Lyme Disease in Dogs

A blood engorged deer tick

Eric Lowenbach / Getty Images

Lyme disease presents very differently in dogs than it does in humans. While humans develop serious and sometimes long-lasting symptoms from a Lyme disease infection, only about 10 percent of dogs infected with Lyme will develop any symptoms that require treatment.

There is no evidence that Lyme disease is spread to humans via direct contact with infected animals. However, keep in mind that ticks can hitch a ride home on your pets and move on to the humans in the household. Since Lyme disease is much more dangerous to humans than dogs, keeping an eye out for ticks on your dog can reduce the risk to you and your family.

What Is Lyme Disease?

Lyme disease is a condition caused by a bacteria called Borrelia burgdorferi that is spread by ticks. These ticks become infected with the bacteria by feeding on infected mice and other small animals. When an infected tick bites other animals, it can transmit the bacteria to these animals.

Lyme disease is primarily transmitted by the deer tick (black-legged tick) and a small group of other closely related ticks. The deer tick is small and may bite animals and people without ever being detected. Lyme disease affects a variety of species, including dogs, cats, and people.

Risk Factors for Lyme Disease

Dogs that spend a lot of time outdoors, especially in the woods, bush, or areas of tall grass, are most commonly infected with Lyme disease. However, ticks can be carried into yards on other animals, and dogs can become infected anywhere ticks are found.

Infections occur during tick season—usually spring through early fall—but the time between infection and the appearance of Lyme disease symptoms can be two to five months. Lyme disease has been reported in every state in the United States and in many other parts of the world.

Since ticks can carry other diseases besides Lyme, be sure to check your dog's fur after it's spent a lot of time outdoors. It's especially important for long-haired dogs to have their fur brushed, and when appropriate, treated with anti-tick and anti-flea remedies.

Young man taking care of a dog
Marc Oeder / Getty Images

Signs and Symptoms

When clinical signs of Lyme disease do develop in dogs, they can be hard to distinguish from other viruses or illnesses, and can include:

  • Fever
  • Decreased appetite
  • Swollen, painful joints—dogs may be reluctant to move
  • Lameness—limping which may be mild at first, then worsen, and may also shift from one leg to another
  • Lethargy
  • Swollen lymph nodes

If Lyme disease isn't treated, some dogs may also suffer kidney problems. The symptoms of kidney problems, which are serious, include lethargy, vomiting, loss of appetite, and increased thirst and urination, and sometimes a lack of urination will develop. Dogs who develop kidney failure can become very ill and may not respond to treatment.

Neurological disease, including behavioral changes and seizures, and heart complications, which are sometimes seen in humans who contract Lyme disease, are rare in dogs.


The diagnosis of Lyme disease is based on a combination of factors, including history of tick exposure, clinical signs, finding antibodies to B. burgdorferi bacteria, and a quick response to treatment with antibiotics. A positive antibody test is not enough to make a diagnosis on its own, because not all dogs that are exposed to B. burgdorferi get sick, and antibodies can persist in the blood for a long time after exposure.

Other diagnostic testing, such as blood and urine tests, X-rays, and sampling of joint fluid, may be done to check for signs of kidney disease and to rule out other conditions with similar signs and symptoms.


Treatment with antibiotics usually produces rapid improvement in symptoms, though antibiotics will be continued for a few weeks. Treatment may not completely clear the bacteria, but produces a state where no symptoms are present—similar to the condition in dogs that don't have symptoms from infection.

If kidney disease is present, a longer course of antibiotics along with additional medications to treat the kidney disease is usually necessary.


Tick control is extremely important for the prevention of Lyme disease, and many other diseases that can be transmitted by ticks. Check your dog daily for ticks and remove them as soon as possible, since ticks must feed for at least 12 hours, and possibly 24 to 48 hours, before transmitting the bacteria that causes Lyme disease.

This is especially important in peak tick season and after your dog spends time in the bush or tall grass—consider avoiding these areas in tick season. Products that prevent ticks such as monthly parasite preventatives or tick collars can be used, but be sure to follow your veterinarian's advice when using these products.

Keep grass and brush trimmed in your yard, and in areas where ticks are a serious problem, consider treating your yard for ticks.

Removal of a dog tick
PK-Photos / Getty Images


Vaccination to prevent infection and appropriate boosters may be recommended by your veterinarian if you live in an area where Lyme disease is common. Many specialists do not recommend routine vaccination because so few dogs develop symptoms of Lyme disease, and when Lyme disease does occur in dogs, it is usually readily treated.

Additionally, because arthritis and kidney problems associated with Lyme disease are at least partly related to the immune response to the bacteria, rather than the bacteria itself, there is concern that vaccination may contribute to problems.

Vaccination is also not 100 percent effective, and it's only helpful in dogs that have not already been exposed to B. burgdorferi. However, vaccination before exposure can help prevent dogs from getting Lyme disease and also prevent them from becoming a carrier of the bacteria.

Where vaccines are used, it is usually recommended to start vaccinating dogs as young puppies at around 12 weeks, with a booster two to four weeks later. The vaccine does not provide long-lasting immunity, so annual re-vaccination, ideally before tick season, is necessary.

If you suspect your pet is sick, call your vet immediately. For health-related questions, always consult your veterinarian, as they have examined your pet, know the pet's health history, and can make the best recommendations for your pet.
Article Sources
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  1. Lyme Disease. Cornell University College of Veterinary Medicine

  2. Lyme Disease (Lyme Borreliosis) In Dogs. Merck Veterinary Manual

  3. Overview Of Lyme BorreliosisVeterinary Manual