Abstract
During 2012–2013, a total of 4325 host-seeking adult ticks belonging to the genus Ixodes were collected from various localities of Hokkaido, the northernmost island of Japan. Tick lysates were subjected to real-time PCR assay to detect borrelial infection. The assay was designed for specific detection of the Relapsing fever spirochete Borrelia miyamotoi and for unspecific detection of Lyme disease-related spirochetes. Overall prevalence of B. miyamotoi was 2% (71/3532) in Ixodes persulcatus, 4.3% (5/117) in Ixodes pavlovskyi and 0.1% (1/676) in Ixodes ovatus. The prevalence in I. persulcatus and I. pavlovskyi ticks were significantly higher than in I. ovatus. Co-infections with Lyme disease-related spirochetes were found in all of the tick species. During this investigation, we obtained 6 isolates of B. miyamotoi from I. persulcatus and I. pavlovskyi by culture in BSK-M medium. Phylogenetic trees of B. miyamotoi inferred from each of 3 housekeeping genes (glpQ, 16S rDNA, and flaB) demonstrated that the Hokkaido isolates were clustered with Russian B. miyamotoi, but were distinguishable from North American and European B. miyamotoi. A multilocus sequence analysis using 8 genes (clpA, clpX, nifS, pepX, pyrG, recG, rplB, and uvrA) suggested that all Japanese B. miyamotoi isolates, including past isolates, were genetically clonal, although these were isolated from different tick and vertebrate sources. From these results, B. miyamotoi-infected ticks are widely distributed throughout Hokkaido. Female I. persulcatus are responsible for most human tick-bites, thereby I. persulcatus is likely the most important vector of indigenous relapsing fever from tick bites in Hokkaido.
Highlights
Borrelia miyamotoi, a member of the relapsing fever group (RF) borreliae, was first discovered from Ixodes persulcatus ticks and the rodent, Apodemus argenteus, in Hokkaido, the northernmost island of Japan [1]
The FAM probe widely detects B. burgdorferi sensu lato, which has been isolated from Ixodes ticks in Japan, including pathogenic borreliae of humans, such as B. garinii, Borrelia bavariensis and Borrelia afzelii, and non-pathogenic borreliae, Borrelia japonica, Borrelia tanuki and Borrelia turdi, whereas the VIC probe detects a narrow range of relapsing fever borreliae, of which the only one reported in Japan is B. miyamotoi
It is known that I. persulcatus principally serves as a tick vector for Lyme disease (LD) borreliae in Hokkaido
Summary
A member of the relapsing fever group (RF) borreliae, was first discovered from Ixodes persulcatus ticks and the rodent, Apodemus argenteus, in Hokkaido, the northernmost island of Japan [1]. B. miyamotoi has been found in Ixodes scapularis and Ixodes pacificus ticks in North America [2,3,4] and Ixodes ricinus in Europe [5,6]. Cases of human infections with B. miyamotoi were initially reported in Russia [7]. Several human cases have been confirmed as B. miyamotoi infections in North America [8,9] and Europe [10]. Tick surveillance for B. miyamotoi was performed in Europe [11] and Russia [7]. The surveys showed that I. ricinus and I. persulcatus in the Eurasian continent consistently harbor B. miyamotoi with low prevalence. Large-scale tick surveillance has not been conducted in Asian countries where I. persulcatus is distributed
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