Abstract
Anisakid nematodes are parasites of cetaceans, their larval stages live in marine fishes. The third-stage larvae of some Anisakis species are also the etiological agents of human anisakiasis caused by consumption of raw or undercooked infected fish. Thus, identification of Anisakis larvae at the species level is crucial for their ecology and epidemiology. In Vietnam, although Anisakis larvae have been reported, they have not been identified to the species level. The aim of this study was, therefore, to identify third-stage larvae of Anisakis collected from marine fishes in Vietnamese water, based on morphological characteristics and molecular analysis. All Anisakis larvae found in this study were morphologically similar to each other and identical to Anisakis typica. In addition, molecular analysis based on ITS1-5.8S-ITS2 sequences confirmed them as A. typica. Vietnamese A. typica population was genetically close to those from Asian countries and Australia. The third-stage larvae of A. typica were collected from eight fish species from three localities in the South of Vietnam. Among them, seven were recorded as new intermediate hosts of A. typica. This is the first identification of A. typica larvae in Vietnamese water with records of new fish hosts.
Highlights
Nematodes of the genus Anisakis (Nematoda: Ani sakidae) are parasites of marine organisms
Type I consists of A. simplex, A. pegreffii, A. typica, A. ziphidarum, and A. nascettii, while type II consists of A. paggiae, A. physeteris, and A. brevispiculata (Mattiucci and Nascetti, 2008)
Anisakis larvae were found from eight fish species from three localities, Khanh Hoa, Vung Tau, and Bac Lieu, in the South of Vietnam
Summary
Nematodes of the genus Anisakis (Nematoda: Ani sakidae) are parasites of marine organisms. Anisakid larvae can be morphologically identified at the genus level by typical characteristics of anterior and posterior regions, and are classified into two types, type I and II, based on the length of the ventriculus and presence/absence of the tail spine (mucron): Anisakis type I larva has a longer ventriculus and a mucron, while type II larva has a shorter ventriculus and no mucron (Berland, 1961). It was not easy to identify anisakid larvae at the species level, because there is a lack of distinct morphological characteristics. Molecular tools allow the accurate identification of anisakid larvae by using sequences of the internal transcribed spacer (ITS) region of ribosomal DNA (D’amelio et al, 2010; Mattiucci and Nascetti, 2008). During our recent comprehensive survey for parasites of marine fishes in Vietnamese water, we collected Anisakis larvae from eight fish species. The aim of the present study was to identify these Anisakis specimens from Vietnamese water by morphological and molecular approaches
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