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In particular, bacterial strains of the genus Vibrio had been shown to be associated with POMS ( 27, 28). Nevertheless, the involvement of other etiological agents was suspected ( 15).
#OYSTER SPAT MORTALITY RATE SERIES#
Because of this, research efforts have historically focused on the viral etiology of POMS and a series of diagnostic assays such as PCR, real-time PCR, and in situ hybridization have been developed to detect OsHV-1 ( 18, 19, 24– 26). Only once this work is complete will we completely understand POMS and be able to propose solutions to ensure the durability of the oyster industry.ĭramatic increases in oyster mortality (observed since 2008) have been found to coincide with the recurrent detection of Ostreid herpesvirus (OsHV-1) variants in moribund oysters in France ( 17– 19) and worldwide ( 9, 20– 23). It is crucial that POMS be fully deciphered by the determination of which factors control disease expression, how these factors control disease expression, the weight of these different factors, and their putative synergistic and antagonistic effects. Although this is a first and important step, POMS remains an incompletely understood multifactorial disease that is controlled by a series of host and environmental factors. These studies have deciphered the polymicrobial nature of the disease.
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In this review, we present the research performed in the past decade that has contributed to a better understanding of POMS. Research efforts have revealed a series of factors that contribute to the disease, including interactions between infectious agents and seawater temperature, oyster genetics, food availability, and oyster growth ( 9– 17). The ecological and economic consequences of POMS can be dramatic ( 9), and POMS represents a threat to the worldwide oyster industry. The corresponding syndrome, referred to as Pacific oyster mortality syndrome (POMS) ( 7), has become panzootic it is observed in all the coastal regions of Franc, and in numerous other countries worldwide ( 8). These outbreaks affect the juvenile stages of the oyster, killing more than 35% of the cultivated and natural oysters in France every year ( 5, 6). gigas has suffered from mortality due to disease ( 4), but the severity of these outbreaks has increased dramatically since 2008. China is, by far, the leading producer, followed by South Korea, Japan, and France.įor decades, C. gigas is estimated at 4.7 million tons per year ( 3). Canada, the USA, Brazil, Australia, New Zealand, Chile, Mexico, Argentina, South Africa, Namibia, and numerous European countries including France) during the 20th century ( 2). The Pacific oyster Crassostrea gigas was introduced from Asia to numerous countries throughout the world ( e.g. Mollusk aquaculture, in which oysters are the most important taxonomic group (by volume), has become one of the largest animal food-producing industries. These discoveries will help in decision-making and will facilitate the development of tools and applied innovations for the sustainable and integrated management of oyster aquaculture.Īquaculture is one of the fastest-growing food industries, representing more than 50% of worldwide seafood production ( 1). The present review discusses current knowledge of this polymicrobial and multifactorial disease process and explores the research avenues that must be investigated to fully elucidate the complexity of POMS. However, we still do not understand the mechanisms by which these different factors control disease expression. oyster genetics and age, temperature, food availability, and microbiota) have been shown to influence POMS permissiveness. This is followed by dysbiosis of the microbiota, which leads to a secondary colonization by opportunistic bacterial pathogens, which in turn results in oyster death. These studies demonstrated that infection by Ostreid herpesvirus type 1 µVar (OsHV-1 µvar) is the first critical step in the infectious process and leads to an immunocompromised state by altering hemocyte physiology. Recently, major steps towards understanding POMS have been achieved through integrative molecular approaches. The most prevalent disease, Pacific oyster mortality syndrome (POMS), has become panzootic and represents a threat to the oyster industry. gigas, which primarily impact juvenile oysters, has increased dramatically since 2008. The severity of disease outbreaks that affect C. gigas is the main oyster species farmed worldwide and represents more than 98% of oyster production. The Pacific oyster ( Crassostreae gigas) has been introduced from Asia to numerous countries around the world during the 20th century.