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General Information

Leptospirosis is a serious bacterial disease that infects dogs, people and several other types of animals. There are numerous types (called serotypes) of leptospires. Though each type is infectious only for certain animals, some infect several species, including people. One important thing about these sub-types of Leptospirosis is that vaccination for one "serovar" does not necessarily protect against other sub-type. In the late 1990's a resurgence of this disease has been seen over the entire United States. The subtypes that have been observe most frequently have been types NOT included in most canine vaccines. In addition to this many vaccines given to dog do not include ANY leptospira serovars. At Foothills Animal Hospital we recommend that all (well, MOST!) dogs be vaccinated against leptospirosis. With the development of vaccines for the newly emerging stains of lepto we are currently recommending adding vaccination against the new strains even though this means needing a BOOSTER for this vaccination. In the early 2000's many of the advisory committees changed their recommendation and have STOPPED recommending leptospirosis for dogs at low risk for exposure. It would be fair to say that we should look at each individual and make a decision.

These bacteria attack the kidneys, liver and nervous system. Recovered animals may shed the organism in their urine for up to 1 year. Infected rats are a common source of leptospirosis.

Vaccination is the best prevention for leptospirosis. All dogs should be vaccinated yearly. This vaccine is commonly combined with the distemper, hepatitis, parvovirus and parainfluenza vaccines. (see the comments on the new "serovars" in the first paragraph)

Important Points in Treatment

1. Laboratory tests of blood and urine are necessary to diagnose and monitor the response to treatment of leptospirosis. Hospitalization is often necessary.

2. Give all medication as directed. Call the doctor if you cannot give the medication.

3. Diet:

4. Activity:

5. Isolation: Because leptospirosis is a contagious disease animals having or suspected of having leptospirosis should not be allowed contact with other dogs until the urine is non-contagious. The doctor will advise you as to the length of time necessary and the frequency of follow-up urinalyses.

6. Avoid contact with your pet's urine. Any urine-soiled area should be cleaned with detergent and rinsed with an iodine-based disinfectant. (I'm not actually sure what we were recommending here, probably Betadine). Many people have caught leptospirosis while handling animals with leptospirosis. Good sanitation can prevent this in most cases. Please discuss any unusual cleaning problems with the doctor.


Leptospirosis is a disease of worldwide significance that infects both animals and humans. The scientific name of the infecting organism is Leptospira interrogans sensu lato. Within this species there are many different strains (serovars). Of these different strains there are 8 that are of importance for dogs and cats. These different strains produce different levels and types of disease depending on the animals they infect. While cats can be infected they rarely show signs of disease. The disease is much more of a problem in dogs, people and livestock. There are vaccines available but usually only for one or two of the more common strains. Unfortunately vaccination against one strain does not protect against the other strains. The current canine vaccines protect against the serovars canicola and icterohaemorrhagiae. These two serovars have been decreasing in total number of infections but unfortunately other serovars that infect dogs such as grippotyphosa, pomona, and bratislava have increased.

Leptospirosis is transmitted between animals through contact with infected urine; venereal and placental transfer; bite wounds; or the ingestion of infected tissue. Crowding, as found in a kennel, can increase the spread of infection. Indirect transmission occurs through exposure of susceptible animals to contaminated water sources, food, or even bedding. Stagnant or slow moving water provides a suitable habitat for Leptospira. As a result, disease outbreaks often increase during periods of flooding. In dry areas infections are more common around water sources.

Freezing greatly reduces the survival of the organism in the environment. This explains why infections are more common in summer and fall and why the infection is more prevalent in temperate areas.

Leptospira bacteria penetrate mucous membranes or abraded skin and multiply rapidly upon entering the blood system. From there they spread to other tissues including the kidney, liver, spleen, nervous system, eyes, and genital tract. As the body fights the infection the organism is cleared from most organs but they may persist in the kidneys and be shed for weeks or months in the urine. The amount of damage done to the internal organs is variable depending on the serovar and the host it infects. After 7 or 8 days of infection the animal will begin to recover if the damage to the kidneys or liver is not too severe.

Infections in dogs with the serovars canicola and grippotyphosa have been associated with kidney infections with minimal liver involvement. Whereas the serovars pomona and icterohaemorrhagiae produce liver disease. Dogs younger than 6 months tend to develop more cases of liver disease regardless of the serovar.

In acute infections a fever of 103-104 degrees, shivering, and muscle tenderness are the first signs. Then vomiting and rapid dehydration may develop. Severely infected dogs may develop hypothermia and become depressed and die before kidney or liver failure has a chance to develop.

In subacute infections the animal usually develops a fever, anorexia, vomiting, dehydration and increased thirst. The dog may be reluctant to move due to muscle or kidney pain. Animals with liver involvement may develop icterus. Dogs that develop kidney or liver involvement may begin to show improvement in organ function after 2 to 3 weeks or they may develop chronic renal failure. Despite the possibility of severe infection and death the majority of leptospiral infections in dogs are chronic or subclinical. Dogs that become chronically infected may show no outward signs but may intermittently shed bacteria in the urine for months or years.

A positive diagnosis can be made through a blood test. A blood sample of the suspected animal is drawn and sent into the laboratory where a microscopic agglutination test is performed. This can test for individual serovars (strains) and the level of antibody (titer) against these strains. Depending on the level of the titer a positive diagnosis to the specific serovar can be made. Titers may be negative in the first 10 days after initial infection so many times additional samples must be drawn and tested to get a positive diagnosis. Previous vaccination can give an elevated titer and this must be taken into consideration when interpreting the titers.

Acutely infected or chronically infected dogs will most likely be shedding Leptospira organisms in their urine. It is possible to culture a urine sample and get a positive diagnosis However, because of intermittent shedding and bacterial contamination this is not always the best way to diagnose the disease.

Treatment consists of antibiotics, fluid replacement, and controlling the vomiting and the problems associated with the corresponding kidney or liver infections. Penicillin or one of its derivatives is the antibiotic of choice for treating the initial infection. After the initial infection is controlled doxycycline is often used to cure and prevent a potential long-term carrier state. Intravenous or subcutaneous fluids are often given to correct dehydration while the corresponding liver or kidney problems are treated.

Vaccination and Prevention
Prevention involves keeping animals out of contact with potential sources of infection including contaminated water sources, wildlife reservoirs or domestic animals that are infected or chronic carriers. Humans can contract leptospirosis and any potentially infected animal should be handled very carefully to avoid human exposure.

There are currently many different vaccines available on the market for a wide variety of species and serovars. The ones currently available for dogs are chemically inactivated (killed) whole culture vaccine, which unfortunately make them much more likely to cause vaccine reactions as opposed to most viral vaccines. Leptospiral vaccines are blamed for the many of the vaccine reactions we see in dogs. Until the beginning of the year 2000, leptospiral vaccines only protected against L. canicola and L. icterohaemorrhagiae. A new vaccine by Fort Dodge now also protects against the serovars L. grippotyphosa and L. pomona. Due to the low infection rate in cats there are currently no vaccines available for them.

Leptospiral vaccines for dogs offer about 6 to 8 months of protection. Dogs that are at high risk of contracting Leptospiral infections should be vaccinated twice a year. Puppies generally aren't vaccinated before 8 weeks of age. If Leptospiral vaccines are used, the animal should receive two to three doses of the vaccine spaced several weeks apart. Be sure to follow the recommendations of the vaccine manufacturer and your veterinarian. Because of the lack of cross protection between strains, the high incidence of reactions, and the need for frequent vaccination many veterinarians have begun to recommend leptospiral vaccinations only for those dogs at higher risk. Because this can potentially be a very serious disease, I recommend that all pet owners consult with their local veterinarian to determine if leptospiral vaccination is necessary for their pet.