Surveillance of Lyme disease borreliae and vector ticks

我们从悉尼地区澳大利亚莱姆病患者皮肤样本中分离并鉴定了螺旋体。通过鞭毛蛋白和rDNA序列比较，该分离物与欧洲加里尼伯氏疏螺旋体亲缘关系较近。结果表明莱姆病borreliae也可能分布在澳大利亚。因此，我们调查了悉尼地区蜱的分布和澳大利亚蜱的感染情况。利用5.8S和28S rRNA基因间的内转录间隔序列（ITS2）和线粒体rrs序列，对莱姆病螺旋体疏螺旋体蜱媒介间的种系关系进行了分析。我们在5%的蜱中肠组织中发现了螺旋体，但它们在BSKII培养基中不生长。使用已知的16S rDNA和/或鞭毛蛋白基因序列引物进行PCR扩增，对此类蜱中肠组织样本也无效。ITS2序列的系统进化分析表明，该蜱与莱姆病borreliae相关的其他蜱类存在较大差异。我们所有的结果表明：(1)未知种类的螺旋体在澳大利亚蜱虫中被感染，Holocyclus(2)它们似乎与媒介蜱虫有特定的联系(3)不知道它是否传播导致人类莱姆病的疏螺旋体。疏螺旋体分类群的系统发育与氧化蜱之间的系统发育关系高度一致，表明蜱-螺旋体组合具有共同进化的历史。结果表明，疏螺旋体在澳大利亚的发生和分布取决于特定蜱类的媒介能力。

We have isolated and characterizedspirochete from skin sample of Australian Lyme disease patient in Sydney area. The isolate was closely related with European Borrelia garinii by comparing its flagellin and rDNA sequences. The outcome indicated that Lyme disease borreliae may also distributed in Australia. We, therefore, investigated tick distribution in Sydney area and infestation of borreliae in Australian tick, Ixodes holocyclus. An internal transcribed spacer (ITS2) sequence between the 5.8S and 28S rRNA genes and mitochondrial rrs sequence were used to estimate the phyletic relationship among Lxodes spp. Tick vectors of Lyme disease-causing Borrelia spirochetes. We found spirochetes in 5% of the tick-mid-gut tissues examined but they did not grow in BSKII medium. PCR amplification using known primer sets for 16S rDNA and/or flagellin gene sequence was also inactive against such tick mid-gut tissue samples. Phyletic analysis by ITS2 sequence indicated that I. Horocyclus is far from the other tick species associated with Lyme disease borreliae. All of out results indicate (1) unknown species of spirochetes is infest in Australian ticks, I. Holocyclus (2) they appear to have a specific association with vector tick species (3) it is not known to transmit the Borrelia-that cause Lyme disease in humans. There is a high degree of concordance in the phylogenetic of Borrelia taxa and the phylogenetic relationships among Oxides ticks, which suggests a history of cospeciation in the tick-spirochete assemblage. The results suggest that the occurrence and distribution of Borrelia in Australia are depend on the vector competence of particular tick species.