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What You Need to Know About Leptospirosis

Because dogs of any age, size, or breed can be affected by leptospirosis, it is important for the public to be aware of leptospirosis and use appropriate prevention measures to keep their animals and themselves safe.


What is leptospirosis?

Leptospirosis, or “lepto,” is a zoonotic bacterial disease found throughout the world. Zoonosis is a scientific term used to describe diseases that can be transmitted from animals to humans.

There are 250 different types, or serovars, of leptospiral bacteria. Eight of these are thought to affect dogs. Although some serovars have shown the ability to infect cats, this is extremely rare.

Leptospira bacteria can live in the kidneys of infected animals for extended periods and are spread to other animals through exposure to urine. The majority of serovars are carried and spread by rodents, skunks, raccoons, and deer.

Dogs most commonly acquire leptospirosis infection through a contaminated environment such as soil, food, bedding, or water. Contact with stagnant or slow-moving water where animals carrying and shedding leptospira bacteria urinate is the most significant form of exposure. Dogs can be infected by drinking contaminated water or through contact with open wounds. It is rare to acquire leptospirosis through direct contact with an animal infected with leptospira bacteria (biting, ingesting affected carcasses). Because leptospira bacteria are usually water-borne, there is often an increase in the number of leptospirosis cases during and shortly after periods of higher rainfall.

After entering the body, leptospira bacteria multiplies rapidly in the blood stream for a few days before invading organs, often the kidney and liver.

What are the symptoms?

Leptospirosis can infect a variety of organs and therefore the symptoms may vary. The most common symptoms we see in dogs are consistent with kidney or liver damage/failure. Some of the signs you may see include:

• Gastrointestinal signs, including vomiting, diarrhea, uncharacteristic lethargy/weakness, and loss of appetite.

• Urinary signs including blood in urine and increased water intake and urination.

These signs are not specific for leptospirosis. If any of these symptoms are noticed, it is advised to consult a veterinarian.

How is it diagnosed?

Your veterinarian may want to run a variety of tests if your pet presents with any of the lepto signs. Tests may include general bloodwork, urine testing, imaging studies (X-rays, abdominal ultrasounds/sonography), or other specific tests.

Based on your pet’s history, exposure potential, past vaccines, physical exam, and the test results, the decision for specific testing for leptospirosis can be made. To diagnose leptospirosis most veterinarians will run either a PCR, or polymerase chain reaction, test or serology (detecting antibodies) to identify the organism in blood and urine.

How is it prevented?

The most effective measure is vaccination. Generally, there is an initial two-injection series of the vaccine (usually as a puppy) and then an annual booster.

At home, control involves limiting exposure to potential sources of leptospirosis. Limiting access to stagnant or slow-moving water while on walks by keeping your dog on a leash could help reduce the risk. Skunk and rodent (carrier animals) control in and around your home may be of benefit.

What is the risk to humans?

The majority of human infections are through water-related activities in infected reservoirs. Urine from infected dogs can cause infection in humans through contact of breaks in the skin (wounds, etc.) or mucosal surfaces (mouth, eyes, etc.). Protective measures should be taken if your animal has leptospirosis. This involves wearing latex gloves and properly disposing of urine or urine-contaminated items. Appropriate antibiotic therapy for dogs with leptospirosis can greatly reduce the risk of transmission from dogs to humans.

What is the treatment of choice?

For successful treatment of leptospirosis, many dogs will require an initial period of hospitalization. There are two main therapies for treatment of leptospirosis infections in dogs. The first is supportive care that may include fluid therapy, anti-vomiting drugs, antacids, and other medications. Appropriate antibiotics, the second main therapy, is the most important treatment for leptospirosis, and early initiation of this therapy is critical. After recovery (when the dog no longer shows symptoms), animals can continue to shed the bacteria in their urine for many weeks. Continuing antibiotic therapy during this period can reduce this shedding. On vary rare occasions, dogs can carry the infection lifelong.

Despite appropriate therapy, a very small number of dogs with leptospirosis suffer severe, sudden renal failure. For these patients, intensive treatment with hemodialysis might be needed. Hemodialysis is available only at a very few specialized clinics around the country.

What is the prognosis?

Prognosis depends on the degree of damage to the kidneys/liver and severity of clinical signs. If treatment is initiated early and is effective, the overall survival rate approaches 80 percent.

Luke Johnston, BVSc (Hons), is a rotating veterinary intern at VCA San Francisco Veterinary Services. An Australian, he obtained his veterinary degree at the University of Queensland. After an internship in Australia at VSS Gold Coast, he moved to America to further his education and experience. His main interest in veterinary medicine is liver disease in dogs and cats. He wanted to credit Craig Maretzki, D.V.M., an internal medicine specialist, for assistance with this article.

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Main article photo by: Jesse Wagstaff-Creative Commons