Lyme Disease in Dogs


Lyme disease is an infectious disease spread by ticks. Typical symptoms in dogs include lameness, fever, fatigue, swollen lymph nodes and joints and loss of appetite. Lyme is of special concern because the pathogenic bacteria can also infect and cause Lyme disease in people. 

Ticks are one of the most common external parasites and are commonly found world wide and year round. These arachnids are vectors for many infectious agents, meaning they transmit diseases across different host species. One of the disease-causing bacteria that ticks carry is Borrelia burgdorferi, the pathogen responsible for Lyme disease. 

The main symptoms of Lyme disease in dogs are fever, lethargy, lameness, loss of appetite, and swollen lymph nodes and joints. In some cases, Lyme disease in dogs can develop into a more serious secondary kidney condition called Lyme nephritis.

Annual testing for Lyme is often included in heartworm screening for dogs living in endemic areas. Dogs with symptoms are usually treated with antibiotics and most make a full recovery in a short period of time. 

Tick control is a matter of public health so it is important for dogs to remain on a vet-recommended external parasite control regimen year round.

Risk Factors

People living in endemic areas who are vigilant about protecting their dogs from ticks and are up-to-date on Lyme vaccination can rest assured they’re doing everything to protect their dogs from Lyme disease. These steps significantly reduce a dog’s chances of developing Lyme disease. 

Current distribution maps define northeast, upper midwest, and West Coast states of the USA as areas where Lyme is endemic.  Minnesota, Wisconsin, and all of the states north and east of North Carolina are particularly heavily infested. Cases of Lyme disease are rare outside of endemic areas. 

With respect to Lyme disease, infection means an infected tick has bitten the dog and has transmitted the bacteria - Borrelia burgdorferi - to the dog. Many infected dogs are asymptomatic.  

The infection develops into Lyme disease when the bacteria has reached high enough levels in the dog’s body to result in lameness, fever, and lethargy; to swell lymph nodes and joints, to dull the appetite, and in rare cases to cause serious kidney complications.  

Many dogs, especially in tick-heavy areas, become infected with the bacteria associated with Lyme disease. Only approximately 5% of infected dogs develop the symptoms of Lyme disease.  Conversely, humans have a 90% likelihood of developing Lyme disease if they get infected.

Possible Causes

Lyme disease is caused by transmission of Borrelia burgdorferi bacteria from a tick to a dog AND by the proliferation of the bacteria to a sufficient level to cause symptoms.

Main Symptoms

The primary symptoms of Lyme disease in dogs include: 

• Fever • Shifting leg lameness • Swollen joints • Enlarged lymph nodes • Fatigue • Loss of appetite • Lethargy

Detailed Characterization

A serious complication of Lyme disease is Lyme nephritis or glomerular disease. The constant stimulation of the immune system by the Borrelia burgdorferi bacteria can lead to this type of kidney damage. Symptoms of nephritis are more severe than similar symptoms of Lyme disease and include 

Vomiting • Not eating • Increased thirst and urinationWeight loss • Extreme lethargy

If nephritis is detected, the vet may prescribe antibiotics, a treatment to slow protein loss in urine, and immune suppression therapy.  Dogs with Lyme nephritis can require aggressive therapy including  IV fluid therapy and medications to reduce the effects of the kidney damage.

Testing and Diagnosis

A blood test can tell the vet if the dog has been exposed to Borrelia burgdorferi. In endemic regions, this test is done as part of the annual checkup along with heartworm testing.

Steps to Recovery

Dogs diagnosed with Lyme disease usually undergo a 2 - 4 week course of antibiotics. Many dogs with Lyme disease improve within 48 hours of starting antibiotics.  Non-steroidal anti-inflammatories and analgesics are indicated for dogs experiencing pain with Lyme disease.

The goal of treatment is to reduce the population of Borrelia burgdorferi to a level where they no longer cause symptoms. Some dogs experience a relapse of symptoms. Relapses may be triggered by reexposure to the pathogen from a new tick bite, so consistent use of a tick control product is recommended.  

In cases where the infection affects the kidneys (Lyme nephritis), permanent kidney damage may result.  Lyme nephritis can be life-threatening.


As with all tick-borne illness, Lyme disease is best prevented by keeping all pets in the household on year round vet-recommended external parasite control. Outdoor animals should be screened regularly for the presence of ticks. All ticks should be removed immediately. Read here for more information about tick control and prevention of tick-borne illness.

Vaccination against Lyme disease is also recommended for dogs in endemic areas, but does not preclude the importance of taking preventative measures to avoid exposure to ticks.

Is Lyme Disease Common in Dogs?

In endemic areas, 1.4 - 13% of dogs test positive for exposure to borrelia. Infection is rare outside of endemic areas, but the geographic distribution of ticks is expanding. The development of full blown Lyme disease depends on the level of bacteria present in the dog’s system.

Typical Treatment

Lyme disease is usually treated with antibiotics and anti-inflammatories. Pain medications may be recommended as needed.

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