Parasitic castration by the digenian trematode Allopodocotyle sp alters gene expression in the brain of the host mollusc Haliotis asinina

Infection of molluscs by digenean trematode parasites typically results in the repression of reproduction - the so-called parasitic castration. This is known to occur by altering the expression of a range of host neuropeptide genes. Here we analyse the expression levels of 10 members of POU, Pax, Sox and Hox transcription factor gene families, along with genes encoding FNIRFamide, prohormone convertase and P-tubulin, in the brain ganglia of actively reproducing (summer), non-reproducing (winter) and infected Haliotis asinina (a vetigastropod mollusc). A number of the regulatory genes are differentially expressed in parasitised H. asinina, but in only a few cases do expression patterns in infected animals match those occurring in animals where reproduction is normally repressed. (c) 2006 Published by Elsevier B.V. on behalf of the Federation of European Biochemical Societies.

Epidemiology of Opisthorchis viverrini

Opisthorchis viverrini is a food home trematode, important because of the sheer numbers of people infected and its serious morbidities such as hepatobiliary diseases and cholangiocarcinoma (CHCA). Although infections are identified throughout Southeast Asia, the epi-center is northeast Thailand, where high prevalence coexists with a high incidence of CHCA. In this review, we present the basic population features and the factors influencing transmission between the different hosts. (C) 2003 Elsevier B.V. All rights reserved.

Case report: unusual presentation of Fasciolopsis buski in a Viet Namese child

A Viet Namese child presented with a history of abdominal pain. Shortly afterwards, he vomited eight live trematode flukes that were collected and morphologically identified as Fasciolopsis buski. The identification was confirmed by DNA analysis. Adult worms of F buski from humans are very rarely seen except at autopsy, and this is the first such report from Viet Nam. (C) 2003 Royal Society of Tropical Medicine and Hygiene. Published by Elsevier Ltd. All rights reserved.

Grammatorcynicola n. g. (Bucephalidae : Dolichoenterinae) from Grammatorcynus spp. (Scombridae) on the Great Barrier Reef, Australia

A new trematode genus, Grammatorcynicola n. g. (Bucephalidae: Dolichoenterinae), and two new species, G. brayi n. sp. and G. nolani n. sp. from the intestines of the scombrids, Grammatorcynus bicarinatus and Gr. bilineatus respectively, are reported from the Great Barrier Reef, Australia. Grammatorcynicola n. g. is placed in the Dolichoenterinae, as the pharynx is in the anterior quarter of the body, the caecum is tube-like and extends to the posterior quarter of the body, the cirrus-sac is small relative to the size of the worm when compared with other bucephalids and the pars prostatica is curved. Grammatorcynicola n. g. differs from other dolichoenterine genera in having a simple sucker-like rhynchus, the ovary anterior to the testes and by not having a particularly thick cirrus-sac wall.

Patterns of digenean parasitism of bivalves from the Great Barrier Reef and associated waters

Digenean parasites of marine bivalves are relatively poorly known, particularly in Australia. We surveyed 2256 bivalve individuals ( 47 species, 17 families) from Queensland marine waters incorporating south-east Queensland, Heron Island ( southern Great Barrier Reef) and Lizard Island ( northern Great Barrier Reef). Infections of trematode species from three families, Bucephalidae, Gorgoderidae and Monorchiidae, were found. Overall prevalence of infection was 2.3%. The Bucephalidae was the most commonly found family; 11 species were found in Tellinidae, Ostreidae, Isognomonidae and Spondylidae - the latter two previously unknown as hosts for bucephalids. A single gorgoderid infection was found in a venerid, Lioconcha castrensis. Five species of monorchiids were found from Tellinidae and Lucinidae. All infections are new host/parasite records. No infections were found in 35 of the 47 bivalve species sampled. The generally low prevalence of infection by digeneans of bivalves suggests that it is unlikely that any of the species reported here are seriously damaging to bivalve populations in these waters. We deduce that, at best, we have some life-cycle information but no actual identifications for 10% of the species of trematodes that infect bivalves of Queensland marine waters.

The use and implications of ribosomal DNA sequencing for the discrimination of digenean species

In just over a decade, the use of molecular approaches for the recognition of parasites has become commonplace. For trematodes, the internal transcribed spacer region of ribosomal DNA (ITS rDNA) has become the default region of choice. Here, we review the findings of 63 studies that report ITS rDNA sequence data for about 155 digenean species from 19 families, and then review the levels of variation that have been reported and how the variation has been interpreted. Overall, complete ITS sequences (or ITS1 or ITS2 regions alone) usually distinguish trematode species clearly, including combinations for which morphology gives ambiguous results. Closely related species may have few base differences and in at least one convincing case the ITS2 sequences of two good species are identical. In some cases, the ITS1 region gives greater resolution than the ITS2 because of the presence of variable repeat units that are generally lacking in the ITS2. Intraspecific variation is usually low and frequently apparently absent. Information on geographical variation of digeneans is limited but at least some of the reported variation probably reflects the presence of multiple species. Despite the accepted dogma that concerted evolution makes the individual representative of the entire species, a significant number of studies have reported at least some intraspecific variation. The significance of such variation is difficult to assess a posteriori, but it seems likely that identification and sequencing errors account for some of it and failure to recognise separate species may also be significant. Some reported variation clearly requires further analysis. The use of a yardstick to determine when separate species should be recognised is flawed. Instead, we argue that consistent genetic differences that are associated with consistent morphological or biological traits should be considered the marker for separate species. We propose a generalised approach to the use of rDNA to distinguish trematode species.