National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan.
Mol Ecol. 2009 Dec;18(23):4757-74. doi: 10.1111/j.1365-294X.2009.04384.x. Epub 2009 Oct 13.
A serious disease of amphibians caused by the chytrid fungus Batrachochytrium dendrobatidis was first found in Japan in December 2006 in imported pet frogs. This was the first report of chytridiomycosis in Asia. To assess the risk of pandemic chytridiomycosis to Japanese frogs, we surveyed the distribution of the fungus among captive and wild frog populations. We established a nested PCR assay that uses two pairs of PCR primers to amplify the internal transcribed spacer (ITS) region of a ribosomal RNA cassette to detect mild fungal infections from as little as 0.001 pg (1 fg) of B. dendrobatidis DNA. We collected swab samples from 265 amphibians sold at pet shops, 294 bred at institutes and 2103 collected at field sites from northern to southwestern Japan. We detected infections in native and exotic species, both in captivity and in the field. Sequencing of PCR products revealed 26 haplotypes of the B. dendrobatidis ITS region. Phylogenetic analysis showed that three of these haplotypes were specific to the Japanese giant salamander (Andrias japonicus) and appeared to have established a commensal relationship with this native amphibian. Many other haplotypes were carried by alien amphibians. The highest genetic diversity of B. dendrobatidis was found in the American bullfrog (Rana catesbeiana). Some strains of B. dendrobatidis appeared to be endemic to Japanese native amphibians, but many alien strains are being introduced into Japan via imported amphibians. To improve chytridiomycosis risk management, we must consider the risk of B. dendrobatidis changing hosts as a result of anthropogenic disturbance of the host-specific distribution of the fungus.
2006 年 12 月，日本在进口宠物蛙中首次发现了一种由蛙壶菌引起的严重蛙类疾病。这是亚洲首例壶菌病报告。为了评估蛙壶菌病对日本青蛙的大流行风险，我们调查了真菌在圈养和野生青蛙种群中的分布。我们建立了一种巢式 PCR 检测方法，该方法使用两对 PCR 引物扩增核糖体 RNA 盒的内部转录间隔区（ITS），以从低至 0.001 pg（1 fg）的 B. dendrobatidis DNA 中检测到轻度真菌感染。我们从日本北部到西南部的宠物店收集了 265 只两栖动物的拭子样本，从研究所收集了 294 只繁殖的样本，并从野外收集了 2103 只样本。我们在本土和外来物种中检测到了感染，无论是在圈养还是在野外。PCR 产物测序显示了 B. dendrobatidis ITS 区的 26 种单倍型。系统发育分析表明，其中三种单倍型是日本大鲵（Andrias japonicus）特有的，似乎与这种本地两栖动物建立了共生关系。许多其他单倍型由外来两栖动物携带。B. dendrobatidis 的最高遗传多样性存在于美洲牛蛙（Rana catesbeiana）中。一些 B. dendrobatidis 菌株似乎是日本本地两栖动物的地方病，但许多外来菌株是通过进口的两栖动物引入日本的。为了改善壶菌病风险管理，我们必须考虑由于人为干扰真菌的宿主特异性分布而导致宿主变化的风险。
