Worldwide bacteria cause significant stock losses in aquaculture. Most of the bacteria that cause disease are facultative pathogens occurring naturally in the environment, only causing disease when the immune system of the host is compromised. There are some obligate bacterial pathogens (obligate = unable to live and survive without a host).
Bacteria reproduce by binary fission; where one cell divides and becomes two. Under good conditions some bacteria are able to reproduce within 20 minutes which means in only eight hours the original bacteria will have multiplied to nearly 17 million new bacteria. Some bacteria can form spores that are resistant to harsh environmental conditions.
Symptoms of bacterial fish diseases may include:
Bacterial diseases - Additional link:
Most bacterial fish diseases are caused by gram negative bacteria however there are a few gram positive bacteria that cause diseases. As a general rule the gram positive bacterial fish diseases are less common but more pathogenic than most gram negative infections.
Aeromonas hydrophila (Bacterial Hemorrhagic Septicemia)
Pseudomonas fluorescens
Vibrio
Edwardsiella tarda (Edwardsiella septicemia)
Edwardsiella ictaluri (Enteric septicemia of catfish)
Aeromonas sp. (Furunculosis, Ulcerative disease)
Yersinia ruckeri (Enteric red mouth)
Streptococcus iniae
Flexibacter columnaris (Columnaris disease or Saddleback disease)
Bacterial Gill Disease:
Cytophaga psychrophila (Rainbow Trout Fry Anemia)
Renibacterium salmoninarum (Bacterial Kidney Disease)
Mycobacterium species (Tuberculosis)
Nocardia sp.
Flavobacterium sp.
Epitheliocystis (Chlamydial infection)
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