What is Leptospirosis?
Leptospirosis is a bacterial infection commonly seen in dogs that can affect a wide array of mammals including humans, wildlife like skunks, rats, racoons, and rarely, cats.
Leptospires are long, spiral shaped kinds of bacteria called spirochetes. Different kinds of spirochetes are responsible for other common diseases such as Lyme Disease.
Signs & Symptoms
There are several forms of clinical leptospirosis and thus the symptoms can vary widely.
Some commonly seen symptoms can include:
- Fever
- Muscle pain
- Vomiting
- Weakness/lethargy
- Increased thirst
- Increased OR decreased urination
- Decreased appetite
- Dehydration
- Yellow skin color or eyes (icterus)
Causes & Risk Factors
Leptospirosis infection usually occurs when the mucous membranes of the mouth, nose, or eyes of susceptible animals contact the bacteria in free standing water, vegetation, urine-contaminated soil or other similar settings.
Infection likely can also be spread by direct contact with infected individuals through grooming, fighting, or by eating infected animals.
Since urbanized wildlife (raccoons, skunks, coyotes, rodents, etc…) may carry and shed leptospirosis, even animals that do not venture into more rural settings should be considered potentially at risk.
The late summer and early fall show a spike in leptospirosis cases nationwide, but it can be seen year-round and it tends to be more prevalent in warmer, wetter climates. Hawaii has the most human cases in the United States.
Diagnosis
The gold standard diagnostic test is the microscopic agglutination test or MAT that is commonly referred to as ‘lepto titers’. MAT results often show false negatives during the first week of illness. The test can take 7 days for a final result, and prior vaccination (especially if within the last 4 weeks) can show false positives. Paired titers can be performed to look for a four-fold increase about 10-14 days after initial clinical signs which is confirmatory for Lepto.
The absence of a convincing serologic diagnosis should not prevent appropriate treatment if the clinical picture strongly supports a diagnosis of leptospirosis.
Paired PCR tests of urine and blood are gaining popularity as a reliable way to diagnose leptospirosis. Samples must be collected before any antibiotic is given or false negative results can occur. False negatives can also result if organisms are in too low a concentration.
At Angell Animal Medical Center, we commonly submit both Leptospirosis titers (MAT) and PCR since the PCR is the more specific test and MAT is more sensitive.
Treatment Options
Doxycycline is the first-line treatment for Leptospirosis. Depending on the severity of the case, supportive care to correct fluid and electrolytes, reduce nausea and vomiting, and provide nutrition may be needed. Furthermore, supporting the liver may be appropriate. Other therapies will be dependent on the severity of clinical signs, and in some severe cases may benefit greatly from dialysis, if available. Dialysis is a type of renal replacement therapy used for dogs with severe acute kidney injury. It is considered when kidney values are very high, electrolytes are dangerously abnormal, or the dog is producing little to no urine. Dialysis helps remove toxins from the bloodstream, restore fluid balance, and correct electrolyte disturbances while giving the kidneys time to rest and recover.
Prognosis
Leptospirosis is typically very responsive to appropriate antibiotic therapy. Survival rates are reported to be 80-90% in healthy dogs with quick and aggressive treatments
Prevention
There is a vaccine available in North America that has been shown to provide protection against Leptospirosis in dogs for up to 1 year. The vaccine is a bacterin, which means it is made from dead or inactivated bacteria that will stimulate the dog’s immune response.The vaccine for Leptospirosis protects against 4 different kinds of Leptospires, so there still may be possibility for vaccinated dogs to develop Leptospirosis from other strains. However, disease in vaccinated dogs is uncommon. Angell veterinarians strongly recommend all dogs receive annual Leptospirosis vaccination, regardless of lifestyle.
Other methods of prevention include decreased access to potential sources of infection, such as marshy areas and/or standing water and minimizing wild animal contact by use of fencing and rodent control measures.
Questions to Ask your Veterinarian
Is my dog up to date on the vaccine for leptospirosis?
Summary
In short: Leptospirosis is a serious but treatable infection. Preventative vaccination, early recognition, and appropriate treatment are key to keeping dogs safe.
This content was reviewed in 2025.
