Prophylactic treatment of viral diseases in fish using native RNA linked to soluble and corpuscular carriers

The potential of double‐ (ds) and single‐stranded (ss) yeast RNA preparations for protection of carp Cyprinus carpio against experimental infection with Rhabdovirus carpio, the infectious agent of spring viraemia of carp, was studied. Prophylactic intraperitoneal injection of fish with dsRNA proved efficient while ssRNA had a much smaller effect. The protective effect of yeast dsRNA in 1‐year‐old carp lasted for at least 3 weeks. The efficacy of the preparations decreased considerably if they were administered by the bath method. Both insoluble and soluble carriers for dsRNA were studied to increase the preparation efficacy. Screening of the preparations revealed the importance of DEAE‐groups on the carriers. Their biological efficiency is confirmed by the method of phagocytosis of the mouse peritoneal macrophages.