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United States Department of Agriculture

Agricultural Research Service

Research Project: NUTRITION, IMMUNE SYSTEM ENHANCEMENT, AND PHYSIOLOGY OF AQUATIC ANIMALS

Location: Aquatic Animal Health Research

Title: Effect of Sub-Lethal Hypoxia 0n Immune Response and Susceptibility of Channel Catfish,ictalurus Punctatus,to Enteric Septicemia

Authors
item Welker, Thomas
item McNulty, Shawn
item Klesius, Phillip

Submitted to: Journal of the World Aquaculture Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 12, 2006
Publication Date: March 1, 2007
Citation: Welker, T.L., Mcnulty, S.T., Klesius, P.H. 2007. Effect of sub-lethal hypoxia on immune response and susceptibility of channel catfish,Ictalurus punctatus,to enteric septicemia. Journal of the World Aquaculture Society. 38(1):12-23.

Interpretive Summary: The effect of low dissolved oxygen (hypoxia) on the stress response (blood glucose and plasma cortisol levels) and susceptibility to Edwardsiella ictaluri infection in juvenile channel catfish (Ictalurus punctatus Rafinesque) was determined. Stress was examined before, during, and after 2 h exposure to <2 mg L-1 dissolved oxygen (DO) and while maintained under normal DO (normoxic) conditions (6.0 mg DO L-1). The stress response increased significantly after exposure to hypoxic conditions. Fish exposed to hypoxia or normoxia were challenged with a high dose (1.3 x 107 CFU mL-1) or low dose (1.3 x 105 CFU mL-1) of E. ictaluri or sterile culture broth by 30 min immersion bath. Exposure to hypoxia significantly increased the susceptibility of channel catfish challenged with the high dose of E. ictaluri. Increased susceptibility of channel catfish to E. ictaluri appears to be the result of the immunosuppressive effects of the stress response to hypoxia.

Technical Abstract: The effect of sublethal hypoxia exposure on plasma cortisol, blood glucose, and susceptibility to Edwardsiella ictaluri infection in juvenile channel catfish (Ictalurus punctatus Rafinesque) was determined. Fish were monitored for temporal changes in glucose and cortisol concentrations before, during, and after 2 h exposure to <2 mg L-1 dissolved oxygen (DO) and while maintained under normoxic conditions (6.0 mg DO L-1). Both blood glucose and plasma cortisol increased significantly (P<0.001) in response to hypoxic conditions. Fish exposed to hypoxic or normoxic conditions were challenged with a high dose (1.3 x 107 CFU mL-1) or low dose (1.3 x 105 CFU mL-1) of E. ictaluri or sterile culture broth by 30 min immersion bath. One percent of fish in both the normoxic and hypoxic groups died when challenged with the E. ictaluri low dose. However, when challenged with the high dose of E. ictaluri, catfish exposed to hypoxic conditions had significantly higher (P=0.02) cumulative mortality (36%) than fish maintained under normoxic conditions (12%). Increased susceptibility of channel catfish to E. ictaluri appears to be the result of the immunosuppressive effects of the stress response to hypoxia.

Last Modified: 10/1/2014
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