Genetic characterization of Contracaecum cf. overstreeti (Nematoda: Anisakidae) larvae in Mugil cephalus fish from the pacific coast of Ecuador

This study reports the genetic characterization of Anisakidae larvae infecting the flathead grey mullet (<i>Mugil cephalus</i>) fish. Larvae were recovered from fish captured by artisanal fisheries and sold in a coastal town in northwestern Ecuador. In total, 19 larvae were obtained from nine fish, all larvae were exclusively encysted within the muscle tissue. Molecular identification was performed by PCR amplification and DNA sequencing of the nuclear ribosomal region ITS1-5.8 S-ITS2, the mitochondrial cox2 gene, and the EF-1α gene. Comparative analyses with sequences available in GenBank, followed by phylogenetic reconstruction, confirmed the larvae as <i>Contracaecum overstreeti</i>. This constitutes the first molecular evidence of <i>C. overstreeti</i> in this edible fish from Ecuador and provides new host-parasite records. The identification of this zoonotic nematode in marine fish of human consumption underscores the need for expanded surveillance in other neotropical marine ecosystems and in other commercially important fish species and highlights potential infection to humans.