Borrelia burgdorferi, the causative agent of Lyme disease, infects humans and animals.

 Straubinger RK, Straubinger AF, Summers BA, Jacobson RH, Erb HN. James A. Baker 
Institute for Animal Health, Ithaca, New York, USA.
BACKGROUND: Borrelia burgdorferi, the causative agent of Lyme disease, infects humans and 
animals. In humans, the disease primarily affects the skin, large joints, and the nervous system 
days to months after infection. Data generated with approp riate animal model help to 
understand the fundamental mechanisms of the disease. OBJECTIVE: 1, More clearly define the 
clinical manifestation and pathogenetic mechanisms of Lyme disease in dogs; 2, evaluate the 
effect of antibiotics in dogs infected with B. burgdorferi; 3, describe the effects of corticosteroids
on dogs persistently infected with B. burgdorferi. DESIGN: Specific-pathogen-free beagles were 
infected with B. burgdorferi using ticks collected in an endemic Lyme disease area. Clinical signs 
were recorded daily. Antibody titers were measured by ELISA at two-week intervals. B. 
burgdorferi organisms were detected in tissues by culture and PCR. Synovial fluids were 
evaluated microscopically and with a chemotaxis cell migration assay. Histological sections were 
examined for pathological lesions. Specific cytokine up-regulation in tissues was detected by 
RT-PCR. INTERVENTIONS: In three separate experiments, B. burgdorferi-infected dogs 
received antibiotic treatment, amoxicillin; azithromycin; ceftriaxone; doxycycline, for 30 
consecutive days. Two subclinical persistently infected dogs received oral prednisone for 14 
consecutive days starting at day 420 post-infection. RESULTS: Dogs developed acute arthritis in 
the joints closest to the tick bites after a median incubation period of 68 days. Synovial
membranes of lame and non-lame dogs produced the chemokine IL-8 in response to B. 
burgdorferi.Antibiotic treatment prevented or resolved episodes of acute arthritis, but failed 
to eliminate the bacterium from infected dogs. Corticosteroid treatment reactivated Lyme 
disease in pe rsistently infected dogs, which had not received antibiotics previously. 
CONCLUSIONS: B. burgdorferi disseminates through tissue by migration following tick 
inoculation, produces episodes of acute arthritis, and establishes persistent infection. The 
spirochete survives antibiotic treatment and disease can be reactivated in immunosuppressed 

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