Infectious hematopoietic necrosis virus.

Abstract

AbstractInfectious hematopoietic necrosis virus (IHNV), the aetiologic agent of infectious haematopoietic necrosis (IHN), is a major viral pathogen of salmonids that causes serious economic losses worldwide. IHNV causes acute clinical infections and sudden mortalities in fry and juveniles and is transmitted horizontally and vertically. An example of this vertical transfer is that IHNV-contaminated eggs have contributed to the spread of the virus worldwide. IHNV is a negative-sense, single-stranded RNA virus in the family Rhabdoviridae, and is the type species in the genus Novirhabdovirus. The viral genome is 11.1 kb and contains six genes that are, in 3′ to 5′ order: nucleocapsid (N), polymerase-associated phosphoprotein (P), matrix protein (M), surface glycoprotein (G), non-virion protein (NV) and viral polymerase (L). Molecular phylogenies using the N, G and NV gene sequences revealed the presence of five major genetic subgroups of IHNV worldwide. These include three genogroups from North America (genogroups upper (U), middle (M) and lower (L) based the IHNV geographical range in North America), one from Europe (E), and one from Japan (J). Biosecurity and good farm management practices in both hatchery and production facilities are essential for IHN control. A DNA vaccine targeting the IHNV G protein (Apex-IHN®, Novartis Animal Health) is now commercially available in Canada and the USA. Despite the availability of a vaccine, periodic occurrences of IHNV-induced epizootics remain a global concern in salmonid aquaculture, which indicates that additional strategies need to be deployed for better disease control. Considering the diversity of IHNV isolates, perhaps structure-based design strategies are needed for production of vaccines with enhanced efficacy and broad-spectrum protection against a number of prevailing strains in IHNV.