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ARS Home » Northeast Area » Leetown, West Virginia » Cool and Cold Water Aquaculture Research » Research » Publications at this Location » Publication #383742
Research Project: Improving Salmonid Health through Breeding, Vaccination and Microbiome Modulation

Location: Cool and Cold Water Aquaculture Research

Title: Genetic characterization of heterologous Edwardsiella piscicida isolates from diverse fish hosts and virulence assessment in a Chinook salmon Oncorhynchus tshawytscha model

Author
item NGUYEN, DIEM THU - University Of California, Davis
item LÓPEZ-PORRAS, ADRIÁN - Mississippi State University
item MARANCIK, DAVID - St George'S University
item HAWKINS, LEIGHANNE - University Of California, Davis
item Welch, Timothy - Tim
item PETTY, B. DENISE - North Florida Research & Education Center
item WARE, CYNTHIA - Mississippi State University
item GRIFFIN, MATT - Mississippi State University
item SOTO, ESTEBAN - University Of California, Davis

Submitted to: Journal of Fish Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/5/2021
Publication Date: 9/4/2021
Citation: Nguyen, D., López-Porras, A., Marancik, D., Hawkins, L., Welch, T.J., Petty, B., Ware, C., Griffin, M.J., Soto, E. 2021. Genetic characterization of heterologous Edwardsiella piscicida isolates from diverse fish hosts and virulence assessment in a Chinook salmon Oncorhynchus tshawytscha model. Journal of Fish Diseases. 44(12):1959-1970. https://doi.org/10.1111/jfd.13509.
DOI: https://doi.org/10.1111/jfd.13509

Interpretive Summary: Edwardsiella piscicida is a globally important fish pathogen with a wide host and geographic range. In this study we investigated the genetic diversity of 37 E. piscicida isolates recovered from 10 different fish species in North America. This analysis resolved the strains into 6 distinct genetic groups showing that E. piscicida is a genetically diverse species. In addition, the groups were generally associated with the fish species from which they were isolated suggesting a host-pathogen specificity. Evaluation of the 6 groups for virulence in Chinook salmon also revealed genetic and host associations with E. piscicida virulence. The observed genetic diversity and host specificity will be critical for the design and development of vaccines against this group of pathogens.

Technical Abstract: Edwardsiella piscicida is an emergent pathogen of finfish aquaculture. Although it is recognized as a pathogen with a wide host range, host associations driving genetic diversity remain unclear. This study investigated the genetic and virulence diversity of 37 E. piscicida isolates recovered from 10 fish species in North America. Multilocus sequence analysis (MLSA) was conducted using concatenated alignments of the gyrB, pgi and phoU sequences. MLSA clustered the tested isolates into six discrete genetic groups. In light of recent disease outbreaks in cultured salmonids, the virulence of each clade was evaluated in Chinook salmon Oncorhynchus tshawytscha fingerlings following intracoelomic challenge of ~106 CFU/fish. Challenged and control fish were monitored for 21d and microbiological and histological examination was performed on dead and survivor fish. Peak mortality occurred 3-5 days post-challenge (dpc) regardless of isolate or genetic group. Edwardsiella piscicida was recovered from all moribund and dead animals. At 21dpc, fish challenged with isolates from clades II, III and IV presented cumulative mortality =83.3%, whereas isolates from clade I, V and VI resulted in cumulative mortality =71.4%. This study suggests an underlying genetic basis for strain virulence and potential host associations. Further investigations using other fish models and variable challenge conditions are warranted.