Tapeworms as pathogens of fish: A review

Tapeworms (Cestoda) represents a species rich (about 5000 species) group of flatworms (Neodermata) parasitizing all groups of vertebrates including humans, with about 1000 species parasitizing elasmobranchs and almost 500 occurring in teleosts as adults. They are common parasites of cultured fish, both as adults and larvae (metacestodes), but only few adult tapeworms are actually pathogenic for their fish hosts. In contrast, cestode larvae can be harmful for fish, especially plerocercoids migrating throughout their tissue and internal organs. Current knowledge of host-parasite relationships, including immune response of fish infected with tapeworms, is still insufficient to enable adequate control of cestodoses, and most data available were obtained several decades ago. Treatment of fish infected with adult tapeworms is effective, especially with praziquantel, whereas the treatment of metacestodes is problematic. Control measures include interruption of the complex life cycle and prevention of transport of uninspected fish to new region.

An annotated list of species of the Proteocephalus Weinland, 1858 aggregate sensu de Chambrier et al. (2004) (Cestoda: Proteocephalidea), parasites of fishes in the Palaearctic Region, their phylogenetic relationships and a key to their identification

A list and key to the identification of valid species of tapeworms of the Proteocephalus Weinland, 1858 aggregate sensu de Chambrier et al. (2004), i.e. species of the genus occurring in fresh- and brackish-water fishes in the Palaearctic Region, are provided, with data on their hosts and geographical distribution. Instead of 32 taxa listed by Schmidt (1986) and subsequent authors, only the following 14 species are considered to be valid: P. ambiguus (Dujardin, 1845) (type-species); P. cernuae (Gmelin, 1790); P. filicollis (Rudolphi, 1802); P. fluviatilis Bangham, 1925; P. gobiorum Dogiel & Bychowsky, 1939; P. longicollis (Zeder, 1800); P. macrocephalus (Creplin, 1825); P. midoriensis Shimazu, 1990; P. percae (Müller, 1780); P. plecoglossi Yamaguti, 1934; P. sagittus (Grimm, 1872); P. tetrastomus (Rudolphi, 1810); P. thymalli (Annenkova-Chlopina, 1923); and P. torulosus (Batsch, 1786). An analysis of sequences of the nuclear genes (ITS2 and V4 region of 18S rDNA) revealed the following phylogenetic relationships for these taxa: P. torulosus ((P. midoriensis, P. sagittus) (P. fluviatilis (P. filicollis, P. gobiorum, P. macrocephalus)) (P. cernuae, P. plecoglossi, P. tetrastomus ((P. longicollis, P. percae) (P. ambiguus, P. thymalli)))). P. pronini Rusinek, 2001 from grayling Thymallus arcticus nigrescens is synonymised with P. thymalli. P. esocis La Rue, 1911 is apparently invalid but its conspecificity with either P. percae or P. longicollis could not be confirmed due to the absence of the scolex in the holotype and the unavailability of other material for morphological and molecular studies. P. osculatus (Goeze, 1782) has recently been transferred to Glanitaenia de Chambrier, Mariaux, Vaucher & Zehnder, 2004. The validity of the genus is supported by the position of G. osculata within the Proteocephalidea, based on molecular data, as well as its morphology and nature of the definitive host (the European wels Silurus glanis). P. hemispherous Rahemo & Al-Niaeemi, 2001, described from S. glanis in Iraq, is transferred to Postgangesia Akhmerov, 1960 as Postgangesia hemispherous (Rahemo & Al-Niaeemi, 2001) n. comb.