Potential risk analysis of human anisakiasis through the consumption of mackerel, Scomber scombrus, sold at Spanish supermarkets

Herein, the potential risk of human anisakiasis through the consumption of mackerel, Scomber scombrus, sold at nationwide Spanish supermarket chains is assessed, by means of the identification of anisakid and other nematode species found, and the analysis of intrinsic and extrinsic factors that may influence the prevalence and abundance of nematode worms, as well as their presence in the viscera or in the flesh. 231 fresh mackerel specimens caught between 2008 and 2014 (140 from the Atlantic and 91 from the Mediterranean), captured in autumn and spring and acquired at nationwide Spanish supermarket chains, were examined dissecting their viscera and submitting their flesh to artificial digestion. Helminthological identification was based on the morphological criteria of L3. Moreover, 62 larvae of different origins and seasons were molecularly characterized by RFLP-PCR. The target region, ITS1-5.8S rDNA-ITS2, was amplified and the restriction enzyme HinfI was used for digestion. The potential influence of intrinsic (fish length and weight) and extrinsic (origin and season of capture, and days after catch) factors was statistically analysed. Total Anisakis type I prevalence was 58.4% (55.4% in viscera; 26.0% in the flesh) and 4.8% Hysterothylacium spp. 45 Anisakis simplex (s.s.), 12 hybrid genotype (A. simplex s.s./Anisakis pegreffi) and only one larva of A. pegreffi were identified in the 58 L3 molecularly characterized. The four Hysterothylacium larvae were identified as belonging to the species H. aduncum. There were statistically significant differences in the presence of Anisakis type I from the Atlantic and the Mediterranean (χ2 = 47.341; p < 0.0001), in viscera as opposed to the flesh (χ2 = 42.630; p < 0.0001), also in the longest specimens (χ2 = 73.170; p < 0.0001) and in the highest weight (χ2 = 27.469; p < 0.0001). A significant correlation (χ2 = 22.458; p = 0.004) was found between the presence of larvae in the flesh and the number of days passed between the catch and the analysis. Hence, apart from the recommendation of freezing fish at −20 °C for at least 24 h in case the fish is consumed raw or poorly cooked, the aforementioned factors should be considered by the consumer when purchasing this fish species to avoid any potential anisakiasis risk.