Occurrence of salmonid alphavirus and piscine orthoreovirus-1 infections in migrating salmon (Salmo salar L.) post-smolt in western Norway.

Viral diseases are a serious problem in Atlantic salmon (Salmo salar L.) farming in Norway, often leading to reduced fish welfare and increased mortality. Disease outbreaks in salmon farms may lead to spread of viruses to the surrounding environment. There is a public concern that viral diseases may negatively affect the wild salmon populations. Pancreas disease (PD) caused by salmonid alphavirus (SAV) and heart and skeletal muscle inflammation (HSMI) caused by piscine orthoreovirus-1 (PRV-1) are common viral diseases in salmon farms in western Norway. In the current study, we investigated the occurrence of SAV and PRV-1 infections in 651 migrating salmon post-smolt collected from three fjord systems (Sognefjorden, Osterfjorden and Hardangerfjorden) located in western Norway in 2013 and 2014 by real-time RT-PCR. Of the collected post-smolts, 303 were of wild origin and 348 were hatchery-released. SAV was not detected in any of the tested post-smolt, but PRV-1 was detected in 4.6% of them. The Ct values of PRV-1 positive fish were usually high (mean 32.0; range: 20.1-36.8). PRV-1 prevalence in post-smolts from the three fjords was 6.1% in Sognefjorden followed by 4.8% in Osterfjorden and 2.3% in Hardangerfjorden. The prevalence PRV-1 was significantly higher in wild (6.9%) compared to hatchery-released post-smolt (2.6%). The occurrence of PRV-1 infection in the fish was lowest in the Hardangerfjorden which has the highest fish farming intensity. Our results suggest that SAV infection are uncommon in migrating smolt while PRV-1 infection can be detected at low level. These findings suggest that migrating smolts were at low risk from SAV or PRV-1 released from salmon farms located in their migration routes in 2013 and 2014.

Occurrence of salmonid alphavirus (SAV) and piscine orthoreovirus (PRV) infections in wild sea trout Salmo trutta in Norway.

Viral diseases represent a serious problem in Atlantic salmon (Salmo salar L.) farming in Norway. Pancreas disease (PD) caused by salmonid alphavirus (SAV) and heart and skeletal muscle inflammation (HSMI) caused by piscine orthoreovirus (PRV) are among the most frequently diagnosed viral diseases in recent years. The possible spread of viruses from salmon farms to wild fish is a major public concern. Sea trout S. trutta collected from the major farming areas along the Norwegian coast are likely to have been exposed to SAV and PRV from farms with disease outbreaks. We examined 843 sea trout from 4 counties in Norway for SAV and PRV infections. We did not detect SAV in any of the tested fish, although significant numbers of the trout were caught in areas with frequent PD outbreaks. Low levels of PRV were detected in 1.3% of the sea trout. PRV-infected sea trout were caught in both salmon farming and non-farming areas, so the occurrence of infections was not associated with farming intensity or HSMI cases. Our results suggest that SAV and PRV infections are uncommon in wild sea trout. Hence, we found no evidence that sea trout are at risk from SAV or PRV released from salmon farms.

The humoral and cellular responses induced locally and systemically after parenteral influenza vaccination in man.

Studies of the immune response after influenza vaccination in man, with focus on the immune activity occurring locally at mucosal surfaces and in associated lymphoid tissue, provide a valuable insight into immunity to influenza. The aim of influenza vaccination is to develop immunological memory resulting in enhanced rapid specific response upon subsequent influenza encounter. The tonsils are thought to play an important role as an activating, effector and memory site for immune responses against influenza. We have shown that normally high numbers of influenza-specific antibody secreting cells (ASC) are present in the nasal mucosa of healthy adults but upon parenteral vaccination the numbers remain stable. However, a rapid transient increase in influenza-specific ASC is observed in the tonsils and peripheral blood after vaccination. In the tonsils and blood, parenteral vaccination results in a significant decrease in CD4(+) cells upon vaccination, which are probably recruited to the draining lymph node.

The humoral immune response and protective efficacy of vaccination with inactivated split and whole influenza virus vaccines in BALB/c mice.

Recently the urgency of developing a pandemic influenza vaccine has lead to the re-evaluation of the use of whole virus vaccine. We have compared the humoral immune response and the protective efficacy of whole and split influenza virus vaccines in mice. Whole virus vaccine was more immunogenic particularly after the first dose of vaccine, generally eliciting higher numbers of systemic antibody secreting cells and an earlier and higher neutralising antibody response. Immunisation with one dose of whole virus vaccine more effectively reduced viral shedding upon non-lethal homologous viral challenge, but two doses of split virus vaccine was most effective at limiting viral replication and this was correlated with high influenza specific serum IgG concentrations. The two vaccine formulations induced different T helper profiles particularly after one dose of vaccine; split virus vaccine induced a type 2 bias response, whereas whole virus vaccine elicited a dominant type 1 response.