Lyme Disease Spirochete may Linger -abx treated Dogs

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Infection With Lyme Disease Spirochete May Linger in Antibiotic-Treated Dogs

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WESTPORT, Apr 20 (Reuters Health) - Although experimentally infected dogs

showed no viable Borrelia burgdorferi spirochetes more than 360 days after

antibiotic treatment, analysis by polymerase chain reaction (PCR) revealed

evidence of the organism in single tissue samples, according to findings

published in the March issue of the Journal of Infectious Diseases.

Dr. Reinhard K. Straubinger, of Cornell University, Ithaca, New York, and

colleagues infected 16 pathogen-free beagles with B. burgdorferi. Starting

120 days after tick exposure, three groups of four dogs were treated with

azithromycin, ceftriaxone or doxycycline. The fourth group of four dogs

received no treatment and acted as controls.

All dogs became infected and 11 developed acute arthritis 50 to 120 days

after exposure. These episodes lasted 3 to 6 days and resolved without

treatment. After day 120, one of the treated dogs showed brief episodes of

lameness, as did two of the controls.

At 420 days after exposure, two dogs from each group were given oral

prednisone for 14 days to determine whether clinical disease could be

reactivated even after antibiotic therapy. All treated dogs remained free of

clinical disease, while both dogs from the control group developed pain and

joint swelling.

Both animals recovered without medical treatment within 7 days. They had

high titers of B. burgdorferi-specific antibodies that did not change in

response to corticosteroid administration.

At necropsy, single tissues from the antibiotic-treated dogs and multiple

tissues from all control animals were positive for B. burgdorferi by PCR.

The researchers, who note that viable spirochetes were not recovered from

antibiotic-treated animals, call for further research to determine whether

the PCR findings " indicate an ongoing persistent infection in these animals

or only the presence of DNA remnants of dead Borrelia. "

J Infect Dis 2000;181:1069-1081.