EPIDEMIOLOGICAL INVESTIGATION OF INFECTIOUS SALMON ANAEMIA (ISA) OUTBREAKS IN NORWAY 2003-2005

摘要

Epidemiological information was summarized from 32 outbreaks of infectious salmon anaemia (ISA) in Norway 2003-2005. Virus isolates from the outbreaks were genotyped, and postulated associations between outbreaks and risk factors were assessed. The ISA outbreaks were distributed along most of the Norwegian coast and showed a variable clinical picture. The virus genotypes clustered into three genogroups, and tended to scatter in time and along the coast. Pairs of ISA outbreaks matched for the risk factors proximity or contact; all shared genogroups, which was a significantly higher number of successes than expected. For the smolt supplier risk factor, corresponding genogroups appeared in seven out of 12 matched pairs, which was not significant. In conclusion, genotyping of virus isolates from ISA outbreaks supports associations between adjacent outbreaks. This is consistent with horizontal transmission. The present study failed to find patterns of genogroups related to smolt suppliers or brood fishcompanies.