title: Transmission potential of infectious hematopoietic necrosis virus in APEX-IHN®-vaccinated Atlantic salmon.
abstract: Infectious hematopoietic necrosis virus (IHNV) outbreaks have had a significant negative impact on Atlantic salmon Salmo salar production in British Columbia, Canada, since the first outbreak was reported in 1992. In 2005, the APEX-IHN® vaccine was approved for use in Canada for prevention of IHN. The vaccine was proven to be safe and efficacious prior to approval; however, it is unknown as to whether APEX-IHN®-vaccinated Atlantic salmon infected with IHNV can support replication and virus shedding in sufficient quantities to provide an infectious dose to a nearby susceptible host. To determine whether vaccinated, infected fish are able to transmit an infectious dose of IHNV, vaccinated Atlantic salmon were injected with IHNV (104 plaque-forming units per fish) and cohabitated with either naïve Atlantic salmon or naïve sockeye salmon Oncorhynchus nerka. APEX-IHN®-vaccinated fish were significantly protected against IHNV with mortality occurring in only 2.6% of the population as opposed to 97% in unvaccinated controls. Vaccination in IHNV-infected Atlantic salmon completely abolished disease transmission to cohabitating naïve sockeye salmon and reduced virus spread among cohabitating naïve Atlantic salmon. At 7 mo post-vaccination, IHNV-neutralizing antibodies were detected in nearly all vaccinated fish (94%) with similar titer occurring between vaccinated, infected fish and vaccinated, uninfected fish, indicating APEX-IHN® vaccination induces a robust seroconversion response. Taken together, these results demonstrate that vaccination greatly reduces the infectious load and potential for IHNV transmission. As such, APEX-IHN® should be included in fish health management strategies when culturing Atlantic salmon in IHNV endemic areas.
authors.affiliation: Fisheries and Oceans Canada, Pacific Biological Station, Nanaimo, BC V9T 6N7, Canada.
authors.forename: Amy
authors.initials: A
authors.lastname: Long
authors.forename: Jon
authors.initials: J
authors.lastname: Richard
authors.forename: Laura
authors.initials: L
authors.lastname: Hawley
authors.forename: Scott E
authors.initials: SE
authors.lastname: LaPatra
authors.forename: Kyle A
authors.initials: KA
authors.lastname: Garver
mesh_terms: D000818:Animals; D057134:Antibodies, Neutralizing / Q000097:blood; D000914:Antibodies, Viral / Q000097:blood; D005393:Fish Diseases / Q000517:prevention & control* / Q000635:transmission / Q000821:virology; D029142:Infectious hematopoietic necrosis virus; D018353:Rhabdoviridae Infections / Q000517:prevention & control / Q000635:transmission / Q000662:veterinary* / Q000821:virology; D020317:Salmo salar; D014765:Viral Vaccines / Q000276:immunology*
chemical_list: D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral; D014765:Viral Vaccines
keywords: APEX-IHN® vaccine; Atlantic salmon; IHNV; Infectious hematopoietic necrosis virus; Sockeye salmon