Location: Cool and Cold Water Aquaculture Research
2010 Annual Report
1: Conduct selective breeding and determine, under field and laboratory conditions, whether rainbow trout bred for bacterial cold water disease resistance exhibit superior performance traits. • 1.a. Evaluate and selectively breed NCCCWA rainbow trout for increased disease resistance and quantify improvement due to selection. • 1.b. Compare improved and reference lines of NCCCWA rainbow trout under farm conditions.
2: Characterize virulence determinants involved in the emergence of vaccine-resistant Yersinia ruckeri strains and develop novel therapeutics to treat or prevent disease. • 2.a. Elucidate the genetic basis of the biotype 2 phenotype. • 2.b. Evaluate the role of flagellar secretion in the function of the traditional ERM immersion vaccine and vaccine failure. • 2.c. Develop novel phage therapeutics for control of ERM and BCWD.
3: Identify genes and non-genetic factors in rainbow trout critical to innate and acquired immunity. • 3.a. Determine if heritable differences in spleen structure and function account for the superior BCWD survival and clearance traits of resistant fish. • 3.b. Determine whether orally-delivered immunostimulants modulate the gut immune system and whether variation exists between resistant and susceptible lines of rainbow trout. • 3.c. Initiate development of a rainbow trout immune-pathway database that is integrated with pathogen genomic information.
Implementation of breeding programs is limited by an incomplete understanding of the immunogenetics of host resistance and correlated traits. Previously a family-based, phenotypic correlation between rainbow trout spleen somatic-index (SI) and family survival following F. psychrophilum challenge was observed. This year the genetic correlation between SI and BCWD were calculated from two independent trout lines evaluated over five year-classes. Spleen index was highly heritable and there was a positive genetic correlation with BCWD survival. In collaboration with Project # 1930-31000-009, the genetic architecture influencing spleen index was examined. Suggestive QTL for spleen weight and spleen index were identified on several chromosomes.
Methods were developed and optimized for isolation of leukocytes from gill and gut tissues of rainbow trout. Flow cytometry analyses demonstrate few IgM positive cells in the gut tissue of rainbow trout under normal conditions. Several immune related genes were modulated in the gut following bacterial challenge.
Immunostimulants and immunomodulators are emerging areas of interests in animal production to improve animal health and decrease antibiotic use. A standard rainbow trout diet was supplemented with chicken egg powder containing an anti-PLA2 antibody and observed improvement in weight gain compared to fish fed standard diet supplemented with control chicken egg powder. Initial studies indicate an 11% improvement in total weight gain over controls and approximately 21 fewer days to reach market weight. No significant differences in immune related mRNA expression were detected in the gut of treated rainbow trout. There was no difference in survival between anti-PLA2 and control fed fish following challenge with Yersinia ruckeri or Flavobacterium psychrophilium.
Bacteriophages have potential as a means for pathogen biocontrol. A model system was developed for quantifying the fish-to-fish transmission of Yersinia ruckeri, a salmonid pathogen. The development of a model is a critical first step for future studies designed to assess and optimize the use of bacteriophage to minimize pathogen transmission in the aquaculture environment.
Evenhuis, J., Lapatra, S.E., Verner-Jefferys, D.W., Dalsgaard, I., Welch, T.J. 2009. Identification of flagellar motility genes in Yersinia ruckeri by transposon mutagenesis. Applied and Environmental Microbiology. 75(20):6630-6633.
Lindsey, R.L., Frye, J.G., Cray, P.J., Welch, T.J., Meinersmann, R.J. 2010. An oligonucleotide microarray to characterize multidrug resistant plasmids. Journal of Microbiological Methods. 81(2):96-100.
Lafrentz, B.R., Lapatra, S.E., Call, D.R., Wiens, G.D., Cain, K.D. 2009. Proteomic analysis of Flavobacterium psychrophilum cultured in vivo and in iron-limited media. Diseases of Aquatic Organisms. 87:171-182.
Wiens, G.D. 2009. Microbial Genomics of Aquaculture Pathogens. In: Overturf, K., editor. Current Status of Molecular Techniques in Aquaculture. Hobolen, NJ: Wiley, John & Sons, Inc. p. 315-335.
Moulana, M., Evenhuis, J., Kountikov, E.I., Wilson, M., Bengten, E., Miller, N.W., Mcconnell, T. 2008. Characterization of anti-channel catfish MHC class II monoclonal antibodies. Veterinary Immunology and Immunopathology. 126:120-130.
Wiens, G.D., Vallejo, R.L. 2010. Temporal and pathogen-load dependent changes in rainbow trout (Oncorhynchus mykiss) immune response traits following challenge with biotype 2 Yersinia ruckeri. Fish and Shellfish Immunology. doi:10.1016/j.fsi.2010.06.010 29:639-647.
Haig, S., Davies, R.L., Welch, T.J., Reese, A.R., Verner-Jefferies, D. 2010. Comparative susceptibility of Atlantic salmon and rainbow trout to Yersinia ruckeri: relationship to O antigen serotype and resistance to serum killing. Veterinary Microbiology. doi:10.1016/j.vetmic.2010.06.022
Verner-Jefferies, D., Welch, T.J., Schwarz, T., Pond, M.J., Woodward, M.J., Haig, S.J., Rimmer, G.S., Roberts, E., Morrison, V., Baker-Austin, C. 2009. High prevalence of multidrug-tolerant bacteria and associated antimicrobial resistance genes isolated from ornamental fish and their carriage water. PLoS One. 4(12):1-9.