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Proliferative gill inflammation in Atlantic salmon – identification of aetiology

Tildelt: kr 4,5 mill.

Prosjektnummer:

164771

Søknadstype:

Prosjektperiode:

2005 - 2011

Proliferative gill inflammation (PGI) is an important cause of losses related to mortality and reduced growth rate in seawater farmed Atlantic salmon (Salmo salar). Although reported since the 1980s, the disease appears to be increasing both in frequency and degree in later years. It is estimated that as many as 150 Norwegian sea-farms were affected in 2003 with mortality levels as high as 40%. The aetiology of PGI is apparently multifactorial and prevention is difficult due to our limited understanding o f its causes. Epithelial cell inclusions (epitheliocysts) containing chlamydia-like organisms (CLO) are frequently seen histologically in significant numbers. The disease has, therefore, often been termed epitheliocystis. Recently we isolated a new virus , Atlantic salmon paramyxovirus (ASPV), from the gills of fish with PGI. This virus has been detected in gills of diseased fish from different farms. There is, therefore, strong circumstantial evidence that CLO and ASPV are at least contributing causes of PGI. Sufficient background material and information has now been gathered such that we are poised to investigate the two agents (CLO and ASPV) of probable importance in development of PGI. The main aims of this project are development of rapid molecular techniques for identification of CLO and ASPV, to place the presence/absence of these agents in relation to development of pathological tissue changes, and to further characterise these agents, thus allowing a better understanding of their biology and in fection. Material from a collaborative project with Marine Harvest Norway and from other farms will be included in an epidemiological approach, achieving the use of common gill samples, which will allow in-depth evaluation of the importance of each age nt in relation to development of disease.

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HAVBRUKS-Havbruk - en næring i vekst