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Diseases of Aquatic Organisms

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DAO 66:187-195 (2005)  -  doi:10.3354/dao066187

Infectious hematopoietic necrosis virus: monophyletic origin of European isolates from North American Genogroup M

P. J. Enzmann1,*, G. Kurath2, D. Fichtner3, S. M. Bergmann3

1Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Paul-Ehrlich-Straße 28, 72076 Tübingen, Germany
2Western Fisheries Research Center, Biological Resources Division, US Geological Survey, 6505 NE 65th Street, Seattle, Washington 98115, USA
3Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Boddenblick 5a, 17493 Insel Riems, Germany

ABSTRACT: Infectious hematopoietic necrosis virus (IHNV) was first detected in Europe in 1987 in France and Italy, and later, in 1992, in Germany. The source of the virus and the route of introduction are unknown. The present study investigates the molecular epidemiology of IHNV outbreaks in Germany since its first introduction. The complete nucleotide sequences of the glycoprotein (G) and non-virion (NV) genes from 9 IHNV isolates from Germany have been determined, and this has allowed the identification of characteristic differences between these isolates. Phylogenetic analysis of partial G gene sequences (mid-G, 303 nucleotides) from North American IHNV isolates (Kurath et al. 2003) has revealed 3 major genogroups, designated U, M and L. Using this gene region with 2 different North American IHNV data sets, it was possible to group the European IHNV strains within the M genogroup, but not in any previously defined subgroup. Analysis of the full length G gene sequences indicated that an independent evolution of IHN viruses had occurred in Europe. IHN viruses in Europe seem to be of a monophyletic origin, again most closely related to North American isolates in the M genogroup. Analysis of the NV gene sequences also showed the European isolates to be monophyletic, but resolution of the 3 genogroups was poor with this gene region. As a result of comparative sequence analyses, several different genotypes have been identified circulating in Europe.

KEY WORDS: Infectious hematopoietic necrosis virus · European strains · Molecular epidemiology · IHNV groups

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