Data/hora: 01/06/2024 11:43:38

Provedor de dados: 	5	
País: 	France	
Título: 	Summer mortality outbreaks of French Pacific oysters Crassostrea gigas in 2008 and 2009	
Autores: 	Renault, Tristan; Allain, Gwenhael; Arzul, Isabelle; Chollet, Bruno; Cobret, Laetitia; De Decker, Sophie; Faury, Nicole; Ferrand, Sylvie; Francois, Cyrille; Garcia, Celine; Haffner, Philippe; Joly, Jean-pierre; Miossec, Laurence; Morga, Benjamin; Nicolas, Jean-louis; Omnes, Emmanuelle; Pepin, Jean-francois; Saulnier, Denis; Schikorski, David; Segarra, Amelie.	
Data: 	2009-09	
Ano: 	2009	
Palavras-chave: 	Abnormal mortality; Oysters; Crassostrea gigas; Pathogens.	
Resumo: 	Abnormal mortality outbreaks occurred in the majority of Pacific oyster (Crassostrea gigas) producing areas in France in 2008 during the summer period. These outbreaks were usually sudden and severe (up to 100%) and affected essentially spat (oysters less than 1 year-old) and juveniles (12 to 18 month-old oysters). Crassostrea gigas was the single affected species Mortality outbreaks were first observed from mid May to mid June in Brittany, Vendée, Charente Maritime and Mediterranean coast A second episode of massive mortality events was reported at the end of June and the beginning of July. All oyster production sites were affected except some particular locations including Arcachon Bay and Brittany. Mortality occurred latter in Arcachon Bay in August.   Different hypothesis including the implication of environmental factors, toxic algae or pathogens have been explored. In this context, samples were collected from all affected locations and tested in order to search pathogens. Different tests were carried out including histology, bacteriology, PCR for the detection of OsHV-1 and Vibrio splendidus and V. aestuarianus, transmission electron microscopy. Some experimental assays were also performed in order to reproduce mortality and to test the hypothesis of an infectious aetiology.   Results of diagnostic tests indicated that (1) there was no listed pathogen involved, (2) OsHV-1 was detected in most of samples especially in moribund oysters, (3) Vibrio splendidus, V. aestuarianus and V. harveyi were detected in many samples and (4) viral particles looking like herpes viruses were observed by TEM in moribund tested oysters.  Results of the experimental assays showed that mortalities were reproducible by injecting in the adductor muscle of healthy oysters tissue suspensions from oysters expressing mortalities.  The suspensions filtrated at 0.22 µm induced mortalities whereas suspensions filtrated at 0.1 µm did not induce any mortality suggesting that these mortalities require an agent between 100 and 200 nm in size. Analysis of experimentally injected oysters revealed the presence of high amounts of OsHV-1 DNA by Q-PCR and TEM analysis demonstrated the presence of herpes virus particles in experimentally infected oysters.   Present conclusions are that there is no listed pathogen and the reported mortalities are associated with bacterial and OsHV-1 infections. However, considering that these pathogens are usually detected in mortality events affecting C. gigas, a question has been arisen: why oyster mortalities were so massive in 2008? Further works are presently conducted in order to identify additional factors including the emergence of highly virulent strains and particular environmental conditions which might be necessary to fully explain the situation encountered in 2008.	
Tipo: 	Text	
Idioma: 	Inglês	
Identificador: 	http://archimer.ifremer.fr/doc/00014/12554/9420.pdf	
Editor: 	14th EAFP International Conference, Diseases of Fish and Shellfish, 14th to 17th September 2009, Prague, Czech Republic	
Relação: 	http://archimer.ifremer.fr/doc/00014/12554/	
Formato: 	application/pdf	
Fonte: 	2009 Ifremer