What is Leptospirosis?

Leptospirosis is a bacterial disease caused by spirochete bacteria of the genus Leptospira. It is a significant zoonotic disease — meaning it can spread from animals to humans — and affects dogs, livestock, wildlife, and people. The bacteria thrive in warm, moist environments and can survive for months in standing water, mud, and damp soil.

Leptospirosis causes serious kidney and liver damage and can be fatal without prompt treatment. It is found worldwide, though its prevalence is increasing in urban and suburban areas as wildlife encroaches on residential spaces.

Symptoms

Leptospirosis can range from subclinical (no obvious symptoms) to severe, life-threatening disease:

  • Sudden fever and lethargy
  • Muscle pain and stiffness
  • Vomiting and diarrhea
  • Loss of appetite
  • Increased thirst and urination (early kidney involvement)
  • Decreased urination (kidney failure)
  • Jaundice (yellowing of skin, gums, and eyes — liver failure)
  • Bleeding disorders
  • Respiratory distress

Some dogs develop a mild, self-limiting form of the disease, while others deteriorate rapidly. Prompt veterinary attention is critical.

Transmission

Dogs become infected through:

  • Contact with contaminated water (puddles, ponds, streams, flooded areas)
  • Contact with contaminated soil or mud
  • Direct contact with urine from infected animals (rats, raccoons, skunks, other dogs)
  • Bite wounds
  • Ingestion of contaminated water or infected tissues

Wildlife — particularly rats and raccoons — serve as reservoir hosts, shedding the bacteria in their urine without becoming ill themselves.

Risk Factors

Dogs at higher risk include those that:

  • Drink from puddles, streams, or standing water
  • Swim in natural bodies of water
  • Live in rural or suburban areas with wildlife
  • Have contact with farm animals
  • Hunt or have access to areas frequented by rodents
  • Live in areas with heavy rainfall or flooding

Vaccination

The Leptospirosis vaccine is classified as non-core but is increasingly recommended for most dogs due to the expanding geographic range of the disease and the zoonotic risk.

Vaccination Schedule

  • Puppies: Two doses starting at 12 weeks, 2–4 weeks apart
  • Adult dogs: Two initial doses 2–4 weeks apart
  • Boosters: Annually (immunity wanes faster than with other vaccines)

The vaccine covers the most common serovars (strains) but may not protect against all of them. Regardless, vaccinated dogs that become infected tend to have milder disease.

Treatment

Early treatment significantly improves outcomes:

  • Antibiotics (doxycycline is the treatment of choice, followed by amoxicillin)
  • Aggressive IV fluid therapy
  • Anti-nausea medication
  • Liver and kidney support
  • Hospitalization in severe cases

Zoonotic Risk

Leptospirosis is a serious human health concern. People can become infected through:

  • Contact with infected dog urine
  • Contact with contaminated water or soil
  • Through broken skin or mucous membranes

If your dog is diagnosed with leptospirosis:

  • Wear gloves when cleaning up urine
  • Wash hands thoroughly after handling your dog
  • Disinfect contaminated areas
  • Inform your physician
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