Weblink: Ulcerative Bacterial Dermatitis of Koi (Cyprinus carpio) and Ornamental Goldfish (Carassius auratus auratus),

By: Shanna L. Siegel; T. Lindsay Lewis, BS; Niraj K. Tripathi, BVScAH; Victoria V. Burnley, BS; and Kenneth S. Latimer, DVM, PhD

Summary:

An undergraduate honors paper

The skin is a barrier against infection.

• outer layer (epidermis)
  • covers the scales
  • secretes mucus (that helps prevent invaders from getting to the skin)
  • usual site for infections
• middle layer (dermis)
  • scales grow out of the dermis
  • contains color pigments
• inner layer (subcutis or hypodermis)
  • lots of blood vessles
  • connective tissue

Signs of bacterial dermatitis (bacterial skin infection) are

• reddened lesions, sores, or ulcers on the body;
• reddening of the base of the fins; and
• dulling or darkening of skin color

Other nonspecific symptoms may include

• anorexia (loss of appetite),
• weight loss, and
• decreased activity.

Gram-negative bacteria:

Most bacteria commonly isolated from fish are Gram-negative bacilli. May be rapidly fatal.

• Aeromonas salmonicida
  • skin nodules (furunculosis) and ulcers
  • secondary septicemia is common
• Aeromonas hydrophila
  • always present in the water
  • symptoms similar to A salmonicida
  • hemorrhagic septicemia
• Flavobacterium columnare (previously known as Flexibacter columnaris)
  • always present in the water
  • gill erosion
  • skin lesions starting as shallow, white erosions and progressing to yellowish-brown ulcers
  • typically found on dorsal area
• Pseudomonas fluorescens
  • lesions similar to Aeromonas
• Edwardsiella sp. (tarda and ictaluri)
  • initially - small ulcers and hemorrhages in the skin and muscles or pinpoint skin hemorrhages
  • later - large abscesses with stinky, gas-filled cavities in muscles
  • lesions similar to Aeromonas

Gram-positive Bacteria

• Rods
  • Nocardia
    • raised masses in mouth, gills, and skin which eventually ulcerate
    • granulomas in organs
• Aerobic, bacilli
  • Mycobacterium (fortuitum and marinum)
    • wasting away
    • granulomas in many tissues and organs, including the skin
    • Treatment is largely ineffective.
    • can be transmitted to humans
• Cocci
  • Streptococcus (iniae and dysgalactiae )
    • skin abscesses and shallow ulcers

Diagnosis:

• Culture and sensitivity testing
• Stains can help figure out which is which

Treatment

• isolate in hospital tank
• antibiotics,
• salting tank to 0.3%
• 8% salt dip
• cleaning the wounds with iodine
• good water quality (partial water changes/tank maintenence/don't overstock)
• good diet

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