Lyme Disease in Dogs

Mary Malucci
Apr 7, 2025
5 min read

Lyme disease is a bacterial infection that will affect both dogs and people. Symptoms include joint pain and swelling, fever, swollen lymph nodes, fatigue and loss of appetite. Dog owners often describe lameness that shifts or rotates from one leg to another, a symptom which appears to be specific to tick borne diseases like Lyme.

Lyme disease is caused by a bacterium called Borrelia burgdorferi. The bacteria are spread through ticks, particularly black-legged ticks, also called deer ticks. Ticks go through three developmental stages; larvae, nymphs and adults. Each of these stages require a blood meal from a mammal in order to transition to the next stage. During the larvae and nymph stages, ticks can acquire Borrelia burgdorferi when they bite an infected animal, usually a rodent. Infected nymph and adult ticks can then transmit the bacteria to a new host, like dogs and humans.

Most dogs who get infected with B. burgdorferi will remain asymptomatic, appearing healthy. Only 5-10% of infected dogs will develop Lyme disease, displaying the signs described above. Compared to dogs, 90% of infected people will become ill.

A small percentage of dogs with Lyme disease will develop kidney disease. Called Lyme nephritis, the symptoms include edema, weight loss, vomiting and diarrhea. Lyme nephritis is often fatal, even with aggressive treatment.

B. burgdorferi must be transmitted through a tick bite. It cannot be directly transmitted from dog to person or visa versa. Once the tick bites a mammal and latches on, it takes 12-24 hours to transmit the bacteria. Symptoms will appear between 2-5 months after the dog is infected, sometimes longer.

Your veterinarian will diagnose Lyme disease based on three things; your dog’s symptoms, a history of tick exposure (keeping in mind the infective bite occurred months earlier) and a blood test to screen for antibodies. Most veterinary clinics carry an ELISA test called a Snap 4DX, which screens for antibodies circulating in your dog’s blood. It’s called a 4DX because it tests for antibodies that are specific to HW disease, B. burgdorferi and two other common tick-borne bacteria, Anaplasma and Ehrlichia. A positive result tells the veterinarian that your dog is circulating antibodies to one or more of these bacteria, thus confirming an active infection that needs treatment. However, dogs can test negative despite exposure resulting in infection if the test is performed too soon after the infective bite, less than 4 weeks.

For a more definitive diagnosis, your veterinarian can send a blood sample out to a referral lab. Most referral labs run a QC6, which gives a numerical value that can confirm your pet’s antibody level. Cornell University has developed a test called the Lyme Multiplex assay, that can detect three different surface proteins on B. burgdorferi. The resulting antibody profile can indicate whether your dog has been recently infected or has been chronically infected. It also helps monitor protective antibodies after vaccination.

If your dog is showing signs of kidney injury, your veterinarian may also want to run blood work and a urinalysis to assess the damage and propose a treatment plan based on that information.

For dogs showing signs of Lyme disease without kidney involvement, a long course of antibiotics, usually 30 days, is the standard treatment. The antibiotic of choice is Doxycycline. If that is not available or appropriate for your dog, amoxicillin or azithromycin may be used. Most dogs will show an improvement in symptoms within a few days, but it is important that the entire 30-day treatment course be completed. Dogs are at risk for re-infection during the treatment period if they are exposed to ticks again. Some dogs may have to repeat the course of antibiotics as a result.

For dogs showing signs of kidney injury, hospitalization with IV fluids and IV antibiotics is recommended with the understanding that the prognosis for these dogs is poor to grave.

As is the case with most parasites, the best treatment is prevention. While Lyme disease can be transmitted any time of year, especially in warmer climates, early spring and late fall seem to be when adult ticks are most active. They are prevalent where grasses get tall and in wooded areas. The ticks will wait on leaves, blades of grass or short trees like cedars until they sense a mammal nearby and drop or crawl onto their new host. If you and your dog like to go camping or hiking or pursue other activities that take you through tall grass or wooded areas, it is important to check yourself and your dog when you get home to remove ticks before they become embedded in the skin. Ticks can be easily killed by dropping them into a jar of rubbing alcohol.

If the tick has already become embedded, remove it carefully by grasping it near the skin and firmly pulling it out so as not to break off the mouth parts under the skin. Clean the area afterwards with soap and water. Monitor for inflammation and watch your dog for the symptoms of Lyme disease, keeping in mind those symptoms will take 4-6 weeks to appear.

We can make our yards less appealing to ticks by keeping the grass short, trimming bushes and trees and removing brush piles. Perform daily tick checks of pets and people in the warmer months of spring through fall.

There are several products available that can help control ticks on our dogs. Frontline Plus and Advantix can be applied topically and usually last for a month. Bravecto comes in topical form and chewables and lasts up to three months. Other chewable products like Nexguard and Simparica are given monthly. Talk with your veterinarian about which product will be best for your dog.

Many products that help control ticks on our dogs are very toxic to cats. If you have both species living in your home, monitor carefully to avoid exposing your cat. Mercifully, cats do not appear to develop Lyme disease.

For dogs who live, work or play in areas with heavy tick infestations and high incidences of Lyme disease, there is a Lyme vaccine available now. Talk with your veterinarian about whether it’s appropriate for your dog.

If you are curious about the incidence of Lyme disease reported in humans in your area, the CDC maintains a detailed map on their website. If there are high numbers of human cases near you, consider the risk high for your dog as well.

https://www.cdc.gov/lyme/data-research/facts-stats/lyme-disease-case-map.html