Morphology of Anisakine Larvae

Abstract

At least four species of larval anisakine nematodes can cause human anisakiasis. They include Anisakis simplex (Rudolphi, 1809) (Anisakis type I), Anisakis type II, Pseudoterranova (=Phocanema) decipients (Krabbe, 1878) (Terranova type A), and Contracaecum sp. Of these, A. simplex and P. decipiens are the most common and important anisakids with regard to human infection in Japan as well as some other countries [1]. The larvae of Anisakis type II, which penetrate the stomach wall, are regarded as another important pathogen [2]. There is also a report that larvae of Contracaecum osculatum (Rudolphi, 1802) found in eosi-nophilic granulomas of the intestine may be a cause of human anisakiasis in Germany [3]. Since the early taxonomic work of Baylis [4] and Yorke and Ma-plestone [5], some confusion has existed in the classification of anisakine nematodes, although revised classifications have been proposed by Punt [6], Johnston and Mawson [7], Hartwich [8], Yamaguti [9], Berland [10], and Davey [11]. Recently, Gibson [12] reviewed the systematics of ascaridoid nematodes and commented on the current taxonomic problems; he noted: “Pseudoterranova must be recognized as the oldest available name with Phocanema as a synonym.” He also pointed out that the criteria for distinguishing Phocanema and Pseudoterranova from Terranova are weak and no longer valid. In recent Japanese literature, “Terranova sp. larva type A” has been used for Pseudoterranova decipiens.