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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.

Fast Facts about Leptospirosis

  • Prevalence of canine leptospirosis has increased in recent years.2,3
  • As many as 8.2% of dogs are shedding leptospires, some asymptomatically.4
  • Weather changes, population growth, and habitat encroachment have all increased human and canine exposure to pathogens and their carriers.2,3


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.13
  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.

Clinical Signs13

  • 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

Dogs at risk for developing leptospirosis include those with:5

  • 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, raccoons, opossum, deer), either through direct contact with urine or through contaminated water

Morbidity Threats

As leptospirosis progresses, it can result in:5,13

  • 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 coagulation 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

Spreading Disease

  • Leptospiruria (urinary shedding)5,13
    • Infected dogs can enter a carrier state
    • Organisms may persist in the kidney and be shed in the urine for weeks to months

Keep Your Staff Protected From Leptospirosis

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

Watch The video Download the Lepto SOP Download Clinic Safety Tips

Merck Animal Health Vaccines

Nobivac® Lepto4

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

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Also Available in Combination Formulation

Easy Ways to Inform Pet Parents about Leptospirosis

Zoonotic Risks

Help pet parents understand the risks associated with leptospirosis and how to take precautions to protect their pets and family.

Signs of Disease

Help pet parents to recognize the signs and symptoms of leptospirosis.

Leptospirosis Basics

Use this informative overview to help your parents understand leptospirosis the disease, its significance and how to minimize risks for their dog.

Diagnosis & Treatment

Share this basic video to help pet parents understand treatment options for leptosiprosis as well as what they can do to reduce their dog's risk.

Risks & Prevention

Help pet parents keep their pets safe with these preventative measures.

Understand Your Dog's Risk
Pet Parent Guide

Share this printable brochure to educate pet parents in your clinic about transmission, risks and outcomes.

Dangers of Lepto
PetLife Radio Podcast

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

Protect Your Pets & Family from Leptospirosis

Renowned pet journalist and radio host Steve Dale discusses protecting your pets & family from leptospirosis.

Rain & Leptospirosis

Renowned pet journalist and radio host, Steve Dale discusses how rain may be linked to increase in leptospirosis.

More Pet Parent Resources

Professional Leptospirosis Resources & Studies

AAHA Vaccine Guidelines
Lifestyle Calculator

Determine vaccination recommendations based on a dog's lifestyle, age, and other risk factors.

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Quick Guide to Lepto

A handy guide to protect dogs and prevent the spread of leptospirosis by identifying risk factors and signs.

Combo Protection
Technical Bulletin

Read about the proven protection NOBIVAC® Canine 1-DAPPv+L4 Vaccine provides to help you protect your patients.

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Disease & Mortality Study
Read the study which proves high efficacy of Nobivac® Lepto4 vaccine under severe challenge.

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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Urinary Shedding Challenge Study
Read the study which proves Nobivac® Canine 1-DAPPv+L4 effectively protects against leptospiremia and leptospiruria of (4) serovars.

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 days,1,3 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 NobivacĀ® 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

More Resources & Studies