Lyme Disease in Dogs: Symptoms, Testing and Tick Prevention

What it is and how dogs catch it

Lyme disease is caused by the bacterium Borrelia burgdorferi, carried by black-legged ticks, which Cornell describes as tiny, about the size of a poppy seed or sesame seed before feeding. A tick has to stay attached for roughly 24 to 48 hours to pass the infection on, so finding and removing ticks quickly genuinely lowers the risk. Lyme is most common in the Northeast, mid-Atlantic and upper Midwest, and its range has been spreading.

The Merck Veterinary Manual notes that spring and fall are the peak seasons, though ticks can be active on mild winter days. Most dogs that are infected never show signs of illness. Dogs do not pass Lyme directly to people, but they can carry infected ticks into the house, where the ticks may attach to family members.

Lyme disease symptoms in dogs

When signs appear, they usually begin two to five months after the tick bite, long after the tick is gone. The typical picture is lameness that comes and goes and shifts from one leg to another, with warm, swollen or painful joints, along with fever, low energy, a poor appetite and swollen lymph nodes. Some dogs walk stiffly with a hunched back or seem reluctant to move.

Less often, Lyme affects the kidneys, a condition called Lyme nephritis. Cornell notes it may be more likely in young to middle-aged Labrador and Golden Retrievers. Signs include vomiting, not eating, drinking and urinating more, weight loss and extreme tiredness. Merck describes kidney involvement as among the most serious forms and often fatal. Lameness and fever have many other causes too, including other tick-borne infections, so testing is important.

When to call your vet today

Call your vet within a day or two if your dog is limping on and off, especially if the lameness switches legs, if its joints look swollen or sore, or if it has a fever, low energy or poor appetite and has been anywhere ticks live, such as woods, tall grass or brush, in the past few months.

Call the same day if a dog that has had ticks or tested positive for Lyme starts vomiting, eating less, drinking or peeing more, or losing weight. These can be early signs of kidney involvement, which needs prompt testing.

When it's an emergency

Go to your vet or the nearest emergency vet immediately if your dog has repeated vomiting and will not eat, is extremely weak or collapses, stops producing urine, has a seizure, sudden facial paralysis or difficulty breathing. Severe kidney disease and, rarely, nervous system or heart involvement can follow tick-borne infection and need urgent care.

Also go in promptly if your dog is suddenly unable to walk or is in severe pain, as these signs have causes other than Lyme that cannot wait.

What you can safely do at home

Check your dog for ticks every day during tick season, running your fingers over the whole body and looking especially around the ears, eyelids, lips, neck, armpits, groin, between the toes and under the tail. Remove any tick promptly with fine-tipped tweezers, gripping close to the skin and pulling steadily straight out, then clean the area and wash your hands. Merck recommends disposing of ticks safely.

Do not use matches, petroleum jelly or essential oils to remove ticks, and do not give human pain relievers to a limping dog; many are toxic to dogs. Note the date of any tick bite and where you were, which helps your vet decide on testing.

Daily tick checks after walks, plus the prevention your vet recommends, are the main defense; see our flea and tick range for related supplies.

What the vet will likely check

Your vet will ask about tick exposure, examine your dog's joints and lymph nodes, and run a blood test for antibodies to the Lyme bacterium. Antibodies take time to appear, so Cornell advises waiting at least four to eight weeks after a tick bite before testing. A positive screening test shows exposure, not necessarily illness, so your vet may also run a urine test for protein, which can be an early sign of kidney involvement, and blood work for other tick-borne infections.

Dogs with signs of Lyme are usually treated with about four weeks of antibiotics chosen by your vet, plus pain relief, and Merck notes that most dogs with joint signs improve quickly. Dogs that test positive but have no signs are often monitored, for example with periodic urine checks. Lyme nephritis needs hospital care and intensive treatment.

Prevention

Tick control is the most important step. Cornell recommends year-round tick prevention, daily tick checks, prompt removal and avoiding high-risk areas such as tall grass and woods where possible. Ask your vet which tick preventive suits your dog and your area, keep lawns mowed and clear leaf litter where your dog plays.

A Lyme vaccine is available. Cornell describes an initial dose followed by a booster three to four weeks later, then yearly boosters, and advises discussing with your vet whether it fits your dog's location and lifestyle. A previous infection does not give lasting immunity, so tick prevention is still needed in vaccinated dogs and dogs that have had Lyme.

This page is general information, not veterinary advice, and it cannot replace an examination by the vet who knows your pet.