Leptospirosis is a bacterial infection caused by various strains of the Leptospira bacteria. It typically spreads through the urine of infected animals, contaminating soil and water, and can survive there for weeks to months.
There are different types of leptospires, but the ones responsible for causing diseases fall under a specific species known as Leptospira interrogans sensu lato. Within this category, Leptospira interrogans sensu lato is further divided into smaller related groups called serovars. There are over 250 named serovars, and at least 10 of them are relevant to pets.
One such serovar is Icterohaemorrhagiae, which is commonly linked to contact with rats and rat urine in stagnant water. This serovar primarily affects the liver.
Humans and animals can contract the disease through contact with contaminated environments, water, or direct exposure to the urine of infected animals.
The classic transmission route for dogs and humans involves the urine of infected animals contaminating environmental water. Leptospirosis is prevalent in tropical areas, particularly in regions where rice is cultivated, and paddies are infested with rats. Urban areas are also facing an increased incidence of canine leptospirosis, with health authorities linking it to rat populations. It's important to note that leptospirosis is no longer confined to rural areas; it has become a concern in urban settings.
The 2021 leptospirosis outbreak in Los Angeles originated in boarding facilities, where dogs often come into contact with the urine of other dogs in play areas and kennel drainage paths. Any place with possible urine exposure becomes a potential environment for Leptospira organisms.
Leptospires thrive in warm, slow-moving water, often after heavy rains or flooding. Even after the water recedes, they can linger in the soil for many months. Wildlife, such as raccoons and rats, are frequent carriers of the infection. Surveys in Connecticut and Illinois revealed significant exposure rates in raccoons, with 36% and 48% respectively. Additionally, 50% of rats in another survey had been exposed.
Dogs contract leptospirosis when irritated or broken skin comes into contact with infected urine or water containing infected urine. Transmission can also occur through bite wounds, exposure to reproductive secretions, or consuming infected tissues.
The bacteria rapidly spread through the bloodstream, initially causing inflammation in blood vessels, with symptoms like fever, abnormal bleeding, bruising, and tissue swelling appearing after a 7-day incubation period.
Around 2 weeks post-infection, leptospires settle in the kidneys, causing ongoing inflammation, pain, and potential kidney failure, leading to an inability to produce urine. Some serovars(strains) may also affect the liver, though liver disease is generally less severe than kidney involvement.
A critical situation arises if the bacteria enter the lungs, resulting in "Leptospira Pulmonary Hemorrhage Syndrome." Lung bleeding associated with this has a high mortality rate of 70%.
In cases where the acute illness is controlled, a chronic form may develop, manifesting as persistent kidney insufficiency, hepatitis, or long-term immune stimulation leading to uveitis—a deep eye inflammation causing cloudy or color changes. Treating the disease at this stage may not reverse the established long-term damage.
Symptoms range from mild flu-like issues to severe conditions such as kidney and liver damage.
In 87-100% of infected dogs, there will be some level of azotemia. Azotemia refers to elevated levels of certain substances like urea and creatinine in the blood. These are indicators checked during routine blood tests to assess kidney function. Elevated azotemia levels often signal potential issues with the kidneys.
There is a vaccine available for dogs, targeting four specific strains of the bacteria. It's important to note that various strains, known as serovars, are associated with different types of the disease and are prevalent in specific geographic regions. Vaccination lessens the severity of the disease but doesn't stop infected dogs from becoming carriers.
Vaccines for Leptospira interrogans sensu lato cover specific serovars: Canicola, Grippotyphosa, Pomona, and Icterohaemorragiae. The vaccine's effectiveness is challenging to gauge due to longstanding use. Recent outbreaks often involve unvaccinated serovars, indicating the vaccine's efficacy.
Leptospirosis vaccination is standard in the basic distemper shot (DHLPP) for dogs. While it's optional per American Animal Hospital Association, if chosen, opt for a vaccine covering all four serovars.
Historically, the leptospirosis vaccine had a higher risk of reactions, but modern protein-free vaccines have reduced this likelihood. Typical reactions include fever, swelling, and joint/muscle pain, often resolving within a day. Smaller dogs may have a higher chance of reactions.
Consult your veterinarian for guidance on treatment and precautions.
Fortunately, the bacteria causing Leptospirosis in dogs are sensitive to doxycycline, a common antibiotic, which can clear the bacteria from the blood within 24 hours. However, it may take about a week for them to clear from the urine, so precautions are needed.
Infected animals should be isolated during treatment, and thorough cleaning with iodine-based products is essential for contaminated areas.
Intravenous fluids are crucial to support damaged kidneys, and the prognosis depends on the extent of organ damage, with reported survival rates of 80-90% with appropriate treatment. However, factors like severe cases requiring dialysis or poor survivability in lung involvement can affect outcomes. Repeated infections are possible, and past infection doesn't guarantee future immunity. Consult your veterinarian for guidance on treatment and precautions.
Source: Center of Disease Control and Prevention: https://www.cdc.gov/leptospirosis/pets/index.html
Source of information:Center of Disease Control and Prevention: https://www.cdc.gov/leptospirosis/pets/index.htmlVeterinary Partner: https://veterinarypartner.vin.com/default.aspx?pid=19239&id=4951453
Genevieve Tan
