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Viral diseases


This is well – known viral disease in fish that effect cells and causes them to become enlarged (Megaloblastic), amounting to tens, and in some instances, hundreds of thousand-fold increase in cellular volume. For the cell, the infection is terminal, but otherwise it is not greatly significant for the host. It is not easily transmitted between fish and is not only associated with bad water quality and stress. Lymphocystis is not fatal but in some cases very disfiguring. I have noticed that in some cases its clears by itself when the water temperature starts to rise. It is said that the virus is transmitted between fish when the virus enters through an injury or wound on a fish. The virus may also be transmitted by fish lice, (Argulus) or leaches when the lesion rapture and viral particles are released into the water. Cannibalism of a diseased fish can also cause the virus to spread.

Symptoms associated with Lymphocystis
  1. Lymphocystis is characterised by multiple creamy-white nodules on the skin and fins.
  2. The viral particles cause an enlargement of the host cells resulting in cells up to a thousand times the normal size.
  3. Individual cells can sometimes be seen with the naked eye.
  4. It soon clumps together to form a cauliflower-like growth on the skin, fins and occasionally on the gills.
  5. This cauliflower-like growths also resemble large warts and is rubbery and rough to the touch.
  6. In time the creamy-white warts may turn pinkish to red.

Prevention of Lymphocystis
  1. Although not scientifically proven, it was noted that the symptoms appear more frequently during winter moths when the immune system is less effective and sometimes disappear spontaneously in the middle of summer.
  2. Fish can develop the symptoms even in immaculate water but stressful situations will aggravate the symptoms of effective fish.
  3. A (cured) fish should be regarded as a carrier of the virus.

Treatment of Lymphocystis
  1. Generally no known treatment for the virus.
  2. Best cure is a stress free situation for the fish with temperatures above 25 degrees Celsius.
  3. The growth may inhabit the fish’s ability to swim, breathe or eat and secondary bacterial infections usually kill the fish, so treat for bacterial infection if necessary.
  4. The lesions can be scraped off but this may cause bacterial infection or the particles can be released in the water, infecting other fish.
  5. A surgical procedure can be successful but should be only done when the lesions interfere with eating, or when there is evidence of infection.

Acriflavine may be effective against this virus but further tests need to be done. (See case study elsewhere on this website where a lesion was surgically remove from a kohaku as well as the use of Acriflavine).

Last Updated on Thursday, 27 August 2009 19:30