Arthritis caused by Borrelia burgdorferi in dogs

From October 1982 to May 1984, we studied 34 dogs from the Lyme, Conn area that had a history of tick exposure and lameness associated with pain, warmth, and/or swelling in one or more joints. Large numbers of polymorphonuclear leukocytes were seen in Giemsa-stained smears of synovial fluid from 9 dogs, and spirochetes (Borrelia burgdorferi) were found in 1 sample by darkfield microscopy and immunoperoxidase techniques. The geometric mean antibody titer to B burgdorferi in the 34 dogs was 1:2,700, compared with 1:285 in 43 clinically normal dogs from the same area (P less than 0.0001) and 1:50 in 29 dogs from an area in New Jersey that is not endemic for human Lyme disease (P less than 0.00001). We concluded that B burgdorferi in dogs may cause arthritis similar to that in human Lyme disease.