Lyme disease is the most common tick-borne illness affecting dogs in Ontario, and cases have climbed alongside the spread of blacklegged ticks across the GTA and southern Ontario. According to the Public Health Agency of Canada (PHAC), the range of blacklegged ticks has expanded significantly over the past decade, pushing risk into suburban yards, ravines, and parks that were once considered low-risk. Dogs are natural tick magnets — they push through tall grass and brush exactly where ticks wait — so understanding how Lyme affects them, what the first signs look like, and what to do is essential for any Ontario pet owner. This guide is general information for pet owners, not a substitute for veterinary care; always consult your veterinarian about your specific dog.
Can dogs get Lyme disease from ticks?
Yes. Dogs contract Lyme disease when an infected blacklegged tick (deer tick, Ixodes scapularis) attaches and feeds long enough to transmit Borrelia burgdorferi, the corkscrew-shaped bacterium responsible for the disease. The tick typically must remain attached for 24 to 48 hours before transmission occurs, which is why fast, correct tick removal is one of the most powerful prevention tools you have.
Not every blacklegged tick carries the bacterium, and not every dog bitten by an infected tick becomes sick. In fact, veterinary consensus is that only about 5–10% of infected dogs ever develop clinical signs — the majority mount an immune response and remain outwardly healthy. That is reassuring, but it also means Lyme can quietly infect a dog without any obvious warning. Blacklegged ticks are active any time the temperature is above roughly 4°C, so in the GTA that can mean risk from early spring through late fall, and even on mild winter days.
If you have just found a tick on your dog, work through what to do when you find a tick on your dog and follow a proper tick removal technique for dogs in Ontario — how you remove it affects infection risk.
Is Lyme disease in dogs contagious to other pets or people?
No — not directly. Lyme disease spreads through tick bites, not through contact between animals. An infected dog cannot pass Lyme to another dog, to a cat, or to a human by licking, sharing bowls, or being in the same house. The real shared risk is the ticks themselves: if your dog is bringing ticks home from the yard or the trail, the whole household is exposed to those same ticks. An unfed tick that hitches a ride on your dog can later attach to a person. This is why tick control is a household project, not just a pet-care task.
What are the first signs of Lyme disease in dogs?
The earliest and most telling sign is lameness — and specifically shifting-leg lameness, where a limp appears in one leg, resolves, then shows up in a different leg days later. This happens because the bacteria trigger inflammation in the joints. Unlike humans, dogs do not develop a bull’s-eye rash, so there is no skin clue to look for.
First signs and symptoms to watch for include:
- Shifting-leg lameness — limping that moves from limb to limb
- Stiffness, reluctance to move, or a hunched, walking-on-eggshells posture
- Fever — often in the 39.5–40.5°C (103–105°F) range
- Lethargy and noticeably lower energy
- Loss of appetite
- Swollen, warm, or painful joints
- Swollen lymph nodes, sometimes near the bite site
Because these signs typically appear 2 to 5 months after the infected bite, most owners have no memory of the tick that caused it. If your dog starts limping for no clear reason or seems feverish and tired, mention any possible tick exposure to your veterinarian — it is a key piece of the puzzle. For the bite itself and what a fresh tick bite looks like, see our guide on tick bite symptoms on dogs.
What are the 3 stages of Lyme disease in dogs?
Veterinary sources often describe Lyme disease in dogs in three broad phases. Staging in dogs is less clearly defined than in people, and many dogs never move past the first phase — or show no signs at all — but this framework helps explain how the disease can progress if left unchecked.
| Stage | Typical timing | What is happening | Common signs |
|---|---|---|---|
| 1. Acute / early | ~2–5 months after bite | Bacteria spread from the bite site through the body | Fever, lethargy, swollen lymph nodes, low appetite |
| 2. Subacute / disseminated | Weeks to months later | Bacteria settle in the joints | Shifting-leg lameness, swollen and painful joints, stiffness |
| 3. Chronic / late | Months to years later | Persistent immune response; possible kidney involvement | Recurring arthritis and, rarely, Lyme nephritis (kidney failure) |
The third stage is where Lyme becomes dangerous. Lyme nephritis — kidney damage caused by the immune response to the infection — is uncommon but can be fatal, and certain breeds appear predisposed, including Labrador and Golden Retrievers, Bernese Mountain Dogs, and Shetland Sheepdogs.
Kidney (Lyme nephritis) warning signs — call your vet urgently: vomiting, increased thirst and urination, weight loss, and fluid swelling of the limbs or belly. Lyme nephritis is a medical emergency. If your dog is seriously unwell, contact your veterinarian or an emergency animal hospital right away.
Can dogs die from Lyme disease?
Yes, but it is uncommon — and when it happens, it is almost always due to Lyme nephritis rather than the joint form. The classic arthritis version of canine Lyme disease is rarely life-threatening and usually responds well to treatment. The kidney form is different: once the kidneys are damaged, the condition can progress to kidney failure, which is often fatal even with intensive care. This stark difference in outcomes is exactly why early recognition and veterinary follow-up matter so much. A limping dog caught early has an excellent outlook; a dog in kidney failure does not.
Is Lyme disease curable in dogs?
In most cases, yes — the clinical signs respond well to a veterinarian-prescribed course of antibiotics, and dogs with joint pain often improve dramatically within a few days of starting treatment. But "cured" deserves an honest caveat. The bacteria are not always completely eliminated from the body, some dogs relapse and need another round of treatment, and antibody blood tests can remain positive for months or years even after a dog feels fine. Dogs that develop Lyme nephritis have a much more guarded prognosis and need ongoing veterinary management. The best results come from catching the disease early and following your veterinarian’s plan.
How is Lyme disease treated in dogs?
Treatment is prescription antibiotics, chosen and dosed by your veterinarian — doxycycline is the most commonly used, typically over a multi-week course. We will not list doses here: never give your dog human medication or leftover antibiotics, and never dose without veterinary direction. Some dogs also receive supportive care to keep them comfortable while the antibiotics take effect.
Diagnosis usually starts with an in-clinic antibody test (the 4Dx or C6 test) that many veterinarians run as part of an annual heartworm and tick-borne disease screen, sometimes followed by a confirmatory quantitative test and urine testing to check the kidneys. Importantly, a positive test in a dog with no symptoms is not automatically treated the same way as an actively ill dog — your veterinarian decides based on the whole picture. Dogs with the kidney form need far more aggressive treatment, potentially including hospitalization, IV fluids, and specialized medications.
Can cats get Lyme disease from ticks?
Cats can carry ticks and can be infected with the Lyme bacterium in laboratory experiments, but naturally occurring clinical Lyme disease in cats is extremely rare and is essentially not seen in everyday veterinary practice. Cats appear to be far more resistant to becoming ill than dogs are. So while the honest answer is "technically possible, practically almost never," that does not mean ticks are harmless to cats.
Outdoor cats still pick up ticks, and those ticks can carry other pathogens and can end up loose in your home. There is no Lyme vaccine for cats. Critically, only use tick-prevention products specifically labelled as safe for cats, and check with your veterinarian first — some tick products made for dogs (including certain permethrin-based ones) are highly toxic to cats and can be fatal.
| Question | Dogs | Cats |
|---|---|---|
| Can be bitten / carry ticks? | Yes | Yes |
| Develop clinical Lyme disease? | ~5–10% of infected dogs | Extremely rare / not seen in practice |
| Typical signs | Lameness, fever, sometimes kidney disease | Rarely any |
| Lyme vaccine available? | Yes (often advised in high-risk areas) | No |
| Tick prevention still needed? | Yes | Yes |
Preventing Lyme disease in your dog
Because the tick has to feed for a day or more to transmit Lyme, prevention is genuinely effective when you layer a few habits together:
- Use a veterinarian-recommended tick preventive. Modern oral and topical products are the backbone of protection. Our guide to tick repellent and prevention for dogs in Ontario covers the options and what to avoid.
- Do daily tick checks after outdoor time — run your hands through the coat and feel around the ears, neck, armpits, groin, and between the toes.
- Remove ticks promptly and correctly, ideally within 24 hours, using the right technique.
- Ask your veterinarian about the Lyme vaccine, which is available for dogs in Canada and often recommended for higher-risk lifestyles in southern Ontario.
- Reduce ticks in the yard, where your dog spends the most unsupervised time.
When to call your veterinarian
Call your veterinarian if your dog develops unexplained lameness, fever, tiredness, or reduced appetite — particularly if there is any chance of tick exposure in the previous few months. Treat vomiting, increased drinking and urination, or limb swelling as urgent, since these can signal the kidney form. And if you are ever unsure whether a symptom is serious, it is always reasonable to phone your clinic or an emergency animal hospital for advice. Early attention consistently produces the best outcomes with canine Lyme disease.
This article is general information for pet owners and is not a substitute for professional veterinary advice, diagnosis, or treatment. Always consult your veterinarian about your specific pet, and never medicate a dog or cat without veterinary guidance. Tick-range and Lyme information reflects Public Health Agency of Canada (PHAC) surveillance and general veterinary consensus as of 2026.