or later, timed to coincide with the rest of the puppy vaccine series; puppies under 12 weeks in very high-risk environments present a difficult decision, and veterinary internists may recommend early vaccination in exceptional circumstances given the risk of unprotected exposure to endemic environments
- Puppies are not inherently more susceptible to severe leptospirosis than adult dogs once maternally derived antibodies wane, but their smaller body size means the fluid volumes required for AKI management are more precise; hypoglycemia is an additional concern during intensive care of small puppies; peritoneal dialysis rather than hemodialysis is often used in small puppies due to the challenges of vascular access for hemodialysis in very small patients
- Transplacental leptospirosis (infection of puppies in utero from an infected dam) can cause stillbirths, weak neonates, or neonatal leptospirosis; pregnant dogs in endemic areas should be kept away from potential Leptospira exposure sources; the leptospirosis vaccine’s safety in pregnant dogs has not been fully established, and vaccination during pregnancy is generally avoided unless the risk-benefit assessment strongly favors vaccination
Adult Dogs (1 to 8 Years)
- Adult dogs represent the majority of leptospirosis cases; the classic presentation is an active, outdoor dog (retrievers, hunting breeds, mixed breeds) with acute onset lethargy, vomiting, and AKI following water or wildlife exposure; the history of water or wildlife exposure may be remote (up to 2 to 4 weeks before clinical signs) and easily overlooked if not specifically asked about; always ask about outdoor activities, water exposure, and travel in the history of any dog with acute AKI or hepatitis of unclear cause
- Adult dogs on annual vaccination schedules must have their leptospirosis booster kept current; owners who lapse on annual exams (and therefore boosters) may allow immunity to wane below protective levels; clients who moved from a low-risk to a high-risk area and did not update their dog’s vaccines are a common scenario for preventable leptospirosis in adult dogs; the initial two-dose series must be restarted if the last leptospirosis booster was more than 15 to 16 months ago (not just an annual single booster)
- Adult dogs with pre-existing chronic kidney disease (CKD) are at substantially higher risk of decompensation if they acquire leptospirosis, because they have reduced renal reserve; even a subclinical or mild leptospiral AKI can be life-threatening when superimposed on already-reduced nephron mass; dogs with known CKD in endemic areas should be prioritized for tetravalent vaccination and strict environmental risk reduction
Senior Dogs (9 Years and Older)
- Senior dogs may have subclinical or pre-existing CKD that reduces their renal reserve, making leptospiral AKI more severe and less reversible; the prognosis for recovery of renal function is more guarded in senior dogs, and the decision to pursue dialysis in an elderly dog with leptospirosis requires careful owner communication about realistic recovery expectations; some senior dogs with severe leptospiral AKI fail to regain adequate renal function even after clearing the infection and require long-term CKD management
- Senior dogs are sometimes assumed to be lower-risk for leptospirosis because their activity level decreases; however, even low-level exposure (drinking from a puddle, walking through wet grass) is sufficient for transmission; the reduced activity assumption can lead owners and veterinarians to skip leptospirosis vaccination in senior dogs in endemic areas, which is inadvisable; the tetravalent vaccine is safe and recommended in healthy senior dogs in high-risk environments
- Ocular leptospirosis (anterior uveitis from Leptospira antigen deposition in the uveal tract) can develop weeks to months after the acute infection resolves, and senior dogs may be presented to ophthalmologists with idiopathic uveitis of unclear cause; a serum MAT titer should be considered in any dog with idiopathic uveitis in an endemic area, as leptospiral uveitis requires specific antibiotic treatment in addition to topical anti-inflammatory therapy
Myths and Facts About Leptospirosis in Dogs
My dog only drinks from its own clean water bowl, so it cannot get leptospirosis.
Leptospira infection does not require drinking directly from contaminated water sources. A dog can become infected by walking through wet grass or mud contaminated with infected wildlife urine, then licking its paws; by swimming or wading in a pond or puddle even briefly; or by direct contact with raccoon, skunk, or rodent urine deposited in the yard. Many suburban dogs are infected from standing water in their own backyard or neighborhood that has been contaminated by passing wildlife. The risk is difficult to completely eliminate in any dog that goes outdoors in an endemic area.
My dog’s regular annual vaccines include protection against all leptospirosis serovars.
This is true only if your dog receives the tetravalent leptospirosis vaccine (covering Canicola, Icterohaemorrhagiae, Pomona, and Grippotyphosa). Older bivalent vaccines (covering only Canicola and Icterohaemorrhagiae) do not protect against Pomona and Grippotyphosa, which are now responsible for the majority of clinical cases in US dogs. Additionally, no currently available US vaccine covers the Bratislava serovar. Ask your veterinarian specifically whether your dog’s leptospirosis vaccine is tetravalent (four-serovar) and when the last booster was given, since the leptospirosis component requires annual or biannual boosting to maintain protective immunity.
Once my dog finishes the antibiotics and feels better, it is no longer contagious to people or other animals.
A dog recovering from leptospirosis continues shedding live Leptospira bacteria in its urine for weeks to months after clinical recovery (the renal carrier state), even if it appears completely healthy. This is why completing the full 14-day doxycycline course is critical: doxycycline specifically eliminates the renal carrier state. A dog that stopped antibiotics early because it felt better may still be shedding leptospires in its urine and poses a direct zoonotic risk to household members and other animals. Gloves and hygiene precautions should be maintained until the full antibiotic course is completed, not just until clinical signs resolve.
Red Flags: Signs That Require Emergency Veterinary Care
- Sudden onset lethargy, vomiting, and refusal to eat within 1 to 3 weeks after swimming in natural water bodies, contact with wildlife, or exposure to wet soil or flooded areas: this combination is leptospirosis until proven otherwise; request urgent bloodwork including kidney and liver values
- Yellow tinting of the whites of the eyes (scleral icterus), gums, or skin alongside lethargy and vomiting: icterus combined with AKI signs is a classic lepto presentation requiring same-day veterinary care
- Sudden decrease in urination or failure to urinate in a dog with acute illness: oliguria or anuria indicates severe AKI requiring immediate IV fluid therapy; delays worsen prognosis
- Sudden onset of labored breathing, rapid respiratory rate, or coughing blood in a dog known or suspected to have leptospirosis: these signs suggest leptospiral pulmonary hemorrhage syndrome (LPHS), the most life-threatening complication; requires immediate ICU care
- Any dog in the household showing the above signs after a confirmed Leptospira-positive dog has shared its environment (yard, water bowl, bedding): exposure of household dogs to an infected dog’s urine is a real transmission risk; all dogs in the household should be evaluated and vaccinated
- Any human household member developing fever, severe headache, and muscle pain within 2 to 4 weeks of contact with a dog later confirmed to have leptospirosis: this person should inform their physician of the potential leptospirosis exposure immediately; early antibiotic treatment of human leptospirosis significantly reduces risk of severe disease
Frequently Asked Questions About Leptospirosis in Dogs
What is leptospirosis in dogs?
Leptospirosis is a bacterial infection caused by Leptospira spirochetes, transmitted through contact with contaminated water, soil, or urine from infected animals (rats, raccoons, skunks, cattle, and other wildlife). The bacteria primarily damage the kidneys (causing acute kidney injury) and liver (causing hepatitis and jaundice). It is a zoonotic disease, meaning it can be transmitted from dogs to humans. Prevention relies on tetravalent vaccination (covering four serovars) and avoiding contaminated water and wildlife contact.
What are the symptoms of leptospirosis in dogs?
Symptoms typically appear 4 to 12 days after exposure and include sudden onset lethargy, anorexia, vomiting, muscle stiffness, increased thirst and urination (progressing to decreased urination in severe AKI), abdominal pain (especially in the kidney region), and fever. Dogs with liver involvement develop jaundice (yellow tinting of eyes, gums, and skin). Severe cases develop respiratory distress from pulmonary hemorrhage. The combination of AKI and hepatitis following water or wildlife exposure is the classic presentation.
How is leptospirosis diagnosed in dogs?
Diagnosis combines clinical findings (AKI, hepatitis, history of water/wildlife exposure) with specific testing: the SNAP Lepto in-clinic ELISA test provides rapid screening; urine PCR detects bacterial DNA and is most sensitive early in illness; and the microscopic agglutination test (MAT) with paired acute and convalescent serum samples is the confirmatory gold standard. Routine bloodwork shows elevated BUN, creatinine, ALT, and ALP, with thrombocytopenia common. Normal routine bloodwork early in illness does not rule out leptospirosis.
How is leptospirosis treated in dogs?
Treatment requires doxycycline (5 mg/kg every 12 hours for 14 days) to eliminate the infection and renal carrier state, combined with supportive care for AKI: aggressive IV fluid therapy, antiemetics, electrolyte management, and close monitoring of urine output. Dogs with severe anuric AKI unresponsive to fluids may require hemodialysis at a specialty center. Dogs with pulmonary hemorrhage syndrome need intensive oxygen support. The full 14-day doxycycline course must be completed even after clinical recovery to eliminate ongoing urine shedding.
Can humans catch leptospirosis from a sick dog?
Yes. Leptospirosis is a zoonotic disease. Infected dogs shed live bacteria in their urine for weeks to months, even during and after clinical recovery. Humans can be infected by direct contact with infected urine, urine-contaminated water, or contaminated soil. Precautions include wearing gloves when handling the dog or its environment, preventing the dog from urinating where people walk barefoot, disinfecting contaminated surfaces with dilute bleach, washing hands thoroughly, and maintaining these precautions until the full 14-day antibiotic course is completed. Household members with fever, headache, and muscle pain after potential exposure should see a physician immediately.
Does the leptospirosis vaccine protect against all serovars?
No. The tetravalent vaccine (the current standard of care) covers four serovars: Canicola, Icterohaemorrhagiae, Pomona, and Grippotyphosa. It does not cover Bratislava or other serovars of regional importance. The bivalent vaccine (older formulation) covers only Canicola and Icterohaemorrhagiae, leaving dogs unprotected against Pomona and Grippotyphosa, which cause the majority of current US cases. Ask your veterinarian specifically whether your dog receives the tetravalent vaccine. Annual boosting is required because leptospiral vaccine immunity wanes faster than most other vaccine components.
How do I prevent leptospirosis in my dog?
Vaccination with the tetravalent leptospirosis vaccine (annual booster required) is the most effective prevention. Reduce environmental risk by preventing your dog from swimming in or drinking from natural water bodies (ponds, puddles, streams, flooded areas), avoiding areas with known wildlife activity (especially raccoons, skunks, rats), controlling rodent access to your property, and not allowing your dog to contact carcasses or urine from wildlife. Even vaccinated dogs should avoid high-risk exposures because no vaccine covers all serovars.
For more guides on keeping your dog healthy, browse all our Dog Health articles.
Explore Dog Health Articles