DAO 55:175-185 (2003)  -  doi:10.3354/dao055175

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

Ryan M. Troyer1,2,3, Gael Kurath1,2,*

1Department of Pathobiology, University of Washington, Seattle, Washington 98195, USA
2Western Fisheries Research Center, United States Geological Survey, Biological Resources Division, 6505 NE 65th St., Seattle, Washington 98115, USA
3Present address: Division of Infectious Diseases, Case Western Reserve University, Cleveland, Ohio 44118, USA
*Corresponding author. Email:

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 · Rhabdovirus

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