Anisakid nematodes in skates (Chondrichthyes: Rajiformes) along a depth gradient: do bathymetry and host size influence the presence of zoonotic parasites?

Some species of Anisakidae are known to cause human anisakidosis due to ingestion of seafood containing larvae L3. Although cartilaginous fishes are infrequently reported as hosts for anisakids, they could play a role in their transmission to definitive hosts. The occurrence and level of infestation by anisakids on 18 species of skates were analysed, based on a sample of 676 specimens. A total of 1692 worms were recorded; the morphologic and genetic analysis of mDNA cox2 gene, confirmed the presence of Anisakis pegreffii, A. berlandi and Phocanema cattani, whose presence and burdens varied among the species of skates examined. The models generated from prevalence and mean abundance data showed that both bathymetric distribution and length of skates influence the anisakid load in the host species studied. Phocanema cattani prevailed in coastal skates, whereas Anisakis spp. were more common at greater depths. Indeed, the molecular analysis showed that A. pegreffii was most frequent in skates species inhabiting coastal to middle shelf waters, while A. berlandi was relatively more common in skate species living in deeper waters. The knowledge of the epidemiology of anisakids in the Southwestern Atlantic is still incipient, particularly those studies employing molecular approaches. Despite this study being geographically limited and restricted to a closely related group of hosts, the observed patterns would be extensive to other latitudes and species. This would contribute to a more comprehensive understanding of the ecology of an emerging zoonoses, which have implications for human health and international trade; even more under a global warming scenario.