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Cyprinid herpesvirus 3 (CyHV-3) is the causative agent of koi herpesvirus diseases (KHVD), a notifiable condition associated with mass mortalities in koi and common carp (Cyprinus carpio L.). Open reading frame 81 (ORF 81) encodes a well characterized nonglycosylated membrane protein of CyHV-3 that is thought to be highly immunogenic due to its C-terminal hydrophilic domain. To test its immunogenic potential, ORF 81 was cloned into a DNA vaccine vector and administered to common carp by intramuscular injection. To assess the protective immunity of the vaccinated carps, antibody titres against CyHV-3 following immunization were measured by ELISA and fish were submitted to a viral challenge. Additionally, a Western Blot was carried out using purified recombinant pORF81 and sera from vaccinated, infected and uninfected fish. Although the gene was found to be reliably transcribed in vitro and in vivo, no antibody response could be detected in vivo following vaccination using the existing method. These results call into question the immunogenicity of the protein derived from ORF 81 of CyHV-3 or suggest that this protein only induces antibody titres that remain below the limit of detection.

The freshwater bryozoan Fredericella sultana (Blumenbach) is the most common invertebrate host of the myxozoan parasite Tetracapsuloides bryosalmonae, the causative agent of proliferative kidney disease in salmonid fish. Culture media play an important role in hatching of statoblasts and maintaining clean bryozoan colonies for Malacosporea research. We developed a novel culture medium, Bryozoan Medium C (BMC), for the cultivation and maintenance of F. sultana under laboratory conditions. Statoblasts of F. sultana were successfully hatched to produce transparent-walled, specific pathogen-free (SPF) colonies that were maintained >12 months in BMC at pH 6.65. Tetracapsuloides bryosalmonae was successfully transmitted from infected brown trout, Salmo trutta L., to newly hatched F. sultana colonies in BMC, then from the infected bryozoan to SPF brown trout. This study demonstrated the utility of BMC (pH 6.65) for hatching statoblasts, long-term cultivation of clean and transparent bryozoan colonies and maintenance of the Tetracapsuloides bryosalmonae life cycle in the laboratory for molecular genetic research and other studies such as host–parasiteinteraction.

While bacteria of the genus Francisella have been reported for many years in association with diseases and mortalities in farmed fish, they have yet to be recognised as a threat to ornamental fish. Here, we describe the isolation of Francisella noatunensis subsp. orientalis that was found to be associated with sporadic mortalities over the course of several years in various ornamental Malawi cichlids from an Austrian breeding facility. The fish displayed unspecific external clinical signs including anorexia, dyspnea, and abdominal distension, quickly followed by death. Pathoanatomical and histological examination revealed an enlarged spleen, pale viscera and ascites, and, in some cases, granulomas, predominantly in the spleen. DNA extracted from different tissues was sequenced and subsequent Blast alignment showed a 99% level of homology with F. noatunensis subsp. orientalis. Culture of this fastidious bacterium was performed on a modified cystein heart agar. Until now, F. noatunensis subsp. orientalis had not been described in relationship with disease and mortality in ornamental fish. Considering the worldwide trade with ornamental African cichlids and the difficulties of diagnosing this disease by routine examination, it seems likely that francisellosis might be widely distributed and its prevalence underestimated.