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The international trade in amphibians is believed to have increased the spread of Batrachochytrium dendrobatidis (Bd), the fungal pathogen responsible for chytridiomycosis, which has caused a rapid decline in amphibian populations worldwide. We surveyed amphibians imported into Japan and those held in captivity for a long period or bred in Japan to clarify the Bd infection status. Samples were taken from 820 individuals of 109 amphibian species between 2008 and 2011 and were analyzed by a nested-PCR assay. Bd prevalence in imported amphibians was 10.3% (58/561), while it was 6.9% (18/259) in those in private collections and commercially bred amphibians in Japan. We identified the genotypes of this fungus using partial DNA sequences of the internal transcribed spacer (ITS) region. Sequencing of PCR products of all 76 Bd-positive samples revealed 11 haplotypes of the Bd ITS region. Haplotype A (DNA Data Bank of Japan accession number AB435211) was found in 90% (52/58) of imported amphibians. The results show that Bd is currently entering Japan via the international trade in exotic amphibians as pets, suggesting that the trade has indeed played a major role in the spread of Bd.

To determine whether the chytrid fungus Batrachochytrium dendrobatidis (Bd) found on the hellbender Cryptobranchus alleganiensis in the southern US is endemic or exotic, we identified the genetic type of this fungus using partial DNA sequences of the internal transcribed spacer (ITS) region. We identified 3 genetic types, which are found on Japanese amphibians other than the Japanese giant salamander Andrias japonicus, a species that belongs to the same family (Cryptobranchidae) as hellbenders. The fungus collected from hellbenders exhibited low genetic diversity and matched the common Bd genetic types which have been detected from around the world. These results support that the chytrid fungus on the hellbender is a novel pathogen, as proposed by previous studies. Although we have not observed disease symptoms directly linked to this fungus on this endangered salamander, further evaluation of the influence of this exotic fungus on this species is warranted.

The purpose of this study was to establish a method for eradicating a chytrid fungus (Batrachochytrium dendrobatidis; Bd) from the Japanese giant salamander Andrias japonicus. The emerging agent (Bd) has a high rate of detection in this endangered amphibian species, which is designated as a special natural monument in Japan. Four Japanese giant salamanders with Bd confirmed by PCR assay were bathed in 0.01% itraconazole for 5 min d-1 over 10 successive days. PCR assays were conducted prior to treatment, on Days 5 and 10 of treatment, and on Days 7 and 14 post-treatment. By treatment Day 5, all individuals tested negative for Bd and remained negative until the end of the experiment. No side effects associated with itraconazole were observed. The present method appears to be a safe and effective approach for Bd eradication and may contribute to reducing the threat and spread of Bd among endangered amphibians. Notably, this study represents the first reported Bd eradication experiment involving Japanese giant salamanders.