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Lyme Disease in Dogs: Causes, Signs & Treatments (Vet Answer)

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By Dr. Karyn Kanowski

ixodic infectious tick stuck to the head of a kitten

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Dr. Karyn Kanowski

BVSc MRCVS (Veterinarian)

The information is current and up-to-date in accordance with the latest veterinarian research.

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Lyme disease is a bacterial infection caused by the spirochete Borrelia burgdorferi and spread by ticks. It can affect a range of domestic animals, particularly dogs, as well as humans. It is an insidious disease, with illness appearing gradually over a period of weeks to months, and clinical signs dependent on the part of the body the bacteria has invaded. Most commonly, dogs affected by Lyme disease will have fever, lethargy, inappetence, enlarged lymph nodes, and painful joints.

Although Lyme disease is quite prevalent throughout the US, only around 5–10% of dogs infected will actually experience clinical signs, which can range from mild to severe, and in some cases, be fatal.1

The following article will tell you all you need to know about Lyme disease: what it does, how it is diagnosed and treated, and most importantly, how it can be avoided.


What Is Lyme Disease?

Lyme disease is caused by infection with the spirochete Borrelia burgdorferi. Spirochetes are a group of bacteria, which includes Leptospirosis, recognized for their distinctive spiral morphology.2 They are well known in human medicine for causing illnesses, such as rat bite fever, syphilis, and, more recently, Lyme disease.

Unable to survive in the environment, Borrelia burgdorferi relies on tick vectors, which transmit the bacteria to their host when they bite. The bacteria enters the body and replicates in fluid—blood, lymph, and even synovial (joint) fluid.

closeup tick on puppy ear
Photo Credit: DrMYM, Shutterstock

What Are the Signs of Lyme Disease?

  • Fever
  • Lethargy
  • Lack of appetite
  • Enlarged lymph nodes

In the majority of cases, infection with Borrelia will not actually lead to clinical Lyme disease, but those that do can be affected by a severe, debilitating, and potentially fatal illness. The way in which the disease presents and progresses will depend on which body system the bacteria has invaded, but virtually all symptomatic cases will experience fever, lethargy, inappetence, and enlarged lymph nodes.

As we’ve mentioned, a relatively low percentage of dogs infected with the bacteria will actually end up showing clinical signs of Lyme disease. Apart from the general signs of fever and malaise, the most common sign of Lyme disease is painful, swollen joints, as the bacterium causes inflammation in the synovial fluid. In severe or prolonged cases, there can be permanent damage to the cartilage, resulting in long-term arthritis.

Lyme disease can also present with neurological signs, such as facial paralysis and seizures, and, left untreated, can cause permanent or fatal kidney damage.

What Are the Causes of Lyme Disease?

tick on the dog
Photo Credit: chanon khunkitti,Shutterstock

There are a number of different tick species that can play host to the Borrelia bacteria, but it is most prevalent in the deer tick, of the genus Ixodes. In fact, it is estimated that around 50% of these ticks carry Borrelia.

The deer tick and, therefore, Lyme Disease, are seen throughout the US and Canada, as well as parts of Europe and Asia. In America, the highest incidence of Lyme disease is typically seen in the Midwest and Eastern states, and around Ontario, Canada. Contrary to popular belief, this is not a “summer only” disease, and owners need to be vigilant all year round.

One very important aspect of infection with Borrelia is that it takes 1–2 days for the bacteria to be transmitted to your dog. More on this later.

How Is It Diagnosed?

There are tests to measure antibody levels in the blood in suspected cases; however, there are limitations to these tests. Antibodies are the body’s defense against infection, and the levels will only be high enough for detection around 4–6 weeks post-infection, so a negative result does not necessarily rule out infection. In some cases, not enough antibodies will be produced to cause a positive result. Because of this, if Lyme disease is suspected, repeated tests are often needed. A positive result, however, gives a reliable diagnosis.

In most cases, the dog’s history, risk of exposure, and clinical signs will be highly suggestive of Lyme disease, particularly if there is a known history of tick bites in the previous month or two.

Veterinarian parasite mite tick removes of the dog's skin
Photo Credit: Iryna Kalamurza, Shutterstock

How Is It Treated?

Because of the delay between infection and the appearance of clinical signs, treatment must be aggressive, as the infection is likely to be widespread by the time Lyme disease is diagnosed.

Treatment typically consists of a long (4+ weeks) course of antibiotics. Depending on the clinical signs of illness, your dog may also need additional supportive treatments, such as intravenous fluids, anti-inflammatories, and medications or food to combat kidney damage. If diagnosed before any significant kidney damage occurs, the prognosis is generally good. However, some dogs may suffer from long-term, painful arthritis as a result of joint damage and inflammation.

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Can Lyme Disease Be Prevented?

The great news about Lyme disease in dogs is that it can generally be avoided with the use of regular tick prevention. As mentioned earlier, the bacteria that causes Lyme disease does not infect the host immediately. Most tick treatments require the tick to bite the host to be effective, and this window of time allows the tick treatment to take effect before Borrelia has the chance to infect your dog.

There is a huge range of products available to treat and prevent ticks on dogs, and your veterinarian is the best source of information about which product is best for you and your dog. Two important things to note about tick treatments for dogs are:

Important Things to Know About Dog Tick Treatments:
  • Never use a flea/tick treatment for dogs on your cat. There is an ingredient found in most dog tick treatments that is extremely harmful to cats.
  • Most pet shop/supermarket/over-the-counter tick prevention medications are able to be sold without a prescription because they use less potent ingredients. Using less effective tick prevention can give you a false sense of security, which could be riskier than using none at all.

In addition to tick prevention, there are also a number of vaccinations against Lyme disease. This can be valuable for dogs in areas of particularly high rates of Lyme disease, or those that are unable to be treated with tick prevention medication. In the majority of cases, however, good tick prevention should also prevent Lyme disease, so talk to your vet.

Removing cat tick with a tick removal tool
Image Credit: Astrid Gast, Shutterstock


Can My Dog Give Me Lyme Disease?

No. Although both dogs and humans can get Lyme disease, the only way for us to become infected is from a tick bite. However, if your dog has been infected with Lyme disease, it is in your area, so you need to be extra vigilant about ticks on you and your pet.

Can My Cat Get Lyme Disease?

Cats can also get Lyme disease but have a much lower infection rate, and incidence of clinical disease, than dogs.

I Found a Tick on My Dog — What Should I Do?

Because it takes 1–2 days for the bacteria to spread from tick to host, the sooner a tick is removed from your dog, the better. There are many myths and misinformation about removing ticks and fears of leaving the head behind.

A tick’s head is essentially fused to its body, so leaving it behind is actually quite difficult. However, it is not uncommon for the mouthparts to stay in the skin after the tick has been removed. In most cases, these will work their way out on their own, but they may cause a localized reaction or infection, or even need to be removed by your vet.

There are lots of different types of tick-removal devices available, but if you don’t feel confident removing the tick yourself, your veterinarian or vet nurse will gladly do it for you.

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Summing Up

Lyme disease is caused by a bacterium that is quite commonly found in ticks, particularly the deer tick. Infection occurs 1–2 days after the tick attaches but only causes clinical disease in around 5–10% of infected dogs. It can take several weeks to several months for affected dogs to show clinical signs, so even if it was quite some time ago, it is important to report any tick bites to your vet if your dog becomes unwell.

Lyme disease is known to occur in all parts of the US, with a higher incidence in the Midwest and Northeast. Year-round tick prevention is the best way to ensure your dog doesn’t become infected with Lyme disease. This infection can have serious long-term health implications for your dog, so early detection and diagnosis are vital, but prevention is even better.

Featured Image Credit: Mironmax Studio, Shutterstock

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