Incursions of Cyprinid herpesvirus 2 in goldfish populations in Australia despite quarantine practices

Abstract

The international trade in ornamental fish is considered a major factor for the transboundary spread of aquatic pathogens that can affect both wild and farmed fish populations. Nearly 18 million ornamental fish were imported into Australia in 2007, including approximately 3.9 million goldfish. Despite quarantine regulations during importation, there have been several incidents in Australia where exotic pathogens from ornamental fish have become established in farmed or free-living fish species. The exotic virus Cyprinid herpesvirus 2 (CyHV2) was first found in Australia in 2003 in goldfish, suggesting that sub-clinically infected goldfish were passing through quarantine regardless of health certification and three weeks of quarantine. Repeated cross sectional surveys were conducted to determine whether CyHV2 has already established in farmed or wild ornamental fish in Australia. Goldfish populations were tested to OIE standard to detect 2% prevalence with 95% confidence assuming a test of 100% sensitivity and specificity. CyHV2 was found at retail outlets, farms and in several populations of wild goldfish in the ACT and Victoria. The prevalence and moderate to high viral loads in sub-clinically infected goldfish from different domestic populations suggested the introduction was not a recent event. This study demonstrated that CyHV2 has established in Australia and informed quarantine policy to revoke the requirement for goldfish exported to Australia to be certified free of CyHV2. The results provided clear evidence that an aquatic pathogen from imported ornamental fish can become established in farmed and wild populations. This is of particular significance to Australia as there are many endemic and ecologically sensitive populations of fish that may be severely affected by exotic pathogens. The incursion of CyHV2 in Australia should be considered a case study to inform pathway analysis for pathogen establishment. © 2014.