Veterinary Services
Centers for Epidemiology and Animal Health
November 2003
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ESC and
Vaccination Practices
Enteric septicemia of catfish (ESC) is an important
disease of farm-raised catfish. Fish kills due to ESC
in wild catfish populations are rare. The channel
catfish is the species most susceptible to ESC
infection, while white catfish, brown bullhead, and
walking catfish are rarely susceptible. Blue catfish
may be somewhat resistant to ESC infection.
Catfish affected with ESC frequently have red
and white ulcers covering their skin; pinpoint red
spots called petechial hemorrhages; and
longitudinal ulcers or raised red “pimples” between
the eyes (at the cranial foramen). Catfish are more
prone to infection when subjected to stressful
conditions, which may include improper diet, poor
water quality, close confinement, handling, low
chloride levels, or water temperature fluctuations.
However, disease also can occur in the absence of
perceptible stress.
The causative agent of ESC is a gram-negative
bacterial species, Edwardsiella ictaluri. Stocking
healthy fish into ponds with carriers or stocking
infected fish into ponds with healthy fish can spread
ESC. Fish that survive an ESC outbreak may carry
bacteria for up to 200 days. Transmission from fish
to fish is likely to occur via water contamination,
with bacteria shed in feces, or by cannibalism of
dead or infected fish. The bacteria also have been
shown to survive in pond mud for up to 95 days at
25° Celsius (77° Fahrenheit). Birds that pick up
infected fish from one pond and drop them into
another can spread disease from pond to pond.
Additionally, E. ictaluri can be transferred from
pond to pond on wet equipment, but air drying in
direct sunlight should kill the bacteria.
ESC outbreaks generally occur in the spring
and fall. Sy