Crassicauda larvae (Nematoda: Tetrameridae) in Argentine hake, porbeagle and Argentine shortfin squid: a zoonotic threat?

Abstract

The genus Crassicauda (Tetrameridae) comprises 13 species of parasitic nematodes infecting several tissues and cavities of different cetaceans. Recently, Spirurina type X larvae, characterized by having two large tubercles at the tail tip and known as causative agents of creeping eruption in humans, were identified as members of this genus by genetic analyses. In humans, the main source of infestation for this zoonosis are squids, although these larvae have been reported in the viscera of several fish species. In the South Western Atlantic, larvae morphologically identifiable as Spirurina type X were found in specimens of 713 Argentine squid Illex argentinus, 144 Argentine hake Merluccius hubbsi and two porbeagle Lamna nasus at relatively high prevalences. Sequencing of the partial mtDNA cox1 gene confirmed the identity of these larvae as belonging to Crassicauda. The K2P genetic distances between the obtained sequences and those species of Crassicauda available in GenBank, were at the level of interspecific differences, not allowing the identification at the species level of the larvae. Furthermore, whereas larvae from hakes and squids resulted conspecific, those found in porbeagle were identified as a different species. If species found were zoonotic, their microhabitats in the hosts (stomach wall of fishes and mantle cavity of squids) would minimize the risk to consumers. Additionally, freezing both hake and squid for commercial purposes ensures the inactivation of parasites.