The endoparasite Perkinsus olseni affecting the Mediterranean mussels (Mytilus galloprovincialis) in the Italian and Spanish waters: A new possible threat for mussel aquaculture and wild animal population

Dinoflagellates belonging to the Perkinsus genus are OIE (World Organization for animal Health)-listed pathogens extremely virulent clams and oysters in many marine ecosystems throughout world. During monitoring activities of Mediterranean mussel ( Mytilus galloprovincialis ) Campania region (Italy), presence typical trophozoites sp. was observed mussels from farms natural banks. Simultaneously, following mortality Spanish waters Catalonia, histopathological studies revealed same parasite. Although perkinsosis is an endemic disease Italy (with prevalence 40 80%), there no reports date its effect on this species. For study, histopathology, Ray’s Fluid Thioglycollate Medium (RFTM), molecular diagnostics with conventional Polimerase Chain Reaction (PCR) qPCR were performed. In samples Italy, histopathology one farm a 26% February 2019, 40% 2020, 16% November 23% April 2021. bank, also detected May 2020 but lower prevalence. Spain, July parasite 20% site 10% second related mortality. both areas, elicited multiple inflammatory capsules different size or infiltrates at level digestive gland gonad. Molecular Internal Transcriber Spacer (ITS) rDNA (ITS1, 5.8S, ITS2) showed 97% similarity P. olseni New Zealand, Australia, Uruguay bivalves such as Pitar rostrata , Astrovenus sp., Haliotis whereas Spain identity 99% South Korean venerids Anadara granosa . Phylogenetic analysis group together Italian place them distant other described Europe (Italy, France, Spain). Direct impact transboundary diseases aquaculture constitutes serious consequence export living animals their products, well international trade. This compromises food security, causing high socioeconomic exporting nations. generalist pathogen able infect bivalve species, possibly passing mussels. Recognized organizations should take into account view possible cross-infection. Other needed define virulence