FIRST RESULTS ON THE PRESENCE AND THE MOLECULAR CHARACTERIZATION OF ANISAKID NEMATODES IN MARINE FISH CAUGHT OFF NORTHERN SARDINIA

Abstract

Anisakidosis is a parasitic zoonosis caused by nematodes of the family Anisakidae, belonging to the genera Anisakis, Contracaecum and Pseudoterranova. Molecular studies have shown that Anisakis larvae comprise a number of sibling species, which have different genetic structures, hosts and geographical distribution. A great variety of fish species can harbour infectious third stage larvae of this nematode. The preliminary results of a study carried out to evaluate the occurrence of this parasite in commercial fish caught off northern Sardinia are herein reported. From October 2008 to November 2009, 599 specimens of 8 commercial fish species were examined for anisakid larvae through visual inspection of body cavity and peptic digestion of the muscle. Isolated Anisakis sp. larvae were observed at light microscope and identified as Type I or Type II (sensu Berland, 1961). Out of 599 fish examined, 239 (40%) were infected by 1187 anisakid larvae, belonging to the genera Anisakis (1169 Type I and 18 Type II) and Hysterothylacium (692). The molecular identification of Anisakis spp. was carried out on a subsample of 30% of Type I larvae and all Type II larvae. Specimens were firstly examined using a species-specific PCR, with primers designed for Anisakis pegreffii (APEF) and Anisakis physeteris (APHF), and ITS-2 of nuclear rDNA. The results were confirmed by the analysis of the ITS region of nuclear rDNA (ITS-1, 5.8S and ITS-2) using the restriction enzymes HinfI and HhaI in PCR-RFLP. Type I larvae examined were all identified as A. pegreffii, and Type II were all A. physeteris. This is the first contribution to the epidemiology and molecular characterization of Anisakis spp. in commercial fish caught off Sardinia.

Keywords

• parasitic zoonosis, commercial fish, Anisakis pegreffii, Anisakis physeteris, PCRRFLP