Towards an in-situ non-lethal rapid test to accurately detect the presence of the nematode parasite, Anguillicoloides crassus, in European eel, Anguilla anguilla

• Published in: Parasitology
• Main Authors: De Noia, M, Poole, R., Kaufmann, Joshka, Waters, C., Adams, C., McGinnity, Philip, Llewellyn, M.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press 2022
• Subjects: Non-lethal test; Fish parasite; Genetic; eDNA; Anguilla anguilla; European eel
• Online Access: http://hdl.handle.net/10468/12468; https://doi.org/10.1017/S0031182021002146

Anguillicoloides crassus is an invasive nematode parasite of the critically endangered European eel, Anguilla anguilla, and possibly one of the primary drivers of eel population collapse. The presence of the parasite has been shown to impact many features of eel physiology and life history. Early detection of the parasite is vital to limit the spread of A. crassus, and to assess its potential impact on spawning biomass. However, until recently, accurate diagnosis of infection could only be achieved via necropsy. To support A. anguilla fisheries management in the context of A. crassus we developed a rapid, non-lethal, minimally invasive and in-situ DNA-based method to infer the presence of the parasite in the swim bladder. Screening of 131 wild eels was undertaken between 2017 and 2019 in Ireland and UK to validate the procedure. DNA extractions and PCR were conducted using both a Qiagen Stool kit at Glasgow University and in situ using Whatman qualitative filter paper No. 1 and a miniPCR DNA Discovery System™. Primers were specifically designed to target the cytochrome oxidase mtDNA gene region and in situ extraction and amplification takes approximately 3h for up to 16 individuals. Our in situ diagnostic procedure demonstrated Positive Predictive Values at 96% and Negative Predictive Values at 87% by comparison to necropsy data. Our method could be a valuable tool in the hands of fisheries managers to enable infection control and help protect this iconic but critically endangered species.