Streptococcicosis was initially described among populations of rainbow trout farmed in Japan. The disease, also known as "pop-eye", is a problem in both farmed and wild fish stocks. The disease symptoms vary but include exophthalmia, distended abdomen and haemorrhages in the eye fins or on the body surface. Internal signs can be accumulation of ascitic fluid, enteritis and damage to the internal organs. Control of streptococcicosis is by good management and antimicrobial agents.