Invasion dynamics and ecological impacts of Anisakis typica in commercial fish from the Western Pacific Ocean.

Background and aim: The Western Pacific Ocean hosts rich marine biodiversity, yet the parasitic infections affecting its commercial fish species remain underexplored. This study investigated the prevalence, intensity, morphological characteristics, molecular identity, and ecological impacts of Anisakis typica infection in commercial fish from this region.

Materials and methods: Between January and April 2024, 178 fish samples from 12 commercial species were collected across three geographical clusters: Sangihe Island, Kahakitang Island, and Marore Island. Fish specimens were morphologically identified and dissected for parasite detection. Morphological identification of larvae was complemented by molecular characterization through polymerase chain reaction amplification of the internal transcribed spacer (ITS)1-5.8S-ITS2 rDNA region, followed by sequencing and phylogenetic analysis.

Results: A. typica infection was observed in 10.7% of the fish sampled, with moderate infection intensity. Euthynnus affinis exhibited the highest prevalence (41.2%) and intensity (15.4). The intestinal wall was the dominant predilection site (96.3%). Molecular analyses confirmed A. typica infection in E. affinis, Katsuwonus pelamis, Decapterus kurroides, and Variola louti, with high genetic similarity (93.38%-100%) to isolates previously reported from China. Notably, this study provides the first documentation of A. typica infection in D. kurroides and V. louti.

Conclusion: This study highlights the ecological and zoonotic significance of A. typica infection in commercially important fish from the Western Pacific Ocean. The findings underscore the potential threats to marine ecosystem stability, fishery sustainability, and public health. High genetic proximity between A. typica isolates from Indonesia and China suggests historical host migrations, emphasizing the need for regional surveillance and integrated management strategies. Enhanced inspection practices and public awareness initiatives are crucial to mitigate the zoonotic risks posed by consuming infected fish.