Identical sequence types of Yersinia ruckeri associated with lethal disease in wild- caught invasive Blue Catfish and cultured hybrid catfish (Channel Catfish female × Blue Catfish male) from disparate aquatic ecosystems

Authors: DENSMORE, CHRISTINE - Us Geological Survey (USGS); HENDRIX, MADELIENE - Mississippi State University; REICHLEY, STEPHEN - Mississippi State University; RAINES, CLAYTON - Us Geological Survey (USGS); BRESSMAN, NOAH - Salisbury University; CRUM, ZACHARY - Salisbury University; KHOO, LESTER - Mississippi State University; Waldbieser, Geoffrey; GRIFFIN, MATT - Mississippi State University; Welch, Timothy; Iwanowicz, Luke

Submitted to: Journal of Aquatic Animal Health
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/2/2024
Publication Date: 4/4/2025
Citation: Densmore, C., Hendrix, M., Reichley, S.R., Raines, C., Bressman, N., Crum, Z., Khoo, L.H., Waldbieser, G.C., Griffin, M.J., Welch, T.J., Iwanowicz, L.R. 2025. Identical sequence types of Yersinia ruckeri associated with lethal disease in wild- caught invasive Blue Catfish and cultured hybrid catfish (Channel Catfish female × Blue Catfish male) from disparate aquatic ecosystems. Journal of Aquatic Animal Health. 37(1):21-33. https://doi.org/10.1093/jahafs/vsae004.
DOI: https://doi.org/10.1093/jahafs/vsae004

Interpretive Summary: Blue catfish were introduced into lower Chesapeake Bay tributaries in the 1970s and their range has since expanded into the north throughout the Chesapeake watershed. The success and spread of this invasive species has raised concerns over their effect on native fish populations including competition for food, predation, and the spread of infectious disease. Blue catfish are also used to establish hybrid catfish as part of commercial aquaculture practices in the Southeastern United States. The report here documents the identification and characterization separate cases of Yersiniosis, a disease caused by the bacterium Yersinia ruckeri, in a wild blue catfish from the Northeastern USA and cultured hybrid catfish in the Southeastern USA. Yersiniosis is a serious disease affecting both wild and farmed fish. This research demonstrates that this strain of the bacterium is not geographically restricted, and that wild blue catfish could be a source of Y. ruckeri infection in catfish production ponds. While this strain of the bacterium clearly causes disease in catfishes, it does not appear to be a threat to rainbow trout.

Technical Abstract: The Blue Catfish (Ictalurus furcatus) is a prominent aquatic invasive species of concern in the mid-Atlantic region. It is also commonly raised in warmwater aquaculture in the United States for the production of Channel Catfish (Ictalurus punctatus) x Blue Catfish hybrids. In April 2022, a blue catfish specimen was collected from a tributary of the Nanticoke River in Maryland. The fish displayed reddened lesions on the head and was swimming abnormally. Lesions were sampled and analyzed through microbial culture, molecular testing, and histopathology. Results were all consistent with Yersinia ruckeri infection. A draft genome of the Y. ruckeri isolate was assembled based on Oxford Nanopore Technology sequencing. Sequencing identified a single genomic replicon (3,791,418 bp) consistent in size to other Y. ruckeri genomes and a plasmid (60, 933 bp). A challenge study was conducted that demonstrated no significant virulence of this isolate for Rainbow Trout (Oncorhynchus mykiss). This isolate was most similar to other strains isolated from ictalurids. Notably, the gyrase B gene from this isolate was identical to that of archived strains isolated from Mississippi hybrid catfish aquaculture during 2016. Similarly, they shared a plasmid that differed by only 6bp.While yersiniosis has been reported in multiple species of freshwater fish in association with clinical disease, this is the first known report of this disease among Blue Catfish or any ictalurid species in this region. Analyses here provide preliminary genetic evidence that geographically distant isolates of Y. ruckeri from catfish are genetically similar.