Location: Aquatic Animal Health ResearchTitle: From lamb to lion: unleashing the beast in "virulent" Aeromonas hydrophila
Submitted to: International Conference on Diseases of Fish and Shellfish
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/2019
Publication Date: 9/9/2019
Citation: Beck, B.H. 2019. From lamb to lion: unleashing the beast in "virulent" Aeromonas hydrophila [abstract]. 19th International Conference on Diseases of Fish and Shellfish. p. 31.
Technical Abstract: An emerging pathotype of Aeromonas hydrophila (vAh) has been responsible for widespread farm losses in the US catfish industry over the last decade. While our genetic and biochemical understanding of vAh has been greatly enhanced in this time frame, our ability to reliably induce the disease in the laboratory remained limited. Utilizing established protocols for Aeromonad challenges resulted in minimal mortality and inconsistent clinical symptoms. Therefore, taking cues from observed farm conditions associated with outbreaks, we perturbed iron scavenging dynamics and catfish feeding status. Addition of a xenosiderophore, deferoxamine mesylate (DFO), to vAh cultures prior to immersion challenge significantly increased virulence in several vAh isolates but not in a non-epidemic strain. DFO addition did not impact vAh growth dynamics or perturb iron-sensitive gene pathways, but did significantly enhance hemolysis of catfish blood. Furthermore, hours between last feeding and immersion challenge (postprandial status), was observed to be a critical determinant of catfish susceptibility. Fish with a full gastrointestinal tract had significantly lower survival than those in a fasted state, and this effect was cumulative with that of DFO-enhanced vAh virulence. Utilizing our more robust challenge model, we are currently examining the practical efficacy of varying protective strategies for the industry including diet modification, vaccination, genetic selection, and modulation of the pond environment. Our latest results in this vein will be presented.