First detection of a viral agent causing disease in farmed sturgeon in Russia

Abstract

A virus was isolated from Siberian sturgeon Acipenser baeri and bester (beluga Huso huso × sterlet A. ruthenus hybrid) fingerlings in SSO-2, SSF-2 and WSSK-1 cell lines during an acute epizootic on a large fish farm producing fertilised sturgeon eggs and fry. Transmission electron microscopic examination of samples from both inoculated cell cultures and skin of affected fish revealed viral particles with a herpesvirus-like morphology. The etiological role of the Siberian sturgeon herpesvirus (SbSHV) was confirmed by fulfilment of Rivers' postulates. Experimental immersion of healthy Siberian sturgeon fingerlings in a suspension of SbSHV resulted in 100% mortality with signs of focal epidermal hyperplasia, skin necrosis and multiple skin haemorrhages. While infecting different organs and tissues, the virus showed clear integumentary tropism. Carp fry and rainbow trout fingerlings were neither susceptible to the virus nor did they transmit it to healthy Siberian sturgeon. KEY WORDS: Siberian sturgeon. Herpesvirus . Pathogenicity Resale or republication not permitted without written consent of the publisherDis Aquat Org 86: 193-203, 2009 In the spring of 2006, an acute disease outbreak occurred in a large warm water sturgeon hatchery situated in Tver Province in the European part of Russia. The outbreak resulted in a mass mortality of fry and fingerlings, with Siberian sturgeon Acipenser baeri being the most susceptible fish among several sturgeon species cultured there. Up to 100% mortality was registered in some fish lots.The disease developed at a water temperature range of 14 to 19°C. Affected fish were lethargic, consumed no food, had a lighter colour than normal and remained at the rearing tank bottom. Multiple haemorrhages on the ventral part of the rostrum, around the mouth and on the abdominal and lateral body surfaces were the most prominent clinical signs. In moribund fish, the liver was extremely pale, almost white. Saprolegnia sp. and myxobacteria were also found in the skin and gill tissues of many of the diseased fish. However, treatments against these secondary invaders did not result in substantial improvement of fish condition. After parasites and bacteria were excluded as possible causes of the disease, affected tissues from diseased fish were sampled for virological examination. MATERIALS AND METHODSVirus isolation. For virological examinations, samples of affected mouth and gill tissues were collected from 17 fingerling Lena sturgeons (a race of Siberian sturgeon) aged 1.5 to 4 mo old, and from 2 fingerling 3 mo old besters (great sturgeon Huso huso × sterlet Acipenser ruthenus hybrids) each with a body weight between 3 and 25 g. The collected samples were pooled from 2 to 7 fish and transported to the laboratory in chilled (2 to 4°C) condition in Eagle's minimal essential medium (MEM) supplemented with 10% foetal calf serum (FCS; Life Technologies), penicillin (300 I.U. ml -1 ) and streptomycin (300 µg ml -1 ). The time interval between sampling the fish tissues and their pr...

Isolation and characterization of an atypical Siberian sturgeon herpesvirus strain in Russia: novel North American Acipenserid herpesvirus 2 strain in Europe?

“…In SK1/0406‐infected 2‐ and 3‐month‐old Siberian sturgeon fingerlings, the disease developed as typical integumental necro‐haemorrhagic syndrome described for this virus in detail earlier (Shchelkunov et al . ). It started with lethargy and anorexia 7–10 days p.i.…”

“…Virus isolation technique was described in detail elsewhere (Shchelkunov et al . ). For virus isolation, tissue from the siphon of the diseased fish was used.…”

“…Siberian sturgeon herpesvirus (SbSHV) was discovered in 2006 in moribund fingerling Siberian sturgeon ( Acipenser baeri ) which experienced an acute outbreak of disease in a sturgeon hatchery located in the central European part of Russia (Shchelkunov et al . ). Since then, it has been found widespread in cultured sturgeon species in Russia.…”

“…SbSHV is the cause of an acute necro‐haemorrhagic skin syndrome complicated by secondary opportunistic infections (fungal, myxobacterial or protozoan) (Shchelkunov et al . ). Partial sequence analysis of the viral genome determined that the SbSHV was a potential member of the genus Ictalurivirus within the family Alloherpesviridae under the order Herpesvirales (Doszpoly & Shchelkunov ).…”

Herpesviruses of Fish, Amphibians and Invertebrates

“…Mortality among experimentally infected juvenile white sturgeons reached a cumulative total of 80%. AciHV-2 has since been isolated from wild white sturgeon in Idaho and Oregon (USA), from farmed shortnose sturgeon (Acipenser brevirostrum) from Canada, and from Siberian sturgeon (Acipenser baeri) in Russia (Doszpoly & Shchelkunov, 2010;Kelley et al, 2005;Kurobe et al, 2008;Shchelkunov et al, 2009). …”