Primed for success: Oyster parents treated with poly(I:C) produce offspring with enhanced protection against Ostreid herpesvirus type I infection

From the first detection in the Eastern oysters (Crassostrea virginica) in 1972, herpes-like viruses/herpesviruses have been identified in at least 20 bivalve species and have caused massive mortalities in six cultured species of bivalves. Among them, the Pacific oyster (Crassostrea gigas) is most threatened by massive mortalities associated with detection of Ostreid herpesvirus 1 (OsHV-1) and its variants. These mortality events have been reported in more than 12 countries, and OsHV-1 itself has been reported in 15 countries worldwide. Traditionally, the genotype OsHV-1 (or OsHV-1 Var) is the main contributor to bivalve mortalities, but the emergence of variants (e.g. OsHV-1 lVar and related ones, acute viral necrosis virus-AVNV, OsHV-1-SB) is now responsible for new mortality outbreaks in Pacific oysters and other bivalve species. In addition to OsHV-1, Vibrio bacteria and other abiotic and host factors also significantly contribute to mortality outbreaks. To this end, the current contribution aims to synthesize the body of literature on our current knowledge of these mass mortality events to provide insights into the role of each risk factor and complex interactions in the disease process. Specifically, this review encompasses our current knowledge and critical gaps. Important suggestions for future investigation are also presented. Figure 1 Classification of main Pacific oyster (Crassostrea gigas) producing countries in 2016 in tonnes (data taken from FAO FishStatJ, version 3.01.0). The map was generated using http://mapchart.net. Asterisks (*) indicate countries with mass mortality events. ( ) >300 000 tonnes; ( ) >100 000 tonnes; ( ) >10 000 tonnes; ( ) >1000 tonnes; ( ) <1000 tonnes.

Section: Current Knowledge Bottlenecks and Future Directionsmentioning

confidence: 97%

Section: Current Knowledge Bottlenecks and Future Directionsmentioning

confidence: 99%

The complex interactions of Ostreid herpesvirus 1, Vibrio bacteria, environment and host factors in mass mortality outbreaks of Crassostrea gigas

Nguyen

Mérien

2018

“…In fact, Green et al . () showed that larvae produced from poly(I:C)‐treated parents had double the chance of surviving exposure to OsHV‐1 compared to controls.…”

Section: Animal Host Factorsmentioning

confidence: 99%

A literature review as an aid to identify strategies for mitigating ostreid herpesvirus 1 in Crassostrea gigas hatchery and nursery systems

Rodgers

Arzul

Carrasco

et al. 2018

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.

“…Additionally, a transgenerational inheritance of the acquired traits during three consecutive unstressed generations was observed. In another study with Pacific oyster (Crassostrea gigas), Green et al (2016) hypothesized a connection between improved offspring phenotype and epigenetic reprogramming. The authors observed that oysters treated with poly(I:C) produced offspring more resistant to Ostreid herpesvirus (OsHV-1), responsible for disease outbreaks in oyster production.…”

Section: Epigenetics In Aquaculturementioning

confidence: 99%

Epigenetics in aquaculture – the last frontier

Granada

Lemos

Cabral

et al. 2017

Aquaculture production is expanding rapidly around the world. To tackle rising production and species diversity issues, innovations in the field of aquaculture feeds, breeding, disease management and other improvements must be addressed. In this framework, the study of epigenetic mechanisms behind different aquaculture rearing processes presents great opportunities. The transcriptional impact of epigenetic modifications, triggered by environmental stimuli, has been shown to influence the organism's phenotype. Therefore, understanding the environmental‐induced epigenetic markers related to disease resistance or other economically important traits will allow the establishment of favourable breeding conditions with increased economical revenue. Several studies have shown epigenetic effects in various species, induced by different rearing conditions, with benefits for the organisms and evidences for heritability of the acquired adaptive phenotypic traits across generations, making these studies even more relevant in a production context. These studies have demonstrated the great potential of epigenetics to positively induce disease resistance, stress tolerance and attain better sex ratios in the aquatic organism. Also, in the field of nutritional epigenetics, the possibility of early nutritional programming to improve the performance of broodstock or even the long‐term performance of their progeny has been suggested. In sum, an increased understanding of epigenetic mechanisms in economically important species, and the epigenetic markers leading to the most favourable phenotypic traits, will contribute to the expansion of economically viable commercial aquaculture industries. The major epigenetic mechanisms and respective analysis methods, as well as the state of the art and potential applications in aquaculture, are addressed in this review.