Persistence of infectious pancreatic necrosis virus (IPNV) in scallops Pecten maximus

In order to investigate the potential role of blue mussels Mytilus edulis as a vector of the fish pathogenic infectious salmon anaemia virus (ISAV), we developed an experimental bioaccumulation system in which mussels can accumulate virus during normal filtration. Detection of virus in mussels was performed by means of real-time RT-PCR. ISAV-RNA was detected in the mussels until 72 h post-challenge. Hepatopancreas homogenate from experimentally challenged mussels was injected into salmon. All the fish injected with homogenate prepared immediately after accumulations were strongly ISAV positive 4 wk post-challenge. In the group injected with homogenate prepared 24 h after the challenge, 1 fish out of 25 was weakly ISAV positive. All of the fish that were challenged with mussel homogenate prepared 96 h after accumulation were ISAV negative. Mussels sampled from a tank with experimentally infected salmon demonstrating clinical signs consistent with ISA (infectious salmon anaemia) and mussels collected on net pen cages during ISA outbreaks in Atlantic salmon were all ISAV negative. The results indicate that the ISAV is rapidly inactivated in mussels and that mussels are not a likely reservoir host or vector for ISAV.

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Fate of infectious salmon anaemia virus (ISAV) in experimentally challenged blue mussels Mytilus edulis

Skår

Mortensen

2007

“…Numerous studies have showed that bivalve molluscs can rapidly accumulate virus from contaminated water (Shieh et al 1999, Muniain-Mujika et al 2003. The most significant example may be infectious pancreatic necrosis virus (IPNV), a fish epizootic pathogen that can also be isolated from scallop Pecten maximus but which appeared to be non-pathogenic for adult scallops (Mortensen et al 1992). In our study, the newly characterized MAbs improved our ability to diagnose infections caused by AVND virus and will make further investigations on the pathogenesis of this scallop etiologic virus possible.…”

Section: Avnd Virus Tissue Distribution and Histopathological Changesmentioning

confidence: 99%

Monoclonal antibodies developed for detection of an epizootic virus associated with mass mortalities of cultured scallop Chlamys farreri

Song

Li³

2005

Recently, an enveloped, spherical RNA virus was identified as the causative agent of mass mortalities among adult scallop Chlamys farreri, which is cultured on the northern coast of China. Hybridomas were prepared from mice immunized with highly purified virions. Four stable hybridomas secreting monoclonal antibodies (MAbs) of IgG isotype were obtained after screening by means of enzyme-linked immunosorbent assay (ELISA) and immunofluorescence assay (IFA). The specificity of the MAbs to this virus was confirmed by immunogold electron microscopy (IEM). All the selected MAbs recognized epitopes on the envelope spikes of the virions. Subsequently, the MAbs were used for in situ immunofluorescent detection of the virus in Davidson's fixed tissue sections. The results showed that the fluorescent cells were mostly observed in epithelia of different organs, but not in the epithelium of the digestive diverticulae. Cytopathological changes and focal lesions corresponding to virus-positive cells were clearly recognized in the affected epithelia, revealing a potential role of this virus in pathogenesis. KEY WORDS: Scallop · Chlamys farreri · Acute virus necrobiotic disease · Monoclonal antibodies Resale or republication not permitted without written consent of the publisherDis Aquat Org 65: [17][18][19][20][21][22] 2005 mass mortalities in mid-July 2001 and 2002 from several private farms in Qingdao and Rizhao (Shandong Province of China). The gills and mantles were removed from the scallops and stored at -85°C before use. Virus purification by centrifugation was performed according to C. M. . Tissues were homogenized in 8 volumes of TEN buffer (50 mM Tris-HCl; 10 mM EDTA; 360 mM NaCl, pH 7.8) and clarified by 2 low speed centrifugations (3500 × g for 15 min followed by 7500 × g for 15 min). All centrifugations were carried out at 4°C. The supernatants were then concentrated by sedimentation through a 6 ml cushion of 35% sucrose (w/w) at 113 000 × g for 90 min and the resulting pellets were resuspended in TEN buffer. After centrifugation at 8000 × g for 20 min, supernatants were layered onto a 30 to 60% (w/w) continuous sucrose density gradient. After centrifugation at 113 000 × g for 2.5 h, the opalescent virus containing band was collected. The virus was washed with TN buffer (50 mM Tris-HCl; 360 mM NaCl, pH 7.8) and resuspended in a small amount of TN buffer. The purity was checked by a transmission electron microscope (TEM, JEOL JEM-1200) using 2% phosphotungustic acid (PTA, pH 7.0) as the negative stain. The concentration of viral proteins was determined using the procedure described by Bradford (1976).Hybridoma production. Eight week old BALB/c mice were immunized intraperitoneally (i.p.) with purified virus (100 µg mouse -1 ) mixed with an equal volume of Freund's complete adjuvant (Gibco). Subsequent boosters with antigen in incomplete adjuvant were given on Days 14, 28, and 42. Three days before cell fusion, mice received the last immunization via intrasplenic injection (20 µg mouse -1 ) with the puri...

“…For instance, blue mussels may have a beneficial effect in a net pen environment by reducing the amount of the kidney disease bacterium Renibacterium salmoninarum present (Paclibare et al 1994). Bivalves are also capable of retaining fish pathogenic viruses, but persistence periods vary greatly, presumably reflecting differences in the robustness of the viruses (Mortensen et al 1992, Skår & Mortensen 2007.…”

Section: Introductionmentioning

confidence: 99%

Fate of Francisella noatunensis, a pathogen of Atlantic cod Gadus morhua, in blue mussels Mytilus edulis

Wangen

Karlsbakk²,

Einen³

et al. 2012

Francisellosis, caused by the bacterium Francisella noatunensis, is one of the most severe diseases affecting farmed cod, and has caused great economic loss for the cod farming industry in Norway. We studied the fate of F. noatunensis in the marine environment, focusing on the role of blue mussels. In experimental challenges, waterborne F. noatunensis was rapidly filtered by the blue mussel and transported to the digestive diverticulae. The bacteria passed through the entire digestive system. Intraperitoneal injection of cod with suspensions prepared from faeces collected from challenged mussels resulted in the development of francisellosis in the recipients, demonstrating that some bacteria were alive and infective when shed in mussel faeces. Bacterial clearance from the mussels was relatively fast, and no evidence was found, suggesting that the bacterium is capable of persisting or multiplying in the mussel tissues. A cohabitation experiment with cod and mussels previously exposed to F. noatunensis did not lead to infection in cod. A direct transmission from contaminated mussels to cod was thus not demonstrated; however, faeces particles with infective bacteria may play a role in the transmission of the bacterium in marine food chains.