DETERMINATION OF BUOYANT DENSITY AND SENSITIVITY TO CHLOROFORM AND FREON FOR THE ETIOLOGIC AGENT OF INFECTIOUS SALMON ANEMIA

Plasma was collected from Atlantic salmon Salmo salar with acute infec tious salmon anaemia (ISA) and used to challenge Atlantic salmon parr by intraperitoneal injection. Treatment of plasma with the lipid solve nt, chloroform, showed that the etiological agent of ISA contained ess ential lipids, probably as a viral envelope. Some infectivity remained following treatment with freon. Injection challenges using fractions from equilibrium density gradient centrifugation of plasma from fish w ith acute ISA revealed a band of infectivity in the range 1.184 to 1.2 62 g cm-3. The band was believed to contain both complete ISA-virus pa rticles and infectious particles lacking a complete envelope, nucleoca psid or genome. Density gradient centrifugation of infectious plasma f or enrichment of the putative ISA virus appeared to offer a suitable m ethod for obtaining virus-specific nucleic acid for use in the constru ction of cDNA libraries.