Leptospirosis in Dogs: Symptoms, Treatment and Prevention

Leptospirosis is a serious bacterial infection caused by spiral-shaped organisms in the genus Leptospira. There are more than 250 serovars (strains), but the ones most commonly affecting dogs include L. icterohaemorrhagiae, L. canicola, L. pomona, and L. grippotyphosa. The bacteria thrive in warm, moist environments and can survive for weeks to months in stagnant water, mud, and damp soil.

"Leptospirosis is one of the most underdiagnosed bacterial infections in dogs. Many pet owners associate it with rural or tropical areas, but we see cases in urban parks, suburban gardens, and anywhere wildlife or standing water is present. It's also zoonotic, meaning it can spread to humans." — Dr. Sarah Chen, DVM

Dogs typically become infected through one of several routes:

• Direct contact with contaminated water — puddles, ponds, streams, and flooded areas where infected wildlife has urinated
• Contact with infected urine or body fluids — from rodents, raccoons, skunks, opossums, or other infected dogs
• Bite wounds — from infected animals, though this is less common
• Ingestion of contaminated water, soil, or prey — hunting and scavenging dogs are at increased risk

The bacteria enter the body through mucous membranes (eyes, nose, mouth) or through cuts and abrasions in the skin. Once inside, Leptospira organisms multiply rapidly in the bloodstream before targeting the kidneys and liver, where they can cause severe, life-threatening damage. Dogs that spend time outdoors, swim in natural water sources, or live in areas with wildlife are at the highest risk. Keeping up with your dog's preventative care schedule is one of the most effective ways to reduce exposure risk.

Leptospirosis can range from a mild, subclinical infection to a rapidly fatal disease. Symptoms typically appear 4 to 12 days after exposure, though this incubation period can vary. Understanding the stages of the disease helps owners recognise early warning signs and seek prompt treatment.

Early / Acute Stage (Days 1-7)

The initial phase often mimics many other illnesses, making early detection challenging:

• Sudden fever — temperatures of 39.5-40.5°C (103-105°F)
• Lethargy and reluctance to move — dogs may seem stiff or painful, especially in the back and legs
• Loss of appetite — complete food refusal is common
• Shivering and muscle tenderness — the bacteria cause widespread muscle inflammation
• Increased thirst and urination — early kidney involvement

Progressive Stage (Days 7-14)

Without treatment, the infection progresses to target the kidneys and liver:

• Vomiting and diarrhoea — often with blood; if your dog shows these signs, review our guide on when to worry about vomiting and diarrhoea
• Jaundice — yellowing of the gums, whites of the eyes, and skin, indicating liver damage
• Dark or blood-tinged urine — a hallmark sign of haemorrhagic leptospirosis
• Dehydration — sunken eyes, dry gums, skin tenting
• Abdominal pain — dogs may hunch their back or cry when touched around the belly

Severe / Late Stage

Advanced cases can rapidly become life-threatening:

• Acute kidney failure — little or no urine production, severe toxin build-up
• Liver failure — worsening jaundice, clotting abnormalities, spontaneous bleeding
• Difficulty breathing — pulmonary haemorrhage (leptospiral pulmonary haemorrhagic syndrome) is an emerging and often fatal complication
• Collapse and shock — requires immediate emergency veterinary care

If you notice any combination of fever, jaundice, and changes in urination, seek veterinary attention immediately. Early treatment dramatically improves survival rates.

Diagnosing leptospirosis can be challenging because its symptoms overlap with many other conditions. Your veterinarian will use a combination of clinical findings, blood work, and specialised tests to reach a diagnosis.

Initial Blood Work and Urinalysis

A complete blood count (CBC) and biochemistry panel are essential first steps. Common findings include:

• Elevated kidney values — blood urea nitrogen (BUN) and creatinine rise as kidney function declines
• Elevated liver enzymes — ALT, ALP, and bilirubin indicate liver involvement
• Low platelet count — thrombocytopenia is a frequent early finding
• Elevated white blood cell count — indicating active infection and inflammation

Urinalysis may reveal protein in the urine, dilute urine (despite dehydration), and sometimes the presence of casts, which indicate kidney tubular damage.

Specific Diagnostic Tests

Two main tests confirm leptospirosis:

• Microscopic agglutination test (MAT) — the gold standard serological test. It measures antibody levels against specific Leptospira serovars. A four-fold rise in titre between acute and convalescent samples (taken 2-4 weeks apart) is considered diagnostic. A single high titre may also be significant, especially in unvaccinated dogs
• PCR (polymerase chain reaction) — detects Leptospira DNA in blood or urine. This test is most useful in the first 10 days of infection before antibodies develop. It provides rapid results and can identify the organism before MAT titres rise

Imaging

Abdominal ultrasound may show enlarged, bright kidneys (a sign of acute nephritis), liver changes, or fluid accumulation in the abdomen. Chest X-rays are increasingly performed to check for pulmonary involvement, particularly in severe cases where breathing difficulty is noted.

Your vet may also recommend regular veterinary check-ups for dogs in high-risk areas, even when symptoms are absent, since subclinical carriers can shed bacteria in their urine for months.

Treatment for leptospirosis depends on the severity of the disease and how quickly it is caught. The good news is that with prompt, aggressive treatment, many dogs make a full recovery — even those with significant kidney or liver involvement.

Antibiotic Therapy

Antibiotics are the cornerstone of treatment and are given in two phases:

• Phase 1 — Doxycycline — this is the antibiotic of choice for leptospirosis. It clears the bacteria from the bloodstream, tissues, and kidneys, and also eliminates the carrier state so the dog stops shedding bacteria in urine. Treatment typically lasts 2-4 weeks
• Phase 2 (if hospitalised) — Intravenous penicillin or ampicillin — used in severely ill dogs who cannot take oral medication. Once the dog stabilises, they are transitioned to oral doxycycline

Supportive Care

Supportive treatment is critical, especially for dogs with organ damage:

• Intravenous fluid therapy — aggressive IV fluids help correct dehydration, support blood pressure, and flush toxins from the kidneys
• Anti-nausea medications — maropitant (Cerenia) and ondansetron control vomiting and allow the dog to tolerate oral medication and food
• Gastroprotectants — omeprazole or sucralfate protect the stomach lining from ulceration
• Blood transfusions or plasma — may be needed if severe bleeding or clotting disorders develop
• Dialysis — in cases of severe kidney failure unresponsive to fluid therapy, haemodialysis can be life-saving, though availability is limited to specialist centres

Prognosis and Recovery

With early treatment, survival rates are generally 80-90%. Dogs with mild to moderate kidney disease often recover normal function within 2-4 weeks. However, some dogs sustain permanent kidney damage and may require ongoing management, including a renal diet and regular blood monitoring. Liver damage typically resolves more completely. Dogs treated late, or those with pulmonary haemorrhage, have a guarded to poor prognosis. Full recovery typically takes 3-6 weeks, during which strict rest and isolation protocols should be followed to prevent transmission.

Prevention is far safer and more cost-effective than treating leptospirosis. The primary tool is vaccination, combined with common-sense environmental precautions.

Leptospirosis Vaccines

Modern leptospirosis vaccines (often called "4-way lepto" or L4) protect against four of the most common serovars. The vaccination schedule for dogs is:

• Puppies — initial vaccine at 12 weeks of age, with a booster 2-4 weeks later
• Adult dogs — annual booster, as immunity from the leptospirosis vaccine wanes faster than for other core vaccines
• High-risk dogs — dogs in endemic areas or those with heavy outdoor exposure may benefit from boosters every 6-12 months per veterinary recommendation

The leptospirosis vaccine is classified as a non-core vaccine in some guidelines, but many vets — including in the UK — now recommend it as routine for all dogs due to increasing case numbers. Review your dog's full preventive care schedule to ensure they are up to date.

Environmental and Lifestyle Precautions

Even vaccinated dogs benefit from reducing exposure to Leptospira:

• Avoid stagnant water — do not allow your dog to drink from or swim in puddles, ponds, slow-moving streams, or flooded areas, especially in warm months
• Rodent control — reduce rodent populations around your property. Rats are the primary reservoir for the most pathogenic serovars
• Leash control in high-risk areas — prevent dogs from roaming in areas frequented by wildlife
• Clean up promptly — if you have multiple dogs and one is diagnosed, isolate the infected dog and disinfect urinated areas with dilute bleach
• Wash hands thoroughly — leptospirosis is zoonotic; wear gloves when handling an infected dog's urine and wash hands immediately after contact

Leptospirosis is a reportable disease in many jurisdictions. If your dog is diagnosed, your vet may need to notify public health authorities, and you should inform your GP or doctor, especially if you or family members have been exposed to your dog's urine.

Leptospirosis is one of the most significant zoonotic diseases — infections that can pass from animals to humans. The World Health Organization estimates over one million human cases globally each year, with approximately 60,000 deaths. While most human cases result from environmental exposure in tropical regions, pet-to-owner transmission is a real and documented risk.

How Humans Become Infected

Humans contract leptospirosis through the same routes as dogs:

• Contact with infected urine — the highest risk period is when a dog is acutely ill and shedding large numbers of bacteria. Even after starting antibiotics, shedding can continue for several days
• Contaminated water or soil — the bacteria can enter through skin cuts, abrasions, or mucous membranes
• Mucous membrane contact — splashes to the eyes, nose, or mouth during cleaning or handling

Protecting Yourself and Family

If your dog is diagnosed with leptospirosis, take these precautions seriously:

• Wear disposable gloves when cleaning up urine, handling the dog, or cleaning food and water bowls
• Disinfect all areas where the dog has urinated with a 1:10 bleach solution
• Wash hands thoroughly with soap and water after any contact with the dog
• Keep immunocompromised individuals away — young children, the elderly, and anyone with weakened immune systems should avoid contact with the infected dog
• Restrict the dog's urination area — ideally, walk the dog on concrete or paved areas that can be easily disinfected, and avoid public parks until the course of doxycycline is complete

Human leptospirosis can cause flu-like symptoms, kidney failure, liver damage, and meningitis. If you develop fever, headache, or muscle pain after your dog is diagnosed, see your doctor immediately and mention the leptospirosis exposure. Early antibiotic treatment is highly effective in humans as well.