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Haematopoietic necrosis virus [cyprinid herpesvirus 2 (CyHV-2)] was isolated during disease outbreaks in goldfish, Carassius auratus, at an ornamental fish retail site in southern England in 2004. Signs of disease included lethargy and inappetence and were first seen after water temperatures increased from 14-15 to 19-21 degrees C. External gross pathology included pale patches on the gills and skin and internally the spleen was enlarged, often with distinctive white nodules. The most prominent histopathological changes observed were necrotic lesions in the spleen and kidney and focal patches of necrosis in the gill lamellae. Necrotic cells often contained nuclei with marginated chromatin and pale intranuclear inclusions. Ultrastructural examination of the spleen tissue revealed typical herpesvirus-like particles measuring 100 nm in diameter. The virus was isolated from extracts of gill tissue in KF-1 cells at 20 degrees C and oligonucleotide primer sets were designed based on conserved gene sequences and used to amplify viral DNA by polymerase chain reaction (PCR). The PCR assays were then used to detect the virus in DNA extracted from tissues sampled during earlier disease investigations at the retail site owner's holding facility in 2002 and 2003 and stored at -70 degrees C since then. Polymerase gene-specific PCR amplification products obtained from tissue samples and from the virus isolated in cell culture shared 100% nucleotide sequence identity with the published sequence for CyHV-2.

Cold water strawberry disease (CWSD), or red mark syndrome (RMS), is a severe dermatitis affecting the rainbow trout Oncorynchus mykiss. The condition, which presents as multifocal, raised lesions on the flanks of affected fish, was first diagnosed in Scotland in 2003 and has since spread to England and Wales. Results of field investigations indicated the condition had an infectious aetiology, with outbreaks in England linked to movements of live fish from affected sites in Scotland. Transmission trials confirmed these results, with 11 of 149 and 106 of 159 naïve rainbow trout displaying CWSD-characteristic lesions 104 to 106 d after being cohabited with CWSD-affected fish from 2 farms (Farm B from England and Farm C from Wales, respectively). The condition apparently has a long latency, with the first characteristic lesions in the previously naïve fish not definitively observed until 65 d (650 day-degrees) post-contact with affected fish. Affected fish from both outbreak investigations and the infection trial were examined for the presence of viruses, oomycetes, parasites and bacteria using a combination of techniques and methodologies (including culture-independent cloning of PCR-amplified bacterial 16S rRNA genes from lesions), with no potentially causative infectious agent consistently identified. The majority of the cloned phylotypes from both lesion and negative control skin samples were assigned to Acidovorax-like β-Proteobacteria and Methylobacterium-like α-Proteobacteria. KEY WORDS: RFLP · 16S rRNA · Clone library · Flavobacterium psychrophilum · Red mark syndromeResale or republication not permitted without written consent of the publisher Dis Aquat Org 79: 207-218, 2008 report that the disease is prevalent at low water temperatures (<15°C), in comparison to the UK experience of WWSD, which generally occurs only when water temperatures exceed 14°C (a summer rather than winter condition). Early signs of CWSD can include severe scale loss prior to the emergence of the characteristic external lesions (Ferguson et al. 2006), and there are no signs of systemic infection (i.e. no affect on appetite, growth or mortality). However, the condition causes losses to farmers both in treatment costs and in downgrading of affected fish at harvest.The objective of the present study was to determine if the disease had an infectious aetiology by conducting a disease investigation on farms affected by the condition. Laboratory trials evaluating whether the condition could be transmitted from affected to naïve fish were also conducted. As a recent report implicated Flavobacterium psychrophilum as potentially being linked to the condition (Ferguson et al. 2006), particular effort was made to identify whether this, or a closely related organism, was associated with diseased fish. MATERIALS AND METHODS Outbreak investigationsOutbreaks of CWSD at 3 farms in England and Wales were investigated between January 2005 and January 2006. Structured interviews with the farmers asked about the chronology of the disease o...

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