The Prevalence of Antibodies against Borrelia burgdorferi Found in Horses Residing in the Northwestern United States

Lyme disease, a bacterial illness caused by Borrelia burgdorferi, is thought to be most prevalent in the heavily tick-infested areas of the northeastern United States. Serum samples from 196 asymptomatic horses residing in the Pacific northwest were tested for the presence of antibodies to Borrelia burgdorferi, using the canine SNAP 4DX (IDEXX Laboratories, Inc., Maine) and the enzyme-linked immunosorbent assay (ELISA). Positive samples were confirmed by Western blot analysis. The ELISA and Western blot analyses identified 29 of 196 horses that had antibodies for Borrelia burgdorferi, whereas the Canine SNAP 4DX only identified 2 of 196 horses as positive for an antibody titer. These results indicate that 14.8% of horses residing in the northwestern United States have been exposed to B. burgdorferi.