Molecular epidemiology of infectious hematopoietic necrosis virus reveals complex virus traffic and evolution within southern Idaho aquaculture

Abstract

Infectious hematopoietic necrosis virus (IHNV) is a rhabdovirus which infects salmon and trout and may cause disease with up to 90% mortality. In the Hagerman Valley of Idaho, IHNV is endemic or epidemic among numerous fish farms and resource mitigation hatcheries. A previous study characterizing the genetic diversity among 84 IHNV isolates at 4 virus-endemic rainbow trout farms indicated that multiple lineages of relatively high diversity co-circulated at these facilities (Troyer et al. 2000 J Gen Virol. 81:2823-2832. We tested the hypothesis that high IHNV genetic diversity and co-circulating lineages are present in aquaculture facilities throughout this region. In this study, 73 virus isolates from 14 rainbow trout farms and 3 state hatcheries in the Hagerman Valley, isolated between 1978 and 1999, were genetically characterized by sequence analysis of a 303 nucleotide region of the glycoprotein gene. Phylogenetic and epidemiological analyses showed that multiple IHNV lineages co-circulate in a complex pattern throughout private trout farms and state hatcheries in the valley. IHNV maintained within the valley appears to have evolved significantly over the 22 yr study period. KEY WORDS: IHNV · Molecular epidemiology · Virus evolution · Fish virus · Idaho trout · RhabdovirusResale or republication not permitted without written consent of the publisher Dis Aquat Org 55: [175][176][177][178][179][180][181][182][183][184][185] 2003 ase (RNase) protection assay and direct nucleotide sequencing (Anderson et al. 2000, Troyer et al. 2000, Emmenegger & Kurath 2002. Collectively, these studies support the hypothesis that IHNV strain-relatedness generally correlates with geography rather than host species or temporal factors.The state of Idaho accounts for 75% of U.S. foodsize trout production 1 . The majority of this industry is located along a stretch of the Snake River in southcentral Idaho associated with an abundance of water flowing from the Eastern Snake River Aquifer through numerous natural springs. For the purposes of simplicity and clarity, this region of intensive Oncorhynchus mykiss (rainbow trout) aquaculture, encompassing the Twin Falls to Hagerman reach of the mid-Snake River from river mile 610 to river mile 569, is referred to in this study as the 'Hagerman Valley,' although it exceeds the technical boundaries of what is commonly known as the Hagerman Valley. Rainbow trout have been farmed continuously in this region since 1928, and the area also has federal and state hatcheries that primarily raise rainbow trout and steelhead trout (Brannon & Klontz 1989). Currently there are 3 state fish hatcheries, 1 national fish hatchery, and approximately 100 trout farms of various sizes (G. Fornshell, University of Idaho Extension, pers. comm.). These facilities are served by a variety of water sources which include: first-use spring water piped directly to the facility, first-use spring water channeled via unprotected waterway, and surface water with previous uses (such as irrigation or fish culture...

Genotyping of Korean isolates of infectious hematopoietic necrosis virus (IHNV) based on the glycoprotein gene

“…The IHNV genome is a non-segmented and single-stranded negative-sense RNA with approximately 11,000 nucleotides containing six genes in the order 3'-N-P-M-G-NV-L-5' encoding the nucleocapsid protein (N), phosphoprotein (P), matrix protein (M), glycoprotein (G), non-virion protein (NV) and polymerase (L) genes, respectively [6,9]. The G, N and NV genes have been used for analyses of IHNV evolution, diversity and phylogenetic relationship among the worldwide isolates [1,3,7,10,11,16,17].…”

“Mid-G” Region Sequences of the Glycoprotein Gene of Austrian Infectious Hematopoietic Necrosis Virus Isolates Form Two Lineages within European Isolates and Are Distinct from American and Asian Lineages

“…Genetic analysis and phylogenetic studies of IHN viruses have previously been performed mostly on American fish samples; only a few Asian or European IHNV isolates have been investigated thus far (14,15,19,22,34,38,39,46,47). These analyses exhibited surprisingly low genetic diversity within the IHNV G genes.…”

A Review of Three Members of the Rhabdovirus Group

“…First, individuals who are infected with rabies experience 2-7 days of a non-specific, flu-like prodrome [1,3,4]. The prodrome is followed by behavioral abnormalities such as anxiety, depression, hyperactivity, and aggression [12]. Next, the unusual symptoms of intolerance of tactile, auditory, and visual stimuli begin.…”

“…Infection can also be controlled by low levels of iodine, 0.1 mg/liter. This effect decreased above pH 7.5 [8,11,12].…”