Leptospira bacteria on stain of liver impression smear. Photo by Mildred M. Galton/CDC

Leptospirosis is a zoonotic disease caused by bacteria. Zoonotic disease, or zoonosis, means the disease can be transmitted to humans from infected animals.

Infection

Water or soil contaminated by the urine of infected animals spreads the bacteria through contact or ingestion.

The bacteria can enter through broken or scratched skin, through mucous membranes (eyes, nose, or mouth), by drinking the contaminated water, or by direct contact with an infected animal, such as a bite wound. Raccoons, rats, squirrels, skunks, deer, and opossums are common carriers of the bacteria.

Host species (animals that continuously harbor an infectious pathogen, in this case, leptospirosis) may continue to excrete bacteria (called shedding) into the environment, either continuously or sporadically, for a few months to several years. The host species of leptospirosis tend to be rodents and other wild animals.

Dogs are not likely long-term shedders.  

It is more likely that a dog becomes infected by contact with contaminated soil or standing water, but transmission is possible if your dog consumes a diseased animal.

An infected mother may pass on the disease to her puppies, and farm animals can become infected through breeding.

Leptospirosis has become a more common disease for domestic dogs because of contact with areas contaminated by urban wildlife.

Leptospirosis is rarely passed from dog to dog.

Cats seem to be less vulnerable to leptospirosis bacteria, and if infected, it is believed that contact with diseased rodents is the most probable cause of infection.

Areas that see more rainfall and where there is standing water increase the risk of exposure. The bacteria die quickly when the standing water dries out.

Signs

Signs of leptospirosis in a domestic dog can include:

• Fever
• Lethargy (sleepiness)
• Appetite loss
• Diarrhea
• Urination changes
• Jaundice
• Joint and/or muscle pain
• Eye and nasal discharge
• Vomiting and back pain from kidney damage

Early Veterinary Treatment

Testing

Your veterinarian may screen for leptospirosis by running blood and urine tests. A PCR test that looks for the bacteria's DNA, in this case the leptospirosis organism, will likely be run. 

Treatment

Early treatment is recommended. Leptospirosis is treated with antibiotics such as doxycycline or another drug from the penicillin-family. Your veterinarian may recommend fluids to prevent dehydration. Support therapy includes medications to prevent vomiting and to relieve gastrointestinal issues if present.

Prognosis

Dogs treated early with appropriate antibiotics and fluid therapy generally have a good prognosis.

Without early intervention, the illness can progress, and possible complications include chronic kidney or respiratory disease.  If these issues are a concern, your veterinarian will discuss additional treatments and possible outcomes depending on how serious the disease is.

Prevention

Preventive measures are recommended.

Vaccinations: vaccinate your dog against leptospirosis. The vaccine does not provide 100% protection. This is because there are many strains (types) of leptospires (the bacteria that cause Leptospirosis), and the vaccine does not provide immunity against all strains.

Currently, there is no leptospirosis vaccine available for cats.

Contact your veterinarian for information on vaccinating livestock.

Husbandry: Rodents can carry and spread the bacteria that cause this disease (see Prevent Rodent Infestations). Keep rodent problems (rats, mice, or other animal pests) under control.

Precautions

In addition, be sure to follow these recommended prevention guidelines:

• Do not handle or come in contact with urine, blood, or tissues from your infected pet before it has received proper treatment.
• If you need to have contact with animal tissues or urine, wear protective clothing, such as gloves and boots, especially if you are occupationally at risk (veterinarians, farm workers, and sewer workers).
• Cover any would you may have with waterproof dressing.
• Always wash your hands after handling your pet or anything that might have your pet’s excrement on it.
• If you are cleaning surfaces that may be contaminated or have urine from an infected pet on them, use an antibacterial cleaning solution or a solution of 1 part household bleach in 10 parts water.
• Make sure that your infected pet takes all prescribed medication and remember to follow up with your veterinarian