animals Article Experimental Horizontal Transmission of Enterospora nucleophila (Microsporea: Enterocytozoonidae) in Gilthead Sea Bream (Sparus aurata) Amparo Picard-Sánchez 1, M. Carla Piazzon 1 , Itziar Estensoro 1 , Raquel Del Pozo 1, Nahla Hossameldin Ahmed 2 , Oswaldo Palenzuela 1 and Ariadna Sitjà-Bobadilla 1,* 1 Fish Pathology Group, Instituto de Acuicultura Torre de la Sal (IATS-CSIC), 12595 Ribera de Cabanes, Spain;
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[email protected]; Tel.: +34-964319500 Simple Summary: Enterospora nucleophila is a microsporidian parasite infecting gilthead sea bream (Sparus aurata) that has been associated with increased mortality, growth arrestment and emaciation in aquaculture settings. The investigations on this parasite depend on material from spontaneous outbreaks in fish farms, which hampers advancements in infection research and control. In the present study, different ways of horizontal transmission were performed in order to establish an in vivo transmission model. Parasite transmission was achieved with all the assayed routes, but with milder clinical signs than in natural infections. Citation: Picard-Sánchez, A.; Piazzon, M.C.; Estensoro, I.; Del Pozo, Abstract: Enterospora nucleophila is a microsporidian enteroparasite that infects mainly the intestine R.; Hossameldin Ahmed, N.; of gilthead sea bream (Sparus aurata), leading to an emaciative syndrome. Thus far, the only available Palenzuela, O.; Sitjà-Bobadilla, A. information about this infection comes from natural outbreaks in farmed fish.