Canine Leptospirosis
Leptospirosis is a bacterial infection that affects many species, including dogs and humans. Various types (serovars) of Leptospira bacteria exist worldwide, and some cause more serious disease than others. Leptospirosis is a zoonotic disease, meaning that humans can become infected through exposure to infected animals. Rodents are the main source of human infection.
What You Should Know
Clinical signs can be mild to severe, and fatal in some cases. The time between exposure to the bacteria and appearance of clinical signs is 2-14 days. Leptospirosis cases may increase during warmer seasons.
Classically, dogs will show clinical signs of kidney and liver dysfunction. Fever, vomiting, diarrhea, dehydration, lethargy, inappetence, abdominal pain, yellowing of skin and drinking an excessive amount of water with increased urination may be seen. Other signs include bruising, bloody urine, nosebleeds and coughing up blood. Respiratory disease or accumulation of fluid in a dog’s chest cavity or abdomen, as well as eye abnormalities, may be present. Leptospirosis can affect multiple organs, and not every dog will have every clinical sign.
Infected rodents and other animal hosts shed Leptospira bacteria in their urine. Dogs become infected when mucous membranes or abraded skin are exposed to infected urine or urine-contaminated water or soil. Dogs can also become infected via bite wounds or ingestion of infected tissue.
Bacteria remain viable for weeks to months in warm, wet environments. Disease may increase during periods of higher rainfall or following flooding. All dogs are at risk for leptospirosis regardless of age, location and lifestyle. Crowding of dogs in unsanitary shelter conditions increases the opportunity for the development of leptospirosis.
Leptospirosis should be considered in unvaccinated dogs with clinical signs and complete blood count (CBC), chemistry profile and urinalysis results consistent with recent onset of kidney and/or liver disease. Although it is possible for dogs vaccinated with a four-serovar Leptospira vaccine to become ill with this disease, other causes of illness should be considered in adequately vaccinated dogs.
The diagnosis of leptospirosis can be challenging. Diagnosis is based on clinical signs in addition to results of antibody and/or polymerase chain reaction (PCR) testing. With recent onset of illness, antibody tests are often negative. Blood and urine samples should be collected for PCR testing prior to administration of antibiotics. Previous vaccination with an inactivated Leptospira vaccine should not produce positive PCR results.
Diagnosis of leptospirosis is confirmed when associated clinical signs are present together with either positive PCR testing or a fourfold or higher increase in antibody titer between acute and convalescent serum samples.
Point-of-care tests are available for rapid detection of associated antibodies. Such tests have limitations that should be understood to accurately interpret results.
Dogs suspected of having Leptospirosis should be treated with an appropriate antibiotic to improve their clinical condition and decrease the risk of transmission to people. Oral doxycycline is administered at a dose specific for the treatment of this infection for 2 weeks. Prior to start of doxycycline, and for 2 full days after initiation of treatment, a dog with Leptospirosis can shed the bacteria in urine. During this time, veterinary staff should utilize personal protective equipment (PPE) (i.e., disposable gloves and gown, eye protection or a face shield and shoe covers) when handling dogs and cleaning urine. Staff should wash hands well after removing PPE.
If vomiting and inappetence make it difficult to administer oral doxycycline, dogs can initially be treated with a penicillin-based drug intravenously. However, treatment with doxycycline should be started once the dog is better able to tolerate oral medication to clear the bacteria from the kidneys.
Supportive care includes fluid therapy, antiemetics, gastroprotectants, good nutrition and pain management. Opioids are typically administered for pain control, and the use of non-steroidal anti-inflammatory drugs is not recommended. Blood disorders may require transfusion.
Infected dogs can be placed in isolation or housed in a floor-level kennel in a low-traffic area. Their movement throughout the shelter should be minimized. Areas where dog was located should be promptly disinfected. The dog’s kennel should have a sign that indicates handling precautions.
When appropriate treatment is provided early in the course of the disease, survival rates are greater than 50%. Repeat performance of CBC, chemistry profile and other blood tests help to monitor the dog’s response to treatment. Dogs may develop chronic kidney or liver disease that requires ongoing management.
Animal shelters should consider their capacity to care for a dog when Leptospirosis is suspected. The shelter should determine:
- Is a veterinarian available to oversee diagnostic testing and treatment?
- Are adequate financial resources and trained staff available to provide care?
- Can necessary precautions be taken to decrease the risk of spreading the infection?
Shelters should consider an outcome for an affected dog that aligns with available resources (e.g., treatment in shelter or at a veterinary hospital or humane euthanasia).
- Sanitation: Accelerated hydrogen peroxide at 1:16 concentration with a 5-minute contact time is an effective disinfectant for Leptospira bacteria. To be fully effective, accelerated hydrogen peroxide must be applied to a surface that has already been cleaned. Effective cleaning and disinfecting protocols should be utilized on a regular basis to limit spread of pathogens in animal shelters.
- Considerations for Animal Shelters: Leptospira vaccines are considered noncore in animal shelters since many dogs’ length of stay is less than 2 weeks and onset of immunity for this vaccine is 10-14 days after completion of a two-vaccine series. Animal shelters can decrease the occurrence of Leptospirosis in dogs by not allowing access to areas that have standing water, placing a fence to minimize dogs’ contact with wildlife and utilizing rodent control strategies.
Since Leptospira is considered a core vaccine for pet dogs, adopters should consult a veterinarian regarding which vaccines should be administered to their newly adopted dog. Vaccines containing 4 Leptospira serovars should be utilized. These produce immunity against those serovars, however partial immunity to other serovars has been documented.
Vaccination requires 2 initial injections, 3-4 weeks apart, starting in dogs at least 12 weeks of age. The effect of vaccination is expected to be 12-15 months, however vaccinated dogs may not be fully protected against leptospirosis. Since it is not known if natural infection provides life-long immunity, dogs recovered from leptospirosis should be vaccinated, especially if dogs have continued exposure to the bacteria.
