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What You Should Know About Leptospirosis

What You Should Know About Leptospirosis

By Jill Lopez, DVM

Leptospirosis is a disease caused by bacteria of the genus Leptospira.(1) Leptospirosis is one of the most widespread and prevalent diseases and it can infect both animals and people.(1,2,3,5) While there are over 200 types (also called serovars), the most common found in the US include grippotyphosa, bratislava, autumnalis, and ponoma.(1,2,3)

Leptospira bacteria prefer warm weather and wet environments. They can be found in rivers, lakes, creeks, and puddles.(1,2,3) Flooding and heavy rainstorms can spread the contaminated water. Under optimal conditions, Leptospira can remain in the environment for months. Peak incidence of the disease in dogs typically occur in the summer and fall, following heavy rainfall.(1,2,3) According to an article from American College of Veterinary Internal Medicine (ACVIM), the regions with the highest areas of prevalence amongst dogs include Hawaii, California, Oregon, Washington, the upper Midwest, the Midwest parts of Texas, Colorado, and the Northeast and Mid–Atlantic coastal regions.(1,5) A study of 1,241 healthy dogs in Michigan showed that 24.9% had Leptospira antibody titers.(1,5)

Clinical Signs

Leptospirosis results in illness of varying severity in dogs. Some dogs may appear normal or display mild signs of disease, while others become severely ill. Leptospirosis is often suspected when a dog shows signs of kidney or liver disease. Fever and lethargy are also common signs of disease.(1,2,3)


Leptospirosis can be transmitted by a variety of domestic and wild animals. Since rats can spread the disease, dogs in urban environments are at risk for this disease. Infected animals shed Leptospires (the infective stage) in their urine.(4,5) Dogs usually become infected through contact with infected urine or bodily fluids. Transmission can occur through exposure to contaminated water or soil.(4,5)

Dogs can become infected by drinking contaminated water from rivers, lakes, puddles, or even contaminated water bowls. Leptospires can easily penetrate the skin and also the mucous membranes. Leptospires then go into the blood stream and multiply.(1,2,3) They then spread throughout the body and replicate in many organs, including the kidneys and liver. Incubation period for this disease is approximately 7 days.(4,5) 

Zoonotic Potential

Leptospirosis is a zoonotic disease, which means it can be passed from animals to people. While people can get Leptospirosis from infected dogs, it is more commonly associated with direct exposure to infected water.(2,5) People can also become infected with Leptospirosis through recreational activities such as boating, freshwater swimming, and hunting.(1,5) Some people have contracted Leptospirosis from direct exposure to infected rodent urine.

People that enjoy outdoor recreation or that work with animals, such as doggie daycare workers, kennel employees, veterinarians, and shelter volunteers, are most at risk for catching this disease. Without treatment, Leptospirosis can lead to kidney damage and liver failure and can be fatal.(1,2,4,5) The severity of the disease varies, just like in dogs. Some people that are infected may look and feel completely normal, while others may have flu like signs. The most severe form of the disease is called Weil’s disease and involves liver and kidney failure.(1,2,5) Although it is not a reportable disease in several countries, there is an estimate of 300,000–500,000 of severe human cases of Leptospirosis reported each year worldwide.(1,5)


There are many tests that can be performed to determine if a dog has a Leptospirosis infection, most require samples of either blood or urine.

The MAT, or Micro–Agglutination Test, is commonly performed to confirm Leptospirosis. In this test, a serum sample is mixed with a culture of Leptospirosis and then it is examined for clumping, which is called agglutination.(1,2,3) IDEXX laboratories recently introduced a snap test for Leptospirosis that can be ran in the veterinary clinic.(2) 


Antibiotics are used to treat Leptospirosis in dogs. According to the American College of Veterinary Internal Medicine (ACVIM), the antibiotic of choice is Doxycycline.(5) In addition, the dog is treated with supportive care, including intravenous fluids to support kidney function. Animals with severe disease have a very poor prognosis.


Leptospirosis vaccines are effective in helping to prevent disease and some vaccines are actually proven to prevent shedding of the disease. Dogs that have contact with wildlife, swim, or roam would be especially at risk. However, even those dogs that live in urban areas may be at risk, since the disease can be spread through rat urine. Most veterinary experts recommend giving vaccines that contain 4–serovars rather than just 2.(4,5) Dogs will receive an initial vaccination and then a booster, usually within 2–4 weeks, and then they would receive the Leptospirosis vaccine on an annual basis. 

To learn more about Leptospirosis, you can visit the Center for Disease Control’s website:


Sykes Jane E, Leptospirosis, World Small Animal Veterinary Association World Congress Proceedings 2014.

Langstom C: Leptospirosis. Atlantic Coast Veterinary Conference 2010.

Greene CE, Sykes JE, Brown CA: Leptospirosis. Infectious Diseases of the Dog and Cat, 3rd ed. Philadelphia, WB Saunders 2006 pp. 402-416.

Goldstein GE: Canine Leptospirosis 2010: Update on Diagnosis, Treatment and Prevention (S21B). Western Veterinary Conference 2010.

Sykes JE, Hartmann K, Lunn KF, Moore GE, et. al: 2010 ACVIM small animal consensus statement on leptospirosis: diagnosis, epidemiology, treatment, and prevention. J Vet Intern Med 2011 Vol 25 (1) pp. 1-13.

Dr. Jill Lopez is a veterinarian with Merck Animal Health. She started her career as a small animal practitioner in West Virginia and has worked in various segments of the Animal Health Industry for over 15 years. She has particular interests in pet safety, infectious disease, and general health issues.