MECHANISMS FOR TRANSMISSION OF INFECTIOUS SALMON ANEMIA (ISA)

Atlantic salmon exposed to organic material (like blood) containing the infectious salmon anaemia (ISA) agent, or to salmon lice from ISA-infected fish, suffered high mortalities. Coprophagy was observed and may be of importance when the disease has reached a fish farm, i.e. during an outbreak. It is suggested that salmon lice may be an important vector for the ISA agent in epidemic and endemic phase. Although passive transmission in seawater may be of lesser importance in the spread of the agent, it was demonstrated in this study that the ISA agent was still infectious after 20 h in seawater and 4 d in blood and kidney tissue kept at 6 degrees C.