DAO 111:139-152 (2014)  -  DOI: https://doi.org/10.3354/dao02770

Isolation of a Bohle-like iridovirus from boreal toads housed within a cosmopolitan aquarium collection

Kwang Cheng1,*, Megan E. B. Jones2,*, James K. Jancovich3, Jennifer Burchell2, Mark D. Schrenzel2, Drury R. Reavill4, Denise M. Imai4, Abby Urban5, Maryanne Kirkendall6, Leslie W. Woods7, V. Gregory Chinchar1, Allan P. Pessier2,**

1Department of Microbiology, University of Mississippi Medical Center, Jackson, MS 39216, USA
2Amphibian Disease Laboratory, Wildlife Disease Laboratories, Institute for Conservation Research, San Diego Zoo Global, San Diego, CA 92112-0551, USA
3Department of Biological Sciences, California State University San Marcos, San Marcos, CA 92096, USA
4Zoo/Exotic Pathology Service, West Sacramento, CA 95605, USA
5National Mississippi River Museum and Aquarium, Dubuque, IA 52001, USA
6Colonial Terrace Animal Hospital, Dubuque, IA 52001, USA
7California Animal Health and Food Safety Laboratory, Davis, CA 95616, USA
*These authors contributed equally to this work.**Corresponding author:

ABSTRACT: A captive ‘survival assurance’ population of 56 endangered boreal toads Anaxyrus boreas boreas, housed within a cosmopolitan collection of amphibians originating from Southeast Asia and other locations, experienced high mortality (91%) in April to July 2010. Histological examination demonstrated lesions consistent with ranaviral disease, including multicentric necrosis of skin, kidney, liver, spleen, and hematopoietic tissue, vasculitis, and myriad basophilic intracytoplasmic inclusion bodies. Initial confirmation of ranavirus infection was made by Taqman real-time PCR analysis of a portion of the major capsid protein (MCP) gene and detection of iridovirus-like particles by transmission electron microscopy. Preliminary DNA sequence analysis of the MCP, DNA polymerase, and neurofilament protein (NFP) genes demonstrated highest identity with Bohle iridovirus (BIV). A virus, tentatively designated zoo ranavirus (ZRV), was subsequently isolated, and viral protein profiles, restriction fragment length polymorphism analysis, and next generation DNA sequencing were performed. Comparison of a concatenated set of 4 ZRV genes, for which BIV sequence data are available, with sequence data from representative ranaviruses confirmed that ZRV was most similar to BIV. This is the first report of a BIV-like agent outside of Australia. However, it is not clear whether ZRV is a novel North American variant of BIV or whether it was acquired by exposure to amphibians co-inhabiting the same facility and originating from different geographic locations. Lastly, several surviving toads remained PCR-positive 10 wk after the conclusion of the outbreak. This finding has implications for the management of amphibians destined for use in reintroduction programs, as their release may inadvertently lead to viral dissemination.


KEY WORDS: Ranavirus · Boreal toads · Bohle iridovirus · Viral taxonomy · Survival assurance colonies


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Cite this article as: Cheng K, Jones MEB, Jancovich JK, Burchell J and others (2014) Isolation of a Bohle-like iridovirus from boreal toads housed within a cosmopolitan aquarium collection. Dis Aquat Org 111:139-152. https://doi.org/10.3354/dao02770

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