Bacterial Diseases

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Bacterial Diseases
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ESC and Columnaris

• These two bacterial diseases are the most common
  and most devastating bacterial problems in the
  commercial catfish industry.
• Estimated economic losses resulting from these
  diseases is millions of dollars

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ESC
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Enteric Septicemia of Catfish (ESC)

• Causative agent - Edwardsiella Ictaluri
• Gram Negative, rod shaped, weakly motile
• Thought to be obligate but can survive in mud for
  90 days.
• Similar to Edwardsiella Tarda

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Which fish can get ESC?

• Channel catfish most susceptible
• White catfish, brown bullhead, walking catfish
  are also susceptible
• Blue catfish can get it but are generally
  resistant

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Which fish can get ESC?

• Esc has been isolated from some diseased tropical
  fish.
• Trout, salmon and tilapia have been
  experimentally infected but natural outbreaks
  have not been reported.

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Clinical Signs

• Behavior
• Tail chasing or spiraling
• Star gazing (head up tail down)
• Stop eating

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Clinical Signs

• External Signs
• Red and white ulcers
• petecial hemorrhages (pin point size)
• Raised pimples (buckshot appearance)
• Hole or lightened area on head
• Exopthalmia
• Swollen belly

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External Signs
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Petechial Hemorrhaging (Buckshot appearance)
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Deteriorating Skull Cartilage
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ESC Hole in the Head
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Clinical Signs

• Internal Signs
• Clear - straw colored or bloody fluid in body
  cavity
• Mottled liver
• Petechial hemorrhages in muscle
• Intestine often filled with bloody fluid

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Diagnosing ESC

• Look at behavioral and external signs
• Necropsy for internal signs
• Isolate bacteria from internal organs
• run diagnostic tests
• determine antibiotic sensitivity

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Causes of ESC

• Combination
• Pathogen - virulent Edwardsiella ictaluri
• Stress
• Environment - that favors rapid proliferation of
  the bacteria
• Generally in the ESC Window 68 - 82 degrees F

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How Does ESC Spread

• Enters through
• Gut
• Nares
• Gills
• Transmitted through water
• Transmitted by cannibalism
• Transmitted by carrier fish, equipment and birds

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Treatment and Prevention

• Prevention by reducing stress
• not always possible
• Nutritional supplements
• Winter Feeding
• Genetic improvement
• Vaccination
• Treatment with medicated feeds

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Medicated Feed Treatment of ESC

• Romet 30 and Romet B
• sulfadinethoxine and ormetoprim
• Fed at recommended rate for 5 days
• 3 day withdrawal period
• Terramycin
• Fed at recommended rate for 10-14 days
• 21 day withdrawal period

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Economic Evaluation

• Need to make sure that treating the fish does not
  cost more than the fish are worth

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Other Methods of Control

• Withhold Feed
• Wait for temperature change
• Vaccines

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Columnaris
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Causes of Columnaris

• Causative agent - Flexibacter columnaris
• Gram negative, rod shaped and motile
• Non Obligate - present in the natural environment
• Stress - particularly in warm weather
• Especially long term exposure to low levels of
  toxic ammonia

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Characteristics of the Disease

• Rarely occurs unless fish are stressed
• Most frequently occurs between March and October
  when water temperatures are above 59F especially
  in the 75 -85 degree range
• Can be external, internal or both

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Characteristics of the Disease

• Chronic at lower temperatures and more acute at
  higher temperatures.
• Likely to reoccur if original stress is not
  removed
• All ages, sizes and species can be effected

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Clinical Signs of Columnaris

• External
• increase in thickness of mucous on skin
• saddleback appearance
• areas of gray or colorless skin leading to ulcers
  and open lesions
• grey/brown areas on the gills esp. at the tips
• yellow colonies inside the mouth
• frayed fins

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Columnaris ColoniesUsing Skin Gill Wet Mounts
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Columnaris on Gills
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Columnaris (Frayed fins, tail rot)
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ColumnarisSkin Lesions Leading to Open Ulcers
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Diagnosis

• External - Microscopic examination of skin and
  gill wet mounts
• Internal - Isolation of bacteria and
  identification proceedurs

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Treatment

• Depends on whether the infection is internal or
  external
• External only - 2 to 4 ppm KMnO4
• Internal only - Terramycin
• Both - Terramycin