Aeromonas hydrophilia

Aeromonas Hydrophilia


Aeromonas hydrophilia, also called ulcer disease or just Aeromonas, is the number one killer of Koi. It does not kill nearly as fast as a virus like KHV, but if not treated, a Koi will usually eventually succumb to the disease. Aeromonas is always present in water, it is also an opportunistic bacteria. Koi will only get an infection if something else has harmed them in any way, especially if portions of their slime coat have been stripped away. Aeromonas and Pseudomonas usually exhibit the same symptoms. The skin ulcer will grow bigger and bigger until muscle tissue is exposed. After that, the infection turns septic and spreads throughout a Koi in their blood stream. The kidneys usually fail next and then a Koi's ability to osmoregulate fails. This causes the condition known as dropsy, or pine cone disease. The Koi will expire, usually within two weeks as more and more bodily functions fail. Nowadays, many strains of Aeromonas are very resistant to antibiotics. This is due to the abuse of antibiotics by the Koi breeders over the years, so they could lower mortality rates, and then increase profit.


Koi can get an Aeromonas infection from:

  • Stress
  • Abrasive Pond or Tank Surfaces
  • Rough Handling
  • Parasites
  • Bad Water Quality
  • Other Immunosuppressant Conditions (i.e.. cold water, moved from tank to pond, being constantly frightened by a person or animal, ect.)


If a Koi gets an Aeromonas infection, remove it from the pond and put it into a heated hospital tank immediately. Warm water will boost a Koi's immune system and will quicken healing. There are a couple options for treatment. One, is Tricide-Neo. Tricide-Neo creates holes in the cell wall of Aeromonas, allowing antibiotics to enter and destroy the drug-resistant strains of Aeromonas. Antibiotic injections can also be used. If injections are the route you take, have a licensed veterinarian come out, take a tissue sample and then send it in for a susceptibility test. With the results, antibiotic treatment will be like a laser guided missile. There will be no guessing which antibiotic will work the best. The Koi can be put back into the general population when it has completely healed up.


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