Fish Vibriosis-Bacterial Disease

Vibrio is a genus of Gram-negative bacteria found primarily in saltwater or brackish water, and consisting of 70 or more strains. Fish Vibriosis involves a variety of infectious strains of Vibrio bacteria, most notably Vibrio anguillarum, V. ordalii, V. damsela, and V. salmonicida.


  • Lethargy
  • Increased respiration
  • Loss of appetite
  • Skin hemorrhages

Fish contract the bacteria through open sores or feeding on dead fish that died from the disease. Hemorrhaging starts with reddening or blood streaks under the skin surface, becoming red spots on the ventral and lateral areas of the fish. Swollen dark lesions develop, turning into ulcers and release bloody pus. There may also be eye problems with cloudy eye, which can lead to pop-eye and eye loss.

WARNING:  People can become infected by Vibrio bacteria when handling infected fish. Hence the nicknames of “fish handler’s disease” and “aquarium handler’s disease”. People can become infected when water containing the bacteria comes into contact with cuts or open sores on the skin. The bacteria may be in swimming pools, aquariums, or coastal waters.


The course of a vibriosis infection in fish is usually very rapid. Most infected fish die without showing more visual signs than the ulcers, and sometimes death may occur suddenly before any signs are noticed at all.

The best treatment includes oral antibiotics. Kanamycin is one of the best, also chloramphenicol or furazolidone are good.  Please note that these are human antibiotics and are not commonly available for treatment of fish in Australia.

When treating with antibiotics, it must be done in a quarantine tank rather than the main aquarium. This is because antibiotics will damage the biological filter in the main tank, throwing the nitrification cycle into reverse and cause a spike in nitrites and ammonia after just a few days.

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