Abstract:

Objective To understand the infection status and morphological identification of Anisakis in the marketed marine fish captured from the Bohai Strait and the Bohai Bay for evidence to plan the prevention and control measures for this parasite. Methods In the spring and winter of 2023, we obtained the marine fish that was caught from the Bohai Strait and the Bohai Bay sold in the coastal markets, and detected Anisakis infection status in the fish samples. Then the detected species were subjected to morphological analysis and intergeneric identification, and the differences in Anisakis infection among fish species, and internal parasitic site were also analyzed. Results In this study, no Anisakis nematodes were detected in the 91 fish samples of 7 species from the Bohai Bay. A total of 210 marine fish samples of 21 species from the Bohai Strait were investigated, in which Anisakis was detected in 48 samples of 11 species. The positive detection rate was 22.86%. A total of 1 370 Anisakis were detected, with an average infection intensity of 28.54 nematodes in individual fish. The top three detection rate for the 48 marine fish was Lophiiformes (100%, 14/14), Trichiurus lepturus (100%, 10/10), and Platycephalus indicus (80.00%, 8/10), and the top three fish species in terms of infection intensity were associated with Lophiiformes (69.00 larvae/fish), Trichiurus lepturus (24.70 larvae/fish) and Ditrema temmincki Bleeker (19.00 larvae/fish). The main parasitic sites of the fish found during physical examination were the intestine, mesentery, abdominal cavity, etc., and no infection was found in the cloaca. The correlation analysis showed that the body weight of Lophiiformes and Trichiurus lepturus were positively correlated with the infection of Anisakis (r=0.77, 0.67, respectively, all P<0.01). In total, 1 226 intact third stage larvae of Anisakis were obtained, and morphologically identified as Anisakis spp.(767 larvae) and Hysterothylacium spp.(459 larvae). Conclusion In current survey, no Anisakis was detected in the marine fish in the Bohai Bay, yet Anisakis infection is relatively serious in fish in the Bohai Strait, and these pathogenic nematodes are mainly involved in Anisakis spp. and Hysterothylacium spp. Our findings suggest that it is necessary to strengthen the health education on anisakiasis in local population in order to reduce the risk of this disease.

Key words: Anisakis, Morphology, Marine fish, The Bohai Strait, The Bohai Bay