Occurrence of Anisakis Larvae in Commercial Fish along the Northern Coast of Taiwan

Anisakis larvae of three commercial fish species, including Trichiurus lepturus, Scomber japonicus and Trachurus japonicus, found in the ocean North of Taiwan, were examined. The morphology of the larvae was analyzed using light and scanning electron microscopes, the population dynamics (including prevalence, mean intensity and abundance) were studied and the molecular characteristics of the Anisakid nematodes were identified. The annual prevalence of the larvae in T. lepturus, S. japonicus and T. japonicus were 91, 39 and 89%, respectively. Using light microscopy and scanning electron microscopy demonstrated that the worms in the three species of fish showed no difference in morphological features. The Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) indicated that the larvae from the three species of fish belonged to a single species. However, using phylogenetic analysis in the molecular identification of ribosomal DNA (rDNA) domains ITS-1 (internal transcribed spacer 1) and ITS-2, the larvae in the three species of fish were not of a single species of Anisakis.