title: Experimental infection of Pacific oyster Crassostrea gigas spat by ostreid herpesvirus 1: demonstration of oyster spat susceptibility.
abstract: In 2008 and 2009, acute mortalities occurred in France among Pacific cupped oyster, Crassostrea gigas, spat. Different hypothesis including the implication of environmental factors, toxic algae and/or pathogens have been explored. Diagnostic tests indicated that OsHV-1 including a particular genotype, termed OsHV-1 μVar, was detected in most of samples and especially in moribund oysters with the highlighting of virus particles looking like herpes viruses by TEM examination. In this study, an experimental protocol to reproduce OsHV-1 infection in laboratory conditions was developed. This protocol was based on the intramuscular injection of filtered (0.22 μm) tissue homogenates prepared from naturally OsHV-1 infected spat collected on French coasts during mortality outbreaks in 2008. Results of the experimental trials showed that mortalities were induced after injection. Moreover, filtered tissue homogenates induced mortalities whereas the same tissue homogenates exposed to an ultraviolet (UV) treatment did not induce any mortality suggesting that oyster spat mortalities require the presence of a UV sensitive agent. Furthermore, analysis of injected oyster spat revealed the detection of high amounts of OsHV-1 DNA by real-time quantitative PCR. Finally, TEM analysis demonstrated the presence of herpes virus particles. The developed protocol allowed to maintain sources of infective virus which can be useful for the development of further studies concerning the transmission and the development of OsHV-1 infection.
authors.affiliation: Ifremer (Institut Français de Recherche pour l'Exploitation de la Mer), Laboratoire de Génétique et Pathologie (LGP), 17390 La Tremblade, France. trenault@ifremer.fr.
authors.forename: David
authors.initials: D
authors.lastname: Schikorski
authors.forename: Tristan
authors.initials: T
authors.lastname: Renault
authors.forename: Denis
authors.initials: D
authors.lastname: Saulnier
authors.forename: Nicole
authors.initials: N
authors.lastname: Faury
authors.forename: Pierrick
authors.initials: P
authors.lastname: Moreau
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Pépin
mesh_terms: D000818:Animals; D017756:Aquaculture; D049896:Crassostrea / Q000235:genetics* / Q000821:virology*; D004267:DNA Viruses / Q000235:genetics / Q000302:isolation & purification*; D004279:DNA, Viral / Q000302:isolation & purification* / Q000378:metabolism; D005602:France; D005838:Genotype; D007814:Larva / Q000235:genetics / Q000821:virology; D046529:Microscopy, Electron, Transmission; D008969:Molecular Sequence Data; D060888:Real-Time Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D014466:Ultraviolet Rays
chemical_list: D004279:DNA, Viral