Cause of disease:

Lymphocystis is a virus that infects the skin of fish.

What does it look like?


The symptoms of this disease are usually described as "warts" or tumors and are commonly seen on the skin and/or fins of adult fish.

Fish species affected:

It has been documented throughout the world on many species of freshwater and marine fishes, but in Minnesota it is most commonly observed on adult walleye.

Life cycle:

The virus spreads from fish to fish through physical contact or water transmission. Lymphocystis infections are usually not fatal to fish, although very severe infections can cause damage to vital organs and possibly death. In addition, secondary bacterial or fungal infections can develop at sites of dislodged growths.

Where is the disease is found?

Although the virus occurs naturally in the environment, infections occur at a much higher rate during cold periods in late winter and early spring.

Is it safe to eat?

This disease is not known to infect humans. However, proper cooking of any freshwater fish is recommended.

How can I prevent the spread?

There is no practical control or treatment for this disease.

Disposal of unused portions:

Dispose of uneaten portions by burying or in household waste. Fish entrails should never be discarded back into the lake.

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