Molecular identification and pathology of Anisakis pegreffii (Nematoda: Anisakidae) infection in the Mediterranean loggerhead sea turtle (Caretta caretta)

Nematodes of genus Anisakis spp. parasitize a wide range of marine hosts with marine mammals (mainly cetaceans) serving as definitive hosts, while fish, squid and other invertebrates serve as paratenic or intermediate hosts. Sea turtles can act as accidental or paratenic hosts for Anisakis spp. larvae, harbouring third-stage larvae unable to complete their life cycle in an ectothermic vertebrate. Post-mortem examination of 96 loggerhead sea turtles (Caretta caretta) stranded along the Italian coast of the Mediterranean Sea showed infection by Anisakis larvae Type I from 4 of 6 locations that were identified as belonging to Anisakis pegreffii by sequence analyses of the mtDNA cox2. Thirteen turtles (11 males and 2 females) were infected with A. pegreffii. Larvae were detected through gross necroscopy from 7 turtles, while in other 6 positive loggerhead sea turtles A. pegreffii larvae were revealed by histopathology. Pathological changes associated with A. pegreffii larvae in the stomach and intestine included necrosis and granulomatous response compatible with larvae migration. The role of the loggerhead sea turtle as an accidental host in the life cycle of this nematode is also discussed. This study is the first description of pathological changes associated with A. pegreffii in a sea turtle.