Occurrence and molecular identification of Contracaecum larvae (Nematoda: Anisakidae) of the marine fish, Dicentrarchus labrax in Egypt

Globally, fish-borne nematodes are a major public health hazard. Anisakidosis is a zoonotic infection caused by members of the family Anisakidae. Contracaecum (Railliet and Henry, 1912) is one of the most common genera in this family. Anisakid larvae in fish pose a risk for humans and reduce their marketability. The present study found anisakid nematodes of the genus Contracaecum as third-stage larvae in the European Seabass Dicentrarchus labrax collected from the Mediterranean Sea, Egypt. The larvae were observed encapsulated on the surface of various abdominal organs and embedded in fish muscles. The prevalence of the parasite was 52.72% (29 out of 55 fishes), with a mean intensity of 7.86 ±0.69. Morphological examinations of using light and scanning electron microscopy revealed a head region with a prominent boring tooth, inconspicuous lips, and a distinct protruded cylindrical mucron. These findings are supported by phylogenetic analysis based on ITS region using maximum likelihood, corroborating the evidence that L3 larvae parasitizing the D. labrax belong to the species Contracaecum quadripapillatum. This study is the first to identify this parasite in the marine fish European Seabass, D. labrax, from Egyptian waters using morphological and molecular approaches.