Canine Leptospirosis

Leptospirosis is considered to be the most widespread zoonotic infection in the world, with infected dogs a source of infection.45,46

Disease Overview

Leptospirosis is an infectious disease that causes serious illness in dogs, other animals, and people. The disease is caused by spiral-shaped bacteria called leptospires that live in water or warm, wet soil.

Initial signs of leptospirosis include fever, lethargy, and lack of appetite. Left untreated, it can develop into a more severe, life-threatening illness that affects the kidneys, liver, brain, lungs, and heart.


  • Prevalence of canine leptospirosis has increased in recent years.47,48
  • As many as 8.2% of dogs are shedding leptospires, some asymptomatically.49
  • Weather changes, population growth, and habitat encroachment have all increased human and canine exposure to pathogens and their carriers.47,48


Transmission of leptospirosis can occur through direct contact or indirectly through environmental exposure.

  1. Leptospires enter the body through mucous membranes in the mouth, eyes, or nose, or through abraded or water-softened skin.50
  2. Leptospires multiply in a host animal’s bloodstream.
  3. Leptospires move from the bloodstream to the kidneys and other tissues to continue reproducing.
  4. Leptospires pass from the kidneys into the urine; then are shed back into the environment.
  5. Other dogs, wild animals, or people can become infected through direct or indirect contact.


  • Fever
  • Lethargy
  • Weight loss
  • Anorexia
  • Depression
  • Acute renal failure
  • Jaundice
  • Abdominal discomfort
  • Vomiting and diarrhea
  • Blood in urine is uncommon, but may occur
  • Respiratory distress


Dogs at risk for developing leptospirosis include those with:51

  • Access to ponds, lakes, streams, or standing water
  • Exposure to urine from other infected animals, including:
    • Other dogs in shelters or other pet care facilities
    • Wildlife (e.g. rodents, racoons, opossum, deer), either through direct contact with urine or through contaminated water


As leptospirosis progresses, it can result in:50,51

  • Leptospiremia
    • Leptospires can multiply in the bloodstream and spread to many tissues and organs
  • Vascular damage/thrombocytopenia
    • Can lead to kidney failure and interfere with liver function
    • Contributes to coagulatory abnormalities and hemorrhages
  • Severe kidney and liver damage
    • Acute renal failure occurs in dogs with severe clinical signs
    • Acute hepatic dysfunction or chronic hepatitis have been caused by specific serovars


Leptospiruria (urinary shedding)50,51

  • Infected dogs can enter a carrier state
  • Organisms may persist in the kidney and be shed in the urine for weeks to months
  • Other dogs, wild animals, and humans can become infected from direct or indirect contact with these leptospires that were shed into the environment


Do you have a Standard Operating procedure to keep your staff and clinic safe if an outbreak occurs?

Merck Animal Health Vaccines


The only 4-way leptospirosis vaccine proven to protect against disease, mortality, and leptospiruria.


Easy Ways to Inform Pet Parents about Leptospirosis

Zoonotic Risks 2


Help prevent the spread of leptospirosis between dogs, other pets and humans with these tips.


Lepto Basics


Stay alert for these signs of leptospirosis to prevent the spread of this potentially deadly disease.


Dangers of Lepto


Hear leading veterinary experts Dr. Courtney Campbell and Dr. Michelle Evason discuss leptospirosis and how to prevent this dangerous zoonotic disease.  


Protect Your Pets & Family from Leptospirosis



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Professional Resources and Educational Materials

Keep your clinic and staff informed and aware of diseases and outbreaks.

Standard Operating Procedure


Learn why it’s important to have a Standard Operating Procedure to reduce the risk of leptospirosis in your practice.


Lepto SOP Technical Booklet

Review this detailed protocol with your staff to teach the “Recognize, React, Reduce” method of safely handling leptospirosis within the clinic.


Quick Guide to Lepto


A handy guide to protect dogs and prevent the spread of leptospirosis.

Learn More

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Urinary Shedding Challenge Study

Prevention of Leptospiremia and Leptospiruria Following Vaccination With a DAPPv + 4-way Leptospira Combination Vaccine

Rhonda L. LaFleur, Jennifer C. Dant, Anna L. Tubbs, Huchappa Jayappa, David Sutton, Ian Tarpey

Background: Leptospirosis, characterized by high fever, anorexia, vomiting, abdominal pain, diarrhea, myalgia, polyuria/polydipsia, jaundice, epistaxis, hematuria, and/or reproductive failure, continues to cause considerable morbidity among infected canines. Direct transmission of Leptospira spp. occurs when dogs come into contact with infected urine or ingest infected tissue. After dogs become infected, the spirochetes circulate in the blood for several days1,3 where they cause extensive damage to the endothelium of small blood vessels (leptospiremia). After the leptospiremic phase, the spirochetes can further colonize various organs, including the kidneys, where dogs can become a carrier and potentially shed organisms in the urine for months (leptospiruria). Leptospira interrogans serovars Canicola and Icterohaemorrhagiae are traditional causative agents of canine leptospirosis, and while the use of bacterins have decreased the prevalence of the disease, significant morbidity can still be attributed to infection with these serovars.

Aim of the Work: In this study, we combined inactivated L interrogans serovars Canicola, Pomona, and Icterohaemorrhagiae and L kirschneri serovar Grippotyphosa with Nobivac® Canine 1-DAPPv (Animal Health at Merck & Co., Inc., Kenilworth, NJ USA), a commercially available vaccine that contains modified live canine distemper virus, adenovirus, parainfluenza virus, and parvovirus. We then vaccinated dogs with the combination product and evaluated the ability of the vaccination to prevent leptospiremia and leptospiruria following challenge with viable organisms of each serovar.


Read More about this study here

Disease & Mortality Study

Prevention of Disease and Mortality in Vaccinated Dogs Following Experimental Challenge With Virulent Leptospira.

R LaFleur, J Dant, T Wasmoen. Intervet / Schering Plough Animal Health, Elkhorn, NE.

Canine Leptospirosis can vary from subclinical infection to illness that ranges from mild to severe, including death, depending on the susceptibility of the dog, virulence of the organism, and route and degree of infection. The objective of this study was to evaluate the ability of a canine Leptospira bacterin to prevent infection and disease following challenge with virulent Leptospira canicola, L. pomona, L. grippotyphosa, or L. icterohaemorrhagiae. Groups of 8-week-old beagles were vaccinated (day 0) and boosted (day 21) with placebo (n = 10) or the 4-way bacterin (n ≥ 20) and subsequently challenged with each serovar. The results demonstrated that blood and various tissue samples from placebo-recipients became reliably infected, and the dogs developed typical clinical signs of Leptospirosis including loss of appetite, ocular congestion, depression, dehydration, jaundice, hematuria, melena, vomiting, petechiae, and death. In addition, placebo-recipients developed kidney and liver dysfunction. In contrast, some vaccine-recipients became infected, but the organisms were cleared quickly from the blood. Vaccinated dogs failed to develop severe clinical disease requiring medical intervention, and no animals died (p > 0.001). A few of the vaccinated dogs developed clinical abnormalities, but the clinical signs remained mild and were self-limiting (p < 0.0001 for each serovar). Administration of the bacterin also prevented thrombocytopenia (p < 0.0001), kidney complications caused by L. canicola (p < 0.0001), L. icterohaemorrhagiae (p < 0.0001), and L. pomona (p = 0.012), and liver dysfunction caused by L. pomona (p < 0.0001) and L. grippotyphosa (p < 0.0001). The results therefore confirmed that vaccinating dogs with the 4-way Leptospira bacterin provided a high degree of protection (99.5%-100%) against the clinical signs of Leptospirosis including mortality.

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