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Diseases of Aquatic Organisms

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DAO 70:193-199 (2006)  -  doi:10.3354/dao070193

Viral gametocytic hypertrophy of Crassostrea gigas in France: from occasional records to disease emergence?

Céline Garcia1,*, Maeva Robert1, Isabelle Arzul1, Bruno Chollet1, Jean-Pierre Joly1, Laurence Miossec1, Thierry Comtet2, Franck Berthe1,3

1Laboratoire de Génétique et de Pathologie, IFREMER, Station de La Tremblade, Ronce les Bains, BP 133, 17390 La Tremblade, France
2Centre National de la Recherche Scientifique (CNRS) 7127, Equipe Ecologie Benthique, Station Biologique, BP 74, 29682 Roscoff Cedex, France
3Department of Pathology & Microbiology, Atlantic Veterinary College, University of Prince Edward Island (UPEI), 550 University Ave., Charlottetown C1A 4P3, Canada

ABSTRACT: Viral gametocytic hypertrophy was reported for the first time in 2001 in Pacific oyster Crassostrea gigas in France. Since this date, the number of reported cases and the distribution area have increased every year; however, the cases are not associated with macroscopic signs or increased mortality rates. Both male and female gametes were hypertrophied and basophilic inclusions were observed in gamete nuclei. Transmission electron microscopy revealed the presence of viral particles in these intranuclear basophilic inclusions. These particles had characteristics similar to those of the Papillomaviridae and Polyomaviridae families: they were small, non-enveloped, icosahedral, and 44 to 56 nm in diameter. The viral particles were found in male, female and hermaphrodite oysters and no significant difference in viral infection was observed between those groups. The frequency of detection and the intensity of infection were low and no host defence reaction was recognised, suggesting that the viral particles had a weak impact on C. gigas. The viral particles described in the present study seem to be similar to these described in C. virginica in the USA and Canada and in C. gigas in Korea, but further studies are required to confirm their identity. The issue of a possible emergence of this infection is discussed.

KEY WORDS: Crassostrea gigas · Pacific oyster · Viral gametocytic hypertrophy · Gonad · Papillomaviridae · Polyomaviridae

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