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Pet Health

Unraveling the Mysteries of Lyme Disease in Dogs

Lyme disease, a common tick-borne illness, is caused by the bacteria Borrelia burgdorferi, which may cause fever, lethargy, enlarged lymph nodes, and joint inflammation.

Dr. Gary Hsia

July 19, 2023

As a pet owner, nothing is more unsettling than the thought of your beloved companion falling ill. One such illness that has caused considerable concern among the pet community is Lyme disease. This guide aims to provide a comprehensive understanding of Lyme disease in dogs, exploring everything from its causes, symptoms, diagnosis, treatment, and most importantly, prevention. By the end of this article, you'll be well-equipped with knowledge and strategies to protect your furry friend from this disease, and ensure they lead a happy, healthy life. Now, let's delve into the world of Lyme disease.

Demystifying Lyme Disease

Lyme disease, a common tick-borne illness, is caused by the bacteria Borrelia burgdorferi. This bacteria primarily resides in black-legged ticks, commonly called deer ticks. When an infected tick feeds on your pet, it can transmit the bacteria into the pet’s bloodstream, potentially leading to Lyme disease. Although the tick serves as the carrier of the bacteria, it is not technically the cause of the disease.

So what’s a lyme? The disease is named for the small coastal town of Lyme, Connectitut where symptoms were first described in the mid 1970s. At the time, researchers called the condition Lyme arthritis. As additional symptoms were described the name was changed to Lyme Disease. In 1982 Dr. Burgdorfer identified its bacterial cause; naming the spiral bacteria Borrelia burgdorferi.

The Prevalence of Lyme Disease in Dogs

Lyme disease is reported across the United States, but its prevalence is higher in specific regions like the Northeast, Upper Midwest, and the Pacific Coast. However, irrespective of where you live, being aware of Lyme disease and its symptoms is essential as the disease has been reported in dogs in all 50 states (and abroad).

Fortunately, only about 5-10% of dogs infected with the bacteria show signs of the disease. But as the disease can be chronic and lead to life-threatening complications it is important to learn about your dog’s risks and you can decrease them..

Lyme disease transmission occurs through tick bites, primarily from the Ixodes ticks (Ixodes pacificus, Ixodes scapularis, Ixodes ricinus, and Ixodes persulcatus). When an infected tick feeds, it may inject the bacteria into the host’s bloodstream, spreading the disease. The risk of transmission is highest during the spring and fall when the nymph and adult stages of the tick are most active.

While any life stage of the tick can transmit the disease causing bacteria, it usually has to be attached to your dog for 24-48 hours before transmission will occur. This is why daily tick checks and removal are so helpful in preventing lyme disease.

Geographical Risks for Lyme Disease

Geographical areas like the Northeast, Upper Midwest, and the Pacific Coast of the United States pose a higher risk for Lyme disease. Factors such as deforestation and migratory animal populations also affect the distribution of ticks. Regardless of your location, awareness and effective tick control measures are your best defenses against Lyme and other tick-borne diseases. To view prevalence by state visit the Companion Animal Parasite Council website.

Recognizing Symptoms of Lyme Disease in Dogs

Identifying Lyme disease in your pet can be challenging as the same symptoms may occur in several different diseases. Once entering the dog’s bloodstream, the spiral shaped bacteria spread which may cause fever, lethargy, enlarged lymph nodes, and joint inflammation. The affected joint may change causing a “shifting leg lameness” accompanied by a swollen, warm, and sensitive joint. The progression of symptoms also deserves attention, as untreated Lyme disease can lead to severe damage to the kidneys, nervous system, and heart.

Further complicating the identification of Lyme disease is the fact that clinical signs usually don’t appear until 2-5 months post infection, or even later. Remember that only 5-10% of affected dogs will show signs and that lameness may be intermittent, disappearing for a while and even shifting from one leg to another. All these factors can confound the clinical picture of a Lyme infected dog.

Unlike many humans, dogs do not display the classic “Bull’s eye” or target shaped rash.

Consultation with A Veterinarian

If you suspect your pet may be suffering from Lyme disease, the first step is to consult a trusted veterinarian. This initial consultation involves a thorough examination of your pet and a detailed discussion about their lifestyle, habits, and symptoms. It's important to provide as much detailed information as possible to help your veterinarian make an accurate diagnosis. Remember signs may take several months to appear, so think back and include any pertinent information.

Diagnostic Tests

Following the initial consultation, your veterinarian will likely recommend a set of diagnostic tests. The specific test for Lyme disease looks for antibodies to B. burgdorferi and may take 4-6 weeks post exposure to become positive. As such, your vet will be interested in testing to find out which body systems are affected and ruling out other diseases which may cause similar signs.

Interpreting Diagnostic Results

Interpreting diagnostic results is a critical part of the process. A positive result indicates exposure to the Borrelia bacteria, but not necessarily an active Lyme disease infection. False negatives can occur in the early stages of the infection before significant antibodies have built up. Additional nuance lies in which stage of the bacteria life cycle is tested for, whether the pet has been vaccinated for Lyme, and whether the infection is acute or chronic.This complexity necessitates a veterinarian's expertise and interpretation of a series of diagnostics.

Differential Diagnoses

Given that Lyme disease symptoms are often similar to other conditions, differential diagnoses must be considered and ruled-out. Conditions such as anaplasmosis and babesiosis, other bacterial tick-borne diseases in dogs, can present similar symptoms and may in fact be present with Lyme.

Treatment for Lyme Disease in Dogs

The first line of treatment for Lyme disease involves a course of antibiotics for at least 30 days. Usually treatment can be done on an outpatient basis, unless significant damage to kidneys or other systems require hospitalization. While the initial antibiotic therapy is effective in most cases, some dogs may require long-term disease management.

Chronic joint inflammation, kidney issues, or severe fatigue are some complications that could necessitate a longer period of treatment or additional supportive therapies. Additionally, reinfection from subsequent tick bites is possible and should be kept in mind.

Caring for a Dog with Lyme Disease at Home

Home care for a dog with Lyme disease goes beyond administering prescribed medication. It involves environmental management, such as reducing exposure to ticks, providing comfort and rest, and maintaining regular, gentle exercise. Most importantly, maintain close observation and contact with your vet, as your dog's condition may change over time, necessitating adjustments to the treatment plan.

Potential Complications from Treatment

While antibiotics are generally safe, some dogs may experience side effects such as vomiting, diarrhea, or loss of appetite. In more severe cases, antibiotics can cause allergic reactions. Always watch for any changes in your dog's behavior or physical condition and report them immediately to your vet. Treatment for Lyme disease can also involve managing secondary diseases or conditions that might result from the infection.

Remember that you're not alone in dealing with Lyme disease. Keep communication open with your vet, ask questions when you need to; together you're doing the best thing for your pet.

Preventing Lyme Disease in Dogs

The best way to avoid the health issues associated with Lyme disease is through prevention. Protecting your dog from ticks is tantamount to avoiding all tick-borne diseases. Tick preventatives come in many formulations including topical drops, collars, and oral chews. Speak to your veterinarian to determine which is best for your dog. Avoid bringing your dog to tick infested areas and, if appropriate, consider the landscaping around your home with an eye toward tick control.

Remember to check your dog’s coat and skin regularly as infected ticks must be attached at least 24 hours to transmit the Borrelia bacteria. Examine your pet from nose to tail paying special attention to dark “cozy” places such as under the collar, inside ears, and between toes. If you find a tick attached to your dog, remove it with a pair of tweezers or tick removal tool.

Do not twist, burn, or apply anything to the tick's body to encourage it to “back out.” Such methods may delay removal or even spill more infected saliva into your pet’s system. You may wish to submit a removed tick for species identification and testing for Lyme or other diseases. Place the tick in a small baggie or container and speak with your veterinarian.

Another topic for discussion with your veterinarian is vaccination against Lyme. Vaccination is not appropriate for all dogs and different Lyme vaccines may interfere with detection of early Lyme infection.

Preventive measures such as regular inspections of your pet’s skin and coat, immediate removal of ticks, and regular application of flea and tick preventatives can significantly contribute to your pet's well-being. Even if your pet stays indoors most of the time, only going outside for “potty breaks,” questing ticks only need a moment to climb aboard.

Final Thoughts

It’s important to note that humans and other animals may contract Lyme disease. However, an infected dog is not a threat to other pets or people in the home. Transmission must still come through the bite of an infected tick and a dog with Lyme disease is not a reservoir host for other ticks to become infected.

Dealing with Lyme disease in your dog can be a complex journey, filled with waxing and waning symptoms and emotional strain. In addition to finding information about Lyme disease, please be sure to seek out additional support where you need it whether from family, friends, or other pet parents.


Dr. Gary Hsia

Fresno, CA


Dr. Gary graduated from the University of Illinois College of Veterinary Medicine in 2010. After graduation, he moved west. Dr. Gary spent a year at a mixed animal practice in Oregon before moving to Fresno where he worked at All Creatures Veterinary Clinic from 2011-2021.  Read More