Fish Pathology Laboratory, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada.
J Fish Dis. 2010 Apr;33(4):347-60. doi: 10.1111/j.1365-2761.2009.01128.x. Epub 2010 Feb 10.
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.
病毒性出血性败血症病毒（VHSV）在大湖地区对鱼类养殖业产生了巨大影响，因为这种报告疾病的存在意味着存在风险。在虹鳟鱼（Oncorhynchus mykiss（Walbaum））和褐鳟鱼（Pimphales promelas（Rafinesque））中进行了 VHSV IVb 的实验感染，以研究它们的易感性和感染的临床影响。三组虹鳟鱼（n = 40）分别经腹腔内（i.p.）注射 100μL 10（6.5）50%组织培养感染剂量（TCID（50））或水暴露于不同剂量（10（4.5）、10（6.5）和 10（8.5）TCID（50）mL（-1））的 VHSV IVb。两组褐鳟鱼（n = 15）分别经腹腔内注射（10（6.5）TCID（50）100μL）或水暴露（10（6.5）TCID（50）mL（-1））。所有实验均使用单通道井水在 12°C 下进行。经腹腔内或水暴露后，通过巢式逆转录聚合酶链反应（nRT-PCR）可早在感染后 4-7 天就检测到虹鳟鱼和褐鳟鱼中的 VHSV RNA。感染的褐鳟鱼和虹鳟鱼在感染后 9 天和 15 天分别表现出 VHS 的特征性病变。感染途径对临床症状的出现影响不大。虹鳟鱼的累积平均死亡率分别为 4.4%、2.6%、2.6%和低于 1%，在腹腔内、高剂量、中剂量和低剂量水暴露组分别为 2.6%和低于 1%。腹腔内和水暴露的褐鳟鱼的累积平均死亡率分别为 50%和 13%。通过 RT-PCR 和病毒分离从虹鳟鱼组织中检测到 VHSV，在感染后 38 天，但不在 74 天，无论暴露途径如何。用针对 VHSV IVb 的兔抗体进行免疫组织化学（IHC）显示了感染后的病毒组织嗜性，在两种鱼类的心肌和坏死的鳃上皮组织以及褐鳟鱼的性腺组织中都鉴定出了病毒抗原。虹鳟鱼对 VHSV IVb 的实验感染相对具有抗性，但褐鳟鱼没有。
