The immune evasion gene family of malaria parasites encodes variant surface proteins that are expressed at the surface of infected erythrocytes and help the parasite in evading the host immune response by means of antigenic variation. The identification of Plasmodium vivax vir orthologous immune evasion gene family from primate malaria parasites would provide new insight into the evolution of virulence and pathogenesis. Three vir subfamilies viz. vir-B, vir-D and vir-G were successfully PCR amplified from primate malaria parasites, cloned and sequenced. DNA sequence analysis confirmed orthologues of vir-D subfamily in Plasmodium cynomolgi, Plasmodium simium, Plasmodium simiovale and Plasmodium fieldi. The identified vir-D orthologues are 1–9 distinct members of the immune evasion gene family which have 68–83% sequence identity with vir-D and 71·2–98·5% sequence identity within the members identified from primate malaria parasites. The absence of other vir subfamilies among primate malaria parasites reflects the limitations in the experimental approach. This study clearly identified the presence of vir-D like sequences in four species of Plasmodium infecting primates that would be useful in understanding the evolution of virulence in malaria parasites.

Four specimens of the pika (Ochotona rufescens Gray) were captured, and on dissection three of them were found to be heavily infested with a Nematode worm in the large intestine.

To date no experimental infection studies have been conducted in laboratory mice using Mus spp. bartonella strains. Therefore we designed a study to evaluate the in vivo infection characteristics of 2 Bartonella tribocorum strains from wild Mus spp. in laboratory mice with the aim of developing a mouse model that reproduces characteristics of naturally acquired bartonella infections in rodents. Groups of outbred CD1 female mice were subcutaneously inoculated with low doses of 2 mouse bartonella strains (10, 100, and 1000 bacteria/mouse). Blood was collected weekly for 27 weeks to evaluate bacteraemia kinetics in infected mice. Mouse urine collected during weeks 3–6 post-inoculation was also tested for viable bacteria to determine whether urine might serve as a source of bacterial transmission. Mice were susceptible to infection with both strains. Bacteraemias in mice lasted up to 25 weeks, sometimes with abacteraemic intervals, and achieved levels up to 107 cfu/ml of blood. Temporal lags in bacteraemia onset of up to 19 weeks in length were noted at different inoculum doses. No viable bacteria were detected in mouse urine. Bacteraemic mice displayed characteristics of infection similar to those observed in natural rodent hosts during longitudinal field studies. This mouse model of persistent bacteraemia should be suitable for a variety of experimental uses.

Bradynema listronoti is a parasitic nematode described from infected specimens of the carrot weevil Listronotus oregonensis. Prevalence of infection by B. listronoti under field conditions was followed over a period of 16 years in an untreated carrot field. Susceptibility of different carrot weevil life stages was evaluated as well as the impact of infection on fecundity and mortality. Gene expression in infected and uninfected carrot weevils was also compared to evaluate the impact of the parasite on the host transcriptome. Prevalence of B. listronoti in carrot weevil populations was sustained over the years ranging from 20 to 63%. All the weevil stages exposed to B. listronoti inoculum were susceptible to infection, larvae being more vulnerable (59 ± 8% infected) compared with pupae (4 ± 3% infected) and adults (7 ± 3% infected). The fecundity of infected female weevils was greatly reduced (60-fold) due to an inhibition of the maturation of the reproductive system. Transcriptomic analyses revealed that this parasitic castration may have been triggered by the inhibition of reproductive hormone production. The B. listronoti–L. oregonensis interaction represents a case of parasitic castration with a unique potential for biological control of an important pest of carrots.

A thymine–uracil transport system is present in the plasma membrane brush-border of the tapeworm, Hymenolepis diminuta. The relation between initial uptake and substrate concentration of either thymine or uracil was sigmoidal when 2-14C-labelled substrates were used. In contrast, absorption kinetics of methy 1-14C- and 3H-labelled substrates were hyperbolic. Since there was no metabolism of the labelled substrates during the incubation period, these differences indicate that the sigmoidal kinetics of pyrimidine transport in this organism is an isotope effect associated with the presence of the 14C label at the 2 position in the pyrimidine ring.

Four-day-old worms of the tapeworms Hymenolepis microstoma, H. diminuta and H. nana and newly excysted H. microstoma were exposed in vitro at 37 °C to immune serum from mice infected for 4–1 2 weeks with H. microstoma. Worms were fixed for electron microscopy after intervals of 5 min to 96 h. Within 10–15 min an homogeneous precipitate occurred between the microtriches of 4-day-old H. microstoma and H. nana, while on some areas of H. microstoma the precipitate extended distal to the microthrix border and contained small vesicles (30 nm in diameter) and shed microtriches. In H. diminuta precipitates were not found until 2 h post-incubation. The thickness of the precipitate and the number of small vesicles and shed microtriches increased with time after incubation. Since a similar precipitate occurred on worms kept in complement-depleted immune serum, antibodies alone may induce immune damage. The precipitate on newly excysted H. microstoma lacked microthrix fragments. After 48 h an extensive precipitate was found protruding from the rostellar glands on some H. microstoma, and within the culture vessel. Antibodies may therefore be complexing with tapeworm secretory products.

Pats of pig faeces containing known numbers of Oesophagostomum dentatum eggs were placed on plots with bare soil, short or tall herbage on 8 occasions during 1 year. The number of eggs and larvae and the relative distribution of larvae in faeces, soil and herbage was monitored for 1 year after deposition. On 2 occasions soil from 8 selected plots was given to pigs, which were later slaughtered and examined for the presence of adult O. dentatum. Less than 1% of the deposited eggs could be recovered as infective larvae. The highest recoveries were generally made on tall herbage plots. The majority of infective larvae was found within the faecal pats, which indicates that infective O. dentatum larvae, to a large extent, do not disperse onto the herbage or into soil. The infective larval stage was reached only when the mean temperature in the weeks post-deposition was above 10 °C. This stage was reached within 1 week when the mean weekly temperature was above 13 °C. After the winter period no infective larvae could be recovered from any plots and no parasitic worms could be isolated from pigs fed soil from 8 selected plots.

The animal under consideration belonging to the family Lernaeopodidae was taken on a codling (Gadus morrhua), 13 ins. in length, caught at Plymouth several years ago, and preserved in formalin since that date. Although about twenty-six valid species of Clavella have been either recorded or described in detail, the subject of the present paper differs from them all in combining several of the more prominent characters of other species, notably the extreme length of the backwardly-arched cephalothorax taken together with the reduction of the “arms” (second maxillae) and their expansion into a disc so that the “bulla” or button appears to be almost directly affixed to the body. For this species I accordingly propose the name Clavella sciatheric.

The aim of this work was to obtain a reagent based on latex particles for ruling out acute toxoplasmosis in pregnant women by immunoagglutination (IA). Latex–protein complexes (LPC) were previously synthesized coupling the recombinant protein of Toxoplasma gondii P22Ag and the homogenate of the parasite to latex particles with different size, chemical functionality and charge density. LPC were tested in IA assays against a panel of 72 pregnant women serum samples. Results were analysed through receiver operating characteristic curves, determining area under the curve (AUC), sensitivity, specificity positive and negative predictive values (PPV and NPV, respectively). It was observed that the antigenicity of proteins was not affected during sensitization by either physical adsorption or covalent coupling. The best results in the sense of maximizing discrimination of low avidity sera from chronic ones were observed for the IA test based on latex particles with carboxyl functionality and the recombinant P22Ag, obtaining an AUC of 0·94, a sensitivity of 100% and a NPV of 100%. In this way, the proposed test could be useful for the toxoplasmosis diagnosis in pregnant women, with the advantages of being cheap, rapid and easy to be implemented.

Fibres isolated from the ventral sucker of Fasciola hepatica were identified as muscle on the basis of their contractility, and their actin and myosin staining. They were voltage-clamped at a holding potential of −40 mV and depolarization-activated outward currents were characterized both electrophysiologically and pharmacologically. Activation was well fitted by a Boltzmann equation with a half-maximal potential of +9 mV and a slope factor of −14·3 mV, and the kinetics of activation and deactivation were voltage-sensitive. Tail current analysis showed that the reversal potential was shifted by +46±3 mV when EK was increased by 52 mV, confirming that this was a K+-current with electrophysiological characteristics similar to delayed rectifier and Ca2+-activated K+-currents in other tissues. The peak current at +60 mV was inhibited by 76±6% by tetrapentylammonium chloride (1 mM) and by 84±7% by Ba2+ (3 mM), but was completely resistant to block by tetraethylammonium (30 mM), 3,4-diaminopyridine (100 μM) and 4-aminopyridine (10 mM). Penitrem A, a blocker of high-conductance Ca2+-activated K+-channels reduced the current at +60 mV by 23±5%. When the effects of Ca2+-channel blocking agents were tested, the peak outward current at +60 mV was reduced by 71±7% by verapamil (30 μM) and by 59±4% by nimodipine (30 μM). Superfusion with BAPTA-AM (50 μM), which is hydrolysed intracellularly to release the Ca2+-buffer BAPTA, also decreased the current by 44±16%. We conclude that voltage-and Ca2+-sensitive K+-channels are expressed in this tissue, but that their pharmacology differs considerably from equivalent channels in other phyla.

It is generally believed that the patterns of in-host migration of the infective stages of most invasive macroparasites of man and domestic animals are matters of established fact. In reality, the textbook treatment of this topic, and much of the experimental approach to it, are a legacy of an uncritical past. With few exceptions the true picture concerning particular host/parasite systems is confused by the acceptance of inadequate criteria of proof. In important instances these bogus ‘proofs’ have been generalized within a suspect inductive framework which employs the basic assumption that all migratory parasites that enter the same portal and travel to the same destination do so by the same route. The discussion of such issues serves as a background to the presentation in detail of a more rigorous conceptual and experimental framework.

The tetrad and companion cells, in association with the oesophagus and dorsal tract of tissue, of Tetradonema plicans, have been investigated in the host Bradysia paupera. The companion cells contain glycogen and mucopolysaccharide. The tetrad cells are rich in RNA and probably synthesize protein and secrete some as enzymes. The gut is functional and the oesophagus is in connexion with the tetrad. The dorsal tract is not connected with the oesophagus or tetrad and contains lipid with characteristics similar to that found in the eggs.

It is suggested that the tetrad and companion cells are homologous with the stichocytes present in the Trichuroidea and some members of the Mermithoidea.

I am grateful to Professor T. R. E. Southwood in whose department this work was carried out. I should like to thank Dr N. A. Croll for supervising and encouraging this work and Dr T. Jenkins for his helpful criticism and advice. The work was supported by the Agricultural Research Council.

Sporozoon Tincae Volf & Dvořak, 1928, is the cause of a fatal disease of the tench (Tinca tinca) in fish-ponds in south Bohemia. We can distinguish in its life cycle two different stages, multiplication by repeated binary fission, resembling schizogony and by sporogony with the formation of elliptical spores measuring 1.5–2 by 0.5–1 μ. The development of all these stages occurs in the cytoplasm of histiocytes. A detailed description of the life cycle is given. This parasite should be placed provisionally in the order Haplosporidia.

The effect of the anthelmintic Mebendazole on Cysticercus cellulosae maintained in culture medium was studied by transmission electron microscopy. In addition to the well-known morphological changes induced by Mebendazole in other cestode and nematode larvae, it also induced the cytoplasmic appearance of paracrystalline bundles in the secretory cells of the bladder wall. These bundles were formed by groups of large parallel tubules arranged in a hexagonal-like pattern. The tubules, which had an external diameter of about 50 nm and a length that might exceed 5 μm, were surrounded by a matrix and a distance between neighbouring tubules of 80–120 nm centre to centre was estimated. The tubules were stable to colchicine and low temperature. The temporary appearance of bundles is described and some alternative explanations on their origin are advanced.