The biology of the life-cycle of Trichuris suis of the pig is described and discussed together with aspects of the hosi-parasite relationship. Development of the infective L. 1 larval stage within the egg was shown to be influenced by temperature. Following ingestion of infective ova by the pig, all subsequent larval development to the adult stage occurred in the mucosa of the caecum and colon. Eggs hatched in the distal region of the small intestine and throughout the large intestine. Larvae then penetrated the caecum and colonic mucosa via the crypts of Lieberkühn, where they entered the cells lining the crypts. The ensuing histotrophic phase lasted 13 days, during which time a gradual larval migration occurred from the deeper regions of the lamina propria to areas immediately beneath the surface mucosal epithelium. Luminal development was initially seen on day 16 when the posterior extremities of larvae were protruded into the gut lumen; from day 20 the entire posterior body region was exposed, while only the filamentous anterior region of the parasite remained embedded in the mucosal surface. The prepatent period varied from 41 to 47 days. Four moults were observed during development within the host and these occurred on days 10, 16, 20, 32 and 37 (to form the L. 2, L. 3, L. 4 and L. 5 or adult stage respectively). It is suggested that although T. suis may not be an important pathogen in its own right, its activities in the caecal and colonic mucosa may cause sufficient damage to enable secondary pathogenic invaders to become established.

The prediction that species richness and diversity of intestinal helminth communities in eels would change over time in response to habitat changes was tested over a period of 13 years in a small stream subjected to extensive human management. Nearly all measures of helminth community structure adopted indicated a decline in richness and diversity over the first 6 years followed by a recovery over the last few years to levels unexpectedly close to those at the start of the investigation. Changes in total number of species suggested that the component community was far richer (from 3–9 species) at the end of the period. By contrast, changes in diversity and dominance measures revealed less variation than expected and suggested that there was an underlying stability of community structure characterized by high dominance by a single species, although the identity of this changed, low diversity and a large proportion of the eel population harbouring 0 or only 1 species. A similar pattern of changes was recorded in the infra-communities, where values of species richness and diversity were very similar at the commencement and termination of the study. It appeared that those helminths that colonized in the recovery period contributed to community richness but had little impact on community structure. The helminth communities clearly did change in response to habitat changes, and the evidence for a fixed number of niches and an underlying constancy in helminth community structure in eels is evaluated.

Cryptosporidium parvum is a protozoan parasite that causes widespread diarrhoeal disease in humans and other animals and is responsible for large waterborne outbreaks of cryptosporidiosis. Unlike many organisms belonging to the phylum Apicomplexa, such as Plasmodium spp. and Toxoplasma gondii, there is no clinically proven drug treatment against this parasite. Aspects of the basic biology of C. parvum remain poorly understood, including a detailed knowledge of key metabolic pathways, its genome organization and organellar complement. Previous studies have proposed that C. parvum lacks a relic plastid organelle, or ‘apicoplast’, but that it may possess a mitochondrion. Here we characterize a mitochondrion-like organelle in C. parvum by (i) ultrastructural and morphological description (ii) localization of heterologous mitochondrial chaperonin antibody probes (iii) phylogenetic analysis of genes encoding mitochondrial transport proteins (iv) identification and analysis of mitochondrion-associated gene sequences. Our descriptive morphological analysis was performed by energy-filtering transmission electron microscopy (EFTEM) of C. hominis and C. parvum. The ‘mitochondrion-like’ organelle was characterized by labelling the structure with a heterologous mitochondrial chaperonin probe (hsp60) both in immunoelectron microscopy (IMEM) and immunofluorescence (IMF). Phylogenetic analysis of the mitochondrial import system and housekeeping components (hsp60 and hsp70-dnaK) suggested that the C. parvum mitochondrion-like organelle is likely to have descended from a common ancestral apicomplexan mitochondrion. We also identified a partial cDNA sequence coding for an alternative oxidase (AOX) gene, a component of the electron transport chain which can act as an alternative to the terminal mitochondrial respiratory complexes III and IV, which has not yet been reported in any other member of this phylum. Degenerate primers developed to identify selected mitochondrial genes failed to identify either cytochrome oxidase subunit I, or cytochrome b. Taken together, our data aim to provide new insights into the characterization of this Cryptosporidium organelle and a logical framework for future functional investigation.

On the Eastern Tibetan Plateau region (Sichuan province, China) dogs are regarded as important definitive hosts of Echinococcus multilocularis. We studied dog spatial behaviour in 4 Tibetan villages in order to determine the role of dogs in environmental contamination and their potential interactions with small mammal intermediate hosts. We identified definitive host species and Echinococcus spp. infection status of feces collected in the field by PCR methods and analysed the spatial distribution of canid feces. Nocturnal space utilization of GPS collared dogs in and around villages was also undertaken. E. multilocularis DNA was amplified in 23% of dog feces (n=142) and in 15% of fox feces (n=13) but this difference was not significant. However, dog feces were more frequently observed (78% of collected feces) than fox feces and are therefore assumed to largely contribute to human environment contamination. Feces were mainly distributed around houses of dog owners (0–200 m) where collared dogs spent the majority of their time. Inside villages, the contamination was aggregated in some micro-foci where groups of dogs defecated preferentially. Finally, small mammal densities increased from the dog core areas to grasslands at the periphery of villages occasionally used by dogs; male dogs moving significantly farther than females. This study constitutes a first attempt to quantify in a spatially explicit way the role of dogs in E. multilocularis peri-domestic cycles and to identify behavioural parameters required to model E. multilocularis transmission in this region.

Lyme borreliosis (LB) is the most common arthropod-borne disease of humans in the Northern hemisphere. In Europe, the causative agent, Borrelia burgdorferi sensu lato complex, is principally vectored by Ixodes ricinus ticks. The aim of this study was to identify environmental factors influencing questing I. ricinus nymph abundance and B. burgdorferi s.l. infection in questing nymphs using a large-scale survey across Scotland. Ticks, host dung and vegetation were surveyed at 25 woodland sites, and climatic variables from a Geographical Information System (GIS) were extracted for each site. A total of 2397 10 m2 transect surveys were conducted and 13 250 I. ricinus nymphs counted. Questing nymphs were assayed for B. burgdorferi s.l. and the average infection prevalence was 5·6% (range 0·8–13·9%). More questing nymphs and higher incidence of B. burgdorferi s.l. infection were found in areas with higher deer abundance and in mixed/deciduous compared to coniferous forests, as well as weaker correlations with season, altitude, rainfall and ground vegetation. No correlation was found between nymph abundance and infection prevalence within the ranges encountered. An understanding of the environmental conditions associated with tick abundance and pathogen prevalence may be used to reduce risk of exposure and to predict future pathogen prevalence and distributions under environmental changes.

The mode of action of bioactive plants on gastrointestinal nematodes remains obscure. Previous in vitro studies showed that exsheathment was significantly disturbed after contact with tannin-rich extracts. However, the role of important factors (extract concentration, parasite species) has not been assessed and no information is available on the occurrence in vivo. These questions represent the objectives of this study. The model incorporated the parasites Haemonchus contortus and Trichostrongylus colubriformis with sainfoin as the bioactive plant. A set of in vitro assays was performed, measuring the changes observed, after 3 h of contact with increasing concentrations of sainfoin, on the rate of artificial exsheathment. The results indicated that sainfoin extracts interfered with exsheathment in a dose-dependent manner and the process overall was similar for both nematodes. The restoration of control values observed after adding PEG to extracts confirms a major role for tannins. A second study was performed in vivo on rumen-cannulated sheep fed with different proportions of sainfoin in the diet to verify these in vitro results. The consumption of a higher proportion of sainfoin was indeed associated with significant delays in Haemonchus exsheathment. Overall, the results confirmed that interference with the early step of nematode infection might be one of the modes of action that contributes to the anthelmintic properties of tanniniferous plants.

When third-stage trichostrongyle larvae exsheathed, they released an exsheathing fluid which eroded the sheath at the anterior end. This led to the formation of a refractile ring and ultimately to the fracture of the sheath which enabled the larva to escape.

Exsheathment was induced by ovine rumen fluid. The exsheathing activity of rumen fluid was impaired by centrifuging, filtering, boiling and aeration, but activity could be restored by the addition of reducing agent. The activity in vitro of either fresh rumen fluid or freeze-dried rumen fluid, after addition of a reducing agent, was comparable with that obtained in vivo.

After stimulation, the process of exsheathment continued in the absence of rumen fluid. The ability of rumen fluid to stimulate larvae was dependent upon temperature, hydrogen-ion concentration and oxidation-reduction potential.

Exsheathing fluid was present in larvae both before and after exsheathment. Larvae which had been stimulated to exsheath released exsheathing fluid for a brief interval and further release could be obtained only after the stimuli had been temporarily withdrawn.

The mechanisms for reception of the stimulus to exsheath and for storing and releasing exsheathing fluid were located in a region between the base of the oesophagus and the excretory pore. The fluid was probably released from the excretory pore.

Exsheathing fluid from one species was not necessarily as active against sheaths from other species as against its own. The activity of exsheathing fluid was dependent upon the presence of a heat-stable cofactor of low molecular weight. Activity of the dialysed fluid could be restored by addition of MnCl2 or MgCl2. Values of Q10 for the action of the fluid on the sheath lay between 1·3 and 1·9. Activity was inhibited by Hg2+, Fe3+ and iodoacetic acid.

Despite the ubiquitous presence of parasites, parasitism has not been considered among the list of regulatory factors in animal populations until recently. A detailed long-term study on the impact of the direct life-cycle nematode Heligmosomoides polygyrus on a breeding population of laboratory mice provides a clear example of the ability of helminths to regulate host abundance. In the absence of the parasite, the mouse population equilibrated at a density of 320 mice/m2 as a result of density-dependent effects on recruitment. When the parasite was added and transmission was maintained at high levels, infected mouse populations equilibrated at densities of < 18 mice/m2. Reduced rates of parasite transmission and elimination of the parasite from the system both resulted in an increase in mouse density. These results have implications for both ecology and parasitology as they demonstrate a potentially important but often ignored component of host populations that may well influence host abundance and community structure.

Cell surface molecules have received intense attention in recent years because of the central roles they play at the interface between the external environment and the cellular interior. Their functions include adhesion to other cells or extracellular matrices, protection against hostile physical, chemical and biological agents and the transport of metabolites into and out of the cell. In addition, cell surface molecules transduce signals across the cell membrane, relaying information inwards and presenting altered characteristics to the exterior as the environment changes.

1. The egg shells of Fasciola are derived from globules or granules contained in the, vitelline cells. These globules contain an orthodihydroxyphenol and protein.

2. The anatomy and histology of the Mehlis's gland region have been described, and the site of liberation of the above granules has been isolated.

3. Mechanical forces, due to the churning action of the uterus, are believed to be responsible for freeing most of the granules. This liberation can be correlated with the presence of spermatozoa in the uterus. The spermatozoa can penetrate the vitelline cells, but this does not free the globules.

4. Active spermatozoa, in alkaline solutions, tend to form aggregates, and incorporate into these aggregates any solid material in the vicinity. This is apparently responsible for the arrangement of cells within the egg, and for the formation of a shell round it from fused vitelline cell globules.

5. The polyphenol of the newly formed egg shell is oxidized into a quinone in the anterior uterine coils. Polyphenol oxidases have not been conclusively demonstrated. The relative uterine coils are surrounded by an especial concentration of a generally distributed tissue haemoglobin.

6. The final egg shell is composed of a quinone tanned protein, similar to the sclerotin of the cockroach ootheca.

7. Suggestions are advanced as to the possible functions of Mehlis's gland and Laurer's canal.

An improved Theileria parva DNA detection assay based on the polymerase chain reaction (PCR) using primers derived from the 104 kDa antigen (p104) gene was developed to detect parasite DNA in blood spots on filter paper. The specificity of the assay was validated using DNA from a wide range of cattle-derived and buffalo-derived stocks of T. parva. DNA of T. annulata, T. buffeli, T. lestoquardi, T. mutans and T. taurotragi was not amplified using the p104 primers. The detection threshold of the assay was ∼1–2 parasites/μl of infected blood. PCR amplification using the p104 primers was applied to sequential samples from groups of cattle experimentally infected with either the T. parva Marikebuni stock that induces a long-term carrier state or the Muguga stock, which does not induce a carrier state. The study extended for up to 487 days post-infection and PCR data from defined time points were compared with parasitological microscopy and serological data, together with xenodiagnosis by experimental application of ticks. Microscopy first detected piroplasms between days 13 and 16 after infection whereas all cattle became PCR +ve between days 9 and 13. Animals infected with the Muguga stock of T. parva had parasite DNA in the peripheral blood, which could be detected by PCR, for between 33 and 129 days post-infection in different animals. By contrast parasite DNA in the blood of cattle infected with the Marikebuni stock could be detected consistently from day 9 up to 487 days, when the study terminated. The data suggest that the nature and persistence of the carrier state may differ markedly between different T. parva parasite stocks.

The biological membranes of Trypanosoma brucei contain a complex array of phospholipids that are synthesized de novo from precursors obtained either directly from the host, or as catabolised endocytosed lipids. This paper describes the use of nanoflow electrospray tandem mass spectrometry and high resolution mass spectrometry in both positive and negative ion modes, allowing the identification of ~500 individual molecular phospholipids species from total lipid extracts of cultured bloodstream and procyclic form T. brucei. Various molecular species of all of the major subclasses of glycerophospholipids were identified including phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, and phosphatidylinositol as well as phosphatidic acid, phosphatidylglycerol and cardolipin, and the sphingolipids sphingomyelin, inositol phosphoceramide and ethanolamine phosphoceramide. The lipidomic data obtained in this study will aid future biochemical phenotyping of either genetically or chemically manipulated commonly used bloodstream and procyclic strains of Trypanosoma brucei. Hopefully this will allow a greater understanding of the bizarre world of lipids in this important human pathogen.

The present review discusses the immune responses to gastrointestinal nematodes in cattle and the different immunological and parasitological parameters used to assess acquired immunity. Measuring acquired immunity to gastrointestinal nematodes in cattle (e.g. for the evaluation of candidate parasite vaccines) is hampered by the limited understanding of bovine immune responses against gastrointestinal parasites. In this paper the available data on protective immunity against gastrointestinal nematodes, and especially Ostertagia ostertagi, in cattle are compared with the current knowledge of protective immune responses against gastrointestinal nematodes in rodent models and small ruminants. In contrast to the immune response in mice, which is controlled by T helper 2 (Th2) lymphocytes and results in mast cell- or goblet cell- mediated expulsion of adult worms, bovine immune responses to O. ostertagi do not show a clear Th2 cytokine profile, nor do they result in rapid expulsion of the parasite. The first manifestation of immunity to O. ostertagi in calves is a reduction of worm fecundity, possibly regulated by the local IgA response. Worm numbers are only reduced after a prolonged period of host–parasite contact, and there are indications that O. ostertagi actively suppresses the host's immune response. Until the mechanisms of protective immunity against O. ostertagi are revealed, the use of immunological parameters to estimate acquired immunity in cattle is based on their correlation with parasitological parameters and on extrapolation from rodent and small ruminant models. Assessing the resistance of calves against a challenge infection by means of parasitological parameters is probably still the most accurate way to measure acquired immunity against gastrointestinal nematodes.

Trypanoplasma borreli and Trypanosoma carassii are kinetoplastid parasites infecting cyprinid fish. We investigated the role of nitric oxide (NO) in immune modulation during T. borreli and T. carassii infection of carp. Phagocytic cells from different organs produced NO and serum nitrate levels increased, demonstrating that T. borreli activates NO production in vivo. In contrast, T. carassii did not induce NO production in vivo and inhibited LPS-induced NO production in vitro. Production of NO was detrimental to the host as T. borreli-infected carp treated with the inducible NO synthase inhibitor aminoguanidine had a higher survival than infected control carp. This detrimental effect can be explained (in part) by the toxicity of NO to cells in vitro as NO inhibited the proliferative response of blood and spleen leukocytes. Head-kidney phagocytes were resistant to the immunosuppressive effects of NO in vitro. The NO-inducing activity of T. borreli may be an adaptation developed to ensure survival and immune evasion in the fish host. Apparently, T. carassii has adopted another strategy by deactivating specific functions of phagocytes. Both strategies may ensure long-term survival of the parasite.

Wistar-Furth strain male rats and CFW strain male mice were immunized against Trichinella spiralis using an antegenic fraction derived from a cell-free homogenate of mature muscle larvae.

In rats, animlas immunized with 250 μg of antigen harboured singnificantly fewer (135000) muscle larvae 30 days after oral challenge than controls (231000). Furhter 7-day-old adult worms derived from immunized rats shed 48% fewer (P < 0·001) newborn larvae over a 24 h period in vitro than adult worms from non-immunized animals.

Mice were injected with either 10 or 100 μg of antigen. In comparison with non-immunized controls, mice immunized with 100μg of antigen harboured significantly fewer adult worms at days 7 and 9 after oral challenge infection, while female worms recovered from immune mice on days 6–10 after challenge shed fewer newborn larvae in vitro. Finally, mice immunized with 100μg of antigen harboured significantly fewer (10391) muscle larvae at 30 days after challenge than did controls (47750).

Immunization of mice with 10μ of antigen did not induce a statistically significant reduction in adult worms at either days 7 or 9 after challenge (P < 0·5). However, adult female worms from mice receiving 10μg of antigen still shed fewer larvae than did adults from control mice (P < 0·05). Mice immunized with 10μg of antigen harboured significantly fewer (13700) recoverable muscle larvae than did controls at 30 days after challenge (39000).

Vaccinia virus, a member of the Poxviridae, expresses many proteins involved in immune evasion. In this review, we present a brief characterisation of the virus and its effects on host cells and discuss representative secreted and intracellular proteins expressed by vaccinia virus that are involved in modulation of innate immunity. These proteins target different aspects of the innate response by binding cytokines and interferons, inhibiting cytokine synthesis, opposing apoptosis or interfering with different signalling pathways, including those triggered by interferons and toll-like receptors.

Dinoflagellates are common and often important parasites of aquatic organisms, but their developmental cycles are poorly known and have not been established in in vitro culture. The parasitic dinoflagellate (Hematodinium sp.) associated with mortality of the Norway lobster (Nephrops norvegicus) in British waters has been cultivated in vitro in 10% foetal calf serum in a balanced Nephrops saline. In culture the parasite undergoes a characteristic cycle of development. Circulating sporoblasts from the host's haemolymph in vitro generate 2 kinds of flagellated uninucleate dinospore, macrospores and microspores, either of which will, after 5 weeks in fresh medium, germinate to produce multinucleate unattached filamentous trophonts. These trophonts multiply by fragmentation and growth and may be serially subcultured in this form, at 2 week intervals, indefinitely. If not subcultured, the filamentous trophonts give rise to colonies of radiating filaments (‘gorgonlocks’) which subsequently attach to the substratum to form flattened web-like ‘arachnoid’ multi-nucleate trophonts. Arachnoid trophonts become arachnoid sporonts when they synthesize trichocysts and flagellar hairs and may give rise to secondary arachnoid sporonts or to dinospores which initiate a new cycle.

Tapeworms of the species complex of Echinococcus granulosus sensu lato (s. l.) are the cause of a severe zoonotic disease – cystic echinococcosis, which is listed among the most severe parasitic diseases in humans and is prioritized by the World Health Organization. A stable taxonomy of E. granulosus s. l. is essential to the medical and veterinary communities for accurate and effective communication of the role of different species in this complex on human and animal health. E. granulosus s. l. displays high genetic diversity and has been divided into different species and genotypes. Despite several decades of research, the taxonomy of E. granulosus s. l. has remained controversial, especially the species status of genotypes G6–G10. Here the Bayesian phylogeny based on six nuclear loci (7387 bp in total) demonstrated, with very high support, the clustering of G6/G7 and G8/G10 into two separate clades. According to the evolutionary species concept, G6/G7 and G8/G10 can be regarded as two distinct species. Species differentiation can be attributed to the association with distinct host species, largely separate geographical distribution and low level of cross-fertilization. These factors have limited the gene flow between genotypic groups G6/G7 and G8/G10, resulting in the formation of distinct species. We discuss ecological and epidemiological differences that support the validity of these species.

Wildlife can act as reservoir of different tick-borne pathogens of veterinary and zoonotic importance. To investigate the role of wild ruminants as reservoir of piroplasm infection, 28 red deer, 69 roe deer and 38 chamois from Northern Spain were examined by reverse line blot (RLB) hybridization. The survey detected a prevalence of 85·7% in red deer, 62·3% in roe deer and 28·9% in chamois. Four different piroplasms were identified: Theileria sp. OT3 (previously described in sheep) as the most prevalent (85·7% in red deer, 46·4% in roe deer and 26·3% in chamois); Theileria sp. 3185/02 (previously described in a red deer in Central Spain) more abundant in red deer (53·6%) than in roe deer (10·1%) but absent from chamois; Babesia divergens detected in 6 roe deer; Theileria ovis present in 1 chamois. Mixed infections (Theileria sp. OT3 and Theileria sp. 3185/02) were only found in red and roe deer. Sequencing analysis of the 18S rRNA gene confirmed the RLB results and showed 99·7% identity between Theileria sp. 3185/02 and T. capreoli, suggesting that they are the same species. Tick distribution and contact of wild ruminants with domestic animals are discussed in terms of piroplasm infection. The results suggest that a considerable number of wildlife ruminants are asymptomatic carriers that may serve as reservoirs of the infection posing a serious concern in terms of piroplasmosis control.

A new Myxozoa species causing enteritis and death in cultured turbot, Scophthalmus maximus, is described at light and electron microscope levels. In addition, small subunit ribosomal RNA gene sequences (SSU rDNA) from the new species and from similar myxozoans were obtained and used for phylogenetic inference, as complementary criteria to resolve its taxonomic classification. The new parasite is closely related to Myxidium leei, another enteric histozoic species from marine fish. However, the ascription of M. leei to the genus Myxidium was based on weak morphological evidence and is not supported by our rDNA data analysis. A close relationship with Zschokkella, the other morphologically related myxozoan genus is also not supported. The combined morphological and molecular study results in the establishment of the new genus Enteromyxum to accommodate the new species E. scophthalmi, and the former M. leei, which is transferred to the new genus as Enteromyxum leei (Diamant, Lom & Dyková 1994) n. comb. This genus of marine, histozoic and enteric myxozoans includes significant parasite species for marine finfish culture.