The Southeast appears to have its own version of the tick-borne ailment Lyme disease that is not detectable by most standard tests, according to Georgia researchers.
Extensive laboratory testing of 23 adults with the characteristic bull's eye rash showed that 70 percent were not infected with the spirochete known to cause Lyme disease, according to the study published in the November issue of Archives of Dermatology.
Thirty percent of patients did test positive for the spirochete, but on closer analysis, even in those patients, the spirochete--called Borrelia burgdorferi--had a different protein composition than that causing Lyme disease in New England and the Midwest, said Dr. Michael Felz, family medicine physician at the Medical College of Georgia and principal investigator on the study.
"There is some kind of tick-transmitted illness here that acts like Lyme disease but only fits the laboratory pattern 30 percent of the time, at least when you apply a test that was designed for New England and the Midwest where Lyme disease is more common," Dr. Felz said. "In other words, we may need a whole new testing system for this illness in the Southeast."
MCG collaborated with Georgia Southern University in Statesboro and the Centers for Disease Control and Prevention in Fort Collins, Colo., on the CDC-funded study.
The three-year study included Georgians and South Carolinians who lived within 200 miles of Augusta and came to the MCG Family Practice Center to see Dr. Felz after developing enlarging red rashes, 2 to 8 inches in diameter. Approximately 90 percent were certain they had been bitten by a tick.
Before each patient began the standard therapy of a three-week oral regimen of the antibiotic doxycycline hyclate, photographs, biopsies and blood samples were taken for a complete series of tests. Tests included the sophisticated polymerase chain reaction assay for spirochete DNA in biopsy samples; the PCR was positive in five of 23 cases.
"These data say yes, there is some Lyme disease here that meets the criteria of current national lab testing standards. Yet the majority of cases-- seven out of 10--are something different," Dr. Felz said. "The tick species transmitting this illness seems to be different and may be transmitting an organism that is very different.
"Lyme disease in the southeastern United States seems to be due to genetically variant strains of the spirochete Borrelia burgdorferi," Dr. Felz said. "These strains probably have a different DNA backbone and cause different clinical symptoms and signs than is the case in other parts of the country."
Dr. Felz, who has studied ticks and the diseases they carry for nine years, says this study is the "most scientifically rigorous analysis" of Lyme disease ever in the southeastern United States.
Lyme disease typically begins with an enlarging, red circular rash and can cause flulike symptoms of malaise, headache, fever and muscle soreness. Left untreated, it also can lead to more serious secondary problems including arthritis, nerve palsy, meningitis and heart arrhythmias.
Researchers found no evidence that the disease progressed to the second stage in any of the study patients, leading them to believe that the Lyme disease organism in the Southeast may be a less virulent strain and/or more responsive to antibiotic therapy.
Dr. Felz's collaborators at MCG on the study include Dr. Francis W. Chandler Jr., director of Immunopathology and Histopathology Laboratories, and Dr. Daniel W. Rahn, rheumatologist and Lyme disease expert who is vice dean for clinical affairs in the School of Medicine. Other collaborators include Dr. James H. Oliver Jr., Institute of Arthopodology and Parasitology at Georgia Southern University, and Dr. Martin E. Schriefer, CDC in Fort Collins.
Journal
Archives of Dermatology