Status of Borrelia burgdorferi infection after antibiotic treatment and the effects of corticosteroids: An experimental study

Sixteen specific-pathogen-free beagles were infected with Borrelia burgdorf eri. Three groups of 4 dogs were treated with antibiotics for 30 consecutiv e days starting 120 days after tick exposure; 4 dogs were untreated control s. At day 420 after tick exposure and again before euthanasia, 2 dogs of ea ch group were treated with prednisone for 14 days. All dogs contracted infe ction and 11 developed acute arthritis 50-120 days after exposure. After da y 120, one of 12 antibiotic-treated dogs and 2 of 4 untreated dogs became l ame. Antibiotic therapy reduced the frequency of Borrelia-positivity in sub sequent skin biopsy samples. After prednisone treatment, both control dogs developed severe polyarthritis, At euthanasia, single tissues of the antibi otic-treated dogs and multiple tissues of all control dogs were Borrelia-po sitive by polymerase chain reaction. Viable spirochetes were not recovered from antibiotic-treated dogs. Two antibiotic-treated dogs showed histologic evidence of minimal lesions, whereas all control dogs had mild polyarthrit is with periarteritis.