A long yellowish cyst can be seen on the head of the sick fish. The cysts are black when they mature, that is, the snipe larvae and the post-cyst larvae. They also invade fish's eyes, muscles, blood vessels, gills and internal organs. If opaque plaque is found in the lens of the eye, it may be infected. The disease is not contagious, but it will damage muscle tissue and make the eyes blind. In severe cases, it can be fatal. At present, there is no cure, only sterilization can be used.