Ulcers on koi pond fish

An ulcer is an external open sore of the skin, eyes or mucus membrane, often caused by an initial abrasion and generally maintained by an inflammation and/or a bacterial infection. It can also be caused by bacterial erosions and bacterial sepsis.
 There no such disease as ulcer disease.

It is important to find the root of the infection before any treatment commences.Using the wrong treatment will worsen the infection.

Aeromonas (a genus of pathogenic rod-shaped gram-negative bacteria (schizomycetes) found in fresh and salt water, soil, and sewag) are the cause of most ulcers and bacterial mortality in Koi. This bacteria is also linked to other disease conditions such as abdominal dropsy, carp erythrodermatitis, hemmorhagic septicemia, for example. Poor conditions will aid any of these.

However it has been found that that aeromonas is not the main invader but a virus known as rhabdovirus carpio, and that the aeromonas attacks as a secondary infection. A so called opportunistic secondary attacker. This happens when the fish is under stress with poor water being one of the contributary factors. Others think that rhabodovirus is a known-infection and is found by incidental findings.

Resistance and susceptibility to ulcers depends on the condition of the fish's environment. To enable fish to recover from ulcers you need to check the following;

do you have too many fish for the size of the pond
is amonia present in the pond
have you checked nitrite levels
have you been feeding high quality food - if it's been poor grade be honest
have you had or do you have parasites
have you tried any treatments, other than injection as only this will work
check the condition of your pond and filter
use a hospital tank for infected fish and maintain the temperature above 20 degrees C
are the fish feeding or off their food
check the water condition, has the pond gone milky or murky

  
Check all of the above and correct them before treatment begins or your fish will just die no matter how hard you try.
The infection you are dealing with has been around for millions of years. Never under rate aeromonas or you will be the loser every time.

Ulcers occur when the fish is stressed. Some of the causes are;
parasites - they carry bacteria into the fish by a direct route e.g. flukes carry aeromonas on their hooks
temperatures below 18.3 degrees C inhibit the distribution of antibiotics through the tissues

The main cause of ulcers is poor quality water, which in turn stresses the fish and lowers the immune system, therefore making it easier for the bacteria to take hold. Aeromonas are present in all bodies of water and a stressed fish will not be able to shrug off an infection like a healthy one.

If flukes are present in large numbers in pond (due to poor water) when the fish injures itself, flukes will attack the wound making the fish flick and scratch so opening the wound and removing scales and allowing the bacterial infection ie Aeromonas to get a hold.


Treating the ulcer

The addition of salt to a treatment tank  acts as an antibacterial agent, but extra supportive treatment is required to enable a koi to completely heal. A koi keeper should aim at treating the infection and relying on the koi to heal itself.

Topical treatment

Regular application of an effective antibacterial treatment directly onto the open wound can be very effective. Solutions containing malachite green or other broad-spectrum antibacterials are readily available. Treatment is more effective if the ulcer is dabbed dry in the early days of treatment to allow the medication to be absorbed deeply into the affected tissue. Later on in the treatment, and to enable healing, the dropping of the solution directly onto the wound is advisable.

Also a gel or starch-based poultice mix may be applied onto the open wound in the early days of treatment to prolong the contact between the antibacterial action and the infection.

Care must be taken when netting and handling an ulcerated koi between treatment so as not to aggravate the wound or the fish. The use of an anaesthetic may be required for repeated close work on an ulcer.

Antibiotics

It is becoming more difficult for vets to find antibiotics that are effective against an increasing range of  bacteria that are resistant to them.

However, if it is possible to find a vet who is willing to prescribe and administer an effective antibiotic, then the chances of a full recovery are greatly increased. This is likely to be a costly method, involving a series of antibiotic injections.

Using the above methods of treating a koi with an ulcer allows a three pronged attack which will be effective in allowing the fish to heal itself if used in conjunction with ideal water conditions, excellent nutrition and a restful environment.

Unfortunately however, if scales are lost through ulceration, although the koi's skin will completely regenerate to show the original colour, the scales will not grow back, leaving a permanent mark at the site of the ulcer.