Lyme disease in dogs is a tick-borne bacterial infection, and most infected dogs never get visibly sick from it — but the ones who do can develop sudden lameness, fever, and in rare cases a form of kidney disease that’s genuinely dangerous. Here’s how it spreads, what to watch for, and what actually works to prevent it.
How Dogs Get Lyme Disease
Lyme disease is caused by the bacterium Borrelia burgdorferi, transmitted through the bite of an infected blacklegged tick (commonly called a deer tick). It is not contagious between dogs, and dogs can’t give it to people directly — you’d need to be bitten by an infected tick yourself.
The timing matters more than most owners realize. According to the Companion Animal Parasite Council (CAPC) and the American Veterinary Medical Association, an infected tick generally needs to be attached for 24 to 48 hours before it transmits the bacteria. That window is exactly why prompt tick checks and fast-acting preventives are so effective — pulling a tick within a day of it attaching can prevent infection even if that tick is carrying Lyme.
Blacklegged ticks are most established in the Northeast, upper Midwest, and Pacific coastal regions of the U.S., but CAPC’s tick surveillance data shows the range expanding most years, so “we don’t have ticks here” is a claim worth rechecking with your vet rather than assuming.
Symptoms to Watch For
Here’s the part that surprises a lot of owners: most dogs exposed to Borrelia burgdorferi never develop symptoms at all. Studies cited by CAPC estimate that only around 5–10% of infected dogs go on to show clinical signs, and when they do, it’s often weeks to months after the actual tick bite, which makes the connection easy to miss.
When symptoms do show up, the classic pattern is:
- Shifting-leg lameness — limping that seems to move from one leg to another over days or weeks, often with visibly swollen joints
- Fever and lethargy — general malaise, reduced appetite, a dog who’s “just not right”
- Swollen lymph nodes
The more serious, though rarer, complication is Lyme nephritis (also called Lyme nephropathy) — an immune reaction that damages the kidneys. It’s uncommon, but it’s the reason vets take Lyme-positive test results seriously even in dogs that look fine, and it’s why routine bloodwork sometimes gets recommended after a positive tick panel even without symptoms.
Diagnosis and Treatment
Most vets test for Lyme using a rapid in-house blood test (commonly a 4Dx or similar SNAP test) during annual wellness visits, which also screens for heartworm and a couple of other tick-borne diseases at the same time — a good reason not to skip it even if your dog seems healthy. A positive result alone doesn’t necessarily mean active disease; vets weigh it alongside symptoms, and sometimes follow up with additional bloodwork (like a urine protein test) to check kidney function, especially before deciding whether treatment is needed.
For dogs showing symptoms, or those with a positive test plus other risk factors, the standard treatment is a 30-day course of doxycycline, which usually resolves lameness and fever within a few days of starting. Most dogs recover fully. The exception is Lyme nephritis, which requires more intensive, ongoing management and carries a more guarded outlook — another reason prevention is worth taking seriously in tick-heavy regions.
Prevention: Tick Control and Vaccination
This is genuinely one of the more solvable problems in dog health. A layered approach works best:
- Year-round tick preventives — oral or topical products that kill ticks before they can transmit disease. Ask your vet which product fits your dog’s health profile and your region’s tick season, which in many areas now runs longer than the traditional “spring through fall” window.
- Daily tick checks after time outdoors, especially in wooded or tall-grass areas — run your hands through the coat, checking armpits, ears, and between toes, where ticks like to hide.
- Prompt tick removal with fine-tipped tweezers, grasping close to the skin and pulling straight out — given the 24–48 hour transmission window, same-day removal meaningfully cuts risk.
- The Lyme vaccine, recommended by the American Animal Hospital Association (AAHA) for dogs in or traveling to high-risk areas. It’s not considered a core vaccine for every dog nationwide, so this is a conversation to have with your vet based on where you live and how much time your dog spends outdoors.
When to See a Vet
Call your vet if your dog develops sudden lameness that shifts between legs, unexplained fever, swelling in one or more joints, or a drop in energy and appetite that doesn’t have an obvious cause — particularly if you’ve found a tick on them recently or live in a tick-endemic area. Also worth a call: any dog with a known Lyme-positive test result who starts drinking or urinating more than usual, which can be an early sign of kidney involvement and warrants prompt bloodwork rather than a wait-and-see approach.
The reassuring bottom line is that Lyme disease in dogs is both preventable and, in the vast majority of symptomatic cases, very treatable. Consistent tick prevention does most of the work; a decent daily tick check does the rest.
Related reading: our guide to essential vaccines for dogs covers where the Lyme vaccine fits into a full vaccination schedule, and if your dog is currently limping, why is my dog limping walks through the full range of possible causes beyond tick-borne disease.