ABSTRACT The consumption of raw or undercooked fish has increased concerns regarding zoonotic parasites, particularly nematode larvae of the genus Anisakis . This study investigates the epidemiology of anisakid infections in commercially important fishes from Portuguese coastal waters, focusing on spatial and seasonal patterns. A total of 538 specimens of five fish species ( Trachurus trachurus , Scomber colias , Scomber scombrus , Merluccius merluccius , and Sardina pilchardus ) were collected from six localities during winter and summer 2024. Parasites were recovered from viscera and muscle by pepsin digestion, identified using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) targeting the internal transcribed spacer (ITS) region, and confirmed by sequencing. Generalized linear models were applied for data analysis. All species were infected with Anisakis spp. larvae, with significant differences among host species, host size, seasons, and regions. Most larvae were in the viscera (90.5–100%), with a smaller proportion in muscles. Trachurus trachurus showed the highest infection levels (45–100% prevalence; mean intensity up to 161 larvae per infected host). Molecular analysis of 424 larvae identified Anisakis pegreffii (56.6%) as the dominant species, followed by A. simplex ( sensu stricto ) (30.9%), putative hybrids (12.3%), and a single Skrjabinisakis physeteris larva. A significant north-south and seasonal gradient was observed, with A. simplex ( s.s. ) predominating in northern and winter samples, particularly in the muscles. These results suggest geographical and seasonal variations in Anisakis spp. distribution. Despite potential sampling bias, the presence of zoonotic species in fish muscles highlights the need for strict post-capture handling, freezing, and cooking practices to reduce consumer risk.
Mendes et al. (Mon,) studied this question.
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