Report on the Occurrence of Anisakid Nematodes in Commercial Fish from the Southwestern Indian Waters

Abstract

Anisakid nematodes are zoonotic parasites with a heteroxenous life cycle involving diverse hosts across multiple trophic levels in the marine ecosystem. Anisakiasis represents a significant global public health issue, with numerous clinical cases documented across the regions where raw and undercooked fish and fishery products are consumed as delicacies. The presence of Anisakis larvae, especially within fish muscle tissue, substantially decreases both the market value and consumer acceptability of fish products. However, their occurrence in Indian marine fishes remains underexplored. Therefore, the present study investigates anisakids in nine commercially important marine fish species sold in the local markets of the southwestern Indian coast through morphological and molecular approaches. A total of 10 anisakid nematodes were recovered from the visceral cavity of frigate tuna, Auxis thazard. Nematodes exhibited the characteristic morphology of the third larval stage of Anisakis spp. Prevalence, mean intensity and mean abundance of larvae were 16.67%, 2.0, and 0.33, respectively. Phylogenetic analysis suggested that Anisakis typica is closely related to isolates from the Asia-Pacific region. Low genetic variation was observed among A. typica isolates from the current study and other geographically distinct locations. The study provides a groundwork for expanding our knowledge on the occurrence of anisakids in commercially important fish from the southwestern Indian waters and their potential implications in food safety and public health.