Genetic identification of zoonotic parasite Anisakis pegreffii (Nematoda: Anisakidae) parasitizing the shortfin squid Illex argentinus under commercial exploitation in the Southwestern Atlantic Ocean.

Despite the shortfin squid, Illex argentinus, is one of the most important commercial species for the Argentine fisheries, being the third frozen product exported to Europe, the occurrence and distribution of zoonotic anisakid nematodes is scarcely reported. A total of 712 I. argentinus distributed in 17 samples, corresponding to its three main commercial stocks, caught along its distribution range in Argentine waters were examined for anisakid parasites. In total, 360 nematodes were detected in the viscera, however no infestations in the mantle were observed. According to their morphology, all the larvae (L₃) were assigned to the genus Anisakis. Genetic identification was performed by sequence analysis of the mitochondrial (mtDNA cox2) gene loci resulting in the record of only Anisakis pegreffii. Distance-based multiple linear regressions (DistLM) evidenced that dorsal mantle length (ML) and date of capture (as surrogate of cohort) were the most important predictors of parasite abundance across infrapopulations in I. argentinus. At component population, DistLM analysis showed that ML and latitude (indirectly representing a gradient in water temperature) were the most important variables determining the prevalence of parasites, however, its mean abundance was only influenced by ML. Parasite burdens were temporally inestable, due to variability in recruitment to host populations, being associated with changing hydrographic conditions and the opportunistic feeding behaviour and annual life cycle of the hosts. The genetic identification of A. pegreffii is relevant for both human health and the fishery industry, given its importance as an etiological agent of human anisakiosis. Due to the restriction of larvae to internal organs, the risk of anisakiosis by the consumption of edible parts of I. argentinus is low.