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The Ecologies of Borrelia spp. in Hokkaido, Japan

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タイトル: The Ecologies of Borrelia spp. in Hokkaido, Japan
その他のタイトル: 北海道におけるボレリア種の生態
著者: Taylor, Kyle Rueben 著作を一覧する
発行日: 2013年 3月27日
抄録: The ecologies of Borrelia spp. are very specific to location, since they are dependent upon the spirochete species, the vectors, and the host vertebrates present. The intent of this research was to describe the poorly studied ecological interactions of each of the most common Borrelia spp. found in Hokkaido, Japan, with their respective vectors and suspected host species. To this end, this research was endeavored in order to identify factors involved in Borrelia spp. maintenance by cross-comparison between sampling areas within Hokkaido (eastern and central), across time (May through September), among host species (deer, five rodent species and three shrew species), and between important vector ticks (Ixodes persulcatus and Ixodes ovatus). First, a study was performed to examine questing tick infection rates with various Borrelia spp., and to contrast those rates between the two sampling areas in Hokkaido. Furthermore, comparison was made for tick abundance between the two areas by species and stage. Notably, tick abundance was significantly greater in eastern Hokkaido, yet infection rates of I. persulcatus with each Borrelia spp. were similar between areas. Borrelia garinii, a Lyme disease Borrelia sp., was the most common species found carried by questing I. persulcatus, and Borrelia miyamotoi, a relapsing fever Borrelia sp., was the least common. Second, a study was performed on whether deer act as important reservoir hosts for Lyme disease Borrelia spp. Although it is difficult to determine with conviction that deer do not act as hosts, the results of this study suggest that, if deer are involved, they play a minor role. However, a novel Borrelia sp. similar to Borrelia lonestari, a relapsing fever Borrelia sp. also found among deer in the United States, was discovered during this study, and is herein reported for the first time. The absence of this Borrelia sp. among rodents or shrews, and the prevalence among deer suggest that deer may be an important host for this species. Third, a study was performed on wild rodents to determine the infection rates with various Borrelia spp., the level of exposure to feeding nymphs and larvae of both I. persulcatus and I. ovatus, and the level of exposure to Lyme disease Borrelia spp. Furthermore, comparisons were made for rodent abundance, infection rates, and tick exposure between the two sampling areas by species. Notably, rodent abundance was greater in eastern Hokkaido, but infection rates between respective rodent species were generally similar between areas. Furthermore, differential infection rates among rodent species were correlated with tick burdens of the respective vectors of each Lyme disease Borrelia sp. Also, this study showed for the first time, in Hokkaido, that infections with Lyme disease Borrelia spp. are age-dependent. For B. miyamotoi, however, this is not true, and this species likely does not cause persistent infections in rodents the way that the Lyme disease Borrelia spp. do. Moreover, B. miyamotoi infections in blood were highly correlated with larval I. persulcatus attachment, suggesting that larvae may be important vectors of this Borrelia sp. Finally, a study determined the infection rates of shrew species with various Borrelia spp. This study agreed with previous research suggesting that these species are only moderately involved in the maintenance of pathogenic Lyme disease Borrelia spp. More importantly, this is the first report of B. miyamotoi in shrew species, and the herein recorded data indicates that shrews may be at least as important for the maintenance of this Borrelia sp. as rodents.
学位授与機関: Hokkaido University(北海道大学)
学位の報告番号: 甲第10813号
取得学位の種別: 博士
取得学位の分野: 獣医学
資料タイプ: theses (doctoral)
出現コレクション:博士 (獣医学)

提供者: Kyle Rueben Taylor


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