Epidemic ranaviral disease in imported captive frogs (Dendrobates and Phyllobates spp.), Japan, 2012: a first report

Abstract

Introduction: Ranavirus infection is associated with mass die‐off and population decline in amphibians worldwide, and is listed by the World Organization for Animal Health (OIE) as a notifiable disease under the Aquatic Animal Health Code. Work is ongoing to control the spread of ranavirus, because this agent is considered an emerging pathogen of amphibians. In Japan, ranaviral diseases have been detected at each episode of die‐off of wild bullfrog juveniles since 2008. However, ranaviral disease has not been found in captive anurans. Case presentation: Epidemic and lethal ranaviral disease in captive Dendrobates and Phyllobates species imported from the Netherlands is reported. Poison dart frogs of three genera were imported from the Netherlands in March 2012. Disease and death were noted approximately 10 days after importation. Fifty‐three adults of five species died in about 1 month, including frogs that had been kept previously. Microscopic examination revealed necrosis and intracytoplasmic basophilic inclusion bodies in the parenchyma of multiple organs. Electron microscopy showed cytoplasmic ranavirus‐like particles within haematopoietic cells of the kidney. These particles were icosahedral, with a diameter of approximately 144 nm. Thirty‐three of 41 dead frogs showed positive PCR results for the major capsid protein gene of Ranavirus. The sequence obtained from five frogs was identical and did not match the registered sequence of any ranavirus. Conclusion: This is the first report, to our knowledge, of ranaviral disease in imported anurans of the family Dendrobatidae and genera Phyllobates and Dendrobates in Japan.