Hamsters (WO strain) with a primary infection of Schistosoma mansoni or S. haematobium rapidly developed immunity to homologous challenge judged by the lung recovery assay. Immunity was detected at 4–5 weeks and reached a plateau 6 weeks after infection.

Using this information, hamsters with an 8-week primary infection with S. mansoni or S. haematobium were tested for resistance to homologous reinfection and resistance to a challenge with the other species of schistosome. Primary infection with S. mansoni or S. haematobium conferred a high level of immunity to reinfection with either species of schistosome judged by the perfusion assay, involving recovery of adult worms 6–10 weeks following challenge. Estimation of the level of immunity with the lung recovery assay, 5 days after challenge, indicated that immunity due to a primary infection with S.mansoni acted at or before migration of the challenge through the lungs but immunity stimulated by a primary S. haematobium infection was only partially effective at the lung stage and substantial destruction of challenging organisms occurred at a later stage of development.

Antibodies in immune sera of hamsters with a primary S. mansoni or S. haematobium infection were shown to bind to common antigens on the surface of young schistosomula of either species by u.v. microscopy using as detecting agent a fluorescein-labelled rabbit antiserum directed against hamster globulins.

The transmission of parasites takes place under exposure to a range of fluctuating environmental factors, one being the changing levels of solar ultraviolet radiation (UVR). Here, we investigated the effects of ecologically relevant levels of UVR on the transmission of the intertidal trematode Maritrema novaezealandensis from its first intermediate snail host (Zeacumantus subcarinatus) to its second intermediate amphipod host (Paracalliope novizealandiae). We assessed the output of parasite transmission stages (cercariae) from infected snail hosts, the survival and infectivity of cercariae, the susceptibility of amphipod hosts to infection (laboratory experiments) and the survival of infected and uninfected amphipod hosts (outdoor experiment) when exposed to photo-synthetically active radiation only (PAR, 400–700 nm; no UV), PAR+UVA (320–700 nm) or PAR+UVA+UVB (280–700 nm). Survival of cercariae and susceptibility of amphipods to infection were the only two steps significantly affected by UVR. Survival of cercariae decreased strongly in a dose-dependent manner, while susceptibility of amphipods increased after exposure to UVR for a prolonged period. Exposure to UVR thus negatively affects both the parasite and its amphipod host, and should therefore be considered an influential component in parasite transmission and host-parasite interactions in intertidal ecosystems.

1. The morphology and histochemistry of the genitalia concerned in the formation of the egg in Multiceps smyihi n.sp. are described.

2. The vitelline cells are devoid of the phenolic protein globules, which occur in the vitelline cells of the Pseudophyllidea; this result is correlated with the absence of a true external egg-shell.

3. The hardened embryophore (often mistakenly termed the egg-shell) gives none of the reactions of sclerotin (tanned protein) or chitin, but gives a strong P.F.A.S. reaction for disulphide bonds, suggesting that it is a ‘keratin’ type of protein.

4. The cells of Mehlis' gland secrete a material which is intensely P.A.S.-positive and is not digested by saliva, α-amylase or hyaluronidase. This suggests that it may be secreting a mucopolysaccharide or muco- or glycoprotein.

The mini-exon gene repeats from three different strains of Endotrypanum schaudinni have been amplified by the polymerase chain reaction (PCR). Sequence analysis of the cloned products shows the gene and intergenic region to be identical in two of the strains (LV86 and M6159); the intergenic region from the mini-exon gene of the third strain (LV59) is significantly different. The LV86 gene and an intergenic probe from the LV59 mini-exon gene do not cross-hybridize with the mini-exon gene from New World Leishmania species. These data provide the basis of a PCR assay to detect E. schaudinni and distinguish it from New World Leishmania species, and which should be applicable to epidemiological studies in insect vectors and mammalian reservoirs. The identification of two different mini-exon gene repeats in E. schaudinni isolates is indicative of further strain variation within this species.

Adult schistosomes can be transferred surgically from donor C57BL/6 mice to the portal veins of naive recipients with complete success. This procedure bypasses larval development and the antibody response of the host is directed against, and can be used to identify, those antigens released only by viable, mature parasites. Serum collected from the recipient mice (WTS) was used in Western blotting studies to probe fractionated parasite protein. Twelve immunodominant proteins were identified, ranging in molecular weight from 14 to 208 kDa. The magnitude of the IgG response against each antigen could be divided into 2 categories, on the basis of optical densitometry of the blots. In addition, defined parasite fractions were probed with WTS by Western blotting, in order to determine the relative abundance and distribution of each antigen in schistosome tissue. To confirm and expand on these initial observations, oligospecific polyclonal antibody for each immunogen was affinity purified from Western blots; it was then used in immunocytochemistry to identify the sources of secretion for 8 of the 12 antigens, at the cellular level. From the results, it appeared that after the transfer of adult worms, the first antibodies detected were mostly directed against the gastrodermis. At later times additional reactivity was expressed against the tegumental membrane. These differences probably reflect the relative abundances of the gut and tegumental secretory products.

1. Leucine aminopeptidase has been detected, histochemically, in the intestine, in the walls of the anterior part of the excretory canals and in the hypodermis of Ascaris lumbricoides.

2. The possible significance of leucine aminopeptidase in the walls of the excretory canal is discussed.

I wish to thank Dr Tate, in whose department this work was carried out, for his advice and encouragement during this investigation and Mr A. Page for technical assistance.

A simple technique for the maintenance in vitro of mature Schistosoma mansoni is described and critically assessed at the ultrastructural level. Females were cultured for 4–6 days with no apparent ultrastructural change, but after this period changes appeared in the cells of the ovary and vitelline gland. At a later stage (10–12 days) lipid bodies appeared in the parenchyma cells. These changes occurred in worms which were active, paired with males and were egg–laying. Thus the activity, pairing behaviour and egg–laying characteristics are not adequate to reveal the true morphological condition and presumably the physiological and biochemical status of cultured worms.

This technique was used to study the effect of Astiban on females and the results were compared with worms treated in vivo. Astiban concentrations greater than 30 µg/ml killed worms within 7–20 h and acted non–selectively. Astiban at low concentrations (10µg/ml) during short–term culture (1–3 h) resulted in a selective action of the drug on maturing vitelline cells. Thus, although the degree of cell damage caused by drug treatment was more severe and occurred earlier than the effects observed in worms cultured in vitro without drugs, both treatments resulted in differential cell death.

Regular distribution of ivermectin reduces onchocerciasis transmission and morbidity by killing, within humans, the microfilarial stage of the parasite (microfilaricidal effect). In addition, ivermectin exerts a so-called embryostatic effect by which microfilarial production by the adult female worm becomes suppressed during a number of weeks after treatment. To assess the overall effect of ivermectin on onchocerciasis transmission and evaluate the likelihood of local elimination of the infection it is important to estimate the magnitude of the anti-fertility effect over the course of a treatment programme. Estimates of the effect of repeated drug treatments on the production of microfilariae by adult Onchocerca volvulus were obtained by developing a model that was fitted to data collected from three hyperendemic communities in Guatemala, where eligible residents received ivermectin twice per year for two and a half years. The data consist of microfilarial load measurements in the skin, collected just before each six-monthly treatment during the programme. The model that is developed describes the dynamics of an individual host's expected microfilarial load over the 30-month study period. We adopt a Bayesian approach and use Markov chain Monte Carlo (McMC) techniques to fit the model to the data. Combining estimates from the three villages, average microfilarial production in the first six months post-treatment was reduced by ~64% of its pre-treatment level, regardless of values chosen for the pre-ivermectin fertility rate within plausible ranges. Increased adult worm death rate after treatment (to mimic removal of macrofilariae via nodulectomy during the programme) resulted in a smaller estimated magnitude of the embryostatic effect (rate of microfilarial production was reduced by ~58% of pre-ivermectin value). After subsequent treatments, the rate of microfilarial production appeared to be similarly decreased. The data and analyses therefore do not support the hypothesis of a cumulative effect of multiple ivermectin treatments on microfilarial production by female worms.

The 13 636 bp mitochondrial (mt) genome sequence of the trichostrongylid nematode Cooperia oncophora was determined.Sequence data have been deposited in the EMBL/GenBank Data libraries under Accession number AY265417. The single nucleotide polymorphisms have been deposited in the dbSNP Database (http://www.ncbi.nlm.nih.gov/SNP) under ID numbers ss8485731-ss8486156. Like the mt genomes of other nematodes it is AT rich (76·75%) and cytidine is the least common nucleoside in the coding strand. There are 2 ribosomal RNA (rrn) genes, 22 transfer RNA (trn) genes and 12 protein coding genes. The relatively short AT-rich region (304 bp) and the lack of a non-coding region between two of the NADH dehydrogenase genes, nad3 and nad5, makes the mt genome of C. oncophora one of the smallest known to date, having only 525 bp of non-coding regions in total. The majority of the C. oncophora protein encoded genes are predicted to end in an abbreviated stop codon like T or TA. In total, 426 single nucleotide polymorphisms (SNP) were mapped on the mt genome of C. oncophora, which is an average of 1 polymorphism per 32 bp. The most common SNPs in the mt genome of C. oncophora were G/A (59·2%) and C/T (28·4%) transitions. Synonymous substitutions (86·4%) were favoured over non-synonymous substitutions. However, the degree of sequence conservation between individual protein genes of different parasitic nematode species did not always correspond to the relative number of non-synonymous SNPs. The mt genome sequence of C. oncophora presents the first mt genome of a member of the Trichostrongyloidea and will be of importance in refining phylogenetic relationships between nematodes. The, still limited, SNP map presented here provides a basis for obtaining insight into the genetic diversity present in the different protein coding genes, trn, rrn and non-coding regions. A more detailed study of the more variable regions will be of use in determining the population genetic structure of C. oncophora. Ultimately this knowledge will add to the understanding of the host–parasite relationship.

Ecological immunology is based upon the notion that activation and use of the immune system is costly and should thus be traded off against other energy-demanding aspects of life history. Most of the studies on insects that have examined the possibility that mating results in trade-offs with immunity have shown that mating has immunosuppressive effects. The connection between mating and immunity has traditionally been investigated using indirect measures of immunity. However, studies that have assessed the effects of mating on the resistance against real pathogens have had conflicting results. A previous study on Tenebrio molitor showed that copulation decreases phenoloxidase activity in the haemolymph, and concluded that copulation corrupts immunity in this species. In the present study we tested whether mating also affects the ability of T. molitor to resist the entomopathogenic fungus, Beauveria bassiana. Interestingly, we found that mating enhanced resistance against the fungal infection and that the effect was stronger on males than females. Furthermore, we found that male beetles were overall more susceptible to the fungal infection than were females, indicating an immunological sex difference in immunity. Our study highlights the importance of the use of real pathogens and parasites in immuno-ecological studies.

Carbohydrates associated with the tegumental surface of Schistosoma mansoni primary sporocyst may serve as potential receptors for mediating recognition by the internal defence system of the molluscan host, Biomphalaria glabrata. Therefore, a combination of SDS-PAGE and lectin probe analyses were carried out on biotin-labelled tegumental glycopeptides as a first step to defining the carbohydrates expressed at the sporocyst surface. The majority of surface polypeptides, ranging in relative molecular masses from 27 to 113 kDa, reacted with horseradish peroxidase-labelled Canavalia ensiformis (Con A), Erythrina corallodendron (ECA), Glycine max (SBA) and Triticum vulgaris (WGA) lectins indicating that most, if not all, tegumental proteins are glycosylated. However, differences in the binding of some lectins to individual glycopeptides suggest a degree of heterogeneity in the structure/composition of sugar moieties comprising these surface glycoconjugates. This notion is supported by the finding that the fucose-specific Tetragonolobus purpureas (TPA) lectin only reacted with approximately 50% of glycopeptides identified at the tegumental surface. Experiments employing biotin-labelled plasma (cell-free haemolymph) from S. mansoni-susceptible and -resistant B. glabrata snails as probes, further demonstrated that many of the identified surface glycoproteins also serve as plasma-binding sites for both snail strains. Binding interactions between plasma and sporocyst surface glycoproteins appeared to be, at least in part, mediated by carbohydrates since periodate treatment of sporocyst proteins or pre-incubation of plasma with the glycoproteins, fetuin or mucin, resulted in a decrease in plasma reactivity to blotted larval proteins.

This paper reviews naturally occurring and synthetic compounds that either enhance immune defences or lower both natural and acquired immunity. Immunomodulatory agents used both for laboratory study and clinically for the management of immunologically based diseases are considered

Harnessing the full utility of extensive gene sequences recently available for the economically important sea louse, Lepeophtheirus salmonis, requires the adaptation of modern molecular biology approaches to this non-model organism. Using a putative microsomal prostaglandin E synthase type-2 (PGES2) as a candidate gene, we investigated gene-knockdown by double-stranded RNA interference (dsRNAi) in the small free-living and the larger parasitic stages of L. salmonis. dsRNA was administered to nauplius and copepodid stages by immersion for 7 h. Pre-adult and adults received dsRNA by intra-haemocoelic injection. The extent, speed and persistence of the knockdown effects were determined by RT-PCR. LsPGES2 was abundantly expressed in all life stages, including the non-parasitic stages. Administration of dsRNA to nauplius and copepodids by immersion had no effect on mortality rates and moulting through to copepodids was observed. Dramatic knockdown of LsPGES2 was observed within 7 h and persisted for at least 48 h. Injection of dsRNA had no effect on mortality in pre-adults and adults, but knockdown of LsPGES2 was apparent within 24 h, reaching 95% over the 72 h and was persistent for at least 120 h. The methods developed resulted in rapid and persistent knockdown in L. salmonis suitable for studies in the different stadia.

Five new species of Myxosporidia are described and figured. They are: Ceratomyxa auerbachi, Davisia longibrachia, Myxidium laticurvum, Parvicapsula unicornis and Sphaerospora irregularis. The first two are parasitic in the gall-bladders, while the remaining three in the urinary bladders of various teleosts in the North Sea.

This paper describes the ability of the Asian fish nematode Camallanuscotti to carry out both heteroxeny, i.e. an indirect life-cycle using copepods as intermediate host, and monoxeny, i.e. direct infection and development in the definitive fish host. C. cotti occurs naturally in various freshwater teleosts in Asia. During the past decades it has been disseminated into closed or semi-closed aquaculture systems and aquaria around the world, mainly due to the ornamental fish trade. Under such conditions the species may frequently face a bottleneck situation with regard to the availability of copepods. It is known that C. cotti may reproduce and persist in copepod-free aquaria for several months. In order to investigate whether C. cotti has selected towards monoxeny in water systems lacking copepods, in contrast to the opposite selection pressure when copepods are present, 2 separate infection trials were run. It was shown that the parasite can infect the fish host both indirectly via copepods, and directly. However, C. cotti has significantly higher fitness, expressed as survival to maturity, when transmitted indirectly compared to the direct transmission mode. We suggest that the ability of aquarium populations of C. cotti to carry out a direct life-cycle is favoured by selection in order to avoid extinction whenever copepods are absent. It still remains unknown, however, whether the parasite shows the same characteristics in the wild.

Neurocysticercosis (NCC) is considered a neglected parasitic infection of the human central nervous system. Its pathogenesis is due to the host immune response, stage of evolution and location of the parasite. The aim of this study was to evaluate the in situ and systemic immune response through cytokines dosage (IL-4, IL-10, IL-17 and IFN-γ) as well as the local inflammatory response of the experimental NCC with Taenia crassiceps. The in situ and systemic cellular and inflammatory immune response were evaluated through the cytokines quantification at 7, 30, 60 and 90 days after inoculation and histopathological analysis. All cysticerci were found within the cerebral ventricles. There was a discrete intensity of inflammatory cells of mixed immune profile, polymorphonuclear and mononuclear cells, at the beginning of the infection and predominance of mononuclear cells at the end. The systemic immune response showed a significant increase in all the analysed cytokines and predominance of the Th2 immune profile cytokines at the end of the infection. These results indicate that the location of the cysticerci may lead to ventriculomegaly. The acute phase of the infection showed a mixed Th1/Th17 profile accompanied by high levels of IL-10 while the late phase showed a Th2 immune profile.

Three nucleotide data sets, one nuclear (ITS-2) and two mitochondrial (COI and l-rRNA), have been investigated in order to determine relationships among species of Strongylinae and Cyathostominae, intestinal parasites of the horse.Nucleotide sequence data reported in this paper are available in the NCBI, GenBank, accession numbers: AF263472 to AF263472 and AF268479. The data exhibited a strong mutational bias towards A and T and in the COI gene, silent sites appeared to saturate rapidly partly due to this substitution bias. Thus, the COI gene was found to be less phylogenetically informative than the l-rRNA and ITS-2 genes. Combined analysis of the l-rRNA and ITS-2 genes supported a monophyletic clade of the cyathostomes with Tridentoinfundibulum gobi, which had previously been classified as a nematode of ‘uncertain origin'. The Strongylinae grouped consistently outside the clade containing the cyathostomes and T. gobi. Molecular analysis failed to provide strong evidence for the separation of cyathostomes into classical genera, as previously defined by morphological classification.

The wall of the trunk, that of the praesoma, and the lemnisci of Acanthocephalus ranae have been studied by electron microscopy. Striations visible in sections of the body wall under the light microscope do not correspond with the ‘striped layer’ revealed by the electron microscope.

A new region, the ‘canal layer’, has been described. This contains canals running into the body wall from cuticular pores.

Structurally the wall of the trunk and that of the praesoma are similar. The lemnisci resemble the ‘inner layer’ of the praesoma wall. However, it is suggested that the wall of the trunk differs physiologically from that of the praesoma, and from the lemnisci. The possible roles of the wall of the praesoma and the lemnisci in fat excretion or uptake have been discussed.

The body wall of A. ranae has been compared with that of the other acantho-cephalans studied with the electron microscope.

Grateful acknowledgement is made to D.S.I.R. (now S.R.C.) for a research grant to the Department of Zoology for the purchase of a Huxley ultramicrotome, a vacuum coating unit, and an AEI EM 6 electron microscope.

I am grateful to Dr D. A. Erasmus for reading and criticizing the manuscript, and to Mr T. Davies for valuable technical assistance.

Objective. Maternal infection has been considered to be a risk factor for filarial infection in offspring. In order to examine the influence of maternal infection in neonates, we have determined the prevalence of circulating filarial antigen (CFA) and anti-filarial antibodies in 119 maternal and corresponding cord blood samples collected from an area endemic for bancroftian filariasis. Method. Prevalence of antigenaemia was detected using Og4C3 circulating filarial antigen enzyme-linked immunosorbent assay. The presence of microfilariae was determined by filtration of a 1 ml sample through a Nuclepore membrane. Antibody isotypes (IgG, IgM, and IgE) to filarial antigen (Setaria digitata antigenic extract) were determined by enzyme linked immunosorbent assay (ELISA). Results. Microfilariae were detected in 14 cases (11·8%), whereas the Og4C3 assay could detect filarial antigen in 44·5% of pregnant mothers. Interestingly, 24·5% of samples born from CFA-positive mothers were found positive for CFA. None of the cord samples from CFA-negative mothers were found positive for CFA. No significant difference was observed in prevalence of filarial-specific IgG, IgM and IgE antibodies in CFA-positive and negative mothers. IgG antibody was detected in 60·5% of maternal and 21·8% of cord samples. IgG antibody in the cord does not differ with the antigen status of the mother. In contrast IgM and IgE antibody prevalence was significantly higher in cord from infected mothers than non-infected mothers (11·3% vs 0 for IgM, 24·5% vs 3·03% for IgE). Conclusion. Our study demonstrates the transplacental transfer of circulating filarial antigen from mother to cord. Filaria-specific IgM and IgE antibodies were higher in cord blood from infected mothers than from non-infected mothers. The findings of the study provide additional circumstantial evidence for pre-natal sensitization to filarial antigens developed in utero.

Anthelmintics are the cornerstone of parasitic helminth control. Surprisingly, understanding of the biochemical pathways used by parasitic helminths to detoxify anthelmintics is fragmented, despite the increasing global threat of anthelmintic resistance within the ruminant and equine industries. Reductionist biochemistry has likely over-estimated the enzymatic role of glutathione transferases in anthelmintic metabolism and neglected the potential role of the cytochrome P-450 superfamily (CYPs). Proteomic technologies offers the opportunity to support genomics, reverse genetics and pharmacokinetics, and provide an integrated insight into both the cellular mechanisms underpinning response to anthelmintics and also the identification of biomarker panels for monitoring the development of anthelmintic resistance. To date, there have been limited attempts to include proteomics in anthelmintic metabolism studies. Optimisations of membrane, post-translational modification and interaction proteomic technologies in helminths are needed to especially study Phase I CYPs and Phase III ABC transporter pumps for anthelmintics and their metabolites.