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Infectious pancreatic necrosis (IPN) is a viral disease principally associated with salmonids, although IPN and lPN-like viruses have been isolated from various nonsa1rnonid fish and marine invertebrates. Acute infection occurs in 1- to 4-month-old salmonids and can result in cumulative mortality approaching 100%. In contrast, fish 6 months o~d or older can undergo subclinical or inapparent infection, but experience no significant mortality. Survivors of the disease can become lifelong carriers of the virus. Epizootics of IPN have been reported worldwide, and several virus serotypes are recognized.
The disease known as IPN was probably first described by M'Gonigle (1941) as acute catarrhal enteritis and attributed by him to nutritional factors. The viral etiology of IPN was established by Wolf and co-workers (1960). Comprehensive reviews of the disease and the virus have been made by Dorson (1982), McAllister (1979), Munro and Duncan (1977), Pilcher and Fryer (1980), Roberts (1978), and Wolf (1972, 1976).