Abstract:

Objective To investigate the Anisakis infection in marine fishes in the Yellow Sea and local resident awareness of anisakiasis in Qingdao. Methods In October 2021, marine fishes were purchased from Fisherman’s Wharf in Qingdao and Taixi Wharf in Langya. The viscera and muscle of the marine fishes were disected to search for Anisakis larvae. The Anisakis infection in different fish species, and different organs were examined to anlyze the correlation between the infection intensity and body length and weight of the marine fishes. Five villages were randomly selected in the West Coast New District to conduct a questionnaire survey on anisakiasis knowledge among residents who were willing to participate in the survey. The knowledge awareness rate and behavior habits of the residents on Anisakis were analyzed. Surveillance for anisakiasis was conducted in local sentinel hospital. The Fisher exact test was used to compare the infection rate and the responders proportion; Spearman rank correlation analysis was performed; Chi-square test was used for analyzing the knowledge awareness rate. Results A total of 196 fish from 22 species were collected, of which 70 were infected with Anisakis. The infection rate was 35.7% (70/196). Total 13 species of marine fishes were found infected with Anisakis, accounting for 59.1% (13/22), among which Muraenesox cinereus, Pleuronichthys cornutus, Gadous macrocephaius, Scomber japonicas (all 10/10) and Nibea albiflora (9/9) were all infected with Anisakis larvae. The infection rate of Anisakis was significantly different between different species (χ² = 147.93, P < 0.01). The average infection intensity was 34.8 larvae/fish (2 439/70). The highest infection intensity was found in Gadous macrocephaius (189.3 larvae/fish), followed by Scomberomorus niphonius (25.7 larvae/fish). In Larimichthys polyactis and Pennahia argentata, Anisakis larvae were only found in mesentery and intestinal wall, accounting for 4/4 and 5/5, respectively. In Esox reicherti and Sebastiscus marmoratus, Anisakis larvae were only found in the body cavity, accounting for 13/13 and 2/2, respectively. Rank correlation analysis show that the infection intensities of Anisakis in L. polyactis and E. reicherti were positively correlated with body length (r = 0.71, 0.81, all P < 0.05) and body weight (r = 0.64, 0.80, all P < 0.05), while the infection intensity of Anisakis in Lophiomus litulon was negatively correlated with body weight (r = -0.98, P < 0.01). The infection intensity of other infected fishes was not correlated with body length and body weight. A total of 387 local residents were surveyed, 8.5% (33/387) of which had heard of anisakiasis, 4.9% (19/387) had knowledge on the harm of anisakiasis, and 7.0% (27/387) preferred to eat raw or semi-raw marine fishes, 17.8% (69/387) of residents processed raw and cooked food with shared cutting boards. The knowledge awareness rates of male and female were 11.2% (18/160) and 6.6% (15/227), respectively (χ² = 7.69, P < 0.05). The knowledge awareness rate of residents in Zhuangjiatong Village [36.7% (26/71)] was higher than that of other villages (χ² = 81.15, P < 0.01). The knowledge awareness rate in ≥ 60 years old residents was the highest, which was 11.8% (16/136), but there was no significant difference among age groups (χ² = 10.89, P > 0.05). Sentinel hospitals monitor did not find any patient infected with Anisakis. Conclusion The infection rate of Anisakis in marine fishes in Qingdao is comparatively high. The knowledge awareness rate on preventrion and control of anisakiasis in resident is low. The locals comsume raw or semi-cooked marine fishes, and process raw and cooked food with shared cutting boards.

Key words: Anisakis, Marine fishes, Infection, Questionnaire investigation