Early life stage rainbow trout (Oncorhynchus mykiss) mortalities due to Flavobacterium columnare in Idaho, USA

• Published in: Aquaculture 2014-01, Vol.418-419, p.126-131
• Main Authors: Evenhuis, Jason P., LaPatra, Scott E., Marancik, David
• Format: Article
• Language: English
• Subjects: 16S rRNA; Bacterial challenge; Biological assays; Genomovar; Gram-negative bacteria; Polymorphism; RNA-protein interactions; Temperature effects; Trout; Virology; Yersinia ruckeri
• ISSN: 0044-8486; 1873-5622
• DOI: 10.1016/j.aquaculture.2013.09.044

Flavobacterium columnare is the etiologic agent of columnaris disease, a pervasive disease of fresh water finfish. During the past 4years, losses that ranged from 5 to 50% in rainbow trout (Oncorhynchus mykiss) fry being reared at a constant 14.5°C (mean weight, 0.2g; ~400°days post-fertilization), have been occurring in 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 at 15°C. These results suggest the emergence of a highly successful F. columnare strain that can affect very early life stages of fish being reared at a constant 14.5°C at a commercial rainbow trout farm in Idaho. •Successful strain of F. columnare•Mortalities in 0.2g trout•Water temp.=14.5°C