Search

Although a wide range of viruses have been reported in marine molluscs, most of these reports rely on ultrastructural examination and few of these viruses have been fully characterized. The lack of marine mollusc cell lines restricts virus isolation capacities and subsequent characterization works. Our current knowledge is mostly restricted to viruses affecting farmed species such as oysters Crassostrea gigas, abalone Haliotis diversicolor supertexta or the scallop Chlamys farreri. Molecular approaches which are needed to identify virus affiliation have been carried out for a small number of viruses, most of them belonging to the Herpesviridae and birnaviridae families. These last years, the use of New Generation Sequencing approach has allowed increasing the number of sequenced viral genomes and has improved our capacity to investigate the diversity of viruses infecting marine molluscs. This new information has in turn allowed designing more efficient diagnostic tools. Moreover, the development of experimental infection protocols has answered some questions regarding the pathogenesis of these viruses and their interactions with their hosts. Control and management of viral diseases in molluscs mostly involve active surveillance, implementation of effective bio security measures and development of breeding programs. However factors triggering pathogen development and the life cycle and status of the viruses outside their mollusc hosts still need further investigations., (Copyright © 2017 Elsevier Inc. All rights reserved.)

From 2006 to 2012, acute mortalities occurred in farmed and wild abalone (Haliotis spp.) along the coast of Victoria, Australia. The disease (abalone viral ganglioneuritis; AVG) is associated with infection by an abalone herpesvirus (AbHV). The relative pathogenicity of 5 known variants of AbHV was evaluated on abalone stocks from different states in Australia. Results indicated that all virus variants (Vic1, Tas1, Tas2, Tas3 and Tas4) cause disease and mortality in all abalone stocks tested (greenlip, blacklip and brownlip). In order to avoid further AVG outbreaks in Australian wild abalone, strict regulations on the transfer of abalone stocks must be implemented.

Complete and transparent reporting of key elements of diagnostic accuracy studies for infectious diseases in cultured and wild aquatic animals benefits end-users of these tests, enabling the rational design of surveillance programs, the assessment of test results from clinical cases and comparisons of diagnostic test performance. Based on deficiencies in the Standards for Reporting of Diagnostic Accuracy (STARD) guidelines identified in a prior finfish study (Gardner et al. 2014), we adapted the Standards for Reporting of Animal Diagnostic Accuracy Studies-paratuberculosis (STRADAS-paraTB) checklist of 25 reporting items to increase their relevance to finfish, amphibians, molluscs, and crustaceans and provided examples and explanations for each item. The checklist, known as STRADAS-aquatic, was developed and refined by an expert group of 14 transdisciplinary scientists with experience in test evaluation studies using field and experimental samples, in operation of reference laboratories for aquatic animal pathogens, and in development of international aquatic animal health policy. The main changes to the STRADAS-paraTB checklist were to nomenclature related to the species, the addition of guidelines for experimental challenge studies, and the designation of some items as relevant only to experimental studies and ante-mortem tests. We believe that adoption of these guidelines will improve reporting of primary studies of test accuracy for aquatic animal diseases and facilitate assessment of their fitness-for-purpose. Given the importance of diagnostic tests to underpin the Sanitary and Phytosanitary agreement of the World Trade Organization, the principles outlined in this paper should be applied to other World Organisation for Animal Health (OIE)-relevant species.

In late 2005, acute mortalities occurred in abalone on farms located in Victoria, Australia. Disease was associated with infection by an abalone herpes virus (AbHV). Subsequently, starting in 2006, the disease (abalone viral ganglioneuritis; AVG) was discovered in wild abalone in Victorian open waters. Currently, it continues to spread, albeit at a slow rate, along the Victorian coast-line. Here, we report on experimental transmission trials that were carried out by immersion using water into which diseased abalone had shed infectious viral particles. At various time points following exposure, naïve abalone were assessed by an AbHV-specific real-time PCR and histological analyses including in situ hybridization (ISH). Results demonstrated that while exposed abalone began displaying clinical signs of the disease from 60 hours post exposure (hpe), they tested positive for the presence of viral DNA at 36 hpe. Of further interest, the AbHV DNA probe used in the ISH assay detected the virus as early as 48 hpe., (Crown Copyright © 2012. Published by Elsevier B.V. All rights reserved.)

The recent emergence of a herpes-like virus in both farmed and wild populations of abalone in Victoria, Australia, has been associated with high mortality rates in animals of all ages. Based on viral genome sequence information, a virus-specific real-time TaqMan assay was developed for detection and identification of the abalone herpes-like virus (AbHV). The assay was shown to be specific as it did not detect other viruses from either the Herpesvirales or the Iridovirales orders which have genome sequence similarities. However, the TaqMan assay was able to detect DNA from the Taiwanese abalone herpes-like virus, suggesting a relationship between the Taiwanese and Australian viruses. In addition, the assay detected < 300 copies of recombinant plasmid DNA per reaction. Performance characteristics for the AbHV TaqMan assay were established using 1673 samples from different abalone populations in Victoria and Tasmania. The highest diagnostic sensitivity and specificity were 96.7 (95% CI: 82.7 to 99.4) and 99.7 (95% CI: 99.3 to 99.9), respectively, at a threshold cycle (C(T)) value of 35.8. The results from 2 separate laboratories indicated good repeatability and reproducibility. This molecular assay has already proven useful in confirming presumptive diagnosis (based on the presence of ganglioneuritis) of diseased abalone in Victorian waters as well as being a tool for surveillance of wild abalone stocks in other parts of Australia.