Lyme Disease in DogsLyme disease is an infectious disease that affects dogs and humans. The disease is caused by transmission of the spirochete bacteria Borrelia burdorfi through the bite of infected Ixodes ticks, also called black-legged ticks or "deer ticks." Deer are important hosts for the adult ticks and therefore Lyme disease is found more commonly in the Northeast, upper Midwest, and Northwest coastal states. However, in recent years, there has been a dramatic increase of Lyme disease infection reported in wider geographic areas. Lyme disease is now the most common tick-borne diseases of humans in the United States, and one of the most common in dogs.
SymptomsUnlike humans, when a dog is infected with B. burdorfi they seldom develop acute signs of infection. It has been estimated that only 10 percent of affected dogs show overt signs of illness. Initial signs in dogs occur two to five months after the tick bite and consist of fever, lack of appetite, lethargy, lameness, and bleeding that doesn't stop on its own (low blood platelets). In a study of infected dogs, the first joint to become affected was the joint closest to the site of the tick bite. The bacteria spreads through connective tissue and therefore other joints may become infected. Dogs may show shifting-leg lameness and sometimes signs of severe pain.
In addition, the severity of the illness is influenced by the breed and age of the dog. For example, Beagle puppies are prone to arthritis affecting one to four joints, while adults more likely develop asymptomatic joint inflammation. In addition, Labrador and Golden retrievers seem to be over-represented in dogs susceptible to Lyme nephritis (kidney disease), as are Shetland sheep dogs and Bernese mountain dogs.
Rarely have dogs contracted chronic stages of Lyme disease as seen in humans. They include renal failure, heart block, or neurological changes such as seizures, aggression and other behavior changes.
DiagnosisDiagnosing canine Lyme disease is difficult and requires testing. The majority (90 percent) of infected dogs experience the subclinical infection, but produce positive antibody titers that may persist for months or years. Dogs with positive antibody titers may develop unrelated illnesses, which results in diagnostic confusion. Currently, one of the most widely used tests for canine Lyme disease is based on a C6 ELISA. The advantages of C6 ELISA assay are it detects antibodies three to five weeks after infection, so when the dog develops clinical signs the test is positive, and it is negative in dogs that have been vaccinated for Lyme disease.
The Western blot test has been considered the top standard assay. The Western blot can distinguish between dogs that have been or are infected with B. burdorfi and dogs that have been vaccinated against Lyme disease.
Another test now available is the rapid immune-chromatographic ELISA assay, VetScan Canine Lyme Rapid Test, a single test to detect B. burdorfi in canine whole blood serum or plasma quickly.
TreatmentAntibiotic treatment is recommended for dogs that test positive and have clinical signs consistent with Lyme disease. There is no evidence that treating healthy dogs with a positive serum test is beneficial. The antibiotic of choice for Lyme arthritis or Lyme nephritis in dogs is doxycycline. It is difficult to know how long to treat but on the average antibiotics are given for three to four weeks. Dogs with polyarthritis generally respond clinically to doxycycline treatment within 24 to 48 hours but need antibiotic for three to four weeks to prevent relapse. For dogs that do not tolerate doxycycline, amoxicillin can also be used.
PrognosisNearly 90 percent of dogs infected show no signs of illness. Dogs with Lyme arthritis seem to recover rapidly with antibiotic treatment and do not develop relapse of the disease. The prognosis for dogs with Lyme nephritis is poor.
PreventionThe best way to protect dogs against Lyme disease is to provide routine tick prevention in the form of repellents or topical preventatives as well as avoiding areas where ticks are prevalent. Exposure to Borrelia burdorfi-infected adult ticks in the early spring or fall is more dangerous for dogs than exposure to infected nymphs later in the spring. If dogs are to be in tick-infested areas, use a Preventic Collar in addition to K9 Advantix II to give them safe, additional protection against ticks.
If ticks are seen, they should be removed with 24 hours of attachment, before transmission of the spirochete can occur. Wear gloves and use a tweezers to carefully grab the exposed section of the tick's body near the dog's skin. Gently pull straight out until the tick lets go. Do not twist or crush the tick when removing. Dispose of the tick by wrapping it in several layers of tissue and flush it down the toilet. Do not crush, burn or suffocate it, as any one of those actions may spread infectious organisms.
Vaccination may be useful in endemic areas. Both whole-cell bacterins and recombinant vaccines are available. Two vaccinations two to three weeks apart are recommended initially in puppies. Lyme vaccines may be combined with other routine canine vaccines following product label instructions for minimum ages. Annual revaccination is currently recommended.
Vaccination has not been proven to be 100 percent effective in preventing Lyme disease. One clinical study on a whole-cell bacterin in an endemic area suggested 78 percent efficacy. Another small study of a recombinant vaccine indicated 100 percent efficacy with a one-year immunity challenge. The value of vaccines preventing Lyme nephritis is unknown.
SummaryLyme disease is one of the most common vector-borne diseases in North America and has steadily increased over the years. The best protection for dogs is to avoid tick infested areas and to use tick repellents and/or topical preventatives. If you suspect your dog has contracted Lyme disease, contact your veterinarian for testing and appropriate treatment.
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-The Revival Education Team
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