Genotyping of Flavobacterium psychrophilum isolates from wild and farmed salmonids in Norway and Chile

Flavobacterium psychrophilum, a member of the family Flavobacteriaceae, has from the first descriptions in North America, been distributed to many countries worldwide causing serious losses to the aquaculture industry. The Norwegian and Chilean aquacultures are also affected by outbreaks due to F. psychrophilum. The bacterium has been one of the most common causes of mortality in fresh water aquaculture in Chile since the 1980’s and outbreaks have occurred more frequently during the last years [1]. Of the farmed fish species, most susceptible are rainbow trout (Oncorhynchus mykiss), Atlantic salmon (Salmo salar) and coho salmon (O. kisutch). F. psychrophilum is also present in farmed and wild trout (S. trutta) and Atlantic salmon in Norway. The biggest losses occur among juvenile fish where mortality can reach up to 90% [2]. The bacterium has also been found in several nonsalmonid species, such as carp (Cyprinus carpio), ayu (Plecoglossus altivelis), tench (Tinca tinca) and eel (Anguilla anguilla). The importance of wild fish as reservoirs is still not very well known. F. psychrophilum can be both horizontally and vertically transmitted and has been isolated from salmonid ovarian fluid and gonads even after routine standard iodophor disinfection. Hence, it is suggested that the transport of embryos from infected broodfish may be important in long distance transmission.