Data from: Amphibian chytridiomycosis in Japan: distribution, haplotypes, and possible entry into Japan

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 2,103 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 3 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.由蛙壶菌（Batrachochytrium dendrobatidis）引发的两栖动物烈性传染病，于2006年12月在日本的进口宠物蛙中首次被发现，这也是亚洲地区首次报道壶菌病（chytridiomycosis）。为评估大流行壶菌病对日本蛙类的威胁风险，本研究针对圈养及野生蛙类种群中的该真菌分布情况开展了调查。我们建立了一套巢式PCR检测法，使用两对PCR引物扩增核糖体RNA盒的内部转录间隔区（internal transcribed spacer，ITS），可从低至0.001皮克（1飞克）的蛙壶菌DNA中检出轻度真菌感染。本次研究共采集三类样本：宠物商店售卖的265只两栖动物、科研机构繁育的294只两栖动物，以及从日本北部至西南部野外采集的2103只两栖动物的拭子样本。我们在本土及外来两栖动物的圈养与野生种群中均检出了真菌感染。对PCR产物的测序结果显示，蛙壶菌的ITS区域共存在26种单倍型。系统发育分析表明，其中3种单倍型仅存在于日本大鲵（Andrias japonicus）中，且似乎已与该本土两栖动物建立了共生关系。其余多数单倍型则由外来两栖动物携带。蛙壶菌遗传多样性最高的宿主为美洲牛蛙（Rana catesbeiana）。部分蛙壶菌菌株为日本本土两栖动物所特有，但另有大量外来菌株通过进口两栖动物传入日本境内。为优化壶菌病的风险管理策略，我们必须考虑因人为干扰破坏真菌宿主特异性分布而引发的真菌宿主转换风险。