Experimental susceptibility of European sea bass and Senegalese sole to different betanodavirus isolates S. Souto a,2, *, B. Lopez-Jimena b,1,2 , M.C. Alonso c , E. Garcı ´a-Rosado c , I. Bandı ´n a a Universidad de Santiago de Compostela, Instituto de Acuicultura, Constantino Candeira C.P.: 15705, Santiago de Compostela, A Corun ˜a, Spain b IFAPA Centro El Torun ˜o, Junta de Andalucı´a, Ctra N.IV, Camino de Tiro Picho ´n, C.P.: 11.500, El Puerto de Santa Marı´a, Ca ´diz, Spain c Universidad de Ma ´laga, Departamento de Microbiologı´a, Facultad de Ciencias, Campus de Teatinos, 29.071 Ma ´laga, Spain 1. Introduction Viral nervous necrosis (VNN), or viral encephalopathy and retinopathy (VER), is a serious emerging disease affecting a wide range of marine farmed and wild fish species (Munday et al., 2002), freshwater fish (Maltese and Bovo, 2007; Bigarre ´ et al., 2009; Vendramin et al., 2012), and invertebrates (Gomez et al., 2006) worldwide. The etiological agent is the viral nervous necrosis virus (VNNV, Betanodavirus genus, Nodaviridae family), which is responsible for high mortalities, particularly in larvae and juveniles, with deleterious economic consequences in the aquaculture industry. Affected fish display lesions in retina, brain and spinal cord. The clinical signs associated to this pathology include abnormal swimming, loss of appetite, changes in pigmentation and hyperinflation of Veterinary Microbiology xxx (2015) xxx–xxx A R T I C L E I N F O Article history: Received 6 November 2014 Received in revised form 18 February 2015 Accepted 23 February 2015 Keywords: Betanodavirus Genotypes Natural reassortant Experimental infection European sea bass Senegalese sole A B S T R A C T The susceptibility of juvenile European sea bass and Senegalese sole to three VNNV isolates (a reassortant RGNNV/SJNNV, as well as the parental RGNNV and SJNNV genotypes) has been evaluated by challenges using two inoculation ways (bath and intramuscular injection). The results demonstrate that these two fish species are susceptible to all the VNNV isolates tested. In European sea bass, RGNNV caused the highest cumulative mortality, reaching maximum values of viral RNA and titres. Although the SJNNV isolate did not provoke mortality or clinical signs of disease in this fish species, viral production in survivor fish was determined; on the other hand the reassortant isolate did cause mortality and clinical signs of disease, although less evident than those recorded after RGNNV infection. These results suggest that the changes suffered by the SJNNV RNA2 segment of the reassortant isolate, compared to the parental SJNNV, may have involved host-specificity and/or virulence determinants for European sea bass. Regarding Senegalese sole, although the three isolates caused 100% mortality, the reassortant strain provoked the most acute symptoms, and more quickly, especially in the bath challenge. This was also the isolate showing less difference between the number of RNA copies and viral titre, reaching the highest titres of infective viral particles in nervous tissue of infected animals. The RGNNV isolate produced the lowest values of infective viral particles. All these results suggest that the RGNNV and the reassortant isolates are the most suited for infecting European sea bass and Senegalese sole, respectively. ß 2015 Elsevier B.V. All rights reserved. * Corresponding author at: Instituto de acuicultura, C/ Costantino Candeira Bloque C 15705, Santiago de Compostela, A Corun ˜a, Spain. Tel.: +34 881 816 091/087. E-mail address: sandra.souto@usc.es (S. Souto). 1 Current address: Institute of Aquaculture, University of Stirling, FK9 4LA, Scotland, United Kingdom. 2 These authors contributed equally to this work. G Model VETMIC-6917; No. of Pages 9 Please cite this article in press as: Souto, S., et al., Experimental susceptibility of European sea bass and Senegalese sole to different betanodavirus isolates. Vet. Microbiol. (2015), http://dx.doi.org/10.1016/j.vetmic.2015.02.030 Contents lists available at ScienceDirect Veterinary Microbiology jo u rn al ho m epag e: ww w.els evier.c o m/lo cat e/vetmic http://dx.doi.org/10.1016/j.vetmic.2015.02.030 0378-1135/ß 2015 Elsevier B.V. All rights reserved.