Phylogenetic position of a paramyxovirus from Atlantic salmon Salmo salar

Abstract

A paramyxovirus has been isolated from Atlantic salmon Salmo salar suffering from epitheliocystis. This virus does not cause any mortality when used to challenge disease-free salmon, but has been associated with 2 cases of mortality in salmon farms in Norway. Atlantic salmon paramyxovirus (ASPV) has been suggested as a name for the virus. The ASP virus is a slow-growing virus in cell cultures (rainbow trout gill cells: RTgill-W1). Little is known about its importance and its phylogenetic position is uncertain. Hence, the need for a fast and sensitive diagnostic method for studying the prevalence of this virus in salmon farms and for more basic knowledge about its identity were the motivation for this study. A partial nucleotide sequence (816 bp) from the large protein (L protein) gene of the ASP virus has been sequenced from 2 different isolates. The putative amino acid sequence has been compared with the L protein of other paramyxoviruses. This sequence gives strong support to a relationship between the ASP virus and members of the subfamily Paramyxovirinae, genus Respirovirus. KEY WORDS: Salmo salar · Paramyxovirus · L protein · Phylogeny Resale or republication not permitted without written consent of the publisherDis Aquat Org 59: [11][12][13][14][15] 2004 Morbillivirus, while the latter contains the 2 genera Pneumovirus and Metapneumovirus. In the present study, a partial amino acid sequence from the large L protein (the RNA-dependent RNA polymerase consists of 2 virus-encoded subunits; the phosphoprotein and the L protein) of an ASP virus (Kvellestad et al. 2003) and an identical virus isolated from Atlantic salmon Salmo salar in western Norway, are compared with the L protein of other paramyxoviruses. Nucleotide and amino acid sequences can be good indicators of phylogenetic relationships between viruses (cf. Knipe & Howlwy 2001). The phylogenetic position of ASPV is discussed. MATERIALS AND METHODSThe Atlantic salmon paramyxovirus (ASPV) was first isolated, using rainbow trout gill cells (RTgill-W1, Bols et al. 1994), from gills of farmed Atlantic salmon postsmolts in Norway during an outbreak of gill disease (Kvellestad et al. 2003). The isolate is named ASPV-VI (ASPV-Veterinary Institute) and was used to challenge disease-free salmon in seawater (Fridell 2003). Later the virus was reisolated from the challenged salmon and cultured in RTgill-W1 cells (Fridell 2003). We have also isolated an identical paramyxovirus, ASPV-Ro, from Atlantic salmon suffering from epitheliocystis on the west coast of Norway (Rogaland county).RTgill-W1 (Bols et al. 1994) cells were cultured in 15 cm 2 tissue-culture flasks (Nunc) at 20°C in Eagle's minimum essential medium (EMEM) (Sigma) supplemented with 10% foetal bovine serum (FBS) (10% v/v), L-glutamine (4 mM) and gentamicin (50 µg ml -1 ). The cells were then subcultured for 7 to 10 d until the tissue flasks were covered with 60 to 80% confluent monolayer.Homogenates from ASP virus-infected tissues were diluted 1:100 in phosphate-buffered saline (PBS) and ...

Diseases of farmed Atlantic salmon Salmo salar associated with infections by the microsporidian Paranucleospora theridion

“…This study is the first attempt to gain a more complete picture of the types and numbers of pathogens that can be involved in the development of diseases in Norwegian production of salmonids with a main focus on PGI, PD, HSMI and CMS. These diseases were selected due to the large discrepancies between the observed pathology and mortality in marine already recognised that several pathogens are associated with gill diseases (A. Nylund et al 1998, 2009a,b, Kvellestad et al 2003, Draghi et al 2004, Fridell et al 2004, Todal et al 2004, Callahan et al 2005, Young et al 2007, Steinum et al 2008, and it has also proven difficult to perform challenge experiments with most of these agents. The other 3 diseases, PD, HSMI and CMS, are all associated with the presence of viruses , 2006, Vågenes et al 1999, Nylund 2001, Kongtorp et al 2004a, Bruno & Noguera 2009, Fritsvold et al 2009, Palacios et al 2010, but it is difficult, in challenge experiments, to reproduce both the mortality and all the pathological changes observed during outbreaks in farms.…”

“…Neoparamoeba perurans seem to be mainly distributed in western Norway (A. , Steinum et al 2008, while the available information about the geographical distribution of ASPV limits it to the southwest of Norway (Kvellestad et al 2003, Fridell et al 2004. Paranucleospora theridion is present in most parts of Norway with sea production of salmonids (A.…”

“…Many of the agents that are associated with PGI are commonly found in all areas with salmon farming in Norway; among these are Parvicapsula pseudobranchicola, Ichthyobodo sp., Trichodina spp., SGP virus, and Chlamydia-like species (A. Nylund et al 1998, Todal et al 2004. Neoparamoeba perurans seem to be mainly distributed in western Norway , Steinum et al 2008, while the available information about the geographical distribution of ASPV limits it to the southwest of Norway (Kvellestad et al 2003, Fridell et al 2004. Paranucleospora theridion is present in most parts of Norway with sea production of salmonids (A. Nylund et al 2009a,b, S. Nylund et al 2009.…”

Salmon gill poxvirus, a recently characterized infectious agent of multifactorial gill disease in freshwater‐ and seawater‐reared Atlantic salmon

“…). PGI could not be reproduced in an infection trial utilizing ASPV alone (Fridell, Devold & Nylund ). This could indicate either that PGI is a complex, multifactorial disease that is difficult to reproduce experimentally or that PGI may represent several different infections/diseases, all leading to a more or less stereotypic, proliferative inflammatory gill response.…”

High yield and rapid growth of Neoparamoeba pemaquidensis in co‐culture with a rainbow trout gill‐derived cell line RTgill‐W1

“…Conditions for high and rapid yields of N. pemaquidensis using RTgill‐W1 as a feeder monolayer were explored and are presented here. RTgill‐W1 has been previously used to support the growth of a novel paramyxovirus isolated from the gills of Atlantic salmon (Kvellestad, Dannevig & Falk 2003; Fridell, Devold & Nylund 2004), and has also been used as a gill model for evaluating aquatic toxicants (Schirmer, Chan, Greenberg, Dixon & Bols 1998b; Schirmer, Dixon, Greenberg & Bols 1998a; Dayeh, Schirmer & Bols 2002; Dayeh, Chow, Schirmer, Lynn & Bols 2004; Dayeh, Grominsky, DeWitte‐Orr, Sotornik, Yeung, Lee, Lynn & Bols 2005a; Dayeh, Schirmer, Lee & Bols 2005b).…”