The spirochete Borrelia burgdorferi causes multisystemic disease in dogs. Cats living in enzootic Lyme disease areas that are positive for antibodies induced by exposure to the bacterium exhibit signs of limb and joint disorders, fever, and anorexia. These signs are similar to those seen with bite-wound cellulitis or trauma. A test for detection of antibodies directed against an invariable region (IR6) of the B. burgdorferi surface protein is available commercially for dogs (SNAP 3Dx-IDEXX Laboratories, Westbrook, ME). Samples were collected from 24 cats in an area hyperenzootic for Lyme disease. When possible, outdoor cats or those with bite wounds or current tick infestations were used. All samples were tested with the C6 ELISA in the clinic. Serum or plasma was frozen and later evaluated by IFA, Western blot, or both. Of the 24 cats tested, 17 were positive for antibodies according to the C6 ELISA test. Five samples were negative upon both C6 ELISA and IFA testing. Two samples were negative on the C6 ELISA test but had low IFA titers. These samples were tested by Western blot, and one sample was negative and one sample was positive for antibodies to B. burgdorferi. The clinical significance of Lyme disease in cats is not clearly understood. If a cat presents with fever or limb or joint abnormalities but has no evidence of bite wounds or trauma, determining the status of B. burgdorferi infection might be useful to make a presumptive diagnosis of Lyme disease. The authors also have unpublished information that shows that cats positive for B. burgdorferi may also be positive for the granulocytic ehrlichiosis organism, Anaplasma phagocytophilum. The significance of this organism in cats is also unknown. However, it may be prudent to choose antibiotics, such as doxycycline or tetracycline, that have activity against both B. burgdorferi and A. phagocytophila for therapy in cats. Funding for this study was provided by IDEXX Laboratories, Westbrook, ME.

COMMENTARY: Most cats in this study were positive for B. burgdorferi, but the population chosen for sampling included cats that were likely to have tick exposure in an enzootic area. Further studies should help determine both the disease potential of B. burgdorferi in cats as well as the incidence in a more random population.

Evaluation of a canine C6 ELISA Lyme disease test for the determination of the infection status of cats naturally exposed to Borrelia burgdorferi. Levy SA, O'Conner TP, Hanscom JL, Shields BS. VET THER 4:172-177, 2003.