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Research Project: Improving Salmonid Health through Breeding, Vaccination and Microbiome Modulation

Location: Cool and Cold Water Aquaculture Research

Title: Seasonal mortality of Atlantic menhaden is associated with neurologic disease caused by a virulent clone of Vibrio anguillarum: Fish kills and implications for biosecurity

Author
item LOVY, JAN - New Jersey Division Of Fish & Wildlife
item Iwanowicz, Luke
item Welch, Timothy - Tim
item ALLAM, BASSEM - Stony Brook University
item GETCHELL, RODMAN - Cornell University
item GERACI-YEE, SABRINA - Stony Brook University
item GOOD, CHRIS - Freshwater Institute
item SNYDER, JEREMY - New Jersey Division Of Fish & Wildlife
item RAINES, CLAYTON - New Jersey Division Of Fish & Wildlife
item DAS, NILANJANA - New Jersey Division Of Fish & Wildlife

Submitted to: Transboundary and Emerging Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/16/2024
Publication Date: 4/12/2024
Citation: Lovy, J., Iwanowicz, L.R., Welch, T.J., Allam, B., Getchell, R., Geraci-Yee, S., Good, C., Snyder, J., Raines, C., Das, N. 2024. Seasonal mortality of Atlantic menhaden is associated with neurologic disease caused by a virulent clone of Vibrio anguillarum: Fish kills and implications for biosecurity. Transboundary and Emerging Diseases. 18:8816604. https://doi.org/10.1155/2024/8816604.
DOI: https://doi.org/10.1155/2024/8816604

Interpretive Summary: Atlantic menhaden are an abundant migratory marine fish common in large schools along the Atlantic Coast ranging from Florida to Nova Scotia, Canada. These fish are a valuable marine fishery used in the production of fish meal and oil and as bait for commercial crab, lobster, and hook-and-line fisheries. Recent seasonal fish kills along the coasts of New Jersey and New York have led to considerable concern due to large numbers of dead menhaden washing ashore in populated areas along estuaries and rivers. Herein, we describe the investigation of three menhaden kills in the mid-Atlantic region between 2020 and 2021. We found that a bacterium, Vibrio anguillarum, was the main pathogen associated with these mortalities and that some fish had secondary infections with Yersinia ruckeri. Genetic analysis and serotyping of the V. anguillarum strains collected demonstrated a highly homogeneous group of serotype 03 bacteria. Vibrio anguillarum and Y. ruckeri are pathogens of farmed trout and salmon and cause significant loss in aquaculture operations world-wide. Our results suggest that migrating menhaden could be a potential pathogen source for the translocation and transmission of these pathogens to salmon aquaculture facilities in the Northeastern US and Canada. This is especially concerning given that V. anguillarum vaccines currently used in these areas are not expected to provide protection against serotype O3 strains.

Technical Abstract: Seasonal mortality has been reported since the 1950’s in Atlantic menhaden, particularly in the mid-Atlantic. Since 2015, chronic menhaden kills with fish showing neurologic signs, including circling at the surface and swimming erratically before death, have become highly apparent in the region. Screening these fish for viruses using viral cell culture assays and molecular methods did not detect a viral etiology. The investigation of three similar menhaden kills in the mid-Atlantic region between 2020 and 2021 has revealed a bacterial etiology consistently associated with the mortality. Vibrio anguillarum was detected in high loads, particularly in brain of moribund fish, by metagenomics and bacterial isolation. Most common histopathological changes in moribund fish were hemorrhagic meningitis and encephalitis with cells sloughing into the third and fourth ventricles of the brain, and degenerative changes, including pyknosis and karyorrhexis, of hematopoietic tissues in kidney and spleen. Herein, V. anguillarum was shown to be a unique strain belonging within serogroup O3. Whole genome sequencing of isolates from moribund fish representing a wide spatial and temporal range showed that isolates were nearly identical clones, suggesting it to be a pathogenic strain circulating in the population. Though V. anguillarum is believed to be the main pathogen associated with these mortalities, secondary infections with Yersinia ruckeri and rarely pure isolation of Y. ruckeri have been detected in moribund Atlantic menhaden. Serotyping and whole genome sequencing has indicated that these Y. ruckeri isolates were nearly identical to those reported to cause disease in farmed salmonids. Considering the highly migratory nature of Atlantic menhaden throughout the eastern United States and their use as bait for other fisheries, the findings of these bacteria identify potential biosecurity challenges that should be considered in Atlantic salmon aquaculture, fisheries, and to emerging marine aquaculture in the northwestern Atlantic Ocean.