Leptospirosis is not a disease that is commonly seen in dogs in our area of Northern California, so it may be easy to overlook this disease when choosing which vaccines to give a dog. But despite its lack of epidemic status, leptospirosis is out there and all dog owners should be aware.
Leptospira interrogans, the causative agent of leptospirosis, is a spirochete bacterium that can be further divided into different serovars, or subtypes. It can infect many different species, including wildlife, dogs, cats (rarely), and humans (making it a zoonotic disease). The bacteria are shed from the infected host via urine. Leptospirosis is spread by infected urine or urine-contaminated water contacting the body through mucous membranes, open wounds, or ingestion.
When the bacteria enter the body, they populate the kidneys and start to multiply. Thus, symptoms of leptospirosis significantly overlap with the symptoms of any cause of kidney disease: lethargy, decreased appetite, vomiting, increased thirst, and increased urination.
Leptospira bacteria do not only affect the kidney, however; other potential symptoms of leptospirosis include generalized pain and stiffness, joint pain, fever, jaundice, and early termination of pregnancy. Some animals never show symptoms if the infection is mild enough, but they can still continue to spread the bacteria into the environment.
There are many reservoirs for leptospirosis in the environment. Wildlife such as deer, opossum, and skunks can all carry and spread the disease. Livestock animals may also spread the bacteria. Historically, dogs considered to be at increased risk for developing leptospirosis were those who spend time hiking or camping, live on a ranch, or play in slow-moving waterways such as agricultural ditches.
As the disease is better understood in dogs, it is being discovered that there are many dogs that do not fit the above profile that still develop leptospirosis. So-called “city dogs” may still contract the bacteria due to urban hosts such as raccoons, squirrels, and rodents.
Diagnosis of leptospirosis in dogs can be difficult. As noted above, the signs of infection are not specific to this disease, so many other conditions are possible in dogs with these symptoms. There is also a lack of a quick and easy diagnostic test for leptospirosis, largely due to wide array of serovars and the way the immune system reacts to the bacteria. Dogs that are suspected to have leptospirosis may be started on treatment even before the diagnosis has been made.
Luckily, Leptospira is typically susceptible to common antibiotics such as penicillin. However, clearing the bacteria is only part of the issue—any damage to the kidneys, liver, or other body systems must be addressed even after the bacteria is gone. For some severe cases, this may mean dialysis treatments until the kidneys can start functioning properly again. Leptospirosis can ultimately be fatal.
It is much preferable to prevent leptospirosis rather than to treat it. There are vaccines available for dogs that protect against a few of the more common serovars of Leptospira. The initial series of this vaccine is two injections, about one month apart. These are followed by yearly boosters. The leptospirosis vaccine may be a standalone injection, or combined in a multi-way vaccine (e.g., the “L” in a “DHLPP” vaccine). Since more dogs are now thought to be at risk for exposure to leptospirosis, this vaccine should be considered even in dogs that have not received it in the past.
Vaccinated dogs can still get leptospirosis, whether from poor immune system response to the vaccine or infection with a serovar that the vaccine does not protect against. Dog owners should be aware of the symptoms of this disease and seek veterinary care immediately if leptospirosis is suspected.
— Keith Rode is a veterinarian at Woodland Veterinary Hospital and a graduate of UC Davis. For more information, call 530-666-2461.