55 research outputs found
Managing marine mollusc diseases in the context of regional and international commerce: policy issues and emerging concerns
Marine mollusc production contributes to food and economic security worldwide and provides valuable ecological services, yet diseases threaten these industries and wild populations. Although the infrastructure for mollusc aquaculture health management is well characterized, its foundations are not without flaws. Use of notifiable pathogen lists can leave blind spots with regard to detection of unlisted and emerging pathogens. Increased reliance on molecular tools has come without similar attention to diagnostic validation, raising questions about assay performance, and has been accompanied by a reduced emphasis on microscopic diagnostic expertise that could weaken pathogen detection capabilities. Persistent questions concerning pathogen biology and ecology promote regulatory paralysis that impedes trade and which could weaken biosecurity by driving commerce to surreptitious channels. Solutions that might be pursued to improve shellfish aquaculture health management include the establishment of more broad-based surveillance programmes, wider training and use of general methods like histopathology to ensure alertness to emerging diseases, an increased focus on assay assessment and validation as fundamental to assay development, investment in basic research, and application of risk analyses to improve regulation. A continual sharpening of diagnostic tools and approaches and deepening of scientific knowledge is necessary to manage diseases and promote sustainable molluscan shellfish industries
Characterization of actin genes in Bonamia ostreae and their application to phylogeny of the Haplosporidia
Bonamia ostreae is a protozoan parasite that infects the European flat oyster Ostrea edulis, causing systemic infections and resulting in massive mortalities in populations of this valuable bivalve species. In this work, we have characterized B. ostreae actin genes and used their sequences for a phylogenetic analysis. Design of different primer sets was necessary to amplify the central coding region of actin genes of B. ostreae. Characterization of the sequences and their amplification in different samples demonstrated the presence of 2 intragenomic actin genes in B. ostreae, without any intron. The phylogenetic analysis placed B. ostreae in a clade with Minchinia tapetis, Minchinia teredinis and Haplosporidium costale as its closest relatives, and demonstrated that the paralogous actin genes found in Bonamia resulted from a duplication of the original actin gene after the Bonamia origi
Recommended reporting standards for test accuracy studies of infectious diseases of finfish, amphibians, molluscs and crustaceans: the STRADAS-aquatic checklist
A herpes-like virus infects a non-ostreid bivalve species: virus replication in Ruditapes philippinarum larvae
Sporadic high mortalities were reported in June 1997 among hatchery-reared larval Manila clam Ruditapes philippinarum in a French commercial hatchery. Cellular abnormalities were observed in semi-thin sections in affected animals. Transmission electron microscopy revealed the presence of herpes-like virus particles in larvae. This is the first description of a herpes-like virus infection in larval R. philippinarum, a non-ostreid bivalve species. Virus particles were similar to other herpes-like viruses described from different oyster species with respect to ultrastructure and morphogenesis. Electron microscopic examination also demonstrated cells with condensed chromatin and extensive perinuclear fragmentation of chromatin. Like viruses infecting oysters, the herpes-like virus detected in clams may induce apoptosis in infected animals
Perspectives of diagnostic approaches for mollusc diseases
Surveillance of mollusc diseases is routinely performed by histology and PGR. Efforts made in re-search and development of DNA-based diagnostic methods currently offer a broad panel of probes and tests. TTiese methods have the theoretical advantages of high sensitivity and high specificity and possible rapid screening of molluscs for the presence of a targeted pathogen. However, validation and standardisation of these tests are still needed. In recent years, the European Union Reference Laboratory (EURL) for mollusc diseases has developed and validated a range of duplex Taqman\uae PCR assays aiming at facilitating the detection of bivalve pathogens notifiable to the EU. These assays offer good performances and allow better monitoring and investigation of the epidemiol\uacogy of these different pathogens. Complementary to these PCR assays, new diagnostic approaches based on the use of passive sensors, Magnetic Beads (MBs), electrochemical biosensors, MALDI-TOF MS or Next Generation Sequencing (NGS) have been developed and tested notably in the context of the European project H2020 VIVALDI. The interest of these tools to better detect, characterise and monitor known pathogens is presented and discussed. These new developments will require further assessment, standardisation and validation before being available for routine diagnostics. Additionally, they will certainly not replace but rather complement diagnostic tools currently used to ensure alertness to emerging diseases
Evidence for interspecies transmission of oyster herpesvirus in marine bivalves
Since 1991, numerous herpesvirus infections associated with high mortality have been reported around the world in various marine bivalve species. In order to determine whether these infections are due to ostreid herpesvirus-1 (OsHV1), a previously characterized pathogen of the Japanese oyster (Crassostrea gigas), PCR analysis was carried out on 30 samples of larvae collected from four bivalve species (C. gigas, Ostrea edulis, Ruditapes decussatus and Ruditapes philippinarum), most exhibiting mortality prior to collection. All samples were shown to be infected by OsHV1. Viral genomes in three samples of C. gigas and three of R. philippinarum that originated from the same hatchery were unusual in bearing a deletion of at least 2.8 kbp in an inverted repeat region. The results demonstrate that OsHV1 is capable of infecting several bivalve species, and this raises the possibility that interspecies transmission may be promoted by intensive rearing in modern hatcheries
Bonamia parasites: a rapidly changing perspective on a genus of important mollusc pathogens
Organisms of the genus Bonamia are intracellular protistan parasites of oysters. To date, 4 species have been described (B. ostreae, B. exitiosa, B. perspora and B. roughleyi), although the status of B. roughleyi is controversial. Introduction especially of B. ostreae and B. exitiosa to naive host populations has been shown to cause mass mortalities in the past and has had a dramatic impact on oyster production. Both B. ostreae and B. exitiosa are pathogens notifiable to the World Organisation for Animal Health (OIE) and the European Union. Effective management of the disease caused by these pathogens is complicated by the extensive nature of the oyster production process and limited options for disease control of the cultured stocks in open water. This review focuses on the recent advances in research on genetic relationships between Bonamia isolates, geographical distribution, susceptible host species, diagnostics, epizootiology, host-parasite interactions, and disease resistance and control of this globally important genus of oyster pathogens
Emergence de maladies chez les organismes dâintĂ©rĂȘt aquacole : quelques scĂ©narios illustrĂ©s dâexemples
National audienceAccording to the world organisation for animal health (OIE) an emerging disease is defined as a recently admitted serious illness, whose aetiology can, or not, have already been established, and which is likely to be propagated within a population or between populations, for example at the time of international exchanges of aquatic animals and/or products of aquatic animals. Even though the emerging diseases that affect human health have been much studied, those which affect marine organisms and species of aquaculture interest in particular are poorly documented. By restricting emergence to only infectious diseases, we aim at presenting in a non-exhaustive way some scenarios of the emergence of the diseases of aquacultured species by illustrating them with three examples available in the scientific literature: one relating to the appearance of a pathogenic agent in a new host with the case of the herpesvirus of the Koi carp, the other with the evolution of a pre-existing pathogenic agent with the case of shrimp vibriosis due to Vibrio nigripulchritudo in New Caledonia, and the last example relating to the introduction of one pathogenic pre-existing pathogen in an unscathed area with the case of Bonamia ostreae infecting the flat oyster Ostrea edulis. The causes of the emergence of diseases are multiple and implicate in an intercurrent way pathogenic agents, the environment, the host or host species and anthropogenic factors. In the marine environment, these causes are very often ignored. In this context, the development of zoosanitary surveillance networks and diagnostic tools present a considerable interest in order to anticipate, prevent and/or intervene on the emergence of the diseases by limiting their sanitary, ecological and political consequences.Selon lâOffice International des Epizooties (OIE) une maladie Ă©mergente dĂ©signe une maladie grave rĂ©cemment reconnue, dont la cause peut, ou non, avoir dĂ©jĂ Ă©tĂ© Ă©tablie, et qui est susceptible de se propager au sein dâune population ou entre des populations, par exemple Ă lâoccasion dâĂ©changes internationaux dâanimaux aquatiques et/ou de produits dâanimaux aquatiques. Si les maladies Ă©mergentes qui affectent la santĂ© humaine ont Ă©tĂ© trĂšs Ă©tudiĂ©es, celles qui touchent les organismes marins et les organismes aquacoles dâintĂ©rĂȘt Ă©conomique en particulier sont en revanche peu documentĂ©es. Câest en restreignant lâĂ©mergence aux seules maladies infectieuses que seront prĂ©sentĂ©s de façon non exhaustive quelques scĂ©narios de lâĂ©mergence des maladies chez les organismes dâintĂ©rĂȘt aquacole en les illustrant par trois exemples disponibles dans la littĂ©rature scientifique : lâun relatif Ă lâapparition dâun agent pathogĂšne chez un nouvel hĂŽte avec le cas de lâherpesvirus de la carpe KoĂŻ, lâautre Ă lâĂ©volution dâun agent pathogĂšne existant avec le cas de la vibriose Ă Vibrio nigripulchritudo sĂ©vissant dans les Ă©levages de crevettes pĂ©nĂ©ides de Nouvelle-CalĂ©donie et enfin le dernier liĂ© Ă lâintroduction dâun pathogĂšne prĂ©existant avec le cas de Bonamia ostreae infectant lâhuĂźtre plate Ostrea edulis. Les causes dâĂ©mergence de maladies sont multiples et font intervenir de façon intercurrente lâagent pathogĂšne, lâenvironnement, lâhĂŽte ou les espĂšces hĂŽtes et des facteurs anthropiques. Dans le milieu marin, ces causes sont bien souvent mĂ©connues. Dans ce contexte le dĂ©veloppement des rĂ©seaux de surveillance et des techniques de diagnostic revĂȘtent un intĂ©rĂȘt considĂ©rable afin dâanticiper, de prĂ©venir et/ou dâintervenir sur lâĂ©mergence des maladies en limitant leur consĂ©quences sanitaires, Ă©cologiques et politiques
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