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Species-specific Real Time-PCR primers/probe systems to identify fish parasites of the genera Anisakis, Pseudoterranova and Hysterothylacium (Nematoda: Ascaridoidea)

Paoletti, Michela, Mattiucci, Simonetta, Colantoni, Alessandra, Levsen, Arne, Gay, Melanie, Nascetti, Giuseppe
Fisheries research 2018 v.202 pp. 38-48
Anisakis, Crustacea, Hysterothylacium aduncum, Pseudoterranova, applied research, biological hazards, definitive hosts, detection limit, etiological agents, fish, fish processing plants, food industry, genes, human diseases, krill, larvae, marine mammals, markets, mitochondrial DNA, mixed infection, parasites, paratenic hosts, quantitative polymerase chain reaction, reverse transcriptase polymerase chain reaction, seafoods, squid
Ascaridoid nematodes belonging to the genera Anisakis and Pseudoterranova are heteroxenous parasites, involving marine mammals as definitive hosts in their life-cycles, whereas crustaceans (krill), fish and squids acting as intermediate/paratenic hosts. These parasites are considered among the most important biological hazards present in “seafood” products. Indeed, larval stages of the Anisakis and Pseudoterranova have been reported as etiological agents of human infections (anisakidosis). We developed a primers/probe system for the identification of five species of anisakid nematodes belonging to the genera Anisakis (i.e. A. pegreffii and A. simplex (s. s.)), and Pseudoterranova (i.e. P. decipiens (s. s.), P. krabbei and P. bulbosa) to be used in a real time polymerase chain reaction (RT-PCR) with specific primers based on the mtDNA cox2 gene. Because those anisakid species could be also found in co-infection in some fish species with the raphidascarid nematode Hysterothylacium aduncum, a species-specific primer probe system to be used in RT-PCR for this nematode species was also developed.The detection limit and specificity of the primer/probe systems were evaluated for each of the six nematode species. Singleplex and multiplex RT-PCR protocols were defined and tested. The detection limit of the nematode species tissue was lower than 0.0006ng/μl. Efficiency (E) of primers/probe systems developed was carried out by standard curve; E value varied between 2.015 and 2.11, with respect to a perfect reaction efficiency value of E=2. Considering the sensibility and quantitative nature of the assays, the new primers/probe system may represent a useful tool for future basic and applied research that focuses on the identification of Anisakis spp., Pseudoterranova spp. and H. aduncum larvae in fish, even in co-infections, with a potential for application in fish farming, fish processing industries, fish markets, and food producers.