Experimental Edwardsiella ictaluri Infection Causes Mortality in White Perch (Morone americana)

Authors: Pasnik, David; Evans, Joyce; Klesius, Phillip

Submitted to: Journal of Animal and Veterinary Advances
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/11/2007
Publication Date: 5/1/2007
Citation: Pasnik, D.J., Evans, J.J., Klesius, P.H. 2007. Experimental Edwardsiella ictaluri Infection Causes Mortality in White Perch (Morone americana). Journal of Animal and Veterinary Advances 6 (5):646-649.

Interpretive Summary: Edwardsiella ictaluri, the causative agent of enteric septicemia of catfish (ESC), receives considerable attention due to its negative impact on the production and harvest of channel catfish (Ictaluri punctatus). This bacterium was initially considered a specific pathogen of channel catfish and other fish in the Ictaluridae family. This conclusion has been supported by several studies reporting fish species from different families as resistant to infection after experimental E. ictaluri challenge or exposure. Some authors have also documented disease susceptibility in natural and experimental E. ictaluri investigations of other fish species from ten families. However, white perch (Morone americana) have not been reported with E. ictaluri infection. White perch is a popular North American food and game fish with a habitat extending from Nova Scotia, Canada to South Carolina, USA. For this study, white perch were captured from the Corsica River in Centreville, Maryland, USA, using a castnet. Four perch and four cultured channel catfish were subsequently challenged by injection with E. ictaluri. While channel catfish exhibited clinical signs characteristic of ESC, the white perch showed limited and non-specific clinical signs. All challenged fish died within 48 h, and most nare, brain, head kidney, intestine, and posterior kidney samples from the catfish and perch produced growth on 5% de-fibrinated sheep blood agar. The bacterial colonies were formed by oxidase-negative, Gram-negative rods, and automated BIOLOG analysis identified the isolates as E. ictaluri. Despite some differences in clinical presentation, both the channel catfish and white perch were susceptible to E. ictaluri and died due to acute systemic infections. The results of this study demonstrated that white perch are experimentally susceptible to E. ictaluri, and this paper provides the first description of E. ictaluri infection in white perch.

Technical Abstract: Edwardsiella ictaluri, the causative agent of enteric septicemia of catfish (ESC), receives considerable attention due to its negative impact on the production and harvest of channel catfish (Ictaluri punctatus). This bacterium was initially considered a specific pathogen of channel catfish and other fish in the Ictaluridae family. This conclusion has been supported by several studies reporting fish species from different families as resistant to infection after experimental E. ictaluri challenge or exposure. Some authors have also documented disease susceptibility in natural and experimental E. ictaluri investigations of other fish species from ten families. However, white perch (Morone americana) have not been reported with E. ictaluri infection. White perch is a popular North American food and game fish with a habitat extending from Nova Scotia, Canada to South Carolina, USA. For this study, white perch were captured from the Corsica River in Centreville, Maryland, USA, using a castnet. Four perch and four cultured channel catfish were challenged by intraperitoneal injection with 1.0 x 107 colony-forming units of E. ictaluri/fish. While channel catfish exhibited clinical signs characteristic of ESC, the white perch showed limited and non-specific clinical signs. All challenged fish died within 48 h, and most nare, brain, head kidney, intestine, and posterior kidney samples from the catfish and perch produced growth on 5% de-fibrinated sheep blood agar. The colonies were formed by oxidase-negative, Gram-negative rods, and BIOLOG analysis identified the isolates as E. ictaluri (Probability = 99%; SI = 0.91). Despite some differences in clinical presentation, both the channel catfish and white perch were susceptible to E. ictaluri and died due to acute systemic infections. The results of this study demonstrated that white perch are experimentally susceptible to E. ictaluri, and this paper provides the first description of E. ictaluri infection in white perch.