The Spreading of Isavirus

Transmission of the virus has been demonstrated to occur by contact with infected fish or their secretions. Contact with equipment or people who have handled infected fish also transmits the virus. The virus can survive in seawater and, not surprisingly, a major risk factor for any uninfected farm is its proximity to an already infected farm.

More recently the sea louse, a small crustacean parasite that attacks the protective mucous, scales and skin of the salmon has been shown to carry the virus passively on its surface and in its digestive tract, although transmission of the disease by sea lice has not been demonstrated. It is not known whether the Infectious salmon anemia virus can reproduce itself in the sea louse, although this is a remote possibility as viruses are usually very host specific unlike bacterial diseases that can replicate in ticks such as Lyme disease and Rocky Mountain Spotted Fever.