Update on viral vaccines for fish

A substantial amount of research has been done on fish viruses affecting species in aquaculture. This review will focus on the salmonid industry, as this is the most industrialised part of fish farming where vaccines are extensively used. In spite of the amount of research performed, both in commercial companies and in academic organisations, few viral vaccines are licensed. As of today, all fish virus vaccines for sale are based upon inactivated virus or recombinant proteins. No live attenuated or DNA vaccines are currently licensed, but one DNA vaccine against IHN is being tested in controlled field trials in Canada. Vaccines against infectious pancreatic necrosis (IPN) have been sold for many years in Norway and are now also available in Chile. Most of the research on these vaccines has been performed by pharmaceutical companies, and not much information is available as scientific publications. It has also been difficult to establish reproducible IPN challenge models suitable for vaccine testing and this probably explains the lack of scientific publications. Quite the reverse is the case for the fish rhabdoviruses viral hemorrhagic septicaemia virus (VHSV) and infectious haematopoietic necrosis virus (IHNV). The challenge models are reproducible, and both inactivated virus and DNA vaccines offer excellent protection. Recombinant subunit vaccines have so far shown unsatisfactory effect. Little information has been published regarding vaccine development against pancreas disease (PD) and infectious salmon anaemia (ISA). PD and ISA vaccines have been tested at the laboratory scale with good results, and two commercial ISA vaccines are currently available in Canada. Regarding nodaviruses, a few publications have shown effect of recombinant subunit formulations. However, nodaviruses cause disease early in the lifecycle of marine fish, and injection of these formulations into fish of a few grams is so far difficult on a commercial scale.