Signs of Lyme Disease in Dogs

The first sign of Lyme disease is a tick feeding on a dog. Not all ticks carry Lyme disease, but it is very difficult to differentiate ticks. Research indicates that a tick only transmits Lyme disease after feeding for a substantial amount of time, usually around 48 hours. By regularly checking your dog for ticks, you can prevent the disease entirely.

Just as humans lose their appetite when they’re sick, dogs can experience the same issue. Lyme disease can cause anorexia in dogs, which often manifests as a loss of appetite. Depending on the severity, a dog may simply eat less or outright refuse all meals and treats. Some dogs may also have other digestive tract issues, such as vomiting or diarrhea.

When a dog is fighting off an infection, their immune system will kick in to fight it. An immune response may cause fever and a general increase in body temperature, known as hyperthermia. Normally, a dog’s body temperature ranges between 99.5 and 102.5 F. As their temperature increases, they may have warm ears or a warm, dry nose. Alternatively, they may shiver or cough.

Dogs are often bundles of energy, though this may not be the case in dogs with Lyme disease. Dogs who contract Lyme disease often become lethargic, meaning they may seem tired and act significantly less energetic. Even offering them treats or a toy to play with may be ineffective. Hyperthermia and lethargy often occur simultaneously, and they may both improve or worsen sporadically.

You may notice that your dog seems to be moving more slowly or limping. This is sometimes the only presenting symptom of Lyme disease. Their lameness may seem to shift from one leg to another. Even if you don’t notice a limp or any lameness, refusal to exercise or an increase in time lying down may be indicators of Lyme disease.

Like humans, a dog’s lymph nodes can swell when fighting an infection. Lymph nodes contain various cells that filter the lymphatic fluid as it travels through the body, destroying invading cells. This immune response can cause the lymph nodes to enlarge. Knowing where your dog’s lymph nodes are can allow you to feel if they’re swollen. Lymph nodes are present under your dog's jaw, in front of their shoulders, in their armpits and knees, and on each side of their groin.

Bites from ticks that carry Lyme disease have a particular “bulls-eye” pattern. This lesion, also known as erythema migrans, is sometimes visible on dogs. However, the presence of fur and the differences in the skin make this an unreliable indicator. Other insect bites have similar patterns, so it’s possible to confuse the lesions.

Though it may be difficult to notice, swollen joints may be another sign of Lyme disease. The disease attacks the cartilage that lines the joints, and the joint nearest the bite will often swell first. As the disease progresses, it will affect other areas. The easiest way to see if a joint has become swollen is to touch it. A swollen joint feels slightly squishy and may be warm to the touch. You can hold two joints at the same time to compare how they feel.

As Lyme disease progresses, it becomes substantially more dangerous. Eventually, it causes Lyme nephritis when the disease spreads to the kidneys, which may lead to severe kidney failure. Dogs with Lyme nephritis become extremely sick and require immediate treatment. Lyme nephritis used to be extremely difficult to combat, but modern medical progress has allowed many dogs to overcome the disease.

Both hyperthermia and kidney issues can cause a dog to feel excessive thirst, known as polydipsia. As the kidneys fail, they lose the ability to process waste products that should be passed through urine. Because of this, the dog will drink more water as their body attempts to excrete toxins from the blood that the kidney would normally filter into the urine. An increase in water consumption leads to frequent urination and increased urine production, also known as polyuria.