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Diseases of Aquatic Organisms

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DAO 40:19-27 (2000)  -  doi:10.3354/dao040019

An RT-PCR-based method for the diagnosis of the sleeping disease virus in experimentally and naturally infected salmonids

Stéphane Villoing1,2, Jeannette Castric2, Joëlle Jeffroy2, Alain Le Ven2, Richard Thiery2, Michel Bremont1,*

1Unité Virologie et Immunologie moléculaires, Institut National de la Recherche Agronomique, INRA, 78352 Jouy-en-Josas Cedex, France
2Laboratoire de Pathologie des Animaux Aquatiques, AFSSA Brest Technopole Brest-Iroise, BP 70, 29280 Plouzané, France
*Corresponding author. E-mail:

ABSTRACT: The sleeping disease (SD) of rainbow trout (Oncorhynchus mykiss) is a worldwide disease for which the causative agent, the sleeping disease virus (SDV), has been recently characterized as an atypical alphavirus (Villoing et al. 2000). Up to now, no diagnostic tools were available and thus no epidemiological studies have been undertaken to evaluate the occurrence of this disease on the field. We present in this paper a sensitive and highly specific 1 working day method, which allows the detection of SDV from experimentally and naturally infected fishes. This method, based on a reverse transcriptase/polymerase chain reaction (RT-PCR) assay on total RNA extracted from SDV-infected fish organs, enables the specific DNA amplification of part of the gene encoding the SDV glycoprotein E2, as early as 2 d post-infection (d.p.i.) and as late as 70 d.p.i., at which time clinical signs of infection are no longer apparent. Moreover, we show that this RT-PCR method can be successfully used for the diagnosis of fish infected by a closely related virus, namely salmon pancreas disease virus (SPDV). This report is the first description of a very powerful diagnostic assay which could provide a more accurate replacement for the classical virological, histological and immunochemistry methods.

KEY WORDS: Sleeping disease virus · Salmon pancreas disease virus · Alphavirus · Rainbow trout · Salmon · RT-PCR · Diagnosis

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