The course of single infections of Nematodirus battus was studied and the developmental phases of the fourth larval stage described. The third moult occurred between days 2 and 4 after infection and the fifth between days 8 and 10. The period of maximum larval penetration of the intestinal mucosa occurred around day 4 and most of the larvae had returned to the mucosal surface by day 6, during the middle of the fourth-stage. Some larvae remained deep in the mucosa and moulted to the fifth-stage in this site.

The relationship between growth and morphological development was not constant and was different in worm populations from different sites. Some larvae grew very rapidly during the early fourth-stage and then entered a period of lethargus while continuing to develop sexually, while others grew and developed throughout the larval stage.

The worms recovered from the second 30% of the small intestine were consistently smaller and less advanced morphologically than those from the first 30%. The worms in the posterior region of the small intestine were preferentially lost from the mucosa in the third- and fourth-stages between days 2 and 4 and from the mucosal surface as adults between days 12 and 16.

A recombinant Echinococcus multilocularis antigen (II/3–10), which had previously been shown to exhibit immunodiagnostic characteristics highly specific for human alveolar echinococcosis, and the corresponding native parasite antigen, were further characterized with immunochemical and molecular biological methods. Immunoblot analysis using a polyclonal antiserum raised in rabbits against the recombinant protein, and subsequent Northern hybridization analysis, revealed that the native antigen was expressed by E. multilocularis at the adult as well as at the metacestode stage. In metacestodes, the antigen was shown by using indirect immunofluorescence and the same antiserum to be localized within the germinal layer and membrane structures of developing protoscolices. Electrophoretic analyses revealed remarkable differences in the apparent molecular weight of the antigen under reducing and non-reducing conditions. In further immunoblot analyses, anti-II/3–10 antibodies identified the corresponding epitopes on bands with identical Mr in all E. multilocularis isolates investigated (European, Asian and North American). By Southern hybridization analyses of the respective gene, phylogenetically related sequences were shown to be present in other helminth species such as E. granulosus and several Taenia spp. In the same respect, immunoblotting revealed that anti-II/3–10 antibodies reacted with antigens of different Mr from various E. granulosus isolates and some other cestode species, indicating the presence of shared and thus potentially cross-reacting epitopes. The relevance of these findings for the immunodiagnostic performance of the recombinant antigen is discussed.

Two nucleoproteins with similar chemical composition have been isolated from the leaves of tobacco plants infected with tobacco necrosis virus. One of these is crystalline and has a sedimentation constant of 130 × 10−13; the other is amorphous and its principal component has a sedimentation constant of 58 × lO−13.

Each preparation will infect plants at a dilution of 1 in 108 and will precipitate specifically with antiserum at a dilution of 1 in 3·2 × 105.

The nature of the difference between preparations in the two states is obscure and it has not proved possible to convert the one into the other.

A new histozoic species of myxosporean was found to infect the gill filaments, gut, kidney and liver of the freshwater teleost Leporinus friderici, collected from the estuarine region of the Amazon, near the city of Belém, Brazil. The plasmodia show asynchronous development, at any one time composed of mature spores and all sporogonic stages. The ellipsoidal spore body, measuring 10·4 μm long and 5·7 μm wide, consists of 2 equal shell valves adhering together along the straight suture line. Each valve has a caudal process measuring 23·3 μm in length. There are 2 symmetric polar capsules, without intercapsular appendix, measuring 5·0 μm×2·1 μm, and each has a polar filament with 7–8 coils. In general, ultrastructural details of sporoblast and spore development are in agreement with previously described myxosporeans. Some ultrastructural aspects such as cellular alterations of the pericyte in the different organs infected and characterization of the sporoplasmosomes during the sporoplasm maturation are described. This parasite was studied under light and electron microscope and compared with others species of the genus Henneguya, considering also host specificity. From our observations we propose the creation of a new species, Henneguya friderici n. sp.

The potential for the non-coding intergenic rDNA spacer (IGS) to DNA fingerprint Giardia duodenalis isolates was investigated. Conserved PCR primers, specific for the flanking large and small rDNA genes, were used to amplify the IGS from 52 in vitro-cultured Giardia isolates. Four distinct IGS–PCR size groups (1·35–1–6 kb) were observed, which correlated closely with the major genetic assemblages established previously for the same isolates using isoenzyme analysis. IGS–PCR size groups A (1·42 kb), C (1·4 kb) and D (1·35 kb) corresponded to isoenzyme assemblage A, and IGS–PCR group B (1·6 kb) to isoenzyme assemblage B. Amplified products from IGS–PCR size groups A and B, which contained 50/52 isolates, were subsequently digested with 8 different restriction enzymes and their profiles compared. Analysis separated isolates within each IGS–PCR size group into 2 distinct clusters which correlated almost exactly with the same genetic groups established previously using isoenzyme electrophoresis. Within each cluster, both methods exhibited a similar capacity to distinguish between Giardia genotypes although they established different genetic relationships between individual isolates. Much of the variability associated with the IGS was attributed to isolates harbouring multiple IGS- sequence types. Restriction analysis of IGS–PCR products amplified from cloned and parent lines of a human isolate BAH 39, which contains multiple IGS variants, showed that trophozoite populations are homogeneous with respect to the types of IGS-variants they maintain. Furthermore, in vitro culture of the cloned isolate BAH39c9 over a 6-year period also failed to reveal variation in IGS–PCR digestion profiles. These results suggest that IGS–PCR RFLP profiles are inherently stable. IGS–PCR analysis was successfully applied to 11 Giardia cyst samples highlighting the potential for this approach to genotype Giardia isolates without the need for in vitro culture.

To clarify the effects of a Cryptocaryon irritans infection on the physiological functions of the marbled rockfish Sebastiscus marmoratus, this study utilized C. irritans at concentrations of 2500; 5000; 7500; 10 000; 20 000; and 30 000 theronts/fish to infect marbled rockfish weighing 45±3 g. The survival rate, food intake, respiratory rate, serum ion concentrations and gill Na+/K+-ATPase activity were determined. With the increase of the infection concentration and the passage of time, the survival rate of the rockfish gradually decreased. The groups infected with more than 5000 theronts/fish had stopped feeding within 4 days. The respiratory rates of the fish in the groups infected with 2500 and 5000 theronts/fish initially increased and then decreased. In contrast, the respiratory rate of the fish in the groups infected with more than 7500 theronts/fish was elevated to levels significantly higher than the control group after 12 h. The Na+/K+-ATPase activity and serum Na+ and Cl− concentrations increased with increasing infection concentration. In conclusion, the physiological functions of the fish infected with low concentrations of C. irritans can be effectively restored, whereas a high concentration infection induced severe stress. The declined food intake and accelerated respiratory rate could be useful for an early warning system as important indicators.

Infection with filarial nematodes produces a chronic, long-lasting illness with adult worms able to survive within human hosts for up to 15 years. A contributor to the longevity of these parasites is the presence of phosphorylcholine (PC) on components of the worms' molecular secretions (ES). PC on ES modulates host immune responses towards an anti-inflammatory phenotype thereby generating an environment favourable for parasite survival. PC is attached to nematode ES via a covalent association with carbohydrate, which, although well-documented in bacteria and fungi, is absent from humans, making it an ideal target for the development of novel drugs. In order to produce such drugs it is first necessary to understand the structure and synthesis of nematode PC-glycans. ES-62 is the major PC-ES-product of Acanthocheilonema viteae and is a homologue of PC-ES found in human filarial nematodes. We have studied the structure and biosynthesis of PC-glycans of ES-62 by a combination of pulse-chase experiments, experiments involving the use of inhibitors of each of intracellular trafficking, oligosaccharide processing and phospholipid biosynthesis and various forms of mass spectrometry. Our indications indicate that PC is transferred in the lumen of the medial Golgi to an N-type glycan consisting of a trimannosyl core with or without core fucosylation bearing between 1 and 4 N-acetyl glucosamine residues. The structure of the PC-N-glycans found in ES-62 appears to be conserved amongst filarial nematodes in that it has additionally been identified in Onchocerca volvulus and O. gibsoni. Also, similar structures have been found in non-filarial parasitic nematodes and in the free-living nematode Caenorhabditis elegans. Finally, PC has also been recently found attached to the carbohydrate moieties of nematode glycosphingolipids and the structure of these will also be considered.

A serine protease was purified 942-fold from culture supernatant of L. amazonensis promastigotes using (NH4)2SO4 precipitation followed by affinity chromatography on aprotinin-agarose and continuous elution electrophoresis by Prep Cell, yielding a total recovery of 61%. The molecular mass of the active enzyme estimated by SDS-PAGE under conditions of reduction was 56 kDa and 115 kDa under conditions of non-reduction, suggesting that the protease is a dimeric protein. Additionally, it was found to be a non-glycosylated enzyme, with a pI of 5·0. The optimal pH and temperature of the enzyme were 7·5 and 28 °C respectively, using α-N-ρ-tosyl-L-arginine-methyl ester (L-TAME) as substrate. Assays of thermal stability indicated that 61% of the enzyme activity was preserved after 1 h of pre-treatment at 42 °C. Haemoglobin, bovine serum albumin (BSA), ovalbumin, fibrinogen, collagen, gelatin and peptide substrates containing arginine in an ester bond and amide substrates containing hydrophobic residues at the P1 site were hydrolysed by this extracellular protease. The insulin β-chain was also hydrolysed by the enzyme and many peptidic bonds were susceptible to the protease action, and 4 of them (L11-V12, E13-A14, L15-Y16 and Y16-L17) were identified. Inhibition studies suggested that the enzyme belongs to the serine protease class inhibited by calcium and manganese and activated by zinc. These findings show that this enzyme of L. amazonensis is a novel serine protease, which differs from all known flagellate proteases characterized.

Developments in the study of the ecology of helminth parasites of freshwater fishes over the last half century are reviewed. Most research has of necessity been field based and has involved the search for patterns in population and community dynamics that are repeatable in space and time. Mathematical models predict that under certain conditions host and parasite populations can attain equilibrial levels through operation of regulatory factors. Such factors have been identified in several host-parasite systems and some parasite populations have been shown to persist over long time-periods. However, there is no convincing evidence that fish parasite populations are stable and regulated since in all cases alternative explanations are equally acceptable and it appears that they are non-equilibrial systems. It has proved particularly difficult to detect replicable patterns in parasite communities. Inter-specific competition, evidenced by functional and numerical responses, has been detected in several communities but its occurrence is erratic and its significance unclear. Some studies have failed to find any nested patterns in parasite community structure and richness, whereas others have identified such patterns although they are seldom constant over space and time. Departures from randomness appear to be the exception and then only temporary. It appears that parasite communities are non-equilibrial, stochastic assemblages rather than structured and organized.

Parasites are able to influence intermediate hosts in a way that optimizes their growth and transmission to the next host. Macrocyclops albidus (Copepoda) suffer from a reduced escaping ability and an increased level of general activity, when infected with Schistocephalus solidus (Cestoda). This facilitates predation by the subsequent host, the three-spined stickleback. However, instead of adaptive host manipulation by the tapeworm, the altered copepod behaviour might be explained more simply as a constraint of the infection. Energy depletion could lead to decreased muscle performance and increased food searching activity. Furthermore, resource allocation among host tissues might change after infection. We therefore analysed the amount of storage lipids and muscle tissue before and after experimental infection. To determine the amount of muscles, we developed a new polarization-microscopic technique. Irrespective of infection, lipids and muscles were predictors of copepod survival. However, we found no effect of the parasite infection on muscles or lipids, and no indication of a change in resource allocation between these tissues. Our study suggests that behavioural changes in infected copepods are mediated by a mechanism different from energy depletion or a re-allocation of resources between muscles and lipids. We rather propose that the tapeworms directly manipulate copepod behaviour.

Murine monoclonal antibodies (mAbs) against Neospora caninum tachyzoites were produced to identify the cross-reactive antigens between N. caninum and Toxoplasma gondii. Ten mAbs recognizing cross-reactive antigens of both parasites were obtained and tentatively classified into 6 different groups based on their reactivity patterns in an indirect fluorescent antibody test and Western blot analysis. Three mAbs in group 1 recognized antigens located on the surface of parasites with molecular masses ranging from 28 to 76 kDa; one mAb in group 2 recognized antigens located on interior organelles of parasites with a molecular mass of 50 kDa; one mAb in group 3 recognized antigens located on interior organelles of parasites with molecular masses of 35 kDa and 14 kDa; three mAbs in group 4 recognized antigens located on interior organelles with a molecular mass of 64 kDa; one mAb in group 5 recognized antigens located on the surface of parasites with an unknown molecular mass; one mAb in group 6 recognized antigens located on the apical end of parasites with an unknown molecular mass. The mAbs in groups 1, 2, 3, and 5 showed inhibitory effects on the growth of the two parasites in vitro in a dose-dependent manner. A cDNA expression library prepared from N. caninum tachyzoite mRNA was immunoscreened with the mAb panel. Three kinds of proteins, protein disulfide isomerase (PDI), heat-shock protein 70 (HSP70), and ribosomal protein 1 (RP1), were identified as cross-reactive antigens recognized by mAbs in groups 2, 3, and 4, respectively. Some of the proteins could be useful in developing vaccines or drugs for controlling the diseases caused by the two parasites.

Immune responses that kill pathogens or reduce their reproductive rate are generally important in protecting hosts from infection and disease. Pathogens that escape the full impact of such responses will survive, and any heritable genetic basis of this evasion will be selected. Due to the memory component of vertebrate immune responses, pathogens with rare alleles of a target antigen can have an advantage over those with common alleles, leading to the maintenance of a polymorphism. At the genetic level, there ought to be detectable signatures of balancing selection in the genes encoding these antigens. Here, methods for identifying these selective signatures are reviewed. Their practical utility for identifying which antigens are targets of protective immune responses is discussed.

Although, in the early part of the nineteenth century, a considerable amount of work on larval trematodes was done on the continent by von Siebold (1835), de Fillippi (1855) and La Valette (1855), so far as I know, no similar work was undertaken in this country. It was not until 1880, when a great controversy raged round the intermediate host of the liver fluke, that any interest was aroused. This culminated in 1883 with the publication, by Thomas, of the life history. Thomas also discovered that Limnaea peregra was infected with cercariae different from those of the liver fluke. Since that time the interest has lapsed, and, excluding a description of two cercariae by Hesse (1923), I do not know of any published records of work on freshwater larval trematodes of this country. On the other hand, work on the continent and in America has increased, and although our knowledge of the life histories of trematodes is still in its infancy, a considerable number of continental larval forms have been found and described. However, Lebour (1905) commenced a study of marine larval trematodes and together with Nicoll (1906) attempted to establish life histories.

It is now recognized, by all competent observers, that emetine is a specific therapeutic agent for the treatment of amoebic dysentery; but although it is known that a thorough course of emetine, in some form, will eradicate an infection with Entamoeba histolytica from most human beings, there is still complete ignorance as to how the cure is effected. The obvious hypothesis, that emetine is a specific poison for E. histolytica, has not hitherto been supported by adequate experimental evidence. It is true that observers have described experiments in which the alkaloid, in high dilution, has apparently killed various amoebae in vitro; but these experiments either ignored the peculiarly specific action of emetine in vivo on E. histolytica, or were carried out without adequate controls.

Recent declines of wild pollinators and infections in honey, bumble and other bee species have raised concerns about pathogen spillover from managed honey and bumble bees to other pollinators. Parasites of honey and bumble bees include trypanosomatids and microsporidia that often exhibit low host specificity, suggesting potential for spillover to co-occurring bees via shared floral resources. However, experimental tests of trypanosomatid and microsporidial cross-infectivity outside of managed honey and bumble bees are scarce. To characterize potential cross-infectivity of honey and bumble bee-associated parasites, we inoculated three trypanosomatids and one microsporidian into five potential hosts – including four managed species – from the apid, halictid and megachilid bee families. We found evidence of cross-infection by the trypanosomatids Crithidia bombi and C. mellificae, with evidence for replication in 3/5 and 3/4 host species, respectively. These include the first reports of experimental C. bombi infection in Megachile rotundata and Osmia lignaria, and C. mellificae infection in O. lignaria and Halictus ligatus. Although inability to control amounts inoculated in O. lignaria and H. ligatus hindered estimates of parasite replication, our findings suggest a broad host range in these trypanosomatids, and underscore the need to quantify disease-mediated threats of managed social bees to sympatric pollinators.

Naive CBA mice and mice vaccinated 4 weeks previously with gamma-irradiated cercariae were challenged percutaneoualy with normal cercariae and the skin site of challenge removed at various times to provide samples for histological examination. Neutrophil abscesses surrounding schistosomula as well as cast cercarial tails were identified at the skin surface in both naive/challenged and vaccinated/challenged mice. The dermis in both groups of animals became infiltrated with mononuclear cells and granulocytes. Neutrophils were the predominant granulocyte in naive/challenged skin but eosinophils replaced neutrophils by 48 h post-challenge in skin from vaccinated mice. Schistosomula with adherent mononuclear cells and granulocytes were identified preferentially in the dermis of vaccinated mice; such larvae frequently exhibited subtegumental vacuolation. A further major characteristic of vaccinated/challenged skin was the formation, from 18 h, of extensive subdermal inflammatory foci, consisting of up to 50% mononuclear cells and 50% eosinophils. These foci invariably surrounded one or more larval parasites which were seen by both optical and scanning electron microscopy to have a morphology typical of lung stage rather than skin stage schistosomula. Dead, infiltrated parasites were also recognized within the subdermal foci. Our data support the view that vaccine immunity in this mouse model is mediated primarily in the skin and indicate that challenge attrition involves immobilization and killing of larval parasites by effector cells within subdermal inflammatory foci.

The material on which the following notes are founded was collected during a short residence at the Marine Biological Laboratory, Millport, in August, 1908. A comprehensive survey of the marine fauna was impossible in so limited a time, but a fair idea of the parasites of some of the common fishes was obtained. I have to thank the Government Grant Committee of the Royal Society for enabling me to undertake this work. It is also necessary to gratefully acknowledge the courtesy of several members of the West of Scotland Marine Biological Association and of Mr Elmhirst, the director of the Millport Laboratory.

The presence of entomopathogenic nematodes in soil from 15 sites on 10 sampling occasions over a period of 28 months was documented. Sites were chosen to represent habitats classified as heathland, hedgerow, roadside verge, pasture or woodland. Bioassays utilized Galleria larvae and most of the nematodes obtained were identified asSteinernema (= Neoaplectana) bibionis (Bovien). A sibling species which fails to interbreed with S. bibionis was also found at 2 of the sites. Bioassays were at 15 and 20°C and there was no significant difference in the results at these temperatures. There was no evidence for seasonality in the presence of the nematodes and at 2 sites they were found on every sampling occasion. Otherwise, sites converted unpredictably from positive to negative or negative to positive over the 28-month sampling period.

We compared helminth communities in spiny mice (Acomys dimidiatus) from 4 wadis in the arid montane region of the southern Sinai in Egypt, in a 4-week period in late summer. Total helminth species richness was 14 (8 nematodes, 5 cestodes and 1 acanthocephalan) with 94% of mice carrying at least 1 species and an overall mean species richness of 1·85. The most prevalent parasites were Protospirura muricola (47·8%) and Dentostomella kuntzi (46·3%). One larval cestode, Joyeuxiella rossicum, represents a new host record. The helminth community was dominated by intestinal nematodes (88·7%) of which 58·2% were arthropod-transmitted heteroxenic species. At the component community level, 70% of the worms were recovered from mice in just two wadis (Gharaba and Tlah) and 48·6% of intestinal nematodes were from Wadi Gharaba. Although only 7 species of helminths were recorded from Wadi Gharaba, this site gave the highest Berger-Parker dominance index because of P. muricola. P. muricola was also dominant in Wadi El Arbaein whilst Syphacia minuta was the dominant species in Wadis Gebal and Tlah. At the infracommunity level, mean species richness and Brillouin's index of diversity were highest in Wadi Tlah and lowest in Wadi Gebal, and the former was age dependent. Whilst mice from different wadis differed in the nematodes that were most common, those from Wadi Gharaba carried the highest mean number of worms/mouse. The abundance of P. muricola in particular varied markedly between sites: Wadi Gharaba was distinct as the site showing the highest mean worm burden whereas mice from Wadi Gebal were uninfected. None of the directly transmitted oxyuroid nematodes showed significant variation in abundance between wadis, or host sex or age classes. Overall, the single extrinsic factor in the study, site of capture, was more important than the intrinsic factors in explaining variation in helminth communities in the region. We conclude that in the high mountains of southern Sinai, each wadi is distinct in terms of its rodent parasites, and hence we expect spatially different coevolutionary pressures on their hosts, with resultant variation in life-histories.

Leishmaniasis is a set of clinically distinct infectious diseases caused by Leishmania, a genus of flagellated protozoan parasites, that affects ∼12 million people worldwide, with ∼2 million new infections annually. Plants are known to produce substances to defend themselves against pathogens and predators. In the genus Lycopersicon, which includes the tomato, L. esculentum, the main antimicrobial compound is the steroidal glycoalkaloid α-tomatine. The loss of the saccharide side-chain of tomatine yields the aglycone tomatidine. In the present study, we investigated the effects of tomatidine on the growth, mitochondrial membrane potential, sterol metabolism, and ultrastructure of Leishmania amazonensis promastigotes. Tomatidine (0·1 to 5 μM) inhibited parasite growth in a dose-dependent manner (IC50=124±59 nM). Transmission electron microscopy revealed lesions in the mitochondrial ultrastructure and the presence of large vacuoles and lipid storage bodies in the cytoplasm. These structural changes in the mitochondria were accompanied by an effective loss of mitochondrial membrane potential and a decrease in ATP levels. An analysis of the neutral lipid content revealed a large depletion of endogenous 24-alkylated sterols such as 24-methylene-cholesta-5, 7-dien-3β-ol (5-dehydroepisterol), with a concomitant accumulation of cholesta-8, 24-dien-3β-ol (zymosterol), which implied a perturbation in the cellular lipid content. These results are consistent with an inhibition of 24-sterol methyltransferase, an important enzyme responsible for the methylation of sterols at the 24 position, which is an essential step in the production of ergosterol and other 24-methyl sterols.