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.

Parasite communities of wild and reared bluefin tuna display remarkable diversity. Among these, the most prevalent and abundant are the Didymozoidae (Monticelli, 1888) (Trematoda, Digenea), considered one of the most taxonomically complex digenean families. The aim of this study was to evaluate phylogenetic structure of Didymozoidae occurring in Pacific (Thunnus orientalis) and Atlantic bluefin tuna (T. thynnus) in order to increase our knowledge of didymozoid zoogeography and identify species that could successfully be employed as biological tags for stock assessment studies. For the present analyses we used 2 nuclear ribosomal DNA loci, part of the 28S gene and the second internal transcribed spacer (ITS-2) as well as a portion of the mitochondrial cytochrome c oxidase subunit 1 gene (cox1). In most parasitic groups, morphology is the primary factor in the structuring of phylogenetic relationships. In rare examples, however, habitat has been suggested as a primary factor affecting parasite evolution. During their evolution, didymozoids have spread and inhabited a remarkable number of different sites in their hosts, colonizing exterior as well as strictly interior niches. Our data suggest that habitat selection has been the leading force in shaping didymozoid phylogenetic relationships. For 2 didymozoid species (D. wedli and D. palati), cox1 sequences indicate intraspecific differences between Mexican and Adriatic populations.

Nematophagous fungi are used in the biological control of the parasitic helminths of animals and plants. The association of ovicidal and predator nematophagous fungi may present a complementary and increased action on the biological control of helminths. Joint growth compatibility and predation tests were carried out on infective larvae of nematode parasites of bovines with the nematophagous fungus ovicide Pochonia chlamydosporia and the nematophagous fungus predator Arthrobotrys cladodes. The tests of antagonism in direct confrontation, antibiosis and the effect of volatile metabolites between the isolates of P. chlamydosporia and A. cladodes indicated the viability of joint growth of these fungi. The association of the fungi P. chlamydosporia and A. cladodes presented a higher predatory capacity of infective larvae of the parasitic nematodes of bovines when compared to the predation of the fungi used alone. Therefore, under laboratory conditions, the fungi studied presented growth compatibility and the association of these increased the nematicidal activity against parasitic helminths of cattle.

Despite the great interest to quantify the structure of host–parasite interaction networks, the real influence of some factors such as taxonomy, host body size and ecological opportunity remains poorly understood. In this paper, we investigate the general patterns of organization and structure of interactions in two anuran–parasite networks in the Brazilian Pantanal (seasonally flooded environment) and Atlantic Forest (non-flooded forest). We present theoretical models to test whether the structures of these host–parasite interaction networks are influenced by neutrality, host taxonomy and host body size. Subsequently, we calculated metrics of connectance, nestedness and modularity to characterize the network structure. We demonstrated the structure networks were influenced mainly by body size and taxonomy of the host. Moreover, our results showed that the seasonally flooded environment present networks with higher connectance/nestedness and lower modularity compared to the other environment. The results also suggest that seasonal floods may promote ecological opportunities for new species associations.

Parasites of the genera Plasmodium and Haemoproteus (Apicomplexa: Haemosporida) are a diverse group of pathogens that infect birds nearly worldwide. Despite their ubiquity, the ecological and evolutionary factors that shape the diversity and distribution of these protozoan parasites among avian communities and geographic regions are poorly understood. Based on a survey throughout the Neotropics of the haemosporidian parasites infecting manakins (Pipridae), a family of Passerine birds endemic to this region, we asked whether host relatedness, ecological similarity and geographic proximity structure parasite turnover between manakin species and local manakin assemblages. We used molecular methods to screen 1343 individuals of 30 manakin species for the presence of parasites. We found no significant correlations between manakin parasite lineage turnover and both manakin species turnover and geographic distance. Climate differences, species turnover in the larger bird community and parasite lineage turnover in non-manakin hosts did not correlate with manakin parasite lineage turnover. We also found no evidence that manakin parasite lineage turnover among host species correlates with range overlap and genetic divergence among hosts. Our analyses indicate that host switching (turnover among host species) and dispersal (turnover among locations) of haemosporidian parasites in manakins are not constrained at this scale.

The completed life-cycle of Cyclospora talpae, an extra-intestinal coccidian (Apicomplexa) of the liver of the mole (Talpa europaea). is reported. Oocysts sporulated within 12–14 days at room temperature (20–22 °C). Both macro- and micro-gametocytes developed independently within the nucleus of epithelial cells lining the bile duct as demonstrated by both light and electron microscopy. Merogony was seen in the mononuclear cells in the capillary sinusoids of the liver. Merozoites showed the typical ultrastructural features of the Apicomplexa. The life-cycle of C. talpae and the ultra-structure of the gametogonic and merogonic stages are reported; the ultrastructure of the merozoites is reported as the first description of this stage for the genus Cyclospora.

A continuous succession of egg capsules is formed in the ootype of Protopolystoma xenopodis and released into the urinary bladder of the host, Xenopus laevis. Since egg capsules are passed out with the aquatic toad's urine several times a day, the rate of parasite egg production can be recorded accurately by direct counts. Temperature has a marked influence on the rate of egg output which doubles in response to a rise from 17 to 25 °C. Under constant temperature conditions regular egg collections from isolated toads infested with single Protopolystoma revealed that rates of production remain stable for periods of several weeks. The overall mean rate of egg production was 8·9 eggs/worm/day (e.w.d.) at 20·0±0·5 °C (based on 5 consecutive egg collections from 58 individual parasites). Significant differences were observed, however, between the mean rates of output from different hosts, ranging from 2·1 e.w.d. (s.d. = 0·6) to 17·7 e.w.d. (S.D. = 3·2). Neither differences in worm age nor host-factors could explain the observed range in output. Worms transferred to new hosts resumed egg production at pre-transfer rates, suggesting inherent differences in the capacity for egg production by individual parasites. Total production increased with increasing worm burden, but output per parasite was significantly reduced in groups of 2, 3 or 4. Whilst competition for some finite resource provides one interpretation, this observation could equally reflect a statistical phenomenon associated with the reduced chance of encountering groups of individuals which are heterogeneous for egg production as worm burden increases and sample size decreases.

The distribution of Trichostrongylus colubriformis in the intestine of the non-immune guinea-pig is described. At day 10 of the primary infection the majority of larvae were found in the anterior half of the small intestine with progressively smaller numbers in all parts of the gut posterior to this. However, soon after day 10 a migration of the worm population took place so that by day 15, before there had been a reduction in the total present, the majority of worms were found in the posterior small intestine. Thereafter the posterior movement continued, but while the numbers in the large intestine increased the movement then coincided with the beginning of the expulsion of the worms.

By the irradiation of guinea-pigs prior to infection the posterior migration was prevented, indicating that the latter was the result of a host response.

The independent migration of two generations of parasites was noted and two possible explanations are put forward.

This work was carried out during the tenure of a Research Training Scholarship awarded by the Animal Health Trust.

The author would like to thank Professor W. I. B. Beveridge in whose Department this work was carried out, and also Mr King of the Department of Radio-therapeutics, University of Cambridge, who irradiated the guinea-pigs used in Expt. 3.

1. “Trichomonas” keilini n.sp. has three anterior flagella, and a short undulating membrane, whose bordering flagellum does not become free. The flagella arise from an anterior blepharoplast. There is a single nucleus, anteriorly placed, and a mouth, but no basal fibre to the undulating membrane. An axostyle may be present or absent, but when present it is siderophilic. The method of multiplication of “T.” keilini is similar to that of T. hominis and T. batrachorum.

2. “T.” keilini was found in water from a pond in Lincolnshire.

3. It has been cultivated in serum-saline media, in hay infusion, and in pond or rain water with boiled wheat grains, from 4 to 31° C.

4. Cysts have never been found.

I should like to record my gratitude to Prof. Keilin, F.R.S., who gave me the sample of water in which I first saw the organism, and who gave me encouragement throughout this study; and to Mr Clifford Dobell, F.R.S., for the gift of the macaque-human strain of Trichomonas and for so kindly reading through and criticising this manuscript.

The effects of pharmacological concentrations of several gastrointestinal hormones on the rate of sucker activity and the frequency and the amplitude of spontaneous longitudinal muscle contractions have been examined in adult Fasciola hepatica. Caerulein and serum decrease the rate of oral sucker activity; motilin decreases and CCK–PZ increases ventral sucker activity when compared to controls. Caerulein, serum and motilin significantly inhibit the frequency of contractions while bile, caerulein and motilin decrease the amplitude of contractions. These results suggest that F. hepatica can recognize and respond to certain gastrointestinal hormones and there may be adaptive value in these behavioural responses.

1. The material which is discussed in the present paper consists of more than 2000 crops of hair collected from Sokoto, Nigeria; Nairobi and Kakamega, Kenya; Colombo, Ceylon; and Jerusalem, Palestine. The amount of material examined is considerable, but it must be admitted that it has not been found possible to obtain an unselected sample representative of any human community as a whole.

2. The paper gives detailed information about the prevalence of head-lice in respect of the individual's race, sex, age, weight of crop of hair and the season of the year.

3. The following general conclusions may be drawn:

(a) The distribution of lice among a population of people is skew. Among infested persons the commonest count is always low (generally 1–10 lice), but occasional counts of many hundreds or a few thousands are recorded.

(b) If the people are grouped by age, sex, etc. a positive correlation is generally found between the proportion of men in each group who are infested and the mean number of lice per infested person.

(c) There is clear evidence from several places that season affects the frequency of infestation. In most but not all places the insect is most widely distributed in the colder, wetter part of the year. It is not known whether this is due to some effect of climate upon the insect itself or upon human habits and activity.

(d) It will doubtless be found that the individual's race is an important factor in determining infestation, but little has yet been established on this subject.

(e) Wherever material has been available from individuals of widely different age, it has been found that boys are more infested than youths, who in turn are more infested than grown men.

(f) In some places females are more frequently infested than males, though it was established that there was no difference between the sexes at Kakamega.

(g) The weight of the individual's crop of hair is in most places positively correlated with infestation.

4. Many of the factors mentioned in 3 (d)–(g) are local and depend on racial customs. It is emphasized that further investigations would be most profitably carried out in the countries concerned by men well acquainted with the local people and their ways.

5. There are probably a large number of individual differences due to sensitiveness, vanity, general health, etc.; these have hardly been studied at present but it is probable that collectively they are very important.

Soluble extracts of adult Schistosoma japonicum and S. mansoni were examined for the presence of proteolytic activities ascribable to dipeptidyl peptidases (DPPs) at a range of pH from 4 to 11 using synthetic peptidyl substrates diagnostic of DPPs I, II, III and IV. Activity capable of cleaving the DPP I-specific substrates H-Gly-Arg-NHMec and H-Gly-Phe-NHMec which exhibited a pH optimum of 5·5 was observed in extracts of schistosomes. Female schistosomes exhibited greater DPP I activity than male schistosomes, while female S. japonicum showed substantially more activity than female S. mansoni. The specific activities against H-Gly-Arg-NHMec were 21·5 and 1·9 nmoles NHMec/min/mg protein for female and male S. japonicum and 8·5 and 1·9 nmoles NHMec/min/mg for female and male S. mansoni. The biochemical properties of schistosome DPP I were similar to mammalian DPP I (=cathepsin C) in that schistosome DPP I was only slowly inhibited by the cysteine protease inhibitor trans-epoxysuccinyl-1-leucylamido (4-guanidino)- butane, partly inhibited by the blocked diazomethyl ketones Z-Phe-Ala-CHN2 and Z-Phe-Phe-CHN2, but enhanced by halide ions. At pH 8·5, activity against the DPP III-specific substrate H-Arg-Arg-NHMec was evident in schistosome extracts, and this activity appeared to be due to a zinc metallo-exopeptidase because it was inhibited by 1,10-phenathroline and by EDTA. DPP II or DPP IV activity was not detected in the schistosome extracts.

High molecular weight proteinases of Trichomonas vaginalis (with apparent Mr values 142 and > 220 kDa) and Tritrichomonas mobilensis (Mr 67, 86, 104 and 120 kDa), optimally active at pH 8, were analysed in gelatin-containing polyacrylamide gels. All of these proteinases were resistant to serine-, aspartic- as well as cysteine proteinase inhibitors. Both proteolytic bands in T. vaginalis and two proteinases in T. mobilensis (67 and 104 kDa) were inhibited by EDTA and EGTA suggesting that they belong to the metallo-proteinase class. The 67 kDa proteinase of T. mobilensis was inhibited also by o-phenanthroline. The other two bands of T. mobilensis (86, 120 kDa) were not classified to any proteinase group since they appeared to be resistant to the chelating agents tested in this study.

In an operational Schistosoma mansoni field-study in an area of about 20 km (population approximately 8000), transmission detection by simple snail sampling was compared with cercariometry. Between 1985 and 1987, 62 field sites were sampled at fortnightly intervals. Of a total of 2758 field observations, 89.8% gave full snail data; 64.4% full cercarial data; and 61.7% complete data for both methods. The complete data sets showed significant but not strong correlations between Biomphalaria pfeifferi (total and infected with S. mansoni or other trematodes) and cercarial (S. mansoni and non-human) recoveries. Non-human (but not S. mansoni) cercarial recovery decreased with deteriorating cercariometry filter quality. Both snail and cercarial recoveries diminished significantly with increasing water flows at the time of collection. Many samples yielded infected snails or cercariae, but not both, and neither method detected significantly more transmission sites. The method of choice for detecting transmission in a large-scale field-study depends on logistical and financial considerations. Relatively simple snail sampling allows quick, cheap and widespread data collection adequate for most purposes but more complicated cercariometry is still valuable for specific, small-scale studies.

Yellow-eyed penguins on Stewart Island were identified with a Leucocytozoon spp. of a novel lineage in association with a high regional incidence of chick mortality (n=32, 100% mortality) during the November 2006 to January 2007 breeding season. Fourteen chicks from Stewart Island were examined post-mortem and histologically for Leucocytozoon infection. In addition, a survey of blood to detect Leucocytozoon spp. infections using PCR was performed on 107 yellow-eyed penguins from 4 distinct nesting areas on the South Island (Oamaru, Otago Peninsula, and Catlins) (n=95), and Stewart Island (n=12). The results of the study revealed that 2 of the 14 (14%) chicks necropsied showed severe, disseminated megaloschizont formation in the liver, spleen, lung, kidney and other tissues characteristic of leucocytozoonosis. Eighty-three percent (83%) of blood samples collected from Stewart Island penguins contained Leucocytozoon DNA, whereas samples from the 3 other nesting areas were negative for the blood parasite. Leucocytozoon spp. DNA sequences isolated from blood and tissues of adults (n=10) and chicks (n=7) were similar and grouped with other published Leucocytozoon spp. sequences but in a distinct cluster together with closely related isolates from a Western march harrier (Circus aerginosus) and common loon (Gavia immer). These findings suggest that yellow-eyed penguins on Stewart Island are infected with a regionally isolated, host-specific Leucocytozoon spp. which may contribute to the high chick mortality observed during this period.

The surface coat of the 2nd-stage juveniles (J2) of plant-parasitic nematodes is considered to be involved in interactions with microorganisms in the soil and rhizosphere, as well as with the host plant. Characterization of surface antigens might be important in the development of new nematode control strategies. In this study, polyclonal and monoclonal antibodies raised against Meloidogyne javanica, M. incognita and other plant-parasitic nematodes were tested for their binding to the surface coat and secreted–excreted products of M. javanica. Some of the monoclonal and polyclonal antibodies raised against M. incognita showed cross-reactivity with the surface coat of M. javanica. Western blot analysis of M. javanica surface coat extracts revealed labelling of several polypeptides with a 48 kDa main band for the polyclonal antibody IACR-PC Mi 373, and a 55 kDa main band for PC Mj E2. Further characterization of the antigens recognized by the polyclonal antibody PC Mj E2, in planta, showed that they were present in the parasitic stages J2 and J3 and that the surface coat was shed during root penetration. The hypodermis of the infective juveniles was labelled by PC Mj E2 and the monoclonal antibody IACR-Misec 3F.4, suggesting that these surface antigens are produced in the hypodermis. Nematode behaviour was affected by all the antibodies that bound to the surface coat of the pre-parasitic J2, and we demonstrated that the movement pattern of the M. javanica J2 was affected by these antibodies. Continuous binding of the antibodies to the M. javanica surface inhibited the infection of Arabidopsis thaliana roots on agar plates.

Trypanosomes isolated from South American bats include the human pathogen Trypanosoma cruzi. Other Trypanosoma spp. that have been found exclusively in bats are not well characterized at the DNA sequence level and we have therefore used the SL RNA gene to differentiate and characterize kinetoplastids isolated from bats in South America. A Trypanosoma sp. isolated from bats in southern Brazil was compared with the geographically diverse isolates T. cruzi marinkellei, T. vespertilionis, and T. dionisii. Analysis of the SL RNA gene repeats revealed size and sequence variability among these bat trypanosomes. We have developed hybridization probes to separate these bat isolates and have analysed the DNA sequence data to estimate their relatedness. A new species, Trypanosoma desterrensis sp. n., is proposed, for which a 5S rRNA gene was also found within the SL RNA repeat.

The transport processes of D-glucose in Plasmodium yoelii-infected mouse erythrocytes were investigated using 2-deoxy-D-glucose (2DOG), a non-metabolizable analogue of D-glucose. Infected cells showed an increase in the uptake of 2DOG compared to uninfected controls, and an effect which was more prominent in cells with mature-stage parasites. Kinetic studies measuring the initial rates of 2DOG uptake revealed two components in infected cells with late trophozoite and schizont-stage parasites: a simple diffusion system and a carrier (transporter)-mediated system. The transporter was common for D-glucose and 2DOG and had a kinetic constant indicating a high affinity for 2DOG (the Km = 0·18 mM and the Vmax = 0·61 mmol/1010 cells/min), as compared to the constant of the mouse erythrocyte carrier (the Km = 10 mM and the Vmax = 1·8 mmol/1010 cells/min). Determination of the distribution of [3H]2DOG in infected cells and experiments with metabolic inhibitors indicated that the simple diffusion system localizes in the membrane of host cells and the transporter in the parasite plasma membrane. The parasite glucose transporter was much less sensitive to cytochalasin B than that of the host cells and the uptake of 2DOG via the transporter was dependent on energy. Based on these findings, the following features emerge: D-glucose first gains access to the cytosol of infected erythrocytes via the simple diffusion system, which appears after infection by the parasite, and an active uptake against the concentration gradient takes place at the parasite plasma membrane via the parasite glucose transporter in an energy dependent manner. Finally, an energy transduction mechanism for the transport of glucose across the parasite plasma membrane is discussed.

(1) Eight species of furcocercous cercariae have been found during a 3-year study of the trematode larvae harboured by certain fresh-water molluscs in Glamorganshire. Of these four are new species, two have previously been reported from South Wales by Rees (1932) and the remaining two species have been recorded in Europe but not in Britain.

(2) Detailed descriptions are given of the four new species and the last two species which had not been completely described hitherto. The life cycles, as far as are known, of all the the species are outlined; the mollusc hosts are listed and for each cercaria a comparison with related species is given.

(3) C. hamburgensis Komiya has been proved experimentally to be the larva of Apatemon gracilis minor Yam. and according to the law of priority becomes C. a.g. minor.