Jpn. J. Infect. Dis., 57, 229-235, 2004 Invited Review Terrestrial Distribution of the Lyme Borreliosis Agent Borrelia burgdorferi Sensu Lato in East Asia Toshiyuki Masuzawa* Department of Microbiology and COE Program in the 21st Century, University of Shizuoka School of Pharmaceutical Sciences, Shizuoka 422-8526, Japan (Received September 3, 2004) CONTENTS: 1. Introduction 4. B. burgdorferi sl complex found in Japan 2. Lyme borreliosis agents and their classification 5. Geographical distribution of B. burgdorferi sl in 3. Relationship to the Borrelia burgdorferi sl complex East Asia 3-1. Transmission 6. Geographical distribution of B. burgdorferi sl in 3-2. Vectors the boundary between Asia and Europe 3-3. Reservoir 7. Conclusion 3-4. Clinical manifestation SUMMARY: Lyme borreliosis is the most prevalent tick-borne zoonosis and an important emerging infection in Europe, North America, and Far Eastern countries. The geographical distribution of Borrelia spp. and the relationship between Borrelia spp. and tick spp. in East Asian countries have been studied. In Northern Asian countries, Ixodes persulcatus carries Eurasian-type Borrelia garinii (20047 type), Borrelia afzelii, and Asian- type B. garinii (variant NT29), whereas Borrelia burgdorferi sensu stricto has not been isolated. In contrast, Asian-type B. garinii has not been found in the European vector tick Ixodes ricinus. These Borrelia spp. cause Lyme borreliosis in their respective countries. The specificity between Borrelia spp. and tick spp. has been confirmed from studies in the Moscow region, which is a sympatric region for the tick spp. I. persulcatus and I. ricinus. In Southeast Asian countries including the southernmost island of Okinawa, the Borrelia valaisiana- related genomic group is carried by Ixodes granulatus. In Japan, a similar borrelia strain Am501, is transmitted by Ixodes columnae. Ixodes ovatus transmits Borrelia japonica but not other species. On other hand, in central China and Nepal, the ticks harbor Borrelia sinica. It is believed that these molecular epidemiological surveys will provide useful information for the diagnoses and prevention of Lyme borreliosis in these countries. the patients reported in the USA has steadily increased, and 1. Introduction more than 18,000 cases have been reported (8). Similarly, in Lyme borreliosis is the most prevalent tick-borne zoonosis Europe a high incidence rate has been reported from Central- and an important emerging infection in Europe, North Eastern Europe. The incidences per 100,000 people in Slovenia America, and Far Eastern countries (1-3). It was known and Austria are 120 and 130, respectively (9). initially as Lyme arthritis in the USA in the 1970s, and the town of Old Lyme in Connecticut, USA, was the initial focus 2. Lyme borreliosis agents and their classification of juvenile rheumatoid arthritis (4). Then, it became apparent that the arthritis was a late manifestation of tick-transmitted, Borreliae are roughly classified into two groups: relapsing multisystemic disease, which had been recognized in Europe fever-associated Borrelia spp. and Lyme borreliosis-related 100 years ago. The pathogen, a kind of spirochete, was discov- Borrelia spp. (B. burgdorferi sl spp. complex) (10). Relapsing ered by Burgdorfer and colleague (5) on the American vector fever-associated Borrelia spp., including Borrelia coriaceae, tick Ixodes scapularis (former Ixodes dammini), and was are transmitted by soft ticks of the genus Ornithodoros. The named Borrelia burgdorferi (B. burgdorferi sensu stricto [ss]) avian borreliosis agent, Borrelia anserina, is also carried by by Johnson et al. (6). Ixodes ricinus complex ticks are the soft tick Argas persicus. Other relapsing-fever-associated infected with the spirochete B. burgdorferi sensu lato (sl) spp. Borrelia spp. are Borrelia recurrentis, transmitted by the hu- complex, which causes the disease (7). To date, the number of man body louse Pediculus humanus, and the bovine borreliosis agent Borrelia theileri, transmitted by Rhipicephalus evertsi *Corresponding author: Mailing address: Department of Micro- and Boophilus spp. (10). Specificity occurs between Borrelia biology and COE Program in the 21st Century, University of spp. and tick spp. Lyme-borreliosis-related Borrelia are trans- Shizuoka School of Pharmaceutical Sciences, Yada 52-1, Shizuoka mitted by hard ticks of the Ixodes spp. complex. Initially, the 422-8526, Japan. Tel: +81-54-264-5710, Fax: +81-54-264-5715, agent occurs as one species. To date, the agents have been E-mail: [email protected] grouped in the B. burgdorferi sl spp. complex (7) and have been further classified into at least 11genomospecies (Fig. 1) This article is an Invited Review based on a lecture presented at (11), including the human pathogens B. burgdorferi ss, the 5th Infectious Diseases Forum at the National Institute of Borrelia garinii (7) and Borrelia afzelii (12). Infectious Diseases, Tokyo, 19-20 January 2004. B. burgdorferi sl is Gram-negative, microareophilic, 229 Species North Europe/ America West Russia East RussiaChina Nepal Japan Research (TIGR) and co-workers (13,14), and the total B. andersonii I. dentatus genome size was found to be 1,521 kbp. The ribosomal RNA I. spinipalpis B. bissettii △ (rRNA) gene of B. burgdorferi sl is unique with two copies I. pacificus B. burgdorferi ○ I. scapularis each of the 23S rRNA gene (rrl) and 5S rRNA gene (rrf) B. lusitaniae being tandemly repeated but only one copy of the 16S rDNA gene (rrs) being located on the chromosome (15, 16). An B. garinii (Eurasian type) ○ I. ricinus intergenic spacer (about 250bp) between rrfA and rrsB is B. afzelii ○ I. persulcatus I. persulcatus highly variable and polymorphic (Fig. 3). PCR-restriction B. garinii (Asian type) ○ fragment length polymorphism (RFLP) analysis by Postic et B. valaisiana △ I. ricinus I. columnae al. (17) showed a system of discrimination for B. burgdorferi sl that has become a widely used typing system (18). The B. valaisiana-related I. granulatus I. granulatus advantage of this method is that no amplification occurs with B. sinica I. ovatus the relapsing fever-associated Borrelia spp. because there is B. japonica I. ovatus no tandem repeat. Using this method, isolates of B. garinii B. tanukii I. tanuki are further divided into two subgroups: the B. garinii RFLP B. turdi I. turdus pattern B isolated from Europe and Asia (Eurasian-type B. Fig. 1. Genomospecies of Borrelia burgdorferi sensu lato and the garinii) and the RFLP pattern C of B. garini, which is only relationship between Borrelia spp. and vector tick spp. ○ and △ indicate found in Asia (Asian-type B. garinii). the species pathogenic to human and suspected of causing disease, respectively. 3. Relationship to the B. burgdorferi sl complex 3-1. Transmission The B. burgdorferi sl complex is transmitted by ixodid ticks spp. during feeding for over more than 48 h. Usually, ixodid ticks have a 2-year life cycle including three stages, larva, nymph, and adult, and at each stage, the tick takes blood from a variety of vertebrates. During feeding, Borrelia is transmit- ted from reservoir hosts to ticks. Borrelia can survive in 1.0μ m 0.5μ m the tick midgut during the digestion process and after tick- molting, the borrelia is transmitted to infested host animals from ticks during its blood-feeding. Since transovarial trans- Fig. 2. The morphology of B. burgdorferi sensu lato. Periplasmic flagella mission of Borrelia has rarely been observed, the agent is and its insertion points are shown. maintained between the ticks and reservoir animals (enzootic transmission cycle). 3-2. Vectors rrfB rrfA rrlA t-RNA rrlB rrs The major vectors are I. scapularis and Ixodes pacificus in the USA, I. ricinus in Europe, and Ixodes persulcatus (Fig. RIS2 BB421 mag BB423 BB424 4) in Western Europe and Northern Asia (19). The American RIS1 PCR vector ticks, I. scapularis and I. pacificus harbor B. burgdorferi Primer RIS1; CTGCCGAGTTCGCCCCAGT ss, whereas I. ricinus is the prominent vector for transmitting RIS2; TCCTAGGCATTCACCATA five species, B. burgdorferi ss, B. garinii, B. afzelii, Borrelia (bp) 300 Amplicon (ca.250bp) Dra I RFLP lusitaniae (20), and Borrelia valaisiana (21), in European countries. Among these species, B. burgdorferi, B. afzelii, and Mse I or Dra I 100 B. garinii are pathogenic to humans. On the other hand, the pathogenicity of B. lusitaniae and B. valaisiana still remains to be elucidated (18). The American tick Ixodes dentatus is RFLP analysis a restricted vector, and only Borrelia andersonii has been 20 ABCD Fig. 3. The unique rDNA organization in B. burgdorferi sensu lato. 23S rRNA gene (rrlA and rrlB) and 5S rRNA gene (rrfA and rrfB) Ixodes persulcatus are tandemly repeated. Since the intergenic spacer between rrfA and rrlB is highly variable, the Borrelia spp. can be differentiated by RFLP analysis of the spacer. Representative RFLP patterns digested by the restriction enzyme DraI are illustrated. Pattern A, B. burgdorferi ss; Pattern B, Eurasian-type B. garinii (20047-type); Pattern C, Asian-type B. garinii (variant NT29 type); and Pattern D, B. afzelii. helical-shaped bacteria with 7 to 11 periplasmic flagella (10). Its length varies from 10 to 20 μm, and its width varies from Female Male 0.2 to 0.5 μm (Fig. 2). The organism has a unique genomic organization of one linear chromosome 910 kb in size and a Fig. 4. The vector tick Ixodes persulcatus found in Northern Asia. variety of 12 linear and 9 circular plasmids. The genome Left, adult female; right, adult male. The scale on the left indicates sequences were determined by the Institute of Genetic 1 mm. 230 isolated from this species. From these findings, the vector Japan. The other rare tick vectors, I. tanuki and I. turdus for B. burgdorferi sl is not strictly species-specific, whereas harbor Borrelia tanukii, and Borrelia turdi, respectively a molecular epidemiological study of the Japanese vector ticks (39,40), while the Japanese strain Am501, which has only spp. and Borrelia spp.