Isolation and experimental challenge of cultured burbot (Lota lota maculosa) with Flavobacterium columnare and Aeromonas sp. isolates

Authors: BRUCE, TIMOTHY - University Of Idaho; MA, JIE - University Of Idaho; OLIVER, LUKE - University Of Idaho; JONES, EVAN - University Of Idaho; Lafrentz, Benjamin; CAIN, KENNETH - University Of Idaho

Submitted to: Journal of Fish Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/20/2020
Publication Date: 5/1/2020
Citation: Bruce, T.J., Ma, J., Oliver, L.P., Jones, E.M., Lafrentz, B.R., Cain, K.D. 2020. Isolation and experimental challenge of cultured burbot (Lota lota maculosa) with Flavobacterium columnare and Aeromonas sp. isolates. Journal of Fish Diseases. 43:839–851. https://doi.org/10.1111/jfd.13169.
DOI: https://doi.org/10.1111/jfd.13169

Interpretive Summary: Burbot are a freshwater fish species that are desired for their white-flesh fillets, liver by-products and eggs. Research is being conducted to determine the potential for commercial production of Burbot in which they may be produced under similar culture conditions as rainbow trout, providing cold water aquaculture producers with the potential to diversify their products. Very little information exists on diseases of burbot but is important to understand for limiting their effects in commercial aquaculture. The objective of this research was to determine the cause of a disease outbreak of burbot at a commercial facility. Diagnostic investigation identified several Aeromonas bacteria as the primary cause of mortality and Flavobacterium columnare as a secondary infection. One Aeromonas bacterium and F. columnare recovered from the disease case were used in experimental infections of burbot in the laboratory. Interestingly, the Aeromonas bacterium and F. columnare caused little mortality in the laboratory. It is hypothesized that another Aeromonas bacterium or an interaction of the numerous Aeromonas bacteria isolated during the diagnostic case was responsible for the clinical outbreak observed. The research also suggests that burbot are relatively refractory to F. columnare. This study provides additional background on burbot disease susceptibility and will aid in developing control or prevention strategies for production related disease. As burbot aquaculture expands in the US and elsewhere, disease management methods targeted specifically towards disease causing pathogens will need to be developed.

Technical Abstract: Burbot (Lota lota maculosa), are a potential new species for commercial aquaculture. As burbot culture expands, there is a need to further define pathogen susceptibility and characterize aspects of the burbot immune response in an effort to assess fish health. A recent clinical diagnostic case from juvenile burbot reared at a commercial production facility resulted in the isolation and identification of Flavobacterium columnare along with several Aeromonas spp. The F. columnare isolate was assigned to genetic group 1 via multiplex PCR, a genetic group commonly associated with columnaris disease cases in rainbow trout (Oncorhynchus mykiss). Virulence of the F. columnare isolate was assessed in vivo in both juvenile burbot and rainbow trout. Additionally, several of the Aeromonas spp. case isolates were identified via sequencing (16S rRNA, gyrB, and rpoD) and a putative A. sobria isolate (BI-3) was used to challenge burbot, along with a known virulent Aeromonas sp. (A141), but BI-3 was not found to be virulent. Burbot were refractory to F. columnare when challenged by immersion and it is likely that this is a secondary pathogen for burbot. Although refractory in burbot, the identified F. columnare isolate (BI-1) was found to be virulent in rainbow trout.