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Diseases of Aquatic Organisms

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DAO 140:55-72 (2020)  -  DOI:

Atlantic salmon Salmo salar and ballan wrasse Labrus bergylta display different susceptibility to clonal strains of Paramoeba perurans

O. M. V. Dahle1,5, S. H. Blindheim1,6, A. Nylund1, E. Karlsbakk1,2, O. Breck3,7, H. Glosvik3,5, L. Andersen4,*

1Department of Biology, University of Bergen, 5020 Bergen, Norway
2Institute of Marine Research, 5817 Nordnes, Bergen, Norway
3Marine Harvest ASA, 5835 Sandviken, Bergen, Norway
4The Aquatic and Industrial Laboratory (ILAB), 5006 Bergen, Norway
5Present address: Mowi ASA, Sandviksbodene 77, 5035 Bergen, Norway
6Present address: The Aquatic and Industrial Laboratory (ILAB), 5006 Bergen, Norway
7Present address: Norwegian Food Safety Authority, 5006 Bergen, Norway
*Corresponding author:

ABSTRACT: Amoebic gill disease (AGD), caused by the marine amoeba Paramoeba perurans, is an important disease of farmed Atlantic salmon Salmo salar L. in Norway. The use of wrasse as cleaner fish in salmon net pens raises questions about interspecies transmission of pathogens such as P. perurans. In this study, cohabitant transmission of clonal isolates of P. perurans between Atlantic salmon and ballan wrasse Labrus bergylta Ascanius was examined, using isolates originating from both salmon and wrasse. The challenges resulted in AGD in both species, although less severely in wrasse. The amoeba isolate originating from ballan wrasse was more virulent than that originating from salmon, suggesting P. perurans strain-related virulence differences. The isolate originating from salmon showed limited proliferation in bath-challenged wrasse and salmon, and limited transfer to cohabitants. Our results support previous observations suggesting that salmon may be more susceptible to P. perurans and AGD than ballan wrasse. Treatment of P. perurans infection in wrasse is challenging, as it is a strictly marine fish species. In this study, brackish water (<15‰ seawater) treatment of AGD affected salmon and wrasse was examined. Both salmon and wrasse were treated for short periods (3 h and 24 h), and treatment of wrasse over longer periods (3-5 d) was also examined. Short exposure to brackish water was not enough to remove P. perurans, although the 24 h treatment reduced amoeba levels. It was not possible to culture or detect P. perurans from wrasse exposed to brackish water for 3 d, suggesting that this treatment would be effective in controlling the parasite.

KEY WORDS: Virulence · Neoparamoeba perurans · Susceptibility · Cleaner fish · Cohabitant transmission · Amoebic gill disease · AGD

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Cite this article as: Dahle OMV, Blindheim SH, Nylund A, Karlsbakk E, Breck O, Glosvik H, Andersen L (2020) Atlantic salmon Salmo salar and ballan wrasse Labrus bergylta display different susceptibility to clonal strains of Paramoeba perurans. Dis Aquat Org 140:55-72.

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