The genus Acanthobothrium van Beneden, 1850, seems to be in a state of slight confusion due, possibly, to some inadequate descriptions which have led to subsequent misidentifications of some of the species. The type species A. coronatum was first recorded and very briefly described by Rudolphi (1819) as Bothriocephalus coronatus from ‘Squali stellaris, Squali squatinus and Torpedinis marmoratae“. Since then specimens have been assigned to this species which probably belong elsewhere; the list of synonyms and the host records are extensive. Baer (1948) divided the species of the genus into two groups, namely, those parasitic in sharks and those in rays. This seems to be a reasonable distinction as specificity is very marked in cestodes and especially in those of elasmobranchs. It was thought that a detailed study of the type species, presented here, would be a useful preliminary to a consideration of the genus as a whole.

Specimens of A. coronatum were obtained from the spiral valve of Scyliorhinus stellaris (L.) caught in Cardigan Bay in July 1956 and at Plymouth in August 1958 and August and September 1959. The number of worms, complete with scoleces varied from 6 to 10 per fish and in one instance 14. Many fragments of two to three proglottids and many individual proglottids were also present. The scoleces were attached in the first turn of the spiral valve and the strobila adhered feebly along the whole length, sometimes as far back as the rectal gland, leaving on removal a distinct groove in the mucosa.

Acanthocephaloides geneticus sp.nov. is described from Arnoglossus laterna (Bothidae) from the Mediterranean littoral (Sète-France). The new species most closely resembles Acanthocephaloides propinquus (Dujardin, 1845) Meyer, 1932, whose type host is Gobius niger (Gobiidae). A genetic comparison of the parasites collected from these two Teleostean fishes has confirmed the value of morphological differences which seemed too slight to raise the populations to species status.

1. Measurements were made of the head length, head width, total body length, antenna length, length and breadth of 3rd antennal segment of head and body lice from natural infestations. In all measurements (except the last) the means were significantly different for. the two forms, but in all cases there was considerable overlap.

2. Head lice reared continuously on the body for forty-three generations (over 2 years) did not change systematically in size. Body lice reared under similar conditions were likewise constant.

3. There was a highly significant difference between mean measurements of all the samples of head lice reared for up to 2 years on the body when compared with body lice reared for a similar period in the same way. The means for lice worn 24 hr. per day were less than those worn 12 hr. per day in both strains. An experiment showed that this is probably due to a difference in average temperature.

4. The mean live weights of head and body strains were even more distinct than linear dimensions on the several occasions when these were recorded.

5. Measurements of the dimensions of the opercula of the eggs of the two races and the numbers of air cells in them were distributed in the same way as the body measurements: that is, distinct means but overlapping individuals.

6. Ventral abdominal muscles in wild head lice are typically confined to segment 5. (The forty specimens examined adhered to this rule.) In wild body lice, muscles are usually also present in segment 4 as well.

7. Hybrids (female body x male head louse) were fertile for several generations. In size, the F1 generation was intermediate, but the F2 and F3 generations became identical with the body louse strain.

8. Eggs of the body louse strain hatched at the same time as those of the head strain, but the body strain reached a significantly higher percentage hatch.

9. The times of moulting during development were studied in both races in relation to differing opportunities to feed (24, 12, 6 and 3 hr. per day). The two strains showed very similar reactions in regard to speed of development, but throughout there was a higher pre-imaginal mortality in the head strain.

10. Head lice were shown to be considerably more susceptible to starvation than body lice.

11. If adults of the two strains are mixed, there is no tendency towards homogeneous mating. Of the mixed matings, those between body louse males and head louse females are much more common than the reverse.

12. Female head lice show a slight difference in their egg-laying preferences when offered a choice of hair, voile and tape.

My thanks are due to Prof. P. A. Buxton, F.R.S., for a number of helpful suggestions based on his extensive knowledge of louse biology and to Dr J. O. Irwin for critical comments on the statistical issues.

The results are described of further studies on a virus found in the roots of certain normal-looking plants. It is shown that the virus is a contamination arriving from outside sources. The virus has been detected in the sludge at the bottom of the water tanks, and the experimental evidence shows that it is water-borne to the soil whence it reaches the roots of the plants. Experiments to test the possibility that the virus is also air-borne have so far proved negative.

The virus is exceedingly resistant, it can be completely desiccated and remains infective in the dry state for many weeks. It is also unaffected by alcohol and is still infective after being stored in absolute alcohol for 6 months.

The virus is thought to be a transitional stage between a pathogen and a non-pathogen.

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.

The entire ribosomal DNA repeat unit of a steinernematid species (Nashes isolate) was cloned as three separate EcoR I fragments in the plasmid pUC18. An equimolar cocktail of these three clones was used to identify Steinernema species on Southern blots as each species displays its own unique restriction fragment length polymorphisms. The clones also identified two new species isolated in a soil survey of coastal regions of Britain. One of the clones (pSn4.0) can detect length heterogeneities in the rDNA repeat unit of various isolates of some of the species, particularly the most common in the United Kingdom, S. feltiae. These differences in the rDNA repeat unit length remained constant over several years for one isolate of S. feltiae, but were different for each of the geographical isolates studied to date.

The biology and life-cycle of Holostephanus lühei is briefly described. The similarities in morphology between the adhesive organ gland cells of H. lühei and Cyathocotyle bushiensis are stressed. Alkaline and acid phosphatases were demonstrated in the adhesive organ gland cells and cuticle. Acid phosphatase also occurs in the caecal cells. Non-specific esterase, sensitive to E600 10−5M and Mipafox 10−3M, is present in the gland cells. The caeca contain a non-specific esterase sensitive to AgNO3 10−2M and PCMB 10−4M. Leucine aminopeptidase is present in the gland cells. The in vitro studies confirmed that the secretory products pass to the exterior of the parasite and have a histolytic action.

The four strigeids studied, Cyathocotyle bushiensis, Holostephanus lühei, Diplostomum spathaceum and Apatemon gracilis minor, are compared and the biological role of the secreted enzymes are discussed.

My sincere thanks are due to Dr D. A. Erasmus for suggesting this line of investigation and for his encouragement during the study. I am also grateful for his performing, on my behalf, the infection experiments and criticizing the manuscript. I wish to thank Professor J. Brough for his interest in the progress of the work, and the University College, Cardiff, for a grant from William E. Morgan's Bequest.

The physiology of the neuromuscular systems in Hymenolepis diminuta and H. microstoma was studied in vitro using intact, adult worm and strips of worm body wall. Intact worms were insensitive to ionic changes in the in vitro buffering system. However, strips of body wall containing longitudinal muscles were extremely sensitive to ionic manipulation. In intact worms tension generated in the strobila had two components; small brief tension peaks up to 500 mg amplitude are superimposed on larger, longer peaks of up to 1200 mg amplitude. Removal of the scolex and neck region either failed to show significant changes in tension, or showed a reduction in amplitude but not of frequency. Muscle contraction of both H. diminuta and H. microsoma were qualitatively similar. In split-worm preparations the concentration of Ca2+ in the bathing solution significantly affected both spontaneous and evoked contractions in H. diminuta and H. microstoma; the addition of CaCl2 greatly reduced the amplitude and frequency of the contractions. The chloride salts of cobalt, barium, cadmium and manganese elicited prolonged contractions of the longitudinal musculature of both H. diminuta and H. microstoma. While CoCl2 was the most effective in stimulating muscle contraction, the magnitude of the response varied with the concentration of Ca2+ in the bath. The results indicate that peripheral inhibition is extremely important in cestode motor control and that extracellular calcium ions may regulate the peripheral inhibitory mechanisms.

A successful attempt was made to induce immunological tolerance to N. brasiliensis in laboratory rats by exposing them to larval infections before the age of immunological maturity.

The adult capacity of rats to eliminate a primary infection in 3 weeks and to acquire resistance to reinfection was developed by 5 weeks of age. On the other hand, primary infections of 250–660 larvae, originating before 4 weeks of age, survived in 61 of 83 rats up to 10 weeks. These rats were not resistant to challenge at 5 or 7 weeks of age, nor did the challenge infection undergo immune elimination. Such tolerance was evident even in rats whose primary worm burden was chemically abbreviated prior to challenge.

It was not always possible to distinguish between tolerant and immune animals on the basis of egg output patterns. Suppression of egg output occurred even in tolerant rats harbouring relatively stable female populations.

For immunological experiments on N. brasiliensis infection in rats, the determination of a ‘take ratio’ is advocated: (20 day take/10 day take) × 100. This ratio eliminates the error inherent in variability of takes and renders comparable the results of different experiments.

The work was carried out in 1965 during tenure by one of us (T.K.) of an Exchange Scholarship under the British–Hungarian Cultural Agreement. Supervision by Professor W. Mulligan and the co-operation of colleagues in the Wellcome Laboratories are gratefully acknowledged.

A study has been carried out to determine the activity of genistein against adult liver fluke, Fasciola hepatica. Flukes were incubated in vitro in genistein at a concentration of 0·27 mg/ml (=1 mm). They ceased to move after 3 h, at which point the experiment was terminated and the specimens prepared for examination by scanning and transmission electron microscopy. Surface changes to the flukes comprised swelling and blebbing, especially in the posterior region of the flukes, and there was particular disruption to the spines, accompanied by some spine loss. Fine structural changes to the tegumental syncytium indicated an accelerated release of secretory bodies at the surface, but a reduction in their production within the cell bodies. Autophagic activity was evident in the tegumental cells, a phenomenon that was also observed in the gastrodermal cells. Disruption to the testis and vitelline follicles was severe, with an apparent block in the normal developmental sequence of the spermatogenic and vitelline cells, respectively. Shell protein production by the vitelline cells was also disrupted. In separate experiments, somatic muscle strips were exposed to concentrations of genistein ranging from 1 μm to 1 mm. There were statistically significant increases in the frequency and/or amplitude of muscle contractions at concentrations of 10 μm, 100 μm and 1 mm. The results suggest that genistein is capable of causing severe morphological and neuromuscular disruption to adult flukes in vitro over a short time-span.

Members of the genus Cryptosporidium, which cause the gastrointestinal disease cryptosporidiosis, still represent a significant cause of water-borne disease worldwide. While intensive efforts have been invested in the development of techniques for parasite culture, in vitro growth has been hampered by a number of factors including low levels of infectivity as well as delayed life-cycle development and poor synchronicity. In this study we examined factors affecting the timing of contact between excysted sporozoites and target host cells and the subsequent impact of this upon the establishment of infection. We demonstrate that excystation rate impacts upon establishment of infection and that in our standard assay format the majority of sporozoites are not close enough to the cell monolayer when they are released from the oocyst to successfully establish infection. However, this can be easily overcome by centrifugation of oocysts onto the cell monolayer, resulting in approximately 4-fold increases in sporozoite attachment and subsequent infection. We further demonstrate that excystation procedures can be tailored to control excystation rate to match the assay end purpose and that excystation rate can influence data interpretation. Finally, the addition of both a centrifugation and washing step post-sporozoite attachment may be appropriate when considering the design of in vitro culture experiments for developmental analysis and stage-specific gene expression as this appears to increase the synchronicity of early developmental stages.

Sera from donors exposed to malaria were tested for their ability to block the transmission of isolates from Cameroonian Plasmodium falciparum gametocyte carriers. Sera were selected from amongst Cameroonian and Gambian donors who had positive antibody reactivity against the surface of activated gametes and against epitopes of Pfs 48/45 (a potential transmission-blocking vaccine candidate antigen). Aliquots of washed blood from gametocyte carriers were resuspended in test and control sera and fed to An. gambiae mosquitoes via a membrane feeder. Comparisons of the prevalence and intensity of infections in dissected mosquitoes showed variations in the ability of sera to block the transmission of the different isolates. Sera were identified that had little or no blocking effect on the transmission of isolates unless the isolate was poorly infectious. Some sera completely blocked the transmission of some isolates whilst having little or no effect on others. The observed variation in transmission-modulating activity may have implications for the development of a transmission-blocking vaccine.

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.

In view of the mandate from the World Health Organization (WHO) for developing novel drug candidates against human lymphatic filariasis, dihydrofolate reductase (DHFR) inhibitors are explored as potential antifilarial agents. The in vitro biological evaluation of an in-house library of 12 diverse antifolate compounds with 2,4-diaminopyrimidine and 2,4-diamino-s-triazine structural features against Brugia malayi is reported. To confirm the DHFR inhibitory potential of these compounds, reversal studies using folic acid and folinic acid were undertaken. Inhibition of DHFR can induce apoptosis; in this light, preliminary evidence of apoptosis by test compounds was detected using ethidium bromide–acridine orange staining and the poly(adenosine diphosphate-ribose) polymerase (PARP) inhibition assay. Among the evaluated compounds, 3 showed significant activity against both microfilariae and adult worms. The effects of 2 of these compounds were mostly reversed by folic acid, validating DHFR inhibitory activity. Partial reversal of the effect of 2 compounds by folinic acid and non-reversal of the effect of the third compound both by folic and folinic acids are discussed. This study opens new avenues for the discovery of lead molecules by exploiting the folate pathway against one of the major neglected tropical diseases, filariasis.

Few papers have been published on tick lectins so far, and therefore more data are needed to complete the mosaic of knowledge of their structural and functional properties. Tissue-specific lectin/haemagglutinin activities of both soft and hard ticks have been investigated. Some tick lectins are proteins with binding affinity for sialic acid, various derivatives of hexosamines and different glycoconjugates. Most tick lectin/haemagglutinin activities are blood meal enhanced, and could serve as molecular factors of self/non-self recognition in defence reactions against bacteria or fungi, as well as in pathogen/parasite transmission. Dorin M, the plasma lectin of Ornithodoros moubata, is the first tick lectin purified so far from tick haemolymph, and the first that has been fully characterized. Partial characterization of other tick lectins/haemagglutinins has been performed mainly with respect to their carbohydrate binding specificities and immunochemical features.

Extensive connective tissue lysis is a common outcome of haplosporidian infection. Although such infections in marine invertebrates are well documented, they are relatively rarely observed in freshwater invertebrates. Herein, we report a field study using a comprehensive series of methodologies (histology, dissection, electron microscopy, gene sequence analysis, and molecular phylogenetics) to investigate the morphology, taxonomy, systematics, geographical distribution, pathogenicity, and seasonal and annual prevalence of a haplosporidian observed in zebra mussels, Dreissena polymorpha. Based on its genetic sequence, morphology, and host, we describe Haplosporidium raabei n. sp. from D. polymorpha – the first haplosporidian species from a freshwater bivalve. Haplosporidium raabei is rare as we observed it in histological sections in only 0·7% of the zebra mussels collected from 43 water bodies across 11 European countries and in none that were collected from 10 water bodies in the United States. In contrast to its low prevalences, disease intensities were quite high with 79·5% of infections advanced to sporogenesis.

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.

Entomopathogenic nematode infective juveniles are likely to encounter both uninfected and infected insects and host quality depends on the stage of the infection. We hypothesized that nematode response to infected hosts will change over the course of an infection. Here, we tested this hypothesis by focusing on the influence of host infection status on long-range attraction to host volatile cues. The attraction response of 3 nematode species (Steinernema carpocapsae, S. glaseri and S. riobrave) with different foraging strategies to infected and uninfected insects (Galleria mellonella and Tenebrio molitor) was tested at 24 h intervals from start of infection to emergence of infective juveniles from depleted host. As expected, based on their foraging strategies, S. carpocapsae was not very responsive to hosts, S. glaseri was highly responsive and S. riobrave was intermediate. Generally, the level of attraction did not change with time after infection and was similar between infected and uninfected hosts. An exception was S. glaseri infected T. molitor, which tended to be less attractive to S. glaseri than uninfected hosts. These results suggest that any influence of host infection status on infection behaviour is occurring at subsequent steps in the host-infection process than host attraction, or involves non-volatile cues.

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.

The aim of the study was to measure the impact of Schistosoma japonicum and Trichuris suis infections in young growing pigs fed low- or high-protein diets. Thirty-two pigs, 6–10 weeks old, were randomly allocated to 2 groups receiving either a high- or a low-protein diet. After 11 weeks half of the pigs from each group were infected with 1500 S. japonicum cercariae and 4000 T. suis eggs. The weight of the pigs was measured throughout the study, and blood and faecal samples were collected every second week from the time of infection. At the time of infection the low-protein pigs had significantly lower mean body weights, haemoglobin and albumin levels compared with the high-protein pigs, and this pattern continued throughout the study. The serum albumin concentration was further significantly reduced in the infected low-protein pigs compared to the non-infected low-protein pigs. Significantly more S. japonicum worms as well as faecal and tissue eggs were found in the low-protein pigs compared with the high-protein pigs. No differences between the 2 diet groups were observed in T. suis establishment rates or faecal egg excretion. We conclude that this low-protein diet increased the establishment rates of S. japonicum, favoured larger deposits of S. japonicum eggs in the liver and faecal egg excretion, reduced weight gains and caused anaemia and hypoalbuminaemia in younggrowing pigs as compared with a high-protein diet.