1. Crepidostomum farionis (Müller, 1784) and C. metoecus (Braun, 1900) were found to occur together in the same host fish, Salmo trutta L., S. salar L. and Anguilla anguilla (L.) in mid-Wales. It is believed that the latter species constituted an accidental host.

2. C. metoecus is recorded in Britain for the first time.

3. There was some evidence of a habitat isolation in individual fish as C. metoecus occurred predominantly within the pyloric caeca, while C. farionis usually occupied a more posterior station in the intestine.

4. A detailed description is given of G. metoecus and the salient features of this species are compared with those of C. farionis.

5. The two species of Crepidostomum commonly occurred in large numbers in their fish hosts, individual fish harbouring up to 157 worms. No lesions attributable to Crepidostomum were, however, detected and there was no evidence of pathogenicity.

6. It would appear that the eel is physiologically immune to both species of Crepidostomum and that the salmon parr is partially resistant.

7. The degree of infestation of trout and parr with both the Crepidostomum species is at a maximum during the winter months and at a minimum in the summer months. This seasonal variation can be attributed to a periodicity in the swarming of the cercariae.

8. There is no evidence of age resistance or acquired immunity of the trout to infestation by Crepidostomum species.

Free-living animals are usually inhabited by a community of parasitic species that can interact with each other and alter both host susceptibility and parasite transmission. In this study we tested the prediction that an increase in the gastrointestinal nematode Heligmosomoides polygyrus would increase the infestation of the tick Ixodes ricinus, in free-living yellow-necked mice, Apodemus flavicollis. An extensive cross-sectional trapping survey identified a negative relationship between H. polygyrus and I. ricinus counter to the prediction. An experimental reduction of the nematode infection through anthelmintic treatment resulted in an increase in tick infestation, suggesting that this negative association was one of cause and effect. Host characteristics (breeding condition and age) and habitat variables also contributed to affect tick infestation. While these results were counter to the prediction, they still support the hypothesis that interactions between parasite species can shape parasite community dynamics in natural systems. Laboratory models may act differently from natural populations and the mechanism generating the negative association is discussed.

Malaria remains a major cause of mortality in African children, with no adjunctive treatments currently available to ameliorate the severe clinical forms of the disease. Rosetting, the adhesion of infected erythrocytes (IEs) to uninfected erythrocytes, is a parasite phenotype strongly associated with severe malaria, and hence is a potential therapeutic target. However, the molecular mechanisms of rosetting are complex and involve multiple distinct receptor–ligand interactions, with some similarities to the diverse pathways involved in P. falciparum erythrocyte invasion. This review summarizes the current understanding of the molecular interactions that lead to rosette formation, with a particular focus on host uninfected erythrocyte receptors including the A and B blood group trisaccharides, complement receptor one, heparan sulphate, glycophorin A and glycophorin C. There is strong evidence supporting blood group A trisaccharides as rosetting receptors, but evidence for other molecules is incomplete and requires further study. It is likely that additional host erythrocyte rosetting receptors remain to be discovered. A rosette-disrupting low anti-coagulant heparin derivative is being investigated as an adjunctive therapy for severe malaria, and further research into the receptor–ligand interactions underlying rosetting may reveal additional therapeutic approaches to reduce the unacceptably high mortality rate of severe malaria.

We test the hypothesis that living on larger fish may impose constraints, i.e. the need to develop large attachment organs, related to the necessity to remain attached on large gills. For this, we compiled data on body size and morphometric measurements of attachment organs of 44 Dactylogyrus species (ectoparasites with direct life-cycle) from 19 cyprinid species. Nineteen dactylogyrid species were considered as specialists (infecting only 1 host species) and 25 as generalists (infecting more than 1 species). The lack of phylogenetic information lead us to perform comparative analyses using raw values and independent contrasts obtained by random phylogenies. Our results show that rich parasite communities are formed by specialists and generalists whereas poor communities are composed mainly of generalist parasites. Moreover, specialists are found on larger hosts, which may reflect a specialization on a predictable resource, as larger fish live longer and offer large gills for parasite colonization. Parasite specialization is shown to be linked with adaptation of attachment organs to their fish hosts. Two morphometric variables of the attachment organ, the total length of anchor and length of base of anchor, were positively correlated with host length for specialists.

Argulus Foliaceus has a remarkably wide distribution, and is found throughout Europe. A. coregoni, which is another European form of the Argulidae, has been recorded in England from such localities as the Birmingham Canal; Barble, Leicestershire; Berkshire Trout Farm; the River Wharfe, Yorkshire; Tring Reservoirs; the Thames; the River Frome in Somerset; and the River Lune.

The small subunit ribosomal RNA (srRNA) gene was amplified from Gyrodactylus salaris using the polymerase chain reaction (PCR), cloned, and the complete gene sequence of 1966 bp determined. The V4 region of the srRNA gene was identified and amplified from single specimens of G. salaris, G. derjavini and G. truttae. Comparison of the V4 sequences from these three species revealed sequence differences from which restriction fragment length polymorphisms (RFLPs) were predicted and an oligonucleotide probe (GsV4) specific to G. salaris designed. Digestion of the amplified V4 region of the srRNA gene with Hae III and either Alw I, BstY I, Dde I or Mbo I provided a means of discriminating between G. salaris, G. derjavini and G. truttae. The GsV4 probe was used to detect the srRNA gene from G. salaris in Southern and dot blots of the amplified V4 region. The nucleotide sequences reported in this paper have been submitted to the EMBL Data Library under accession numbers Z26942 (G. salaris), Z35128 (G. derjavini) and Z35129 (G. truttae).

Experimental infections of lambs with Fasciola hepatica are described. The growth rate of the parasite, time of entry to the bile ducts, and time of patency are recorded and a preferential migration of the parasite in the liver parenchyma noted. The gross and histological lesions produced in the liver from 1 to 40 weeks after infection are described and compared with previous observations in cattle.

The parenchymal migration of the parasite is shown to consist of two phases, a free migrating phase up to the 6th week, and a localized phase after the 6th week prior to entry into the bile ducts. Hepatic cell regeneration is observed and hepatic fibrosis is minimal. The localized phase of migration is associated with a unique peripheral palisade of giant cells in the fluke tracts and with the formation of pseudofollicular aggregation of lymphocytes. The presence of flukes in the bile ducts produces fibrosis of the duct walls. The walls, however, remain pliable and expanded to accommodate the parasites and calcification was never observed.

Myxobolus cyprini has, until now, been considered an ‘organo-cosmopolitan’ parasite of the common carp (Cyprinus carpio) and less frequently of other carps, producing spores in various organs in small plasmodia and possible in cysts. The present observations of naturally infected common carp fry and two-summer carp have revealed that M. cyprini is a specific muscle parasite, developing intracellularly in the muscle fibres of the skeletal muscle. The sarcoplasm of the infected muscle fibres is filled with developmental stages, followed by spores of M. cyprini, which are held together in a 1–1·5 mm long pseudocyst by the sarcolemma of the muscle fibre. After maturation of the spores and disintegration of the pseudocysts the spores are transported in the bloodstream to different parts of the body where they are retained in the capillaries.

The Myxozoa demonstrate extensive morphological simplification and miniaturization relative to their free-living cnidarian ancestors. This is particularly pronounced in the highly derived myxosporeans, which develop as plasmodia and pseudoplasmodia. To date, motility in these stages has been linked with membrane deformation (e.g. as pseudopodia and mobile folds). Here we illustrate a motile, elongate plasmodium that undergoes coordinated undulatory locomotion, revealing remarkable convergence to a functional worm at the cellular level. Ultrastructural and confocal analyses of these plasmodia identify a highly differentiated external layer containing an actin-rich network, long tubular mitochondria, abundant microtubules, a secreted glycocalyx layer, and an internal region where sporogony occurs and which contains homogeneously distributed granular/fibrillar material. We consider how some of these features may support motility. We also describe the species based on spore morphology and SSU rDNA sequence data, undertake molecular phylogenetic analysis to place it within an early-diverging clade of the ceratomyxids, and evaluate the resultant implications for classification (validity of the genus Meglitschia) and for inferring early host environments (freshwater) of ceratomyxids.

Antigenicity of adult Opisthorchis viverrini, metacercariae and eggs was investigated by radio-immunoprecipitation and polyacrylamide gel electrophoresis using sera from patients with opisthorchiasis and from hamsters experimentally infected with 0. viverrini metacercariae. 125I-labelled aqueous somatic extract and in vitro metabolic products of adult worms, and the extracts of metacercariae and eggs were immunoprecipitated, electrophoresed and autoradiographed and major antigens were characterized. Although components with Mr of > 116, 89, 78 and 20 kD appeared to be specifically associated with the somatic extract of adult fluke, the 89 kD protein was the most prominent component found in the in vitro culture fluid of adult worms and the metacercarial extract. Hamsters, experimentally infected with 0. viverrini, also showed the presence of antibody reactive with the 89 kD component within 15 days of infection. The potential of this antigen in immunodiagnosis is discussed.

Fecal samples from wild-caught common voles (n = 328) from 16 locations in the Czech Republic were screened for Cryptosporidium by microscopy and PCR/sequencing at loci coding small-subunit rRNA, Cryptosporidium oocyst wall protein, actin and 70 kDa heat shock protein. Cryptosporidium infections were detected in 74 voles (22.6%). Rates of infection did not differ between males and females nor between juveniles and adults. Phylogenetic analysis revealed the presence of eight Cryptosporidium species/genotypes including two new species, C. alticolis and C. microti. These species from wild-caught common voles were able to infect common and meadow voles under experimental conditions, with a prepatent period of 3–5 days post-infection (DPI), but they were not infectious for various other rodents or chickens. Meadow voles lost infection earlier than common voles (11–14 vs 13–16 DPI) and had significantly lower infection intensity. Cryptosporidium alticolis infects the anterior small intestine and has larger oocysts (5.4 × 4.9 µm), whereas C. microti infects the large intestine and has smaller oocysts (4.3 × 4.1 µm). None of the rodents developed clinical signs of infection. Genetic and biological data support the establishment of C. alticolis and C. microti as separate species of the genus Cryptosporidium.

A midgut trypanolysin and an agglutinin from Glossina palpalis subspecies were isolated and partially characterized using anion-exchange chromatography and polyacrylamide gel electrophoresis. FPLC fractions of midgut extracts of Glossina palpalis palpalis caused agglutination and lysis of two trypanosome species (Trypanosoma congolense and Trypanosoma brucei brucei). although Glossina palpalis gambiensis caused only agglutination. The trypanolysin and agglutinin were active only in the posterior midguts, were heat labile above 50%C, had a periodic cycle of ‘activity’ in response to bloodmeal intake and were not affected by protease inhibitors or trypsin but were inactivated by pronase. The lytic substance contained two proteins with approximate molecular weights (Mr) of 12000 and 10000 Da respectively. The agglutinin had an approximate Mr of 67000 Da. Gamma-irradiation of the two subspecies caused a temporary inhibition of trypanolytic and agglutinin activities in midgut extracts.

In the literature relating to the Ixodoidea there are a number of cases recorded of injurious effects following the bites of ticks. We do not refer to diseases like piroplasmosis and spirochaetosis which are known to be tick-transmitted, nor to other infective processes which may start at the seat of tick's bite. The effects we refer to follow almost immediately upon the infliction of the bite and are distinctly toxic in character. These effects appear to have been more frequently observed following upon bites inflicted by species of Argas and Ornithodoros.

In connexion with studies on bat malaria carried out by Prof. G. Mer and Dr N. Goldblum at the Malaria Research Station of the Hebrew University, a great number of ectoparasites of bats were submitted to us for identification. Together with material collected by us, over a thousand nycteribiids, streblids, Hemiptera, Siphonaptera, ticks and mites were examined.

Scabies is an infectious disease that is endemic in poorly resourced communities, and also common in industrialized countries. Although the disease, which is caused by infestation of Sarcoptes scabiei, is generally mild, the need for a vaccine against S. scabiei is proposed. The immunological mechanisms that control S. scabiei infection are discussed and the current status of scabies vaccine development reviewed. Future directions for scabies vaccine development are also addressed.

The objective of this experiment was to investigate a possible interaction between protein and energy malnutrition (PEM) and intestinal nematode infections. We report on a 3×2 factorial study in which pigs were fed either a low protein energy (LPE), low protein (LP) or a normal protein energy (NPE) diet, and 6 weeks later inoculated with Trichuris suis (4000 infective eggs). Secondarily, in order to obtain a polyparasitic status, pigs were concomitantly inoculated with Ascaris suum (600 infective eggs). The number of T. suis-infected pigs was higher in LP pigs compared with NPE pigs (100 versus 58%; P = 0·037), although the differences in median T. suis worm burdens between groups at necropsy 10 weeks post-infection (p.i.) (LPE: 795; LP: 835; NPE: 48 worms; P = 0·33) were not significant. Interestingly, only T. suis in NPE were highly aggregated (k = 0·44), in contrast to a more uniform distribution among pigs in LPE (k = 1·43) and LP (k = 1·55) i.e. the majority of pigs harboured moderate worm burdens in LPE and LP, while most pigs had few or no worms in NPE. Further, T. suis worms in the LPE and LP groups were decreased in length (mean: LPE: 23·5 mm; LP: 24·3 mm; NPE: 29·4 mm; P = 0·004). The pre-patency period of T. suis was also extended in the LPE and LP groups, as reflected by lower faecal egg output at week 6 (P = 0·048) and/or 7 p.i. (P = 0·007). More A. suum worms were recovered from LP compared with the NPE group (mean: 5·4 versus 0·6; P = 0·040); this was accompanied by a higher faecal egg output in the former (P = 0·004). The low protein diets resulted in lower pig body weight gains, serum albumin, haemoglobin and packed cell volume (PCV) levels as well as diminished peripheral eosinophil counts. Infection significantly altered these parameters in the low protein groups, i.e. the pathophysiological consequences of infection were more severe in the PEM pigs. These results demonstrate that reduced protein in the diet leads to malnourishment of both the host pigs and T. suis, and compromises the pig's ability to resist infection by T. suis and A. suum.

Two species of Eimeria isolated from jungle fowl of Malaysia were examined in infections of chickens. Eimeria diminuta reproduced well in the embryo CAM and caused severe infection of the lower small intestine and caeca of chickens, but did not develop in the duodenum. It reproduced well in chickens and severely affected their body weight gain. The endogenous stages and oocysts were similar to E. acervulina var. mivati and cross-protection tests with this parasite and E. acervulina confirmed the close relationship between them. It is suggested that the parasite should be referred to as E. acervulina var. diminuta.

The oocysts of another species examined (E. indentata) were similar to E. maxima: the parasite reproduced well in chickens, was pathogenic and showed marked cross-protection against two strains of E. maxima isolated in Britain. The name E. maxima var. indentata is suggested for this parasite.

When low immunizing doses of two strains of E. maxima isolated and maintained in Britain were given, they did not completely cross-protect against re-infection with the heterologous strain.

Although the poultry red mite Dermanyssus gallinae (De Geer, 1778) is the major parasitic pest in poultry farming causing substantial economic losses every year, nucleotide data are rare in the public databases. Therefore, de novo sequencing covering the transcriptome of D. gallinae was carried out resulting in a dataset of 232 097 singletons and 42 130 contiguous sequences (contigs) which were subsequently clustered into 24 140 isogroups consisting of 35 788 isotigs. After removal of sequences possibly originating from bacteria or the chicken host, 267 464 sequences (231 657 singletons, 56 contigs and 35 751 isotigs) remained, of which 10·3% showed homology to proteins derived from other organisms. The most significant Blast top-hit species was the mite Metaseiulus occidentalis followed by the tick Ixodes scapularis. To gain functional knowledge of D. gallinae transcripts, sequences were mapped to Gene Ontology terms, Kyoto Encyclopedia of Gene and Genomes (KEGG) pathways and parsed to InterProScan. The transcriptome dataset provides new insights in general mite genetics and lays a foundation for future studies on stage-specific transcriptomics as well as genomic, proteomic, and metabolomic explorations and might provide new perspectives to control this parasitic mite by identifying possible drug targets or vaccine candidates. It is also worth noting that in different tested species of the class Arachnida no 28S rRNA was detectable in the rRNA profile, indicating that 28S rRNA might consists of two separate, hydrogen-bonded fragments, whose (heat-induced) disruption may led to co-migration with 18S rRNA.

Numerous studies have been conducted on the cellular morphology of Cryptocaryon irritans. However, details regarding the tomont stage of its life cycle remain lacking. In this study, we investigated the morphology of the tomont stage throughout encystment and cell division using light and electron microscopy. Results showed that there was no secretion of encystation-specific secretory vesicles or extrusomes during formation of the cyst wall. Instead, the synthesis and construction of the C. irritans cyst wall materials may involve molecular events at the pellicle. The somatic cilia and the cytostome were present during encystment and covered by the newly formed cyst wall. New somatic cilia were continuously created between old cilia and showed various lengths during cell division, a process that was similar to morphogenesis in many free-living ciliates. During cell division inside the tomont, dividing daughter cells formed temporary cell chains with no oral primordia before separating from each other into dissociative tomite precursors. The process of cell division may not be accompanied by stomatogenesis, and new oral primordia in offspring cells likely formed before the dividing cell chains split into dissociative spherical tomites. Mitochondrial autophagy was observed in encysting C. irritans cells. Numerous endosymbionts and Golgi structures were observed in the tomont cytoplasm. Cellular metabolic activity in the C. irritans tomont was quite high, with large amounts of materials or cellular organelles potentially being synthesized and prepared for the following infective theront stage.

Trichomonas vaginalis is an anaerobic protist, responsible for the most prevalent non-viral sexually transmitted infection in humans. One of the most intriguing aspects of T. vaginalis pathobiology is the complex relationship with intracellular microbial symbionts: a group of dsRNA viruses belonging to family of Totiviridae (T. vaginalis virus), and eubacteria belonging to the Mycoplasma genus, in particular Mycoplasma hominis. Both microorganisms seem to strongly influence the lifestyle of T. vaginalis, suggesting a role of the symbiosis in the high variability of clinical presentation and sequelae during trichomoniasis. In the last few years many aspects of this unique symbiotic relationship have been investigated: M. hominis resides and replicates in the protozoan cell, and T. vaginalis is able to pass the bacterial infection to both mycoplasma-free protozoan isolates and human epithelial cells; M. hominis synergistically upregulates the proinflammatory response of human monocytes to T. vaginalis. Furthermore, the influence of M. hominis over T. vaginalis metabolism and physiology has been characterized. The identification of a novel species belonging to the class of Mollicutes (Candidatus Mycoplasma girerdii) exclusively associated to T. vaginalis opens new perspectives in the research of the complex series of events taking place in the multifaceted world of the vaginal microbiota, both under normal and pathological conditions.