During this period, the water temperature was below 16☌. An initial increment in the number of PCR-positive oysters was reported at both field sites during the survey in the absence of significant mortality. Mass mortality was observed among oysters a few days after increases in the number of PCR-positive oysters and viral-DNA amounts were recorded. This difference may be related to earlier increases in water temperature. Although similar massive mortality rates were reported at the 4 sites, mortality was detected earlier in the pond and in the nursery than at both field sites. Mortality rates were recorded based on regular observation, and samples were collected to search for and quantify OsHV-1 DNA by real-time PCR. For this purpose, a single batch of Pacific oyster spat was deployed in 4 different locations in the Marennes-Oleron area (France): an oyster pond ("claire"), a shellfish nursery, and two locations in the field. Additional data are necessary to better describe mortality events in relation to environmental-parameter fluctuations and OsHV-1 detection.
gigas in Europe have been related to the detection of a variant of OsHV-1 called μVar. Since 2008, mass mortality outbreaks among C. This virus has been classified as Ostreid herpesvirus 1 (OsHV-1) within the family Malacoherpesviridae. A particular herpesvirus was purified from naturally infected larval Pacific oysters, and its genome was completely sequenced. N2 - A number of bivalve species worldwide, including the Pacific oyster, Crassostrea gigas, have been affected by mass mortality events associated with herpesviruses, resulting in significant losses. JF - Applied and environmental microbiology T1 - Ostreid herpesvirus 1 infection among Pacific oyster (Crassostrea gigas) Spat: relevance of water temperature to virus replication and circulation prior to the onset of mortality. All rights reserved.A number of bivalve species worldwide, including the Pacific oyster, Crassostrea gigas, have been affected by mass mortality events associated with herpesviruses, resulting in significant losses. Finally, viral detection was significantly different in function of tissues (p<0.005), time (p<0.005) with an interaction between tissues and time (p<0.005) for each probe.Ĭrassostrea gigas In situ hybridization Ostreid herpesvirus 1 Viral DNA Viral RNA.Ĭopyright © 2015 Elsevier Inc. This study also allowed observing kinetics of viral DNA and RNA detection in different tissues of oyster spat. RNA transcripts were detected in oysters receiving the highest dose of viral suspension whereas no transcript was observed in oysters injected with the low dose. Real time PCR demonstrated significant differences in terms of viral DNA amounts between the two virus doses.
This study compares OsHV-1 DNA and RNA detection and localization in experimentally infected oysters using two virus doses: a low dose that did not induce any mortality and a high dose inducing high mortality. Although the viral infection has been experimentally reproduced in oyster larvae and spat, little knowledge is currently available concerning the viral entry and its distribution in organs and tissues. High mortality rates are reported in spat and larvae of Pacific oyster Crassostrea gigas and associated with ostreid herpesvirus 1 (OsHV-1) detection in France.
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