DAO 117:187-195 (2016)  -  DOI: https://doi.org/10.3354/dao02946

Sublethal concentrations of ichthyotoxic alga Prymnesium parvum affect rainbow trout susceptibility to viral haemorrhagic septicaemia virus

Nikolaj Gedsted Andersen1,*, Ellen Lorenzen2, Torsten Snogdal Boutrup3, Per Juel Hansen1, Niels Lorenzen

1Marine Biological Section, University of Copenhagen, Strandpromenaden 5, 3000 Helsingør, Denmark
2Department of Animal Science, Aarhus University, Blichers Allé 20, 8830 Tjele, Denmark
3National Veterinary Institute, Technical University of Denmark, Bülowsvej 27, 1870 Fredriksberg C, Denmark
*Corresponding author:

ABSTRACT: Ichthyotoxic algal blooms are normally considered a threat to maricultured fish only when blooms reach lethal cell concentrations. The degree to which sublethal algal concentrations challenge the health of the fish during blooms is practically unknown. In this study, we analysed whether sublethal concentrations of the ichthyotoxic alga Prymnesium parvum affect the susceptibility of rainbow trout Oncorhynchus mykiss to viral haemorrhagic septicaemia virus (VHSV). During exposure to sublethal algal concentrations, the fish increased production of mucus on their gills. When fish were exposed to the algae for 12 h prior to the addition of virus, a marginal decrease in the susceptibility to VHSV was observed compared to fish exposed to VHSV without algae. If virus and algae were added simultaneously, inclusion of the algae increased mortality by 50% compared to fish exposed to virus only, depending on the experimental setup. We concluded that depending on the local exposure conditions, sublethal concentrations of P. parvum could affect susceptibility of fish to infectious agents such as VHSV.


KEY WORDS: Viral haemorrhagic septicaemia virus · VHSV · Oncorhynchus mykiss · Fish disease · Harmful algal blooms · Susceptibility


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Cite this article as: Andersen NG, Lorenzen E, Snogdal Boutrup T, Hansen PJ, Lorenzen N (2016) Sublethal concentrations of ichthyotoxic alga Prymnesium parvum affect rainbow trout susceptibility to viral haemorrhagic septicaemia virus. Dis Aquat Org 117:187-195. https://doi.org/10.3354/dao02946

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