The potential role of hobby and pest fish in spreading systemic iridoviruses

Leigh Owens and Bradford Cullen

Microbiology and Immunology, School of Biomedical and Molecular Sciences, James Cook University, Townsville, Queensland, Australia 4811

Email: lee.owens@jcu.edu.au

Powerpoint presentation of talk (240 kb)

Over the past few years, the world has been experiencing a pandemic of iridoviral and nodaviral epizootics in finfish. Similarly, there is evidence of an epizootiological declines in amphibians on a global scale. Are these two events linked?

A search of the published literature suggests that hobby fish are often vectors of iridoviruses. The Ram Cichlid, Chromide Cichlid, Angelfish, Dwarf Gourami, Goldfish, Guppy, Doctor Fish and Grouper have all been documented to be infected with systemic iridoviruses. Similarly in Australia, Angelfish, Goldfish and Tilapia have been found to carry agents that caused presumptive, based on histopathology, iridoviral diseases, in in-contact conspecific and contraspecific fishes. Eight of the 11 cases involved fish from the fish redistribution businesses in Singapore.

Using a systemic ranavirus, Bohle Iridovirus, experimental infections of goldfish, golden perch, barramundi, tilapia, barcoo grunter and silver perch all show histopathological lesions consistent with ranaviral infections. The virus could be re-isolated on BF2 cell cultures from mosquito fish, goldfish, golden perch, barramundi, and barcoo grunter, albeit at low frequqency (2-60%). Only striped grunter showed no evidence of viral replication. Two models of infection are proposed; an acute, usually lethal infection targeting the haematopoietic tissues and a chronic infection characterised by low PCV and a build up of haemosiderin in the tissues. The parallel diseases in amphibians are highlighted. The intercontinental movement of live hobbyfish has the potential to move ranaviruses into environments where the virus could contribute to amphibian declines.