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On request of the EU Commission, EFSA carried out an Extensive Literature Review (ELR) to provide a list of vector species or reservoirs species of pathogens of crustaceans, listed in Annex II to the AHL, aiming to update the Annex of Implementing Regulation (EU) 2018/1882. In this Technical Report, the detailed review protocol of the ELR and assessment of potential vector and reservoir species is described of the crustacean pathogens listed in Annex II to the AHL: Taura syndrome virus (TSV), Yellow head virus (YHV) or White spot syndrome virus (WSSV). In total 2,530 research publications were collected for abstract screening and from these, 110 were selected for further full text analysis. In the final data collection and assessment 34 relevant research publications were used for extracting information on vector and reservoir species of the above crustacean pathogens. The results for crustacean species for which scientific evidence indicates that a role as vector species or reservoir species is likely are presented as tables in the supplementary material of this report. This publication is linked to the following EFSA Journal articles: http://onlinelibrary.wiley.com/doi/10.2903/j.efsa.2023.8172/full, http://onlinelibrary.wiley.com/doi/10.2903/j.efsa.2023.8173/full, http://onlinelibrary.wiley.com/doi/10.2903/j.efsa.2023.8174/full This publication is linked to the following EFSA Supporting Publications articles: http://onlinelibrary.wiley.com/doi/10.2903/sp.efsa.2023.EN-8122/full, http://onlinelibrary.wiley.com/doi/10.2903/sp.efsa.2023.EN-8124/full [ABSTRACT FROM AUTHOR]

On request of the EU Commission, EFSA carried out an Extensive Literature Review (ELR) to provide a list of vector species or reservoirs species of pathogens of crustaceans, listed in Annex II to the AHL, aiming to update the Annex of Implementing Regulation (EU) 2018/1882. In this Technical Report, the detailed review protocol of the ELR and assessment of potential vector and reservoir species is described of the crustacean pathogens listed in Annex II to the AHL: Taura syndrome virus (TSV), Yellow head virus (YHV) or White spot syndrome virus (WSSV). In total 2,530 research publications were collected for abstract screening and from these, 110 were selected for further full text analysis. In the final data collection and assessment 34 relevant research publications were used for extracting information on vector and reservoir species of the above crustacean pathogens. The results for crustacean species for which scientific evidence indicates that a role as vector species or reservoir species is likely are presented as tables in the supplementary material of this report. This publication is linked to the following EFSA Journal articles: http://onlinelibrary.wiley.com/doi/10.2903/j.efsa.2023.8172/full, http://onlinelibrary.wiley.com/doi/10.2903/j.efsa.2023.8173/full, http://onlinelibrary.wiley.com/doi/10.2903/j.efsa.2023.8174/full This publication is linked to the following EFSA Supporting Publications articles: http://onlinelibrary.wiley.com/doi/10.2903/sp.efsa.2023.EN-8123/full, http://onlinelibrary.wiley.com/doi/10.2903/sp.efsa.2023.EN-8124/full [ABSTRACT FROM AUTHOR]

Crassostrea gigas oysters represent a significant global food source with 4.7 million tons harvested per year. In 2001, the bacterium Vibrio aestuarianus subsp. francensis emerged as a pathogen that causes adult oyster mortality in France and Ireland. Its impact on oyster aquaculture has increased in Europe since its re‐emergence in 2012. To better understand the evolutionary mechanisms leading to the emergence and persistence over time of this pathogen, we conducted a survey of mollusc diseases through national reference laboratories across Europe. We analysed 54 new genomes of Vibrio aestuarianus (Va) isolated from multiple environmental compartments since 2001, in areas with and without bivalve mortalities. We used a combination of comparative genomics and population genetics approaches and show that Va has a classical epidemic population structure from which the pathogenic Va francensis subspecies emerged and clonally expanded. Furthermore, we identified a specific cus‐cop‐containing island conferring copper resistance to Va francensis whose acquisition may have favoured the emergence of pathogenic lineages adapted and specialized to oysters. [ABSTRACT FROM AUTHOR]

The conservation and active restoration of European flat oyster (Ostrea edulis) populations are a major focus of ecological restoration efforts to take advantage of the wide‐ranging ecosystem functions and services this species provides. Accordingly, additional and new demands for seed oysters have arisen. In commercial aquaculture (mariculture), the production of O. edulis is still largely based on natural seed collection. Considering the specific requirements, related to ecological restoration, such as the absence of pathogens and the preservation of high genetic diversity, the current supply is insufficient. Despite the development of breeding and controlled reproduction techniques for this species since the late 1930s, seed production today is mainly based on empirical concepts. Several of the issues that producers still face are already subjects of research; many others are still unanswered or even unaddressed. This review provides a summary of all available knowledge and technologies of O. edulis seed production. Furthermore, it provides a detailed reflection on implications for restoration, future challenges, open questions and it identifies relevant research topics for sustainable seed supply. The study covers the following aspects on (i) biology of the species, (ii) stressors – including pathogens and pollutants, (iii) genetics, (iv) history of production technologies, (v) seed production in polls, (vi) seed production in ponds and (vii) seed production in hatcheries. Future research needs on sex determinism, gametogenesis, cryopreservation, nutrition, selective breeding, pathogens and disease, and the development of reliable protocols for production are highlighted. [ABSTRACT FROM AUTHOR]

Summary: Environmental DNA approaches are increasingly used to detect microorganisms in environmental compartments, including water. They show considerable advantages to study non‐cultivable microorganisms like Bonamia ostreae, a protozoan parasite inducing significant mortality in populations of flat oyster Ostrea edulis. Although B. ostreae development within the host has been well described, questions remain about its behaviour in the environment. As B. ostreae transmission is direct, seawater appears as an interesting target to develop early detection tools and improve our understanding of disease transmission mechanisms. In this context, we have developed an eDNA/eRNA approach allowing detecting and quantifying B. ostreae 18S rDNA/rRNA as well as monitoring its presence in seawater by real‐time PCR. B. ostreae DNA could be detected up to 4 days while RNA could be detected up to 30 days, suggesting a higher sensitivity of the eRNA‐based tool. Additionally, more than 90% of shed parasites were no longer detected after 2 days outside the oysters. By allowing B. ostreae detection in seawater, this approach would not only be useful to monitor the presence of the parasite in oyster production areas but also to evaluate the effect of changing environmental factors on parasite survival and transmission. [ABSTRACT FROM AUTHOR]

There is a growing effort throughout Europe to restore populations of native oysters (Ostrea edulis), with the ecological objective of enhancing ecosystem biodiversity and resilience.The introduced parasite, Bonamia ostreae, caused catastrophic mortalities during the 1980s, furthering the decline of this species, and is now present throughout much of the natural range of O. edulis. It is therefore important that restoration attempts avoid further introduction and spread of this parasite, which can cause lethal infections of O. edulis.This article presents a comprehensive overview of the scale and distribution of current infection, transmission pathways, and preventive measure guidelines, focusing on the seas, inlets, and estuaries of north‐west Europe, where most ecological restoration attempts for the native European oyster have occurred so far.This is critical information for restoration project planning in which the risk of Bonamia infection must be taken into account. [ABSTRACT FROM AUTHOR]

An understanding of husbandry strategies and any associated risk factors is important for designing management control measures that can reduce mortality in Pacific oysters, Crassostrea gigas, caused by ostreid herpesvirus 1 (OsHV‐1). The type of culture facility can be considered in relation to the potential pathways that could lead to the entry of a pathogen and its survival. In addition, the animal host (e.g. age, physiological state, selective breeding programmes), husbandry procedures (e.g. stocking density), the pathogen itself (e.g. pathogenicity, virulence) and environmental effects (e.g. temperature) represent other relevant interconnected factors. However, all these factors provide valuable background information for outlining the mitigation strategies needed by the industry, as well as in the context of surveillance and biosecurity programmes. These control mechanisms for hatchery or nursery areas are related to movement restrictions, water treatment, virus inactivation, the production calendar and practical farm management decisions. This comprehensive literature review compiles information related to such approaches and also includes the different existing guidelines suggested for control of OsHV‐1. Therefore, the review represents a solid foundation for a more critical appraisal currently being developed to support recommendations for disease management strategies. [ABSTRACT FROM AUTHOR]

In this study, we described the cytosolic HSP90 of Bonamia ostreae, an intracellular parasite of Ostrea edulis hemocytes. The complete open reading frame was assembled by Rapid Amplification cDNA Ends reactions on cDNA of B. ostreae-infected hemocytes. HSP90 amplification was corroborated in infected oysters and B. ostreae purified cells. The functionality of the HSP90, studied by inhibitory assays with radicicol, suggests that this protein may play a role in hemocyte invasion. Our results inform the molecular basis that governs B. ostreae- O. edulis interactions. [ABSTRACT FROM AUTHOR]