Molecular Characterization of Tickborne Relapsing Fever Borrelia, Israel

T relapsing fever (TBRF) is caused by Borrelia species and is transmitted to humans by Ornithodoros soft ticks. Worldwide, a dozen Borrelia species are known to cause this disease (1). In Israel, TBRF is considered to be caused by Borrelia persica and transmitted by the cave tick Ornithodoros tholozani (1). This tick and TBRF are distributed through Central Asia (2) and the Middle East (1). Other Borrelia species that cause TBRF have been described in Iran (3), but their precise range of distribution is not known. In Israel, from 1980 through 2002, 184 cases of TBRF were reported among the civilian population (8 cases/year), and 88% of the case-patients were infected in caves (4). Among military personnel, TBRF incidence averages 6.4 cases/100,000 persons (5). In Jordan, an average of 72 civilian cases per year was reported from 1959 through 1969 (6). In Iran, an average of 100 cases per year has been recently reported (7). TBRF in Israel was first reported by Nicholson (8) at the time World War I. Detailed clinical and epidemiologic features of the disease are well described in this article, particularly the transmission by ticks (8). However, Nicholson incorrectly attributed the disease to the soft tick Argas persicus. In 1937, Adler et al. clearly identified O. papillipes (tholozani) as the vector of the disease (9) and characterized the causative agent as Spirochaeta persica (10). Although American (11) and African TBRF Borrelia (12) are now better characterized, no definitive molecular characterization of Borrelia species responsible for relapsing fever has been achieved in Israel. The aim of this study is to provide initial molecular characterization of the etiologic agent of TBRF in Israel from both ticks and human samples and to compare it with previously described agents of TBRF in other parts of the world.