Gill lamellar pillar cell necrosis, a new birnavirus disease in Japanese eels

Abstract

Since the late 1980s, a birnaviral gill disease has been occurring in Japanese eels Anguilla japonica reared in warmwater ponds in western regions in Japan. Diseased eels mostly displayed marked formations of aneurysmal hematomas within gill lamellae and high mortalities. Histological examination revealed necrosis of pillar cells and subsequent aggregation of erythrocytes inside the lamellar capillaries, and proliferation of interlamellar epithelia onto the lamellae. Gastric gland cells were also necrotized. Electron microscopy revealed birnavirus infection in lamellar pillar cells. The causative birnavirus was isolated and cultured in fish cell lines and was found to be related to an infectious pancreatic necrosis virus (IPNV) Sp serotype by neutralization tests. The viral pathogenicity was confirmed by the results of histopathological examinations and infectivity experiments.

Viral diseases of wild and farmed European eel Anguilla anguilla with particular reference to the Netherlands

“…Electron microscopy (EM) revealed that EVE virions were non-enveloped polyhedrons with a diameter of 68 to 77 nm, only present in the cytoplasm of infected cells. EVE also resembled IPNV in terms of biological properties, such as polypeptide composition and the bisegmented double-stranded RNA genome (Nishimura et al 1981a, T. Sano et al 1981, Hedrick et al 1983a Lee et al 1999aLee et al , 2001.…”

“…The EVE-like virus isolated by Ueno et al (1984) caused 40% mortality in juvenile A. japonica after intraperitoneal injection at 20 to 25°C. EVE/ PCNV caused about 70% mortality in A. japonica (~40 g) during a 21 d experiment at 25°C, after intramuscular injection (Lee et al 1999a). All inoculated eels showed aneurysmal haematoma formation in gill lamellae and stasis of gill filamental arteries, similar to natural infections, and it was possible to reisolate the virus from diseased gill filaments.…”

“…Hence, EVE is a tentative member of the genus Aquabirnavirus in the family Birnaviridae. Other names for EVE or IPNV of eel include eel virus (EV) [Berlin] (SchwanzPfitzner et al 1984) and pillar cell necrosis virus (PCNV; Lee et al 1999aLee et al , 2001.…”

“…EVE/IPNV type Ab and IPNV type VR-299 were later also isolated from various A. japonica farms in Taiwan (Chen et al 1985, Hsu et al 1989, 1993. EVE/PCNV from diseased A. japonica in Japan was serologically most similar to IPNV serotype Sp (Lee et al 1999a), but genetically closer related to strain Ab (Lee et al 2001).In , Castric & Chastel (1980 isolated an IPNVlike agent called B 6 from Anguilla anguilla elvers along the French Atlantic coast, and showed its relatedness to IPNV serotype Sp by serum neutralisation tests. EVE related to IPNV serotype Ab was repeatedly isolated from an eel farm in the UK (Bucke 1981, Hudson et al 1981.…”

“…Electron microscopy (EM) revealed that EVE virions were non-enveloped polyhedrons with a diameter of 68 to 77 nm, only present in the cytoplasm of infected cells. EVE also resembled IPNV in terms of biological properties, such as polypeptide composition and the bisegmented double-stranded RNA genome (Nishimura et al 1981a, T. Sano et al 1981, Hedrick et al 1983a Lee et al 1999aLee et al , 2001.Aquabirnaviruses form an antigenically diverse group of viruses, with the type species IPNV being the aetiological agent of an acute contagious systemic disease of several species of freshwater and marine fish, molluscs and crustaceans (Rodriguez Saint-Jean et al 2003). Mortality caused by IPNV in salmonids is high in fry and fingerlings, but rare in older fish.…”