A mortality event primarily affecting freshwater drum Aplodinotus grunniens was noted during April and May 2005 in the Bay of Quinte, Lake Ontario, Canada. A conservative estimate of the number of dead drum was approximately 100 metric tonnes. Large numbers of dead round goby Neogobius melanostomus were also seen, as well as a few muskellunge Esox masquinongy. In the drum, there was a consistent histological pattern of variably severe panvasculitis, a necrotising myocarditis, meningoencephalitis and a segmental enteritis. Moderate numbers of bullet-shaped viral particles consistent with a rhabdovirus were identified by transmission electron microscopy (TEM) in affected heart tissue. Following primary isolation from pooled tissues on fathead minnow (FHM) cells, a morphologically similar virus, ~165 × 60 nm in size, was visualised. Identification of the isolate as viral haemorrhagic septicemia virus (VHSV) was confirmed by enzyme immunoassay and by polymerase chain reaction. An appropriately sized product (468 bp) of the G-glycoprotein gene (nucleotides [nt] 340 to 807) was generated with RNA extracted from FHM cell supernatant. Analysis of a 360 nt partial glycoprotein gene sequence (nt 360 to 720) indicated a 96.4 to 97.2% nucleotide identity with known strains of North American (NA) VHSV. Analysis using Neighbour-joining distance methods assigned the isolate to the same lineage as the NA and Japanese isolates (Genogroup IV). However, there was sufficient sequence divergence from known NA VHSV isolates to suggest that this isolate may represent a distinct subgroup. The effects of ongoing mortality in freshwater drum and in multiple species during spring 2006 suggest that this newly recognised virus in the Great Lakes will have continued impact in the near future. KEY WORDS: Freshwater drum · Aplodinotus grunniens · Viral haemorrhagic septicemia virus · VHSV · Genogroup IV · Vasculitis · Meningoencephalitis · Necrotising myocarditis · EnteritisResale or republication not permitted without written consent of the publisher Dis Aquat Org 76: [99][100][101][102][103][104][105][106][107][108][109][110][111] 2007 Nishiziwa et al. 2002). In NA, a VHSV Genogroup IV was first isolated from returning Chinook Oncorhynchus tshawytscha and coho O. kisutch salmon (Brunson et al. 1989, Hopper 1989, Winton et al. 1989) and subsequently has been isolated on numerous occasions from a variety of apparently normal marine fish (Meyers & Winton 1995). Epizootics have been described in herring Clupea pallasi, hake Merluccius productus and pollock Theragra chalcogramma in Alaska (Meyers et al. 1999), as well as herring C. pallasi, pilchards Sardinops sagax and black cod Anoplopoma fimbria in British Columbia (Traxler et al. 1999). Subsequent surveillance has documented the species and geographical range extensions in healthy fish in Pacific coastal waters (Hedrick et al. 2003). It has been proposed that VHSV has likely been historically present in Pacific NA marine waters and may have been involved in epizootics in Pacifi...

Viral haemorrhagic septicaemia virus (VHSV) in the Great Lakes has had a dramatic impact on fish husbandry because of the implications of the presence of a reportable disease. Experimental infections with VHSV IVb were conducted in rainbow trout, Oncorhynchus mykiss (Walbaum), and fathead minnows, Pimphales promelas (Rafinesque), to examine their susceptibility and the clinical impact of infection. Triplicate groups of rainbow trout (n = 40) were injected intraperitoneally (i.p.) with 100 microL 10(6.5)50% tissue culture infective doses (TCID(50)) or waterborne exposed to graded doses (10(4.5), 10(6.5), and 10(8.5) TCID(50) mL(-1)) of VHSV IVb. Duplicate groups of fathead minnows (n = 15) were i.p. injected with (10(6.5) TCID(50) 100 microL) or waterborne exposed (10(6.5) TCID(50) mL(-1)). All experiments were performed with single-pass well water maintained at 12 degrees C. Following either i.p. or waterborne exposure, VHSV RNA was detectable in both rainbow trout and fathead minnows by nested reverse transcription polymerase chain reaction (nRT-PCR) as early as 4-7 days post-infection (p.i.). Infected fathead minnow and rainbow trout exhibited lesions characteristic of VHS at 9 and 15 days p.i., respectively. Route of exposure had little effect on the onset of clinical signs. Cumulative mean mortality in rainbow trout was 4.4%, 2.6%, 2.6% and less than 1% in the i.p., high, medium and low dose waterborne exposures, respectively. Cumulative average mortality of 50% and 13% occurred in i.p. and waterborne-exposed fathead minnows, respectively. VHSV was detected from pooled rainbow trout tissue by RT-PCR and virus isolation at 38 days p.i., but not at 74 days p.i., regardless of the exposure route. Immunohistochemistry (IHC) with a rabbit antibody to VHSV IVb revealed the viral tissue tropisms following infection, with the identification of viral antigen in myocardium and necrotic branchial epithelium of both species and in gonadal tissue of fathead minnows. Rainbow trout, but not fathead minnows, are relatively refractory to experimental infection with VHSV IVb.

ABSTRACT:Koi herpesvirus (KHV) was identified as being associated with more than one mortality event affecting common carp in Canada. The first was an extensive mortality event that occurred in 2007 in the Kawartha Lakes region, Ontario, affecting Lakes Scugog and Pigeon. Fish had branchial necrosis and hepatic vasculitis with an equivocal interstitial nephritis. Several fish also had branchial columnaris. Subsequent mortality events occurred in 2008 in additional bodies of water in south-central Ontario, such as Lake Katchewanooka and outside of Ontario in Lake Manitoba, Manitoba. Koi herpesvirus was detected in fish submitted for examination from all of these lakes by polymerase chain reaction (PCR), and sequence of the PCR product revealed 100% homology to KHV strains U and I. Real-time PCR analysis of KHV-infected wild carp revealed viral loads ranging from 6.02310 1 to 2.4310 6 copies mg 21 host DNA. This is the first report of KHV in Canada.

Seahorses, pipefish and seadragons are fish of the Family Syngnathidae. From 1998 to 2010, 172 syngnathid cases from the Toronto Zoo were submitted for post-mortem diagnostics and retrospectively examined. Among the submitted species were yellow seahorses Hippocampus kuda Bleeker (n=133), pot-bellied seahorses Hippocampus abdominalis Lesson (n=35) and weedy seadragons Phyllopteryx taeniolatus (Lacépède; n=4). The three most common causes of morbidity and mortality in this population were bacterial dermatitis, bilaterally symmetrical myopathy and mycobacteriosis, accounting for 24%, 17% and 15% of cases, respectively. Inflammatory processes were the most common diagnoses, present in 117 cases. Seven neoplasms were diagnosed, environmental aetiologies were identified in 46 cases, and two congenital defects were identified.

A novel viral hemorrhagic septicemia virus (VHSV) (genotype IVb) has been isolated from mortality events in a range of wild freshwater fish from the Great Lakes since 2005. In 2005 and 2006, numerous new freshwater host species (~90 fish from 12 different species) were confirmed to have VHSV by cell culture and reverse transcriptase polymerase chain reaction. A prominent feature observed in infected fish were the petechial and ecchymotic haemorrhages on the body surface and in visceral organs, as well as serosanguinous ascites; however, many fish had few and subtle, gross lesions. Histologically, virtually all fish had a vasculitis and multifocal necrosis of numerous tissues. Excellent correlation was found between the presence of VHSV IVb antigen detected by immunohistochemistry and the pathological changes noted by light microscopy. Intact and degenerate leukocytes, including cells resembling lymphocytes and macrophages, also had cytoplasmic viral antigen. By contrast, renal tubules and gonadal tissues (ovary and testis), were strongly immunopositive for VHSV IVb, but no lesions were noted.