MSD Manual

Please confirm that you are a health care professional

honeypot link
Pet Owner Version

Lyme Disease (Lyme Borreliosis) in Dogs


Reinhard K. Straubinger

, DrMedVetHabil, PhD, Institute for Infectious Diseases and Zoonoses, Department of Veterinary Sciences, Faculty of Veterinary Medicine, LMU

Reviewed/Revised Jun 2018 | Modified Oct 2022
Topic Resources

Lyme disease, which is caused by Borrelia burgdorferi bacteria and transmitted through the bite of a tick, affects domestic animals (dogs, horses, and possibly cats) and humans. At least 4 known species of ticks can transmit Lyme disease. However, the great majority of Lyme disease transmissions are due to the bite of a very tiny tick commonly called the deer tick, or black-legged tick. The scientific name of the tick involved on the west coast is Ixodes pacificus and Ixodes scapularis in the northeast and Midwest. Ixodes ricinus and Ixodes persulcatus are the primary vectors in Europe and Asia. It is important to note that ticks themselves do not cause Lyme disease; they harbor and transmit the bacteria that cause it.

Deer tick

Deer tick

Although the tick prefers certain creatures—such as voles, white-footed mice, or deer—upon which to feed during the various stages of its life cycle, it is quite willing to feed on people or dogs. Regardless of its stage of development (larva, nymph, or adult Ixodes tick), if the tick carries the bacteria in its body, people and dogs can become infected if bitten. Once a tick attaches, it takes 1-2 days for it to transmit the bacteria that cause Lyme disease, so prompt removal of ticks is important. Risk of transmission is highest during periods when the nymphs (spring) and adults (spring and fall) are actively seeking hosts.

Lyme disease in dogs has been reported in every state in the United States, but certain geographical areas are much more likely to harbor bacteria-carrying ticks than others. Infection rates of ticks vary, but can be as high as 50%. Areas in the United States where it occurs most often include the northeast (especially the New England states), upper Midwest, and Pacific coast. The disease is actually named after the town Lyme, Connecticut, where an early outbreak was first described. Lyme disease is also seen in Europe and Asia. The risk of Lyme disease being transmitted to people is increasing. In the last 20 years, the number of cases reported to the Centers for Disease Control has about doubled, to around 30,000/year. Although the rate of occurrence of the disease in a geographic area is similar in both animals and people, animals, especially dogs, are at significantly higher risk because of their greater exposure to ticks.

The signs of Lyme disease vary. Many animals can have Lyme disease and show no signs. In dogs, the most common signs include fever, loss of appetite, painful or swollen joints, lameness that comes and goes, swollen lymph nodes, and lethargy. If Lyme disease is left untreated it can lead to damage in the kidneys, nervous system, and heart. Lyme disease affecting the kidneys is the second most common syndrome in dogs and is generally fatal. Facial paralysis and seizure disorders have been reported in the disease form affecting the nervous system. The form of the disease that affects the heart is rare.

Prevention of Lyme Disease

  • Dogs should be treated regularly with a readily available, effective, tick-control product. Ask your veterinarian to recommend the best product for your pet.

  • In areas where Lyme disease is common, ask your veterinarian about whether vaccination is recommended.

  • Dogs should be routinely checked for ticks after they have been outside, especially if they have been in tall grass and brush during the spring, summer, or fall.

  • Remove any ticks by using fine-pointed tweezers to grasp the head of the tick (right where it enters the skin). Pull the tick straight off, making sure not to grasp or squeeze its body.

  • Dogs should be brushed regularly. Watch carefully for any ticks that are removed and capture and dispose of them before they can either reattach to the dog or migrate to other pets or people in the household.

The diagnosis of Lyme disease is often based on the signs and history. For example, a veterinarian might suspect Lyme disease in a dog with recent lameness, a mild fever, and a history that includes possible exposure to ticks. Standard blood studies are not very helpful in diagnosis because the results tend to fall within normal ranges despite signs of infection. However, these tests may be important in order to rule out other causes of disease. Antibodies against the disease-causing bacteria can often be detected 4 to 6 weeks after the initial infection and help confirm the diagnosis.

Antibiotics (usually for 4 weeks) are appropriate for all dogs that have signs of Lyme disease. Rapid response is seen in limb and joint disease in most cases, although incomplete resolution of signs is seen in a significant number of affected animals. Infection in animals may persist in spite of antibiotics and may require a second round of treatment. Additional therapy to help the affected organ systems and signs is also important, especially when the disease affects the kidneys, heart, or nerves. Some affected dogs will experience chronic, lifelong joint pain from the damage caused by the bacteria.

Tick avoidance plays a role in disease control. While highly effective products (such as sprays and monthly oral or “spot-on” products) are available for use with dogs, they must be used consistently in order to provide effective longterm tick control. Vaccines that prevent infection in dogs are available; these appear to work best when given to dogs before they are exposed to Lyme-causing bacteria. Vaccination and appropriate boosters may be recommended by your veterinarian if you live in an area where Lyme disease is common. Any ticks found on your dog should be promptly removed in order to help prevent transmission of Lyme disease and other diseases spread by ticks. Dogs are not the direct source of infection in people. Pets may bring unattached infected ticks into the household and if they then attach to another animal or person, they may transmit Lyme disease.

quiz link

Test your knowledge

Take a Quiz!