Inter-Research > DAO > v38 > n3 > p169-175  

DAO 38:169-175 (1999)  -  doi:10.3354/dao038169

Pathogenicity of nodavirus strains from striped jack Pseudocaranx dentex and Atlantic halibut Hippoglossus hippoglossus, studied by waterborne challenge of yolk-sac larvae of both teleost species

Geir K. Totland1,*, Sindre Grotmol2, Yuseku Morita3, Toyohiro Nishioka4, Toshihiro Nakai3

1Department of Zoology, University of Bergen, Allégt. 41, 5007 Bergen, Norway
2Department of Aquaculture, Institute of Marine Research, PO Box 1870 Nordnes, 5024 Bergen, Norway
3Fish Pathology Laboratory, Faculty of Applied Biological Science, Hiroshima University, Higashihiroshima 739, Japan
4Goto Station of Japan Sea-Farming Association, Tamanoura, Nagasaki 0853-0501, Japan

ABSTRACT: The present study shows that differences in pathogenicity exist among fish nodavirus strains. In challenge trials, a Japanese strain (SJ93Nag) was highly virulent to larvae of the striped jack Pseudocaranx dentex but replication was not detected in larvae of Atlantic halibut Hippoglossus hippoglossus at 6°C. Conversely, a Norwegian nodavirus strain (AH95NorA) that was highly virulent to the Atlantic halibut larvae did not replicate in striped jack larvae at 20°C. Occurrence of the disease viral encephalopathy and retinopathy (VER) and cumulative mortality were significantly different in the 2 species when challenged with the 2 nodavirus strains. The presence of nodavirus in nervous tissue was monitored by immunohistochemical methods. Our results support the view that the genetic diversity among nodavirus strains reflects the existence of different viral phenotypes which may be adapted to infect different host species and/or for replicating at different temperatures. Fish nodaviruses represent surveyable pathogens well suited for studying the relation between viral genotypic and phenotypic properties such as host specificity, temperature optima, neuroinvasiveness and neurovirulence.

KEY WORDS: Striped jack · Atlantic halibut · Fish nodavirus · Pathogenicity · Virulence · Host specificity · Immunohistochemistry

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