Herpesviral haematopoietic necrosis virus (CyHV-2) infection: case studies from commercial goldfish farms A E Goodwin 1 , J Sadler 2 , G E Merry 1 and E N Marecaux 1 1 University of Arkansas at Pine Bluff, Aquaculture/Fisheries Center, Pine Bluff, AR, USA 2 Department of Primary Industries and Fisheries, Northern Fisheries Centre, Cairns, Qld, Australia Abstract Herpesviral haematopoietic necrosis is a disease of goldfish, Carassius auratus, caused by Cyprinid herpesvirus-2 (CyHV-2) infection. Quantitative PCR was carried out on tissue homogenates from healthy goldfish fingerlings, broodfish, eggs and fry directly sampled from commercial farms, from moribund fish submitted to our laboratory for disease diagnosis, and on naturally-infected CyHV-2 carriers subjected to experimental stress treatments. Healthy fish from 14 of 18 farms were positive with copy numbers ranging from tens to 10 7 copies lg )1 DNA extracted from infected fish. Of 118 pools of broodfish tested, 42 were positive. The CyHV-2 was detected in one lot of fry produced from disinfected eggs. Testing of moribund goldfish, in which we could not detect any other pathogens, produced 12 of 30 cases with 10 6 –10 8 copies of CyHV-2 lg )1 DNA extracted. Subjecting healthy CyHV-2 carriers to cold shock (22–10 °C) but not heat, ammonia or high pH, increased viral copy numbers from mean copy number (ÆSE) of 7.3 Æ 11 to 394 Æ 55 lg )1 DNA extracted after 24 h. CyHV-2 is widespread on commercial goldfish farms and outbreaks apparently occur when healthy carriers are subjected to a sharp temperature drop fol- lowed by holding at the permissive temperature for the disease. Keywords: goldfish, hematopoietic, herpes, latency, PCR. Introduction Herpesviral haematopoietic necrosis (HVHN) of goldfish was first described as producing severe epizootics among all ages of goldfish, Carassius auratus (L.), during the spring and autumn seasons in western Japan. Lesions associated with these outbreaks included pale gills, ascites, splenomegaly with white nodules, swollen kidney and anorexia. Necrotic lesions occurred in exocrine pancreas, haematopoietic tissues, spleen and intestinal sub- mucosa. The virus responsible for HVHN was identified as a herpesvirus, and later named Cyprinid herpesvirus 2 (CyHV-2) (Jung & Miyazaki 1995). There have been no further reports from Japan, but there have been a number of outbreaks in other countries. An outbreak occurred in a recirculating aquaculture system on a small goldfish farm in California, USA, and later in hobby and small breeder ponds in Delaware and Ohio, USA (Groff, LaPatra, Munn & Zinkl 1998; Goodwin, Khoo, LaPatra, Bonar, Key, Garner & Hanson 2006a). The disease has also occurred in Taiwan (Chang, Lee, Chiang & Jong 1999), and in a private goldfish collection in Australia (Stephens, Raidal & Jones 2004). Most recently, HVHN has produced Ôlow- levelÕ mortality at goldfish retail outlets in southern England (Jeffrey, Bateman, Bayley, Feist, Hulland, Longshaw, Stone, Woolford & Way 2007). While the HVHN cases described above do include four continents, all reports other than the first report in Japan describe losses occurring in private ponds and aquaria or on small scale breeding facilities. There is little evidence that CyHV-2 is responsible for widespread mortality or that it has serious impacts on large-scale commercial goldfish production. One possibility is that the virus Journal of Fish Diseases 2009, 32, 271–278 doi:10.1111/j.1365-2761.2008.00988.x Correspondence A E Goodwin, University of Arkansas at Pine Bluff, Aquaculture/Fisheries Center, 1200 N. University Dr., Mail Slot 4912, Pine Bluff, AR 71601, USA (e-mail: agoodwin@uaex.edu) 271 Ó 2009 The Authors. Journal compilation Ó 2009 Blackwell Publishing Ltd