Community Research and Development Information Service - CORDIS

Pathogenesis study of pancreas disease in salmon based on experimental disease reproduction (and including discovery of existence of carrier fish)

Experimental infection of Atlantic salmon by injection with the reference PD isolate induces a very mild infection with no mortality and only minor histopathological changes. Injection with new field isolates from Ireland and Norway produced in this project induces more severe disease, more like the PD outbreaks seen in the field. An experimental study by injecting Atlantic salmon pre-smolt with an Irish subtype 1 and a Norwegian subtype 3 PD virus isolate in separate tanks was performed in this project. Samples of blood and tissue from each group and from a control group of non infected fish were collected during a period of 20 weeks and examined for virus, virus RNA, antibodies, histopathology and by immune histochemistry. The results were used to follow and compare the pathological changes induced by the two different subtypes of PD virus. Results suggested that the Norwegian subtype 3 PD virus isolate may induce more severe histopathological lesions and a more prolonged infection than the Irish subtype 1 PD virus isolate, but it is recognised that there may be differences in pathogenicity among isolates from the same subtype. The sequential study has given valuable information about the pathogenesis and about the usefulness of diagnostic methods for PD. In particular, the application of sensitive real time RT-PCR testing showed that virus RNA could be detected in some fish as late as 20 weeks post infection, supporting the view that a “carrier” state may exist. In addition the results will be used to development a challenge model for development of vaccines against PD in Atlantic salmon.

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Intervet Norbio
Thormohlensgt. 55
5008 Bergen
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