Location: Cool and Cold Water Aquaculture Research
Title: Early life stage rainbow trout (Oncohynchus mykiss) mortalities due to Flavobacterium columnare in Idaho, USA Authors
Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 25, 2013
Publication Date: N/A
Interpretive Summary: Outbreaks of columnaris disease have occurred over the past four years at a rainbow trout aquaculture facility in the Hagerman Valley of Idaho. Genetic analysis of 70 individual bacterial isolates indicates that these outbreaks are the result of a highly successful strain of Flavobacterium columnare. Challenge studies reveal that this pathogen is considered highly virulent to rainbow trout in water temperatures less than 16 degrees Celsius. This study illustrates that columnaris disease is an emerging disease problem for the rainbow trout industry.
Technical Abstract: Flavobacterium columnare is the etiologic agent of columnaris disease, a pervasive disease of fresh water finfish. During the past 4 years, losses that ranged from 5-50% in rainbow trout (Oncorhynchus mykiss) fry, as small as 0.2 g, have been occurring in an early life stage production facility in the Hagerman Valley, Idaho, USA. A total of 70 different F. columnare isolates were obtained from diseased fish and the water they were reared in. All of the isolates were confirmed to be genomovar I by 16S rRNA restriction fragment length polymorphism. Sequencing of the 16S rRNA, 16S-23S rDNA spacer region and the gyrase B subunit genes from these 70 strains revealed no sequence differences among these isolates. Whole-cell protein profiling by SDS-PAGE also indicated low variation between isolates. Virulence was assessed for a representative isolate and demonstrated a high degree of pathogenicity against rainbow trout fry. These results suggest the emergence of a highly successful F. columnare strain that can affect very early life stages of fish at a commercial rainbow trout farm in Idaho.