Anisakis pegreffii (Nematoda: Anisakidae) in European anchovy Engraulis encrasicolus from the Mediterranean Sea: Fishing ground as a predictor of parasite distribution

European anchovy Engraulis encrasicolus represents one of the principal target species for commercial fishing in Europe. This fish is mostly consumed in different raw dish preparations, which represents a major risk for the fish-borne zoonosis anisakiasis. The present study provides a detailed epidemiological report on ascaridoid larvae in E. encrasicolus from several fishing areas in the Mediterranean basin. Between June 2013 and June 2016, a total of 4152 specimens of E. encrasicolus were obtained from 13 sampling areas. Parasitological analysis was carried out using the UV-press detection method. Anisakis larvae (N = 547), identified by diagnostic allozymes and analyses of partial sequences of the EF1 α-1 region of nDNA and mtDNA cox2 gene, corresponded to Anisakis pegreffii. Additionally, sequence analyses of the ITS region of rDNA revealed the presence of Hysterothylacium aduncum larvae. The levels of infection with A. pegreffii significantly varied between the selected fishing areas. Fish from the Central and South Adriatic Sea showed the highest levels of infection. In contrast, anchovies from Southern Sicily, Ionian and Alboran Seas, were uninfected. A great majority of A. pegreffii larvae (95.8%) were located in the body cavity, whereas only a small percentage of them (4.2%) were detected in the flesh of the fish. A significant positive correlation between fish length and abundance of A. pegreffii was observed. The fish body condition index and infection levels observed in different sampling areas did not correlate significantly. The infection levels by H. aduncum also showed a significantly uneven distribution between different fishing areas of the Mediterranean Sea, and no larval specimens of H. aduncum were detected in examined fish flesh. This study is the first Mediterranean-wide epidemiological assessment of infection in the viscera and flesh of E. encrasicolus by A. pegreffii, an important causative agent of human anisakiasis.