Comparative experimental transmission of cardiomyopathy syndrome (CMS) in Atlantic salmon Salmo salar

Abstract

Cardiomyopathy syndrome (CMS) has been recorded in wild and farmed Atlantic salmon Salmo salar. Characteristic heart lesions primarily involving the myocardium are reported in natural outbreaks with associated mortality. To date, no experimental trials have reproduced these lesions in the laboratory. The present study reports on the first successful experimental transmission of CMS in Atlantic salmon in Scotland, with full development of the histological lesions that are described for the syndrome. Tissue homogenates of CMS-infected fish indicative of mild and severe lesions from Scottish and Norwegian natural outbreaks, respectively, were injected into naïve fish, and both induced heart lesions consistent with CMS. Lesion development was earlier and progression faster in the fish group receiving the Norwegian homogenate, but equivalent in both groups by the end time point of the experiment. The study demonstrated that the reported condition for both countries is identical, as evaluated through light microscopy, and that tissue homogenates from either mild or severely affected fish contain the transmissible agent. KEY WORDS: Cardiomyopathy syndrome · Atlantic salmon · TransmissionResale or republication not permitted without written consent of the publisher OPEN PEN ACCESS CCESS

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

“…Several studies have suggested that HSMI and CMS are associated with viruses , 2006, Vågenes et al 1999, Nylund 2001, Kongtorp et al 2004a, Bruno & Noguera 2009, Fritsvold et al 2009, Palacios et al 2010. However, using homogenates containing these viruses in challenge experiments will not reproduce all the signs of these diseases and the mortality observed in field outbreaks (A. Nylund pers.…”

“…during the second year at sea (Bruno & Noguera 2009, Fritsvold et al 2009). It is believed that CMS is caused by viruses , Vå-genes et al 1999, Nylund 2001, Bruno & Noguera 2009, Fritsvold et al 2009. CMS is diagnosed on characteristic changes in the atrium and the spongiosum of the ventricle of the heart (Fig.…”

“…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. In the present study we present the pathogens that are associated with these diseases in Norwegian culture of salmonids with a special emphasis on the possible importance of Paranucleospora theridion.…”

“…CMS occurs most often during the last 6 mo before termination of the sea production, i.e. during the second year at sea (Bruno & Noguera 2009, Fritsvold et al 2009). It is believed that CMS is caused by viruses , Vå-genes et al 1999, Nylund 2001, Bruno & Noguera 2009, Fritsvold et al 2009.…”

Piscine myocarditis virus (PMCV) in wild Atlantic salmon Salmo salar

“…This was based on the presence of eosinophilic inclusions in nuclei of myocardial fibres in the vicinity of degenerated areas. Experimental transmission studies have supported this hypothesis (Bruno & Noguera 2009, Fritsvold et al 2009, and in 2010 a doublestranded RNA virus tentatively of the Totiviridae family was described as the causative agent of CMS (Løvoll et al 2010, Haugland et al 2011.…”