Infeccion por alfavirus en salmonidos

Journal of Fish Diseases 2007, 30, 511–531

Review Alphavirus infections in salmonids – a review
M F McLoughlin1 and D A Graham2
1 Aquatic Veterinary Services, Belfast, UK 2 Veterinary Sciences Division, Agri-food & Biosciences Institute, Belfast, UK

Abstract

The first alphavirus to be isolated from fish was recorded in 1995 with the isolation of salmon pancreas disease virus fromAtlantic salmon, Salmo salar L., in Ireland. Subsequently, the closely related sleeping disease virus was isolated from rainbow trout, Oncorhynchus mykiss (Walbaum), in France. More recently Norwegian salmonid alphavirus (SAV) has been isolated from marine phase production of Atlantic salmon and rainbow trout in Norway. These three viruses are closely related and are now considered to represent threesubtypes of SAV, a new member of the genus Alphavirus within the family Togaviridae. SAVs are recognized as serious pathogens of farmed Atlantic salmon and rainbow trout in Europe. This paper aims to draw together both historical and current knowledge of the diseases caused by SAVs, the viruses, their diagnosis and control, and to discuss the differential diagnosis of similar pathologies seen incardiomyopathy syndrome and heart and skeletal muscle inflammation of Atlantic salmon. Keywords: alphavirus, pancreas disease, salmonids, sleeping disease.
Introduction

Salmonid alphaviruses (SAVs) are recognized as serious pathogens of farmed Atlantic salmon, Salmo salar L. and rainbow trout, Oncorhynchus mykiss

Ó 2007 The Authors. Journal compilation Ó 2007 Blackwell Publishing LtdCorrespondence M McLoughlin, Aquatic Veterinary Services, 35 Cherryvalley Park, Belfast, BT5 6PN, Northern Ireland, UK (e-mail: mfmcloughlin@ntlworld.com)

(Walbaum), in Europe. Salmon pancreas disease virus [SPDV or SAV subtype 1 (SAV 1)] is the causative agent of pancreas disease (PD) in farmed Atlantic salmon in Ireland and Scotland (Nelson, McLoughlin, Rowley, Platten & McCormick 1995; Rowley,Doherty, McLoughlin & Welsh 1998; Weston, Welsh, McLoughlin & Todd 1999; Welsh, Weston, Borghmans, Mackie, Rowley, Nelson, McLoughlin & Todd 2000). Sleeping disease (SD) is an infectious disease of rainbow trout reared in fresh water. The viral aetiology of SD was suspected for some time (Boucher, Castric & Baudin Laurencin 1994) and it was confirmed by the isolation of sleeping disease virus (SDV) inFrance (Castric, Baudin Laurencin, Bremont, Jeffroy, Le Ven & Bearzotti 1997), which was characterized as an atypical alphavirus of the family Togaviridae and is now known as SAV subtype 2 (SAV 2) (Villoing, Bearzotti, Chilmonczyk, Castric & Bremont 2000a). SAV 2 has recently been isolated from diseased rainbow trout in England and Scotland (Branson 2002; Graham, Rowley, Walker, Weston, Branson &Todd 2003a) and in Germany (Bergman, Castric, Bremont, Riebe & Fichtner 2005). Infection with SAV 2 has also been shown to be present in fresh water in Italy and Spain (Graham, Rowley, Fringuelli, Bovo, Amedeo, McLoughlin, Zarza, Khalili & Todd 2007b). Salmon pancreas disease virus (SAV 1) and SDV (SAV 2) are closely related subtypes of the same virus species with the proposed name salmonid ´alphavirus (Weston, Villoing, Bremont, Castric, Pfeffer, Jewhurst, McLoughlin, Rødseth, Christie, Koumans & Todd 2002). Norwegian salmonid alphavirus (NSAV) was subsequently isolated from

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Journal of Fish Diseases 2007, 30, 511–531

M F McLoughlin & D A Graham Salmonid alphaviruses – a review

Table 1 Summary of salmonid alphavirus virus (SAV) infections, their geographical distributionand species susceptibility
Virus subtype SAV 1 SAV 2 SAV 3

Virus name Salmon pancreas disease virus Sleeping disease virus Norwegian salmon alphavirus

Location Ireland, Scotland France, England, Scotland, Spain, Italy, Germany Norway

Species Atlantic salmon Rainbow trout Atlantic salmon, rainbow trout

Disease Pancreas disease Sleeping disease Pancreas disease

Expt. infections...