Mass mortality in bivalves and the intricate case of the Pacific oyster, Crassostrea gigas

Abstract

Massive mortality outbreaks in cultured bivalves have been reported worldwide and they have been associated with infection by a range of viral and bacterial pathogens. Due to their economic and social impact, these episodes constitute a particularly sensitive issue in Pacific oyster (Crassostrea gigas) production. Since 2008, mortality outbreaks affecting C. gigas have increased in terms of intensity and geographic distribution. Epidemiologic surveys have lead to the incrimination of pathogens, specifically OsHV-1 and bacteria of the Vibrio genus, in particular Vibrio aestuarianus. Pathogen diversity may partially account for the variability in the outcome of infections. Host factors (age, reproductive status...) including their genetic background that has an impact on host susceptibility toward infection, also play a role herein. Finally, environmental factors have significant effects on the pathogens themselves, on the host and on the host-pathogen interaction. Further knowledge on pathogen diversity, classification, and spread, may contribute toward a better understanding of this issue and potential ways to mitigate the impact of these outbreaks.

A review of the multiple benefits of mussel farming

“…; Barbosa‐Solomieu et al . ). The survival rate is close to 100% under optimum environmental conditions and ideal farming densities (Myrand et al .…”

A Production Calendar Based on Water Temperature, Spat Size, and Husbandry Practices Reduce OsHV-1 μvar Impact on Cultured Pacific Oyster Crassostrea gigas in the Ebro Delta (Catalonia), Mediterranean Coast of Spain

“…Regarding cold temperatures and absence of oyster mortality associated to herpesvirus, recent experiments have demonstrated that mortality of oysters infected with herpesvirus can be greatly reduced at 10 and 13°C (Pernet et al, 2015); however, the virus does not disappear and can be reactivated when temperatures increase again until 21°C producing high mortalities. Further recent observations have shown that viral transmission among oysters, in absence of mass mortality, can also occur when water temperature is below 16°C (Renault et al, 2014; Barbosa-Solomieu et al, 2015). …”

“…In France recent studies reported temperatures between 16 and 20°C (up to 24°C) associated with disease outbreaks (Petton et al, 2013; Pernet et al, 2014), while in Australia the threshold for inducing mortalities was observed between 21 and 27°C (Paul-Pont et al, 2014). However, the important point seems to be the rapid temperature increase, passing by the 16°C threshold, until a virus peak is reached (Pernet et al, 2014; Renault et al, 2014; Barbosa-Solomieu et al, 2015). Horizontal transmission between different individuals, seems to occur when temperatures are between 16.2 and 21.9°C (Petton et al, 2013).…”

New Insights into Pathogenic Vibrios Affecting Bivalves in Hatcheries: Present and Future Prospects

“…Vibrio aestuarianus is an important pathogenic species responsible of massive mortalities of spat, juveniles and adult Pacific oyster ( C. gigas ) in France (Saulnier et al, 2010; Madec et al, 2014; Barbosa-Solomieu et al, 2015; Green et al, 2016; Azéma et al, 2016). Taxonomic studies let to classify these pathogenic French isolates as a new subespecies, V. aestuarianus subsp.…”