What Is It?

Leptospirosis is a disease caused by a spiral-shaped bacteria (spirochete) called Leptospira interrogans. Several strains or serovars of this bacteria may infect dogs including L. icterohaemorrhagiae, L. canicola, L. grippotyphosa, L. pomona, L. bratislava, and L. autumnalis. Dogs usually become infected when infected urine is ingested in water, food, bedding, soil, plants, or other contaminated material. Infection may also occur if the bacteria is absorbed through damaged skin. Less commonly, bite wounds, reproductive secretions, or consumption of infected tissues can lead to infection. Wild animals (raccoons, squirrels, rodents, skunks, opossums, deer) and farm animals serve as reservoirs for this disease. Less commonly, infection may be transmitted between dogs. The organism can survive in the environment for weeks to months.

Following infection, the bacteria target the kidneys and liver. Clinical signs of leptospirosis vary. Often, pets have no clinical signs or nonspecific signs such as fever, vomiting, diarrhea, abdominal pain, decreased appetite, increased water consumption, lethargy, or weakness. Unfortunately, many other more common clinical conditions cause these clinical signs, so leptospirosis is easily missed in these early stages. Kidney failure, liver failure, joint pain, muscle pain, stiffness, spontaneous bleeding, reproductive abnormalities, pneumonitis, and meningitis are some of the more severe clinical abnormalities seen with this disease.


Diagnosis begins with a complete medical history and a thorough physical examination. Routine laboratory tests including a complete blood count (CBC), chemistry profile, urinalysis, and urine culture should be performed to exclude less common diseases. Antibody testing can detect the most common serovars that infect dogs. However, if a pet has been recently vaccinated, titers may be difficult to interpret. High titers (greater than 1:800) suggest infection, but vaccination within the last 3 months can stimulate a marked elevation of antibody titers. A single titer of greater than 1:800 in an unvaccinated dog or for one of the serovars in which vaccination is not available is considered diagnostic for disease. In questionable cases, a second titer may be submitted 2-4 weeks later. A rising titer (4-fold increase) suggests an active infection.

Recently, a DNA polymerase chain reaction (PCR) test became available to detect Leptospira in the blood and urine, though it is not performed routinely.


Fortunately, Leptospira is sensitive to penicillin. Initially, penicillin, ampicillin, or amoxicillin is administered for 2 weeks. This phase of treatment eliminates the organism from the blood stream. This must be followed with a 2-week course of doxycycline, a second antibiotic that eliminates the carrier state and reduces the risk of continued shedding of the organism in the urine.

Depending on the degree of organ damage, additional therapy may be necessary. Intravenous or subcutaneous fluid therapy, medications to control vomiting and diarrhea, nutritional support, and additional supplements may be prescribed depending on your pet’s clinical status.

Until your pet has completely finished therapy, bacteria may be shed in the urine and be infectious to other dogs or humans. Every effort should be made to limit exposure to your pet’s urine.


A vaccination is available that offers protection against four serovars: L. icterohaemorrhagiae, L. canicola, L. grippotyphosa, and L. pomona. Some cross-protection exists for L. autumnalis, but unfortunately, at this time, there is no vaccine for L. bratislava. While this vaccine does not offer 100% protection, vaccination is still recommended. While any vaccine can lead to a vaccine reaction, most pets tolerate this vaccine well. Always monitor for vomiting, diarrhea, decreased appetite, lethargy, facial swelling, or lumps at the injection site after any vaccine.

If possible, keep rats, mice, squirrels, raccoons, opossums, and deer out of your yard. In addition, avoid contact with urine from farm animals. Lastly, prevent the accumulation of standing water or moist areas in your yard that may harbor Leptospira organisms and prevent your dog from drinking from water puddles.

Is Leptospirosis Zoonotic?

Yes, humans are susceptible to infection with Leptospira. Infection occurs by ingestion of contaminated urine or absorption through damaged skin. If your pet has been diagnosed with this disease, caution must be taken when handling your pet’s urine. Wear gloves and practice good hand-washing techniques. A dilute bleach solution (1 part bleach to 10 parts water) should be used to clean any surfaces contaminated with urine.

In humans, clinical signs are generally flu-like in nature and may include fever, chills, vomiting, diarrhea, or headaches. Leptospirosis can develop into a more severe, life-threatening illness with infection of the kidney, liver, brain, lung, and heart. If you have concerns about possible infection with leptospirosis, contact your physician. A fact sheet is available from the Centers for Disease Control (CDC) at the following website:


Contact your veterinarian if you have concerns about leptospirosis in your pet. It can be a serious, life-threatening disease.

Written by Jennifer Blair, DVM

Content prepared by St. Francis Animal Hospital, 1227 Larpenteur Ave. West, Roseville MN. 55113