Identification of larval Anisakis spp. (Nematoda: Anisakidae) in Alaska pollock (Theragra chalcogramma) in northern Japan using morphological and molecular markers.

The Alaska pollock, Theragra chalcogramma (Pallas), is an important raw source for surimi and other food products in Japan. However, Alaska pollock caught in the Atlantic and Mediterranean regions has been reported to harbor Anisakis species that pose considerable food safety problems. Here, we identified the third-stage (L3) Anisakis spp. sampled from Alaska pollock caught in northern Japan using a combination of morphological and molecular analyses which included PCR-RFLP and sequencing of the ITS (ITS1-5.8S rDNA-ITS2) region and mtDNA cox2 gene markers. Four Anisakis spp. were confirmed, namely Anisakis simplex (sensu stricto [s.s.]), A. pegreffii, A. brevispiculata, and an Anisakis sp. belonging to the Anisakis Type II group. The identification of 4 different Anisakis spp. occurring in Alaska Pollock, and the identification of A. brevispiculata and an Anisakis sp. (Anisakis Type II) in the northwest Pacific region, are first reports. Anisakis simplex (s.s.) composed the majority of Anisakis spp. in Alaska pollock at 91.0%, followed by A. pegreffii (5.2%), Anisakis sp. (Anisakis Type II) (2.4%), and A. brevispiculata (1.4%).