PERFORMANCE OF A BORRELIA-BURGDORFERI BACTERIN IN BORRELIOSIS-ENDEMICAREAS

The safety and efficacy of a commercially available Borrelia burgdorfe ri bacterin were examined under field conditions in 1,969 dogs that re ceived a total of 4,033 doses of bacterin during a 20-month period. Fo r comparison, 4,498 dogs that were not vaccinated also were evaluated. All dogs were examined at 1 of 3 veterinary practices in borreliosis- endemic areas. Owners of all dogs were educated about the benefits of and methods for avoiding infected ticks. Vaccination was found to be s afe regardless of previous exposure to B burgdorferi or history of bor reliosis. Thirty-eight (1.9%) of the 1,969 dogs had minor reactions; 1 of these dogs had a reaction after the first and second doses of B bu rgdorferi bacterin. Reactions resolved without complications immediate ly or within 72 hours after vaccination. Cumulative incidence of borre liosis was 1.0% (20/1,969) in vaccinated dogs and 4.7% (211/4,498) in nonvaccinated dogs. Preventable fraction, a measure of the reduction o f incidence of disease in vaccinated dogs vs nonvaccinated dogs, was 7 8%. Preventable fraction in dogs that were seropositive prior to vacci nation (ie, previously exposed to B burgdorferi) was 58% and in dogs t hat were seronegative prior to vaccination (ie, without evidence of pr ior exposure to B burgdorferi) was 86%. This suggested that, in borrel iosis-endemic areas, dogs may be most effectively protected by vaccina ting them when they are young and before they are exposed to infected ticks, and that in areas where borreliosis is not endemic, it may be u seful to initiate vaccination programs so that dogs will be protected prior to exposure to infected ticks.