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Pathogen Page

Edwardsiella ictaluri

I. General Information

1. NCBI Taxonomy ID:

2. Disease:

Enteric septicemia of channel catfish (ESC)

3. Introduction

Edwardsiella ictaluri are Gram-negative, rod shaped, motile bacteria belonging to the family Enterobacteriaceae akin to the phylogenetically closely related Salmonella spp. The disease, enteric septicemia of channel catfish (ESC) caused by E. ictaluri, accounts for considerable economic loss to the catfish farming industry world wide. Recent attempts to control ESC through prophylactic immunization have shown that live attenuated E. ictaluri vaccines are efficacious in protecting catfish fingerlings, fry, and eyed-eggs following immersion vaccination (Russo et al., 2009). ESC causes signs typical of bacterial septicemia in its acute form. In this disease form, producers experience economic losses due to rapid mortalities . In its chronic form, ESC typically has a slower progression and causes a "hole-in-the-head" lesion that may remain localized or progress to septicemia and death. Farmers experience losses from chronic ESC due to decreased production, with fish manifesting signs 3 to 4 weeks after an acute outbreak. The only treatments currently available are oxytetracycline and sulfadimethoxine/ormetoprim, which are both delivered orally in feed. However, one of the earliest clinical signs associated with ESC is anorexia; therefore, oral antibiotics are only effective in limiting the spread of an outbreak (Microgen).

4. Host Ranges and Animal Models

E. ictaluri is specifically adapted to the channel catfish host. Although it has been isolated from other fish species, disease has only been described in channel catfish (Microgen).

5. Host Protective Immunity

Several studies have alluded that protective immunity in channel catfish against E. ictaluri is largely mediated by a cellular immune response with humoral antibodies having a secondary function. This observation is also supported by the fact that E. ictaluri, like Salmonella, could survive and replicate intracellularly and it is the cell mediated immune response that is primarily important in combating these infections (Russo et al., 2009).

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