Borrelia burgdorferi, the causative agent of Lyme disease, has never been isolated from a patient thought to have acquired Lyme disease in any southeastern state.
To investigate 14 cases of an erythema migrans (EM)—like rash illness that occurred during 2 summers at an outdoor camp in central North Carolina in an effort to determine the etiologic, epidemiological, and clinical aspects of this illness.
Using active surveillance, we identified cases of clinically diagnosed EM in residents and staff of the camp. We collected clinical and demographic information; history of exposure to ticks; acute and convalescent serum antibodies to B burgdorferi, Rickettsia rickettsii, and Ehrlichia chaffeensis; and cultures for spirochetes from biopsy specimens of skin lesions. Serum samples from a group of residents and staff who did not develop rashes were tested for the same antibodies. We speciated ticks removed from people and collected from vegetation.
We identified 14 cases of EM-like rash illness during the 2 summers. Of the 14 case-patients, 10 had associated mild systemic symptoms and 1 had documented fever. All 14 case-patients had removed attached ticks, and 8 remembered having removed a tick from the site where the rash developed a median of 12 days earlier (range, 2-21 days). One tick removed from the site where a rash later developed was identified as Amblyomma americanum, the Lone Star tick; 97% of ticks collected from vegetation and 95% of ticks removed from people were A americanum. No spirochetes were isolated from skin biopsy specimens. Paired serum samples from 13 case-patients did not show diagnostic antibody responses to B burgdorferi or other tick-borne pathogens.
This investigation suggests the existence of a new tick-associated rash illness. We suspect that the disease agent is carried by A americanum ticks. In the southern United States, EM-like rash illness should no longer be considered definitive evidence of early Lyme disease.Arch Intern Med. 1997;157:2635-2641