A fast and reliable molecular method to detect Anisakidae in zooplanktonic Euphausiacea.

Anisakidae is a family of marine nematodes, largely monitored in fish and cephalopods due to their zoonotic risk for human consumers. However, there is a need to further study the ecology of this family to better predict infection dynamics, particularly as global change affects marine ecosystem functioning generally, and specifically Anisakidae behaviour and infection levels, in line with the principles of the One Health approach. However, in-depth studies are hampered by technical difficulties in collecting data on members of the cycle that are not consumed by humans, namely zooplankton. This results in a glaring imbalance in terms of available data between fish and cephalopods on the one hand, and zooplankton on the other. Development of robust, rapid, and efficient methods for the detection of Anisakidae in zooplankton is therefore needed. Euphausiacea is considered to be the major zooplanktonic group hosting Anisakidae larvae. We therefore calibrated a PCR technique followed by Sanger sequencing to determine the presence of Anisakidae larvae in zooplanktonic Euphausiacea from the North Sea. This calibration was based in particular on the creation of artificially infested zooplanktonic samples, on which several molecular methods have been tested. When calibrated, we then applied this method to a small set of zooplanktonic samples and performed a preliminary parasitological survey. Prevalence values were higher (2.5% to 4.5%) than those reported in the literature, either due to the increased sensitivity of the molecular method and/or to changes in ecosystem functioning. This method has clear potential to push forward an integrated understanding of Anisakidae infection in zooplankton.