Infectious pancreatic necrosis virus

Infectious pancreatic necrosis virus (IPNV) is a double-stranded RNA virus from the family Birnaviridae, in the genus Aquabirnavirus. Causing the highly infectious disease Infectious pancreatic necrosis, the virus primarily affects young salmonids resulting in high mortality, occasionally surpassing 90 percent in the early stages. IPNV or IPNV-like viruses have been isolated worldwide from at least 32 families of saltwater and freshwater salmonids and non-salmonids fish including salmon, flatfish, pike, eels and others. Other aquatic organisms infected include 11 molluscs and 4 species of crustaceans. Due to its wide host range and high mortality, the virus is of great concern to global aquaculture. In addition to persistence in hosts, IPNV is also perpetual in the environment, surviving across a range of conditions and capable of infecting fish with as little as 10¹ TCID₅₀/ml of the virus. Found in Europe, North America, South America, Africa, Asia, and Australia, the virus has led to significant losses in the mariculture of Atlantic salmon, brook trout, and rainbow trout.

First described in 1940 in farmed trout, IPNV outbreaks occur primarily in fry as the most susceptible stage, first in freshwater and then again after a transfer to seawater as post-smolts. Survivors as asymptomatic carriers pose a significant threat to continued outbreaks through both horizontal and vertical transmission of the virus by way of excreted matter. The virus is classified into serogroups A and B, with group A containing nine serotypes and B one serotype. With a virion 65-70 nm in diameter and icosahedral structure, the genome of the virus is split into two segments of double-stranded RNA, encoding 5 proteins. An infection of the host is often identified based on visual inspection, with various key external and internal characteristics. A commonly used molecular biological method of diagnosis is RT-PCR assays. Attempts at controlling IPNV have included the reduction of horizontal and vertical transmission, vaccinations, and selective breeding.