What is Lyme disease?
Lyme disease is an infectious disease caused by the bacterium Borrelia burgdorferi. The bacteria are commonly carried by the deer tick (also known as the black-legged tick). Ticks become infected when they feed on infected mice, birds, or deer. Dogs generally become infected after a tick has been attached for one to two days.
Where is Lyme disease found?
In the United States, Lyme disease has been reported in every state, but over 95% of cases are from the northeastern, mid-Atlantic, and upper midwestern states, with a few cases reported along the west coast, especially northern California. In Canada, Lyme-positive dogs are found mostly from Manitoba eastward, through to the Maritime provinces.
Can dogs spread Lyme disease to other dogs or to humans?
There are no reports of dogs spreading Lyme disease to other dogs, even when infected and uninfected dogs live together for long periods. Likewise, there are no reports of dogs spreading Lyme disease to humans. However, humans are equally at risk for Lyme disease if they are bitten by an infected tick.
How is Lyme disease diagnosed?
Veterinarians commonly use screening tests to check for Lyme disease (e.g., SNAP 4DX PLUS™, Accuplex ™4). These tests can detect antibodies to Borrelia as early as three to five weeks after a tick bite—sometimes before the dog shows any signs of illness. These tests are often part of a test kit that screens for other tick-borne diseases, such as ehrlichiosis and anaplasmosis. Your veterinarian can do the test in a clinic or send a blood sample to an outside laboratory for testing.
What happens if the screening is positive?
If your dog tests positive on one of the screening tests, your veterinarian may recommend an additional test, such as a Quantitative C6 antibody test. Your veterinarian may also want to take samples of blood and urine to assess kidney function and to look for protein in the urine. A positive test for protein in the urine could signal serious underlying kidney disease, which is a complication of Borrelia infection.
If the tests are positive, does my dog need treatment?
The decision to treat Lyme disease is somewhat controversial because many infected or exposed dogs show no signs of illness. Remember that a positive test only means that a dog has been exposed to Lyme disease, not that they are infected. Factors that support treatment include:
- Signs of Lyme disease at the time of testing
- Abnormal levels of protein in the urine
How effective is treatment?
Antibiotic treatment (doxycycline) may be used as an additional diagnostic test: dogs experiencing joint pain due to Lyme disease often significantly improve within one to three days of starting antibiotic treatment. Unfortunately, this response to treatment is not 100% reliable, as Lyme disease naturally comes and goes with time.
If your dog does not respond to treatment or clinical signs recur during treatment, they are likely to have another disease. Additional diagnostic testing and alternative treatment is required.
Often, the obvious signs of Lyme disease resolve completely with antibiotics; however, it is unknown whether the bacterial infection is completely killed off in every patient or how to look for ongoing infection. Further research is needed to fully understand Lyme disease in dogs.
