A treponema-like spirochete was detected in and isolated from adult Ixodes dammini , the incriminated tick vector of Lyme disease. Causally related to the spirochetes may be long-lasting cutaneous lesions that appeared on New Zealand White rabbits 10 to 12 weeks after infected ticks fed on them. Samples of serum from patients with Lyme disease were shown by indirect immunofluorescence to contain antibodies to this agent. It is suggested that the newly discovered spirochete is involved in the etiology of Lyme disease.

We recovered a newly recognized spirochete from the blood, skin lesions (erythema chronicum migrans [ECM]), or cerebrospinal fluid of 3 of 56 patients with Lyme disease and from 21 of 110 nymphal or adult Ixodes dammini ticks in Connecticut. These isolates and the original one from I. dammini appeared to have the same morphologic and immunologic features. In patients, specific IgM antibody titers usually reached a peak between the third and sixth week after the onset of disease; specific IgG antibody titers rose slowly and were generally highest months later when arthritis was present. Among 40 patients who had early disease only (ECM alone), 90 per cent had an elevated IgM titer (≥1:128) between the ECM phase and convalescence. Among 95 patients with later manifestations (involvement of the nervous system, heart, or joints), 94 per cent had elevated titers of IgG (≥1:128). In contrast, none of 80 control subjects had elevated IgG titers, and only three control patients with infectious mononucleosis had elevated IgM titers. We conclude that the I. dammini spirochete is the causative agent of Lyme disease. (N Engl J Med. 1983; 308:733–40.)

We isolated spirochetes from the blood of 2 of 36 patients in Long Island and Westchester County, New York, who had signs and symptoms suggestive of Lyme disease. The spirochetes were morphologically similar and serologically identical to organisms recently found to infect Ixodes dammini ticks, which are endemic to the area and have been epidemiologically implicated as vectors of Lyme disease. In both patients, there was a rise in specific antispirochetal antibodies in paired specimens of serum. We conclude that the I. dammini spirochete has an etiologic role in Lyme disease. (N Engl J Med. 1983; 308:740–2.)

Lyme disease, unknown in the United States two decades ago, is now the most common arthropod-borne disease in the country and has caused considerable morbidity in several suburban and rural areas. The emergence of this disease is in part the consequence of the reforestation of the northeastern United States and the rise in deer populations. Unfortunately, an accurate estimation of its importance to human and animal health has not been made because of difficulties in diagnosis and inadequate surveillance activities. Strategies for prevention of Lyme disease include vector control and vaccines.