disease has been recognized in humans since 1975 when it was associated with an outbreak of oligoarthritis in children in Lyme, Connecticut. Erythema chronicum migrans (ECM) is a clinical marker for the human disease, which usually appears within 3 to 32 days after an infected tick bite. Lyme disease is caused by spirochete, Borrelia burgdorferi, which is vectored by the hard ticks Ixodes dammini or Ixodes pacificus in the United States. In humans, Lyme disease has been found to cause a variety of clinical syndromes including cardiopathy, neuropathy, dermatopathy, and arthropathy. Human Lyme carditis is characterized by varying degrees of atrioventricular (AV) heart block that usually resolve regardless of therapy. Lyme disease has been reported in the dog as an arthropathy. This article reports a case of complete heart block and myocarditis in a dog with a positive titer for B burgdorferi, in which clinical and pathologic findings were similar to those seen in human Lyme myocarditis.
The detection of antibody to the Borrelia burgdorferi C 6 peptide by use of enzyme-linked immunoassays is a widely accepted method for the diagnosis of Lyme disease spirochete infection in dogs and in humans. Antibody to the C 6 peptide is highly specific for B. burgdorferi and declines following treatment of dogs and humans exposed to B. burgdorferi. A quantitative assay for determining C 6 antibody levels was developed and used to measure changes in antibody levels following antibiotic treatment of B. burgdorferi antibody-positive nonclinical dogs. One hundred thirty-two client-owned dogs were used in the study; 64 were negative, 53 of 68 positive animals received treatment, and 15 were untreated controls. Test sera were collected at 3, 6, and 12 months from seropositive dogs receiving treatment and untreated controls. Dogs in the treated group were assigned to moderate-to-high (>29 U/ml)-and low (<29 U/ml)-C 6 -level groups because the change in the C 6 level after treatment was dependent on the level prior to treatment. There were significant declines in the 30 dogs with moderate-to-high initial C 6 levels that exceeded the maximal declines of the untreated control dogs in all cases at 6 months (16 data points) and 12 months (29 data points) posttreatment. There was little change in C 6 level following antibiotic therapy in the 23 dogs with low initial C 6 levels. The quantitative C 6 antibody test can be used to measure changes in C 6 antibody levels following treatment of antibody-positive nonclinical dogs.
Amitraz-impregnated collars prevented transmission of B. burgdorferi in 4 of 4 treated dogs and may be a useful management tool for prevention of borreliosis in dogs.
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