Overview of Lyme Disease in Dogs
Lyme disease is a clinical disorder caused by a microscopic organism, the spirochete, Borrelia burgdorferi, and is spread by ticks. The bacteria normally feed on small mammals, especially mice. Ticks then feed on the mammals and carry the bacteria to their victims. The deer tick is the most common tick involved in spreading the disease, although other ticks can pass it along, too. Ticks capable of spreading Lyme disease are most commonly found in the eastern United States, the upper Midwest and the Pacific Northwest. Lyme disease can affect different organs and body systems. The disease is named because of the initial discovery in human beings that occurred in 1975 in Lyme, Connecticut.
Lyme disease is most common in dogs but has been reported in other species. There appears to be no breed or sex predisposition. Outside, hunting and working dogs are more likely to be exposed to ticks than dogs kept indoors. Puppies appear to have a higher risk, and it is thought that less than five percent of dogs exposed to Lyme disease in an endemic (prone) area may develop clinical signs.
Human data from the Centers of Disease Control suggests that 85 percent of cases are from Eastern coastal states, 10 percent from the Midwest, 4 percent from the western states and 4 percent from the remaining states. The same figures may be true for dogs.
For more information about the relative risk of Lyme disease in the United States, see the risk map at: www.cdc.gov/ncidod/dvbid/lyme/riskmap.htm.
What to Watch For
The most consistent clinical sign in dogs includes lameness with swollen joints that are warm to the touch. Other symptoms may include heart, nervous system and kidney disease. Many dogs show no symptoms at all. Other signs include:
Recurrent lameness in a joint with complete recovery
Reluctance to move (pain)
Swelling in one or more joints
Diagnosis of Lyme Disease in Dogs
Lyme disease is usually diagnosed by the presence of clinical symptoms and by blood tests. Diagnostic tests are also needed to exclude other diseases. After obtaining a history and performing a physical examination, your veterinarian may recommend the following diagnostic tests:
Blood tests for titers to Lyme disease (IFA or ELISA) may help to determine disease. This test detects the presence of antibodies against the bacteria. However, the test indicates exposure to the disease and does not always indicate infection.
Western blot test
Joint fluid analysis may be needed to exclude other causes of joint inflammation
Treatment of Lyme Disease in Dogs
In the early stages of the disease, treatment with antibiotics is usually successful. Treatment will probably include:
Antibiotic therapy. This usually provides complete clinical recovery in 24 to 48 hours although antibiotics should be continued for 14 to 21 days (recommendations vary from 2 to 4 weeks). Antibiotics recommended may include tetracycline, doxycycline, minocycline, cephalexin, amoxicillin or ampicillin.
Treatment of Lyme disease must be individualized based on the severity of the condition. Dogs with clinical signs and a positive high titer should be treated with antibiotics. Treating serology-positive asymptomatic dogs is not recommended.
In-depth Information on Lyme Disease in Dogs
Other medical problems can lead to symptoms similar to those encountered in Lyme disease. It is important to exclude these conditions before establishing a definite diagnosis.
Bacterial endocarditis causing septic arthritis caused by the presence of microorganisms or toxins in the blood or tissue, or immune-mediated arthritis
Chronic hemarthrosis, or blood in the joints, due to coagulation defects, either congenital or acquired
Crystal-induced arthritis (gout, pseudogout)
Degenerative joint disease
Drug reaction (sulfadiazine reaction in Doberman pinschers)
Ehrlichiosis. This disease caused by parasite infection can be diagnosed with Ehrlichia serology and platelet counts.
Immune mediated polyarthritis
Musculoskeletal injury or trauma
Osteochondritis dissecans (OCD) – inflammation of the bone and cartilage
Osteopathy (any bone disease)
Panosteitis (inflammation of every part of a bone)
Rocky Mountain spotted fever
Systemic lupus erythematosus
In-depth Information on Diagnosis of Canine Lyme Disease
Certain diagnostic tests must be performed to confirm the diagnosis of Lyme disease and exclude other diseases that may cause similar symptoms. The following diagnostic tests are often recommended:
A complete medical history and physical examination should be obtained by your veterinarian. Special attention should be paid to joints, lameness evaluation and auscultation (stethoscope examination) of the heart.
Diagnosis is based on physical examination, history, clinical signs, rule-outs, positive serology and response to antibiotics.
Blood tests called IFA or ELISA may help to determine disease. The ELISA can detect antibodies to Lyme disease in dogs that have not been vaccinated for Lyme disease. A single positive titer can be an incidental finding in an endemic area and does not indicate disease. Most veterinarians consider a fourfold rise in antibody titer diagnostic of disease.
Western blot is useful to distinguish between antibody levels generated due to infection vs. those due to vaccination.
Joint fluid analysis may be done in arthritic or lame joints. This test can also help determine the cause of the lameness and rule out other infections.
Radiographs (X-rays) may be performed on swollen or lame joints. Swelling in the joint (effusion) is a common finding with Lyme disease but the radiography should otherwise should be normal.