A new aquareovirus causing high mortality in farmed Atlantic halibut fry in Norway

Abstract

A new aquareovirus was isolated from cultured Atlantic halibut (Hippoglossus hippoglossus) fry at a facility where massive mortalities had occurred during the start-feeding phase. The same virus was also detected in juveniles (about 10 grams) of the 2013 generation at two other production sites, but not in larger fish from generations 2007–2012. The virus replicated in BF-2 and CHSE-214 cell cultures and produced syncytia and plaque-like cytopathic effects. This Atlantic halibut reovirus (AHRV) was associated with necrosis of the liver and pancreas, syncytium formation in these tissues, and distinct viroplasm areas within the syncytium in halibut fry. Transmission electron microscopy revealed that the viroplasm contained virions, non-enveloped, icosahedral particles approximately 70 nm in diameter with a double capsid layer, amorphous material, and tubular structures. The RNA-dependent RNA polymerase (RdRp) gene from the AHRV isolates showed the highest amino acid sequence identity (80 %) to an isolate belonging to the species Aquareovirus A, Atlantic salmon reovirus TS (ASRV-TS). A partial sequence from the putative fusion-associated small transmembrane (FAST) protein of AHRV was obtained, and this sequence showed the highest amino acid sequence identity (46.8 %) to Green River Chinook virus which is an unassigned member of the genus Aquareovirus, while a comparison with isolates belonging to the species Aquareovirus A showed <33 % identity. A proper assessment of the relationship of AHRV to all members of the genus Aquareovirus, however, is hampered by the absence of genetic data from members of several Aquareovirus species. AHRV is the first aquareovirus isolated from a marine coldwater fish species and the second reovirus detected in farmed fish in Norway. A similar disease of halibut fry, as described in this paper, has also been described in halibut production facilities in Canada and Scotland.

First Description of a New Disease in Rainbow Trout (Oncorhynchus mykiss (Walbaum)) Similar to Heart and Skeletal Muscle Inflammation (HSMI) and Detection of a Gene Sequence Related to Piscine Orthoreovirus (PRV)

“…Some strains have been isolated from diseased fish concurrently with other disease problems, and it is discussed whether reoviruses suppress the immune system, thereby making the fish more susceptible to other diseases, or if they are the main cause of the disease [ 10 ]. Recently a new aquareovirus was detected in Norwegian farmed Atlantic halibut fry ( Hippoglossus hippoglossus ) with high mortality rates [ 11 ] and this emphasises the need for more knowledge about the impact of these viruses on fish health. Diseases associated with reoviruses are to our knowledge previously not recorded from rainbow trout.…”

Syncytial Hepatitis of Tilapia (Oreochromis niloticus L.) is Associated With Orthomyxovirus-Like Virions in Hepatocytes

“…9 Previously described examples of piscine viral diseases that feature hepatic necrosis include infectious salmon anemia (ISA), 24 viral hemorrhagic septicemia in several species, 10,12,19 channel catfish virus, 21 adenovirus-like disease of cultured white sturgeon, 11 and halibut reovirus. 3 Interestingly, the latter also presents with syncytia formation in the liver, which is a feature of SHT.…”

Characterization and virus susceptibility of a continuous cell line derived from the brain of Aequidens rivulatus (Günther)

“…The genome sequences of MEIPNV1310 (Wen, ) and PCNV (Nam‐Sil et al, ) are close to that of the Ab strain of infectious pancreatic necrosis virus. Aquareoviruses also have caused diseases to numbers of fishes (Blindheim et al., ; Cusack et al., ; Ferguson, Millar, & Kibenge, ; John et al, ; Lupiani et al, ; Sibley et al., ) but not have reported in cichlids. As ARB8 cells are susceptible to GSIV‐K1, RSIV‐Ku, MEIPNV1310 and CSV, the cells can be used to isolate the similar viruses from green terror and other cichlids.…”