Analyses of laboratory-based helminth-rodent model systems have been immensely useful in delineating the workings of the mammalian immune system. Investigations in the 1970s–1980s on the fate of the rat tapeworm, Hymenolepis diminuta, in rats and mice and the systemic and local responses evoked following infection have contributed directly to our knowledge of how permissive and non-permissive hosts respond to the challenge of infection with a helminth parasite. This convenient laboratory model system has, in the authors' opinion, regrettably received considerably less attention in recent years. With the goal of highlighting the utility of this model system, data is presented on: (1) the immune and enteric responses of rats and mice to infection with H. diminuta; (2) the ability of excretory or secretory products derived from H. diminuta to significantly reduce T cell and macrophage activation in vitro; and (3) how assessment of H. diminuta-rodent models can be used to identify immune effector or regulatory mechanisms that can be translated into novel treatments for inflammatory and autoimmune disorders.

Myxosporean parasites are significant parasites of fishes not only for their apparent high diversity but also for their potential impact on fish health and/or marketability. Regardless, our knowledge of most myxosporeans, especially those found in elasmobranch hosts, is superficial. A study of multivalvulidan diversity in a range of elasmobranchs from Queensland, Western Australia and the Northern Territory (Australia) was conducted to address this knowledge gap. Specimens were collected from a total of 3 orders, 9 families and 31 species of elasmobranchs. Myxosporean infections referable to the genus Kudoa were discovered in host muscle and characterized morphologically and genetically. Both small subunit (SSU) and large subunit (LSU) rDNA sequences were used in molecular phylogenetic analyses. Kudoa spp. infected 27 of the 31 species of elasmobranchs examined, representing new records of this parasite genus in 26, of the 27, host species. Kudoids were observed in all 3 orders, and 7 out of the 9 families of elasmobranchs investigated. This paper reports the first 2 multivalvulidan species to be formally described from elasmobranchs, Kudoa hemiscylli n.sp. characterized from Hemiscyllium ocellatum (and 8 other host species) and Kudoa carcharhini n. sp. characterized from Carcharhinus cautus (and 2 other host species). Phylogenetic analyses revealed that kudoids from elasmobranchs form a separate lineage to those of teleosts, but are anchored within the overall kudoid clade.

Scarce and inconclusive information on general biological impact of Toxocara invasion on paratenic hosts, and people in particular, has led us to undertake a comprehensive study of the problem. The study has been conducted in a rural environment, which is considered a toxocarosis risk factor. In total 200 soil samples have been screened for Toxocara eggs by flotation, of which 14·5% were positive. Backyards close to households were most heavily contaminated with infectious eggs – 21·7% of positive samples. ELISA serological tests performed on 242 lower-secondary students found 14·5% of the studied population to be definitely positive – 16·5% of boys and 12·8% of girls, respectively. The odds of being infected with Toxocara were 2 times (CI: 1·15–3·85) more likely for individuals who owned a cat than those who did not own a cat. Strong significant correlation between seropositivity and the presence of a dog in a household was found with boys. The level of developmental age was significantly higher in seropositive than in seronegative students. No significant correlation has been observed between the motor abilities and seropositivity of students. Seropositive boys had significantly lower end-of-year grades than their seronegative counterparts.

We asked whether the occurrence and the extent of host gender-biased parasitism vary among higher parasite taxa, among individual species within these taxa and within parasite species among localities. To answer this question, we studied prevalence, abundance, species richness and the level of aggregation of ectoparasites (ticks, mites, lice and fleas) collected from male and female striped mice (Rhabdomys pumilio) in 9 localities of the Western Cape Province of South Africa. We used meta-analyses to compare parasitological variables between male and female hosts across localities for individual parasite species and higher taxa as well as across parasite species within a higher taxon. Whenever gender-biased parasitism was found, it indicated higher infestation of male than female hosts (except 1 low abundant mite species). We found that the occurrence and extent of gender-biased infestation varied mainly within a parasite species among localities and among parasite species within a higher taxon but not among parasite taxa. Our results suggest that the extent of a gender-biased pattern of parasite infestation of the same host may not only involve host-related mechanisms but also depends on biological features of a particular parasite species.

Recent schistosomiasis control efforts in sub-Saharan Africa have focused nearly exclusively on treatment of humans with praziquantel. However, the extent to which wild mammals act as reservoirs for Schistosoma mansoni and therefore as sources of renewed transmission following control efforts is poorly understood. With the objective to study the role of small mammals as reservoir hosts, 480 animals belonging to 9 rodent and 1 insectivore species were examined for infection with schistosomes in Kisumu, in the Lake Victoria Basin, Kenya. Animals were collected from 2 sites: near the lakeshore and from Nyabera Marsh draining into the lake. A total of 6·0% of the animals captured, including 5 murid rodent species and 1 species of shrew (Crocidura olivieri) were infected with schistosomes. Four schistosome species were recovered and identified using cox1 DNA barcoding: S. mansoni, S. bovis, S. rodhaini and S. kisumuensis, the latter of which was recently described from Nyabera Marsh. Schistosoma mansoni and S. rodhaini were found infecting the same host individual (Lophuromys flavopunctatus), suggesting that this host species could be responsible for the production of hybrid schistosomes found in the area. Although the prevalence of S. mansoni infection in these reservoir populations was low (1·5%), given their potentially vast population size, their impact on transmission needs further study. Reservoir hosts could perpetuate snail infections and favour renewed transmission to humans once control programmes have ceased.

The adult cestode, Hymenolepis diminuta, is essentially anaerobic energetically. Carbohydrate dissimilation results in acetate, lactate and succinate accumulation with succinate being the major end product. Succinate accumulation results from the anaerobic, mitochondrial, ‘malic’ enzyme-dependent utilization of malate coupled to ATP generation via the electron transport-linked fumarate reductase. A lesser peroxide-forming oxidase is apparent, however, fumarate reduction to succinate predominates even in air. The H. diminuta matrix-localized ‘malic’ enzyme is NADP-specific whereas the inner membrane (IM)-associated electron transport system prefers NADH. This dilemma is circumvented by the mitochondrial, IM-associated NADPH→NAD+ transhydrogenase in catalyzing hydride ion transfer from NADPH to NAD+ on the IM matrix surface. Hydride transfer is reversible and phospholipid-dependent. NADP+ reduction occurs as a non energy-linked and energy-linked reaction with the latter requiring electron transport NADH utilization or ATP hydrolysis. With NAD+ reduction, the cestode transhydrogenase also engages in concomitant proton translocation from the mitochondrial matrix to the intermembrane space and supports net ATP generation. Thus, the cestode NADPH→NAD+ system can serve not only as a metabolic connector, but an additional anaerobic phosphorylation site. Although its function(s) is unknown, a separate IM-associated NADH→ NAD+ transhydrogenation, catalyzed by the lipoamide and NADH dehydrogenases, is noted.

We measured seasonal changes in the prevalence of haematozoa (Leucocytozoon fringillinarum, Haemoproteus fringillae, and Trypanosoma avium) in free-ranging White-winged Crossbills, Loxia leucoptera, over 1·5 year in Fairbanks, Alaska, USA. This prevalence was low during early winter. L. fringillinarum prevalence increased in late winter/early spring, in the absence of vectors, suggesting relapse of latent infection. By contrast, the prevalence of T. avium and H. fringillae did not increase until mid-spring, coincident with the emergence of putative vectors and suggestive of new inoculations. The winter breeding period was not associated with lower body condition or elevated blood heterophil/lymphocyte ratios than the summer post-breeding period. Thus, birds unlikely perceived their breeding effort as particularly stressful. Adult males in May and June had low plasma testosterone and their blood prevalence of L. fringillinarum, but not other haemoparasites, was higher than in adult females. This difference may have resulted from sex differences in behaviour and/or plumage colouration – bright red in males, dull green/yellow in females. Species in which reproduction and vector abundance are seasonally dissociated may constitute important models for investigating the respective contribution of reproductive hormones, breeding effort, and vector abundance to patent and latent hemoparasitic infections and to new inoculations.

Uptake of triclabendazole by the liver fluke, Fasciola hepatica has been studied by experiments designed to block either oral uptake of drug, by use of ligatures, or trans-tegumental diffusion, by allowing the drug to bind to an excess of bovine serum albumin (BSA) in the medium. Changes to the tegumental system, musculature and gut were assessed using transmission electron microscopy. Flukes were incubated in vitro for 24 h in TCBZ.SO (15 μg/ml). Disruption to the tegument and muscle was similar in ligatured and non-ligatured flukes, suggesting that closing the oral route did not affect drug uptake. The ultrastructure of the gastrodermal cells remained unchanged. Non-ligatured flukes were also incubated for 24 h in vitro in TCBZ.SO (15 μg/ml) in the presence of red blood cells (RBCs). Oral uptake of blood was demonstrated, but gut ultrastructure remained normal, whereas the tegument was severely disrupted. In separate experiments, ligatured and non-ligatured flukes were incubated in TCBZ.SO (15 μg/ml) in the presence of BSA (30 mg/ml) for 24 h in vitro. There was a marked decrease in the degree of tegumental disruption observed compared with TCBZ.SO action alone; again, the gut remained normal. The findings support previous morphological and pharmacological studies indicating that trans-tegumental uptake of triclabendazole predominates in the liver fluke.

Chagas' disease is a debilitating but comparatively neglected illness that affects about 15 million people. There is an urgent need to develop new, more effective, and less-toxic compounds. In this study, we assessed the in vitro anti-trypanosomal activity of the sesquiterpene elatol from the Brazilian red seaweed Laurencia dendroidea. We used electron microscopy to evaluate the effect of elatol on the morphology and ultrastructure of the parasite. Elatol showed a dose-dependent effect against the epimastigote, trypomastigote, and amastigote forms, with IC50 values of 45·4, 1·38, and 1·01 μm, respectively. Observation of treated intracellular amastigotes by light microscopy demonstrated a total elimination of the infection at a dose of 3·0 μm. In addition, the compound did not affect the red blood cells, and the CC50 value for LLCMK2 cells was 27·0 μm. Transmission and scanning electron micrographs showed aberrant-shaped cells and breaks in the plasma membrane, prominent swollen mitochondria, and extensive formation of cytoplasmic vacuoles in all the forms. This is the first report of the anti-trypanosomal effect of the sesquiterpene elatol.

The highly pathogenic avian protozoan Leucocytozoon caulleryi infects host chicken cells, and interference by the host genome results in difficulty in obtaining protozoal DNA for genetic analysis. We used flow cytometry analysis to separate expelled L. caulleryi gametocytes from infected chicken blood and to analyse cell populations and sorting by FACS efficiency. Infected blood cells stained with SYTO-24 showed a specific area on 2-dimensional scattergrams compared to uninfected blood. The specific area was sorted, and approximately 85% of the sorted cells were identified as L. caulleryi gametocytes by microscopic observation. DNA was also extracted from the sorted fraction, and a clear increase in polymerase chain reaction (PCR) amplification of protozoal DNA was observed compared to infected blood without sorting. Host-derived DNA was also detected by PCR; however, its amplification was decreased compared to that in unsorted infected blood. This is the first report of the separation of L. caulleryi gametocytes from infected host blood using flow cytometry. This method may be applied to further genetic analyses such as studies of the dynamics of stage-specific L. caulleryi gene expression.

The parasitic mite, Varroa destructor, is the most important threat for apiculture in most bee-keeping areas of the world. The mite is carried to the bee brood cell, where it reproduces, by a nurse bee; therefore the selection of the bee stage by the parasite could influence its reproductive success. This study investigates the role of the cuticular hydrocarbons of the European honeybee (Apis mellifera) in host-selection by the mite. Preliminary laboratory bioassays confirmed the preference of the varroa mite for nurse bees over pollen foragers. GC-MS analysis of nurse and pollen bees revealed differences in the cuticular hydrocarbons of the two stages; in particular, it appeared that pollen bees have more (Z)-8-heptadecene than nurse bees. Laboratory experiments showed that treatment of nurse bees with 100 ng of the pure compound makes them repellent to the varroa mite. These results suggest that the mite can exploit the differences in the cuticular composition of its host for a refined selection that allows it to reach a brood cell and start reproduction. The biological activity of the alkene encourages further investigations for the development of novel control techniques based on this compound.

Plasmodium falciparum, the agent responsible for malaria, is an obligate intracellular protozoan parasite. For proliferation, differentiation and survival, it relies on its own protein-encoding genes, as well as its host cells for nutrient sources. Nutrients and subsequent metabolites are required by the parasites to support their high rate of growth and replication, particularly in the intra-erythrocytic stages of the parasite that are responsible for the clinical symptoms of the disease. Advances in mass spectrometry have improved the analysis of endogenous metabolites and enabled a global approach to identify the parasite's metabolites by the so-called metabolomic analyses. This level of analysis complements the genomic, transcriptomic and proteomic data already available and should allow the identification of novel metabolites, original pathways and networks of regulatory interactions within the parasite, and between the parasite and its hosts. The field of metabolomics is just in its infancy in P. falciparum, hence in this review, we concentrate on the available methodologies and their potential applications for deciphering important biochemical processes of the parasite, such as the astonishingly diverse phospholipid biosynthesis pathways. Elucidating the regulation of the biosynthesis of these crucial metabolites could help design of future anti-malarial drugs.

In non-permanent parasites the separation from the host should take place in suitable habitats that allow the continuation of their life cycle. Furthermore, detachment strategies determine the parasites' dispersal capability, a characteristic on which epidemiological dynamics and the evolution of host specificity centre. In this study we experimentally investigate in the laboratory how 2 congeneric tick species, with contrasting habitat requirements, time detachment from one of their current songbird hosts (Parus major). Ixodes arboricola is a nidicolous tick, infesting bats and birds breeding or roosting in tree holes. Ixodes ricinus is a non-nidicolous generalist that parasitizes mammals, birds and even reptiles. We experimentally infested full-grown great tits, P. major, and found that I. arboricola detaches during the night, the moment when P. major sleeps in tree holes. In contrast, I. ricinus detaches during the day, the moment when birds are most active. In addition we found that all I. ricinus immatures left the birds within 5.5 days, while in I. arboricola the detachment time was long (up to 20 days) and highly variable. We discuss these findings with respect to their implications on the ticks' dispersal capability and host specificity.

Trypanosoma brucei is exposed to the adaptive immune system and complement in the blood of its mammalian hosts. The aim of this review is to analyse the role and regulation of the proteins present on the external face of the plasma membrane in the long-term persistence of an infection and transmission. In particular, the following are addressed: (1) antigenic variation of the variant surface glycoprotein (VSG), (2) the formation of an effective VSG barrier shielding invariant surface proteins, and (3) the rapid uptake of VSG antibody complexes combined with degradation of the immunoglobulin and recycling of the VSG.

Glycogen synthase kinase-3 (GSK-3) is classically described as a key enzyme involved in glycogen metabolism in mammals. It has been shown to be highly conserved among several organisms, mainly in the catalytic domain region. This enzyme has already been described in Rhipicephalus (Boophilus) microplus and the ovaries of females appeared to be the major site of GSK-3 transcription. The treatment with GSK-3 specific inhibitor (alsterpaullone, bromo-indirubin-oxime 6 and indirubin-3-oxime) caused a reduction in oviposition and egg hatching in completely engorged female ticks. The effect was more pronounced in partially engorged females when alsterpaullone was administrated by artificial capillary feeding. Moreover, GSK-3 gene silencing by RNAi in partially engorged females reduced significantly both oviposition and hatching. The study of tick embryogenesis and proteins that participate in this process has been suggested as an important means for the development of novel strategies for parasite control. GSK-3 is an essential protein involved in embryonic processes and for this reason it has already been suggested as a possible antigen candidate for tick control.

We analysed data on the abundance and distribution of 26 species of mesostigmate mites with different feeding habits collected from bodies of small mammalian hosts in 2 geographical regions (West Siberia and Argentina). We tested whether prevalence of a mite can be reliably predicted from a simple epidemiological model that takes into account mean abundance and its variance. We theorized that the difference between prevalence predicted from the model and observed prevalence would be smallest in obligatory haematophagous mites, intermediate in facultatively haematophagous mites and greatest in non-haematophagous mites. We also theorized that prevalence of mites from the region with sharp seasonality (Siberia) would be predicted accurately only if host number would be taken into account. We found that the success of a simple epidemiological model to predict prevalence in mites was similar to that reported earlier for other ectoparasitic arthropods. Surprisingly, the model predicted prevalence of obligatory exclusively haematophagous mites less successfully than that of mites with other feeding habits. No difference in the model performance between mites occurring in the 2 geographical regions were found independent of whether the model took the number of hosts into account.

This study reports that the cytopathic effect of Trichomonas vaginalis, an important human parasite of the urogenital tract, occurs due to mechanical stress and subsequent phagocytosis of the necrotic cells. The investigation was done using a primary culture of bovine oviduct epithelial cells (BOECs), grown either in monolayers or as floating cells. Trophozoites displaying different virulence levels were co-incubated with BOECs for times varying between 1 min and 48 h. Analyses were performed using videomicroscopy, scanning and transmission electron microscopy, colourimetric assays and cytochemistry. Injury was observed as early as 1 h after incubation, while after 12 h the host cells were severely damaged when a fresh trichomonad isolate was used. Trichomonads attack the host cells by clustering around them. Mechanical stress on the microvilli of the host cells was observed and appeared to induce plasma membrane damage and cell death. After membrane injury and lysis, fragments of the necrotic cells were ingested by trichomonads. Phagocytosis occurred by trichomonads avidly eating large portions of epithelial cells containing the nucleus and other organelles, but living or intact cells were not ingested. Necrotic fragments were rapidly digested in lysosomes, as shown by acid phosphatase and ruthenium red assays where only the BOECs were labelled. The lytic capacity of the trichomonads was more pronounced in host cell suspensions.

The use of chemotherapy on a mass scale in endemic areas may lead to the appearance of resistant isolates through the mechanism of selective drug pressure. Studies have demonstrated that praziquantel (PZQ) is able to inhibit the excretory activity and to cause tegumental damage in Schistosoma mansoni adult worms. The use of the probe resorufin to evaluate excretory activity, as well as the probe Hoechst 33258 to detect tegumental damage in adult worms, may represent a method to identify resistant (or less susceptible) isolates. The purpose of the present work was to compare the changes caused by PZQ in the function of the excretory system and in the integrity of the tegument of adult worms from the LE isolate (susceptible to PZQ) and the LE-PZQ isolate (less susceptible to PZQ). Worms from the isolate LE-PZQ showed less severe tegumental lesions, in both in vitro and in vivo experiments, detected by labelling with Hoechst 33258 and continued to have a functional excretory system as shown by labelling with resorufin in vitro.

Understanding the impacts of endemic parasites on protected hosts is an essential element of conservation management. However, where manipulative experiments are unethical, causality cannot be inferred from observational correlative studies. Instead, we used an experimental structure to explore temporal associations between body condition of a protected reptile, the tuatara (Sphenodon punctatus) and infestation with ectoparasites (ticks and mites). We surveyed tuatara in a mark-recapture study on Stephens Island (New Zealand), which encompassed the pre-peak, peak and post-peak infestation periods for each ectoparasite. Tick loads during the peak infestation period were negatively related to body condition of tuatara. Body condition before the peak was not related to subsequent infestation rates; however, tick loads in the peak were negatively related to subsequent changes in body condition. Mite loads during the peak infestation period were not correlated with body condition of tuatara. Body condition before the peak had no effect on subsequent mite infestation rates, but mite loads of small males during the peak were negatively related to subsequent changes in body condition. Our results suggest that both ectoparasites reduce the body condition of tuatara, which has implications for the long-term conservation management of this host and its parasites.

In case of cercarial dermatitis after exposure to fresh water lakes, managers responsible for bathing water quality wish to confirm the presence of Trichobilharzia, which substantiates taking measures to protect bathers from further exposure. A novel approach, including concentration of suspected water samples by filtration and PCR detection of the parasite, is proposed. This approach has been applied to bathing sites with a history of cercarial dermatitis, sampled from 2005 to 2008. Examination of snails, the standard procedure for confirmation of the parasite's presence, and analysis of water samples, appear to be complementary procedures that enhance the chance of parasite detection in implicated bathing water. Water analysis is particularly valuable when snails cannot be found; it confirmed the presence of Trichobilharzia on 25% of sampling days with reported skin conditions and no snails found. PCR of the ToSau3A repeat directly confirmed the parasite in the water. The application of the combination of analysis of water samples and examination of snails is suggested when cases of (presumptive) cercarial dermatitis are reported or when lakes with a history of cercarial dermatitis are inspected prior to the bathing season, in order to guide interventions to prevent (further) cases of swimmers' itch.