New advances in molecular epidemiology of emerging enteric parasites in farmed gilthead sea bream (Sparus aurata) and insights into zoonotic parasites of new relevance in Italian freshwater fish

Fish products are essential to the food and economic security for almost a billion people around the world. Parasitic diseases outbreaks are a major concern for aquaculture and fishery industries, and they may represent a major constraint for sectors’ expansion. Fish-borne parasitic zoonoses due to the consumption of fishery products are an increasing phenomenon in European Countries. This work maps the available information on Enterospora nucleophila and Cryptosporidium molnari presence in gilthead sea bream Mediterranean aquaculture. The existing diagnostic techniques for the detection of E. nucleophila and C. molnari were reviewed and a new in situ hybridization assay for the detection of E. nucleophila developmental stages is provided. Data from a survey involving 17 gilthead sea bream facilities showed a wide distribution pattern of E. nucleophila and C. molnari, with their detection in 41% and 47% farms, respectively. Data also showed a non-homogeneous distribution within different production phases and type of facilities. Parasites were mainly detected in post-weaning production phases, with higher detection of E. nucleophila at ongrowing in-land and cage-based rearing systems, and higher positivity percentages of C. molnari at pre-growing and in-land tanks. The absence of positivity at early production stages including eggs led to consider vertical transmission unlikely and to confirm the role of water in transmitting the infection. This work aimed at shedding light on emerging zoonotic parasites in European freshwater fishery products. This work provided consistent information on Eustrongylides excisus epidemiology in Central Italy lakes and confirmed the presence of infective stages in freshwater fish. A molecular assay for the identification of adult and larval stages of E. excisus is reported. A novel multiplex PCR assay for the simultaneous identification of Opisthorchis felineus, Pseudamphistomum truncatum, Metorchis spp., Metagonimus spp. and Apophallus spp., the main zoonotic or potentially zoonotic trematodes described in Europe, is also provided.