Host manipulation by trophically transmitted parasites may predispose infected hosts to predation and in this way enhance parasite transmission. In most study systems, however, the evidence comes from laboratory studies, and therefore knowledge of the effect of manipulation on parasite transmission efficiency in the wild is still limited. Here we examined the effect of Diplostomum spathaceum (Trematoda) eye flukes on the susceptibility of fish intermediate hosts to predation by bird definitive hosts. Our earlier studies have shown that the parasite alters fish phenotype and increases their susceptibility to artificial predation under laboratory conditions. In the present field study, we allowed wild birds to feed on fish from cages placed into a lake, and found that predation vulnerability of infected fish did not differ from that of controls. However, we suggest that the experimental set-up likely affected the result because the cages allowed gulls, which caught most of the fish in the study, to feed on fish in an easy, unnatural manner by standing on the edges of the cages. Nevertheless, considerable predation was observed, which provides important initial evidence of how this question should be addressed in the wild.

There are comparatively few studies concerned specifically with chemotherapy of parasitic infections and its relationship with the immune status of the host being treated. In one sense this is hardly surprising. The disciplines of chemotherapy and immunology have developed independently, and the search for effective drugs has for the most part been an empirical process; when a compound showing some activity has emerged the tendency has been to look for analogues with even greater parasiticidal properties rather than to consider whether effectiveness of the parent compound could be improved if the immune status of the host were different. In many cases, test systems for drug development have actually been selected to reduce as far as possible the complications f an immune response. Thus acute, fatal infections are commonly used for the screens, and questions such as the level of specific resistance at the time of treatment, immunodepression by the parasite, and increased resistance to challenge following chemotherapy are generally irrelevant.

1. The bucephalid cercaria from Crassostrea virginica (Gmelin), the commercial oyster of the Atlantic and Gulf coasts of North America, has been called Bucephalus haimeanus Lacaze-Duthiers and Bucephalopsis haimeana (Lacaze-Duthiers). Neither of these names is correct. Bucephalus haimeanus Lacaze-Duthiers, 1854, is a parasite of the European oyster, Ostrea edulis L. (and possibly of cockles, Cardium spp.) in oceanic or near-oceanic habitats, while the American species is a parasite of an estuarine oyster and is found almost entirely in the least saline parts of its host's range. The correct name of the American oyster bucephalid is Bucephalus cuculus McCrady, 1874.

2. The life cycles of all European marine bucephalids are still unknown. The life cycles described in the European literature are based entirely on morphological resemblances which are not close enough to be convincing, and none of them has been tested by experiment. Bucephalid cercariae do not show any of the features which are used to distinguish genera. So far as present evidence goes, Bucephalopsis haimeana is just as likely to develop into a Rhipidocotyle, a Bucephalus, or a Prosorhynchus as it is to develop into a member of the genus Bucephalopsis Nicoll, 1914, nec Diesing, 1855.

3. Bucephalopsis Diesing, 1855, is the name proposed by Diesing for a subgenus created especially for the cercaria Bucephalus haimeanus Lacaze-Duthiers, 1854. Nicoll had no right to use this name for the genus of gasterostomes which, as adults, have a muscular sucker at the anterior end and do not have accessory structures such as a hood or papillae. Up to the present, there is still no evidence that this genus has any connexion with Lacaze-Duthiers's cercaria, other than common membership in the family Bucephalidae. Therefore the new name Bucephaloides Hopkins has been proposed to replace the generic name Bucephalopsis Nicoll, 1914, nec Diesing, 1855, with Bucephaloides gracilescens (Rudolphi, 1819) as the type species. This genus does not include Bucephalus haimeanus Lacaze-Duthiers because the metacercaria and the adult form of that species remain unknown.

4. Tennent (1905, 1906, 1909) did not prove that there was any connexion between the oyster cercaria, Bucephalus cuculus McCrady, and the immature bucephalids in Menidia or the adult bucephalids in Strongylura. His drawings show that at least some of the bucephalids which Tennent studied had a hood and therefore belong in Rhipidocotyle. Re-examination of the bucephalids in Strongylura marina reveals that at least three species of bucephalids occur as adults in that host; these are described in this paper as Rhipidocotyle transversale Chandler, 1935, R. lintoni Hopkins, and Bucephaloides strongylurae Hopkins. Rhipidocotyle transversale and Bucephaloides strongylurae were also found in an immature (metacercaria) stage in Menidia, and were the only bucephalids found in Menidia during this study. The excretory systems of the three species in Strongylura all have features which exclude the possibility that they could develop from the oyster cercaria, Bucephalus cuculus.

5. Tennent's (1906) drawing (fig. 46) of an adult bucephalid from Strongylura marina, which Eckmann (1932) mentions as the best representation of the species characteristics of Bucephalopsis haimeana (Lacaze-Duthiers), was probably made from a specimen of Rhipidocotyle lintoni.

6. Tennent (1909) proved that eggs or larvae from an unknown adult bucephalid in Lepisosteus osseus could infect oysters, Crassostrea virginica, and develop into sporocysts which would grow in oysters for at least one month. This is the only experimental proof of a connexion between an adult bucephalid in a fish and a larval bucephalid in an oyster. Until the present, no bucephalid from a gar (Lepisosteus) had ever been described. In the present paper Rhipidocotyle lepis-ostei Hopkins is described from adults in Lepisosteus spatula, the alligator gar, in Louisiana. The metacercariae of Rhipidocotyle lepisostei are abundant in the fin rays of mullets, Mugil cephalus and M. curema. The excretory system of this species is not identical with that of Bucephalus cuculus, but is not so different as to exclude the possibility that the oyster cercaria might develop into R. lepisostei. If, in the future, R. lepisostei is proved to be the adult form of Bucephalus cuculus, the name of the species will become Rhipidocotyle cuculus (McCrady), and R. lepisostei will become a synonym.

The parameters of species richness, abundance and diversity of the intestinal helminth infracommunities of a sample of 269 Common gulls, Larus canus, were examined over one season at Agdenes, Norway. The communities developed rapidly in unfledged gulls and the diversity parameters were of similar magnitude in immature and adult birds. All parameters were low in the early part of the season, reached maxima in June or July and fluctuated erratically or declined thereafter. Comparison of summary parameters with those from other species of gulls indicated that helminth community diversity in Common gulls is fairly typical of gulls in general. In gulls as a group, helminth communities show common features of high species richness, low abundance, few or no core species and a number of species that occur rarely and in low numbers. Expectations of particularly high parasite community diversity were not fully realised because species lists and diversity of the component community are not a very good basis for predicting diversity at the infracommunity level.

The activation of peritoneal macrophage effector functions after therapy with free PZQ and PZQ incorporated in liposomes (lip.PZQ) was studied in the Mesocestoides corti–mouse model system. Each drug formulation was administered to an infected group of mice in 6 daily doses from day 14 p.i. Phagocytic activity of macrophages increased significantly after the administration of both drug formulations, more after lip.PZQ with an earlier peak observed for PZQ (day 3) than for lip.PZQ (day 6). Empty liposomes had no significant effect. The average counts of ingested particles in phagocytosing cells were significantly higher only after lip.PZQ administration. The pattern of changes in phagocytic activity correlated with the reduction of parasite numbers in the peritoneal cavity, with the highest observed on day 6 after therapy with lip.PZQ. Phagocytosis of lip.PZQ in vivo stimulated significantly the respiratory burst in peritoneal macrophages, with the highest concentration of superoxide anions recorded on day 1 after the last dose, whereas therapy with PZQ itself did not increase this process significantly. The capacity for the respiratory burst declined in all groups with progressing infection. It is proposed that the phagocytic activity of peritoneal macrophages after therapy was stimulated indirectly as a consequence of activation of the specific immune response. The larvicidal effect of lip.PZQ on the tetrathyridia in the peritoneal cavity was synergistic with the phagocytic activity and might be the result of double action of drug and superoxide anions generated during the respiratory burst stimulated by this drug formulation.

This study aimed to evaluate in vitro and in vivo trypanocidal activity of free and nanoencapsulated curcumin against Trypanosoma evansi. In vitro efficacy of free curcumin (CURC) and curcumin-loaded in lipid-core nanocapsules (C-LNCs) was evaluated to verify their lethal effect on T. evansi. To perform the in vivo tests, T. evansi-infected animals were treated with CURC (10 and 100 mg kg−1, intraperitoneally [i.p.]) and C-LNCs (10 mg kg−1, i.p.) during 6 days, with the results showing that these treatments significantly attenuated the parasitaemia. Infected untreated rats showed protein peroxidation and an increase of nitrites/nitrates, whereas animals treated with curcumin showed a reduction on these variables. As a result, the activity of antioxidant enzymes (superoxide dismutase and catalase) differs between groups (P<0·05). Infected animals and treated with CURC exhibited a reduction in the levels of alanine aminotransferase and creatinine, when compared with the positive control group. The use of curcumin in vitro resulted in a better parasitaemia control, an antioxidant activity and a protective effect on liver and kidney functions of T. evansi-infected adult male Wistar rats.

Due to side-effects and inefficiency of the drugs used in malaria treatment, finding alternative medicine with less side-effects has attracted much attention. In this regard, in the present study, nanocomposite synthesized and its effects on the metabolites of P. falciparum were investigated. Subsequent to synthesis of nanocomposites, characterization was carried out using nuclear magnetic resonance (NMR), liquid chromatography-mass spectrometry (LC-MS), scanning electron microscopy, dynamic light scattering and Fourier-transform infrared tests. Solubility and drug release were measured and its toxicity on Vero cell was assessed using the MTT assay. The antiparasitic effect of the nanocomposite on the metabolites of P. falciparum was investigated by 1H NMR spectroscopy. Among synthesized nanocomposites, the average size of 239 nm showed suitable solubility in water as well as slow drug release. The MTT assay showed no toxicity for Vero cell lines. Concentrations of 2.5 μg mL−1 of nanocomposite eliminated 82.6% of the total parasites. The most effected metabolic cycles were glyoxylate and dicarboxylate metabolism. In this study, 1H NMR spectroscopy was used with untargeted metabolomics to study the effect of the nanocomposite on P. falciparum. Playing an essential role in understanding drug-target interactions and characterization of mechanism of action or resistance exhibited by novel antiprotozoal drugs, can be achieved by targeting metabolic using LC-MS.

Human–wildlife interactions have reached unprecedented levels, and humans are influencing the earth's ecosystems more rapidly and extensively than ever before. This situation is cause for serious concern, especially since disease interactions between wildlife and humans have been recognized as major conservation threats. In this study, long-tailed macaques, Macaca fascicularis, from 2 forest parks located in north-eastern Thailand were investigated to determine the influence of habitat modification by humans on helminth parasite associations in non-human primates. Macaque populations with contact to anthropogenically modified environments were compared with sylvatic groups in nearby natural environments. In order to test for human–non-human primate transmission of parasites, the local human populations were also examined. Humans were infected with a number of potentially pathogenic parasites, including Opisthorchis viverrini and Strongyloides stercoralis. However, eggs of these helminths were not detected in macaque feces. Thus, no direct parasite transfer from humans to non-human primates could be confirmed. However, macaque groups with more frequent contact with human-modified habitats, and a higher portion of human-provided food in their diet, had significantly higher prevalences and intensities of Strongyloides fuelleborni and of an intestinal fluke (probably Haplorchis sp.) than sylvatic groups. Positive correlations were found between the time foraging on the ground and infection with S. fuelleborni, and the amount of human-provided food and intestinal fluke infection. Human alteration of habitat and associated modifications in non-human primate behaviour are likely to play a role in determining the occurrence, prevalence and intensity of zoonotic helminth infection of wild non-human primates.

Variations in levels of parasitism among individuals in a population of hosts underpin the importance of parasites as an evolutionary or ecological force. Factors influencing parasite richness (number of parasite species) and load (abundance and biomass) at the individual host level ultimately form the basis of parasite infection patterns. In fish, diet range (number of prey taxa consumed) and prey selectivity (proportion of a particular prey taxon in the diet) have been shown to influence parasite infection levels. However, fish diet is most often characterized at the species or fish population level, thus ignoring variation among conspecific individuals and its potential effects on infection patterns among individuals. Here, we examined parasite infections and stomach contents of New Zealand freshwater fish at the individual level. We tested for potential links between the richness, abundance and biomass of helminth parasites and the diet range and prey selectivity of individual fish hosts. There was no obvious link between individual fish host diet and helminth infection levels. Our results were consistent across multiple fish host and parasite species and contrast with those of earlier studies in which fish diet and parasite infection were linked, hinting at a true disconnect between host diet and measures of parasite infections in our study systems. This absence of relationship between host diet and infection levels may be due to the relatively low richness of freshwater helminth parasites in New Zealand and high host–parasite specificity.

The feral Soay sheep (Ovis aries L.) population on Hirta, St Kilda, is host to a diverse component parasite community, but previous parasitological studies of the population have only focussed on the metazoan species. This paper reports the first epidemiological study of the protozoan species comprising Cryptosporidium parvum, Giardia duodenalis and 11 species of Eimeria in Soay sheep across 3 years of varying host population density. Prevalence and intensity of almost all species of protozoa significantly decreased with host age, with the exception of E. granulosa, which increased in prevalence with host age. The prevalence of C. parvum appeared to vary positively with host population density but that of G. duodenalis did not vary significantly with density. Most species of Eimeria showed a distinct lag in infection level following the host population crash of 2002, taking up to 2 years to decrease. Mixed Eimeria species intensity and diversity were highest in 2002, a year of low host density. Parasite diversity decreased with host age and was higher in males. There were 5 positive pair-wise associations between protozoa species in terms of prevalence. The results of this study highlight the potential for protozoal infection to shape the evolution of parasite resistance in wild host populations harbouring diverse parasite species.

We report the pharmacological activity of organoruthenium complexes containing chloroquine (CQ) as a chelating ligand. The complexes displayed intraerythrocytic activity against CQ-sensitive 3D7 and CQ-resistant W2 strains of Plasmodium falciparum, with potency and selectivity indexes similar to those of CQ. Complexes displayed activity against all intraerythrocytic stages, but moderate activity against Plasmodium berghei liver stages. However, unlike CQ, organoruthenium complexes impaired gametocyte viability and exhibited fast parasiticidal activity against trophozoites for P. falciparum. This functional property results from the ability of complexes to quickly induce oxidative stress. The parasitaemia of P. berghei-infected mice was reduced by treatment with the complex. Our findings demonstrated that using chloroquine for the synthesis of organoruthenium complexes retains potency and selectivity while leading to an increase in the spectrum of action and parasite killing rate relative to CQ.

The blacklegged tick (Ixodes scapularis) spends up to 10 months in the soil between feeding as larvae and questing for hosts as nymphs the following year. We tracked the survival and energy use of 4320 engorged larvae evenly divided across 288 microcosms under field conditions from September to July on sites with high (>12 nymphs/150 m2) and low (<1.2 nymphs/150 m2) densities of naturally questing I. scapularis in New York State. Subsets of microcosms were destructively sampled periodically during this period to determine tick survivorship and physiological age. Across all sites tick mortality was low during the winter and increased in the spring and early summer, coincident with increasing energy use. Neither energy use nor mortality differed significantly between sites with high vs low natural tick density, but we did observe a significant positive relationship between soil organic matter content and the survival of I. scapularis during the spring. Our results suggest that the off-host mortality and energy use of I. scapularis nymphs is relatively low in the winter and increases significantly in the spring and early summer.

Mice experimentally infected with the hydatid parasite Echinococcus granulosus (secondary echinococcosis), were used as spleen cell donors for hybridoma production. Two hybridomas were produced which secreted antibody with anti-E. granulosus cyst fluid (EgCF) activity. Radio-immunoassays comparing the binding of these hybridoma-derived antibodies to E. granulosus versus several other antigen preparations from sheep parasites showed that the antibodies had a high degree of specificity for the hydatid parasite. However, using a panel of clinically defined sheep sera in a competitive radio-immunoassay, the binding of the hybridoma-derived antibodies to EgCF was inhibited strongly by sera from sheep infected with the common parasites Fasciola hepatica and Taenia hydatigena. When the hybridoma-derived antibodies were conjugated to CNBr-activated Sepharose and the crude EgCF applied to the affinity column, the ‘run through’ antigen preparation showed a significant increase in specificity for experimental E. granulosus infection. A useful means of applying the hybridoma technology in the development of new immunodiagnostic reagents may be to select those murine hybridomas which produce high-affinity, cross-reacting antibodies and to use these antibodies in the processing of homologous antigen by affinity chromatography.

In order to reveal the mechanisms underlying nurse cell formation during Trichinella spiralis infection, the expression of the factors of tumor necrosis factor-alpha (TNF-α)/TNF receptor 1 (TNFR-1) signalling pathway mediating apoptosis was investigated. The analysed factors included TNF-α, TNFR-1, TNF receptor-associated death-domain (TRADD), caspase 3, caspase 8, TNF receptor associated factor-2 (TRAF2) and receptor interactive protein (RIP), all of which are involved in the TNF-α/TNFR-1 signalling pathway-mediated apoptosis. The quantitative RT-PCR indicated that the infected muscle tissues up-regulate the expression of pro-apoptosis genes (TNF-α, TNFR-1 and TRADD, caspase 3 and caspase 8), and anti-apoptosis genes (TRAF2 and RIP) at the beginning of cyst formation. The expression returned to the normal level after cyst formation. The quantitative RT-PCR analysis of mRNA from tissue samples isolated by laser capture micro-dissection confirmed that the up-regulation of these genes was restricted in infected muscle cells, was not in the inflammation cells around infected muscle cells nor in normal muscle cells. The in situ localization study of pro-apoptosis (TRADD, caspase 3) and anti-apoptosis gene products (TRAF2) indicated that these were expressed in the basophilic cytoplasm (infected muscle cell origin) of the nurse cells. Thus the present study suggests that the TNF-α/TNFR-1 signalling pathway is involved in nurse cell formation.

The in vitro activity of artemether against 63 African isolates of Plasmodium falciparum from Libreville, Gabon was evaluated using an isotopic drug susceptibility semi-microtest. The 50% inhibitory concentration (IC50) values for artemether were in a narrow range from 0·8 to 34·8 nm (mean IC50 5·0 nm) and the 95% confidence interval (CI95%) was 3·6–6·3 nm. In vitro decreased susceptibility or resistance were observed with artemether (14%), to chloroquine (90%), to quinine (32%). Isolate susceptibility to amodiaquine and halofantrine was high i.e. 100% and 98%, respectively. There was a significant positive correlation between responses to artemether and amodiaquine (r2=0·45, P<0·001), artemether and chloroquine (r2=0·36, P<0·001), artemether and quinine (r2=0·31, P<0·001), and artemether and halofantrine r2=0·19, P<0·01). Positive correlation between these drugs suggests in vitro cross-resistance or at least common features in drug uptake and/or mode of action or resistance.

To investigate the prevalence of Cyclospora cayetanensis in a longitudinal study and to conduct a population genetic analysis, fecal specimens from 6579 patients were collected during the cyclosporiasis – prevalent seasons in two urban areas of central China in 2011–2015. The overall incidence of C. cayetanensis infection was 1·2% (76/6579): 1·6% (50/3173) in Zhengzhou and 0·8% (26/3406) in Kaifeng (P < 0·05), with infections in all age groups (P > 0·05). All the isolates clustered in the C. cayetanensis clade based on the small subunit ribosomal RNA gene sequence phylogenetic analysis. There were 45 specimens positive for all the five C. cayetanensis microsatellite loci, and formed 29 multilocus genotypes (MLGs). The phylogenetic relationships of 54 distinct MLGs (including 25 known reference MLGs), based on the concatenated multilocus sequences, formed three main clusters. A population structure analysis showed that the 79 isolates (including 34 known reference isolates) of C. cayetanensis produced three distinct subpopulations based on allelic profile data. In conclusion, we determined the frequency of C. cayetanensis infection in humans in Henan Province. The clonal population structure of the human C. cayetanensis isolates showed linkage disequilibrium and three distinct subpopulations.

The ability of haemocytes, from the haemolymph of the gastropod mollusc Lymnaea stagnalis, to recognize and eliminate the bacterium Aeromonas salmonicida was shown using an in vitro bacterial clearance assay. The assay employs a dye which is reduced by A. salmonicida in direct proportion to the number of viable bacteria resulting in a colour change which can be determined spectrophotometrically. Addition of cytochalasin B resulted in a marked decrease in bacterial clearance, implicating both intracellular and extracellular cytotoxicity of haemocytes. A comparison of haemocytes from uninfected snails and snails infected with the avian schistosome parasite Trichobilharzia ocellata showed that both juveniles and adults of L. stagnalis were susceptible to infection with T. ocellata. After exposure to the trematode for 1·5 h the haemocytes from these infected snails had an enhanced clearance capacity, whilst cells obtained from snails with 24–96 h infections showed decreased clearance of the bacteria, indicating suppression by the parasite. Haemocytes, as well as plasma, which was tested on haemocytes from uninfected snails, were used and hence a distinction was made between cell and humoralassociated effects. The results show that both cellular and humoral components of immunity were activated, then suppressed, following exposure to the parasite. Infection with T. ocellata seems to have a modulating effect on the bactericidal activity of the internal defence system of the snail host, L. stagnalis.

Sarcoptes scabiei is an important parasitic mite in both man and animals. Little is known about the molecular interactions between this pathogen and its host. This is in part explained by the paucity of mite-derived material, including antigens. To extend the knowledge of the molecular repertoire in S. scabiei, we have performed a gene survey by an expressed sequence tag (EST) analysis. A total of 1020 ESTs were generated from an S. scabiei cDNA library. The average sequence read was 510 bp after editing and the overall sequencing success was 89%. Clustering of the sequences resulted in 76 clusters, comprising 36% of the ESTs. Sequence similarity searches showed that almost half of the S. scabiei ESTs could be assigned a putative identity. Many of these transcripts shared similarity with genes involved in basic metabolism and cellular organization. In the data set we also identified several proteases and other types of potential allergens implicated in various disease mechanisms. A relatively large fraction of the ESTs coded for different proteins carrying protease inhibitor-like domains. The clones with no similarity to previously identified genes constituted 11% of our transcripts. The EST data generated in this study will be a valuable resource in further studies of the biology of S. scabiei and in the identification of genes that can serve as potential targets in the control of the parasite.

The ectoparasitic copepod Lepeophtheirus pectoralis exhibited a regular annual cycle of abundance on its hosts. Both the incidence and intensity of infection were greatest in August or September and both declined over winter to their minimum values in April. Very similar cycles were observed in both 1972 and 1973. Analysis of the age structure of the parasite population showed that the increase in abundance coincided with the onset of the breeding season. Although females always outnumbered males the sex ratio approached unity during the breeding season, which extended from May to October. Copulating pairs were most commonly observed during this period.

There was a marked bimodal peak of egg production each year, with the first mode occurring around May and the second mode around August or September. This pattern was produced by a system of alternation of generations operating within the parasite population, with a summer type generation (distinguishable by its rapid maturation rate and reduced longevity) alternating with an overwintering type of generation.

There can be no doubt that reasoning by analogy contributes enormously to the progress of Science by suggesting the hypotheses which form the basis of experimental investigation. But although it is useful, it is also dangerous and it is not infrequently the source of plausible but inaccurate and misleading catchwords.