Further observations on the influence of husbandry practices on OsHV-1 μVar mortality in Pacific oysters Crassostrea gigas: Age, cultivation structures and growing height

Effect of water temperature on mortality of Pacific oysters Crassostrea gigas associated with microvariant ostreid herpesvirus 1 (OsHV-1 µVar)

“…Our experiment used 2 batches of oysters to demonstrate a marked and direct effect of water temperature on the outcome of challenge with OsHV-1 µVar. The results are consistent with effects of water temperatures observed during disease in field conditions (Paul-Pont et al 2014, Whittington et al 2015a). Further work is required to replicate the experiment, test temperatures between 14 and 18°C in more detail and evaluate oysters with different genetic and life histories.…”

“…While the disease risk will be influenced by many factors, including those that affect transmission, the importance of dose and tem-perature was highlighted by this laboratory investigation, which controlled for extrinsic factors that complicate field observations. Disease mitigation strategies have been proposed based on field observations of factors that influence disease , Whittington et al 2015a. Improved disease management and prediction of epidemics can be achieved based on better knowledge of the direct influence of water temperature and initial quantity of OsHV-1 µVar on pathogenesis and total mortality.…”

“…Seasonal changes include the availability and type of food and the metabolic changes of the oyster (Soletchnik et al 2006). The incidence of disease has varied with factors including: seasonal changes in reproductive effort and energy balance (Pernet et al 2012(Pernet et al , 2014; feeding ; and management practices such as farming structures, immersion time and the density of oysters (Pernet et al 2012, Paul-Pont et al 2013a, Normand et al 2014, Whittington et al 2015a. Furthermore, the immune function of oysters is altered by water temperature (Green et al 2014a,b).…”

Infectious diseases in oyster aquaculture require a new integrated approach

“…B 371: 20150213 background, life-history traits and physiological status of oysters [21]. For instance, mortality is much lower in adults than in juveniles [10,17,23,33,36,40,42,56,57], reflecting natural resistance to the disease [10,56], possibly conferred by the maturation of the immune system [33,58]. However, OsHV-1 reference strain has already been detected in subclinical infections in adults [59], raising the question as to what factors trigger viral persistence and reactivation in apparently healthy oysters.…”

“…Manipulation of immersion time by raising the growing height above sea bottom has a major effect in adult oysters, reducing mortalities by 50% [23,36]. Improved survival at high intertidal height can be explained by a lower immersion time leading to a lower exposure to viral particles in the water or a reduction of host metabolic rates which in turn reduce replication rate of the virus [21].…”