1. Ixodes auritulus group of ticks and Ixodes percavatus group of ticks are both characterized by having the palpal article I drawn out to a horn anteriorly, but in the percavatus group there is a strong meso-dorsal ‘spur’ on this article, which is lacking in the auritulus group.

2. The mutilated types of I. auritulus and I. percavatus sp. revocata are re-described and electotypes established for both.

3. Variations from I. auritulus sensu stricto are described from Peru and Guatemala, and a revised description given of the male, female and nymph from Snares Island.

4. I. percavatus and I. zumpti sp.nov. have been diagnosed from material from Nightingale Island, Tristan da Cunha. Ticks from Marion Island are identified as a new species, I. pterodromae. Female and nymphs from the Paris Museum originally identified by Neumann as I. auritulus now fall into the percavatus group and are named I. cornuae sp.nov.

Parasites competing over limited host resources are faced with a tradeoff between reproductive success and host overexploitation jeopardizing survival. Surprisingly little is known about the outcome of such competitive scenarios, and we therefore aimed at elucidating interactions between the trematodes Himasthla elongata and Renicola roscovita coinfecting the periwinkle first intermediate host. The results show that the success of Himasthla colonies (rediae) in terms of cercarial emission is unaffected by Renicola competition (sporocysts), whereas deteriating host condition decreases fitness. Furthermore, double infection has no bearing on Himasthla’s colony size but elevated the proportion of non-reproductive rediae that play a decisive role in colony defence. Opposite, the development of the Renicola colony (size/maturity), and in turn fitness, is markedly reduced in presence of Himasthla, whereas the nutritional state of the host appears less important. Hence, the intramolluscan competition between Himasthla and Renicola is asymmetrical, Himasthla being the superior competitor. Himasthla not only adjusts its virulence according to the hosts immediate nutritional state, it also nullifies the negative impact of a heterospecific competitor on own fitness. The latter is argued to follow in part from direct predation on the competitor, for which purpose more defensive non-reproductive rediae are strategically produced.

Echinococcus multilocularis is the causative agent of alveolar echinococcosis (AE), one of the most threatening zoonoses in Eurasia. Human AE is widespread in the Erzurum region of Turkey, but the situation of the disease in intermediate and definitive hosts is unknown. A Eurasian lynx (Lynx lynx) was killed in a traffic accident in the north of Erzurum, and was taken to our laboratory. Sedimentation and counting technique (SCT), DNA isolation and polymerase chain reaction (PCR) analysis were performed. The SCT results showed that the lynx was infected with E. multilocularis with a medium (745 worms) worm burden. The DNA of adult worms obtained from the lynx was analyzed with a species-specific PCR, and the worms were confirmed to be E. multilocularis by 12S rRNA gene sequence analysis. This is the first report of E. multilocularis from Eurasian lynx in Turkey.

A point mutation in codon 540 of the dihydropteroate synthetase (dhps) gene affecting sulfadoxine resistance has previously been found in parasites from patients with Plasmodium falciparum infection. Here, we investigated 4 methods of identifying this mutation in clinical specimens and established a reliable quantitative assay to estimate the percentage of resistant type in mixed infections. A diagnostic PCR assay based on allele-specific amplification was developed, which clearly typed the clinical specimens examined. The mutation in codon 540 introduces an additional FokI cleavage site which provided a second method to differentiate mutant from wild type, where the former gives rise to 2 characteristic fragments of 538 and 326 bp that are absent from the latter. To calibrate quantitatively the ratio of alleles in mixed samples, we constructed artificial mixes containing 2 plasmid DNAs, one carrying the mutation and the other a wild-type insert. When 32P-labelling was employed, the allele-specific PCR assay could detect the level of resistant type in a mixture down to 0·1–1%, while for the restriction enzyme/PCR analysis, the figure was approximately 10%. Furthermore, neither fluorescent dye-labelled terminator nor dye-labelled primer cycle sequencing was able to detect the mutant allele if it was present at less than 20–30%. We conclude that the allele-specific PCR assay is the most sensitive method of detecting the codon 540 mutation in P. falciparum dhps, and the method of choice for estimating the composition of mixed samples.

As we have recently shown that GABA should be considered a putative neurotransmitter in Schistosoma mansoni, the present work aimed to search for GABAA receptors in adult worms using [3H]-flunitrazepam to label the allosteric benzodiazepine binding site which is classically present on GABAA receptor complexes. We detected a large population (Bmax=8·25±1·1 pmol . mg protein−1) of high affinity (Kd=33·6±1·5 nm) binding sites for flunitrazepam. These sites harboured a singular pharmacological modulation that does not fit well with a mammalian central benzodiazepine receptor, mainly due to a very high affinity for Ro5-4864 and a very low affinity for clonazepam. We also detected a second population of benzodiazepine binding sites labelled with high affinity (IC50=85 nm) by [3H]-PK11195, a selective ligand of the mammalian peripheral benzodiazepine receptor. In conclusion, this work describes the pharmacological properties of a large population of central-like benzodiazepine receptors supporting their study as putative new targets for the development of anti-parasitic agents. We also describe, for the first time, the presence of peripheral benzodiazepine receptors in this parasite.

1. Eleven new species of cercariae are described from China. Of this number ten have been obtained from species of bithynoid snails and one from Planorbis möllendorfi.

2. One of these species, Cercaria beatifica, a heterophyid larva, needs to be differentiated from the cercaria of Clonorchis sinensis, which develops experimentally in the same mollusc.

3. The forms described are much more common parasites of bithynoid snails than is the larva of Clonorchis.

4. Wherever it has been possible the larval characters, particularly those of the excretory system, have been utilised to show the relationship of the cercariae to adult groups.

Full development of Oswaldofilaria chlamydosauri (Breinl) was obtained in Culex fatigans Wied. and Culex annulirostris Skuse. Infections in four lizards were observed 4–6 months after inoculation of infective larvae from both species of mosquitoes.

1. Different shapes and forms found in Toxoplasma gondii are associated with reproduction and growth. The functions of the toxoneme and the conoid are discussed.

2. A new structure, ‘lamella spiralis', is described in relation to the nucleus and the endoplasmic reticulum.

3. T. gondii reproduces either by dividing into two (binary fission) or by multiple division (schizogony), and by a type of endogenous budding. In the latter case small portions pinched off from the nucleus are rounded up to form several small organisms named ‘morulae'.

The author gratefully acknowledges the interest and valuable suggestions of Dr G. A. Gresham, M.D., who supervised this work; Dr J. M. Davis and Mr F. Allen, who were kind enough to read the manuscript critically, and Mr W. A. Mowlam for his technical help and advice on fixation techniques.

This work was carried out during the tenure of a research scholarship awarded by the United Kingdom Department of Technical Co-operation and the Eastern Nigerian Government.

Eimerian sporozoites can be recovered from intestinal washings after oral administration of oocysts to chickens but suspensions of sporozoites are usually prepared in the laboratory by incubation of sporocysts or fractured oocysts in vitro, at body temperatures, with relatively high concentrations of trypsin and bile salts. Since these agents affect membrane structure, the surface membrane of proteins of Eimeria tenella sporozoites excysted in vivo and in vitro have been compared. Surface radio-iodination followed by sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS–PAGE) showed that more 125I was incorporated into polypeptides on sporozoites excysted in vivo than on sporozoites excysted in vitro. The 125I-polypeptide profile of sporozoites excysted in vivo was more resistant to subsequent incubation with pure trypsin than that of sporozoites excysted in vitro, but incubation with bile salts resulted in the loss of some iodinated polypeptides from both preparations of iodinated sporozoites. Reaction with combinations of crude trypsin and bile salts led to the lysis of sporozoites. The method of excystation had no effect on the reaction of convalescent chicken serum with Western blots of sporozoites but the results of immunofluorescent staining carried out with mouse monoclonal antibodies indicated that the structure of the cell surface was altered and some antigenic determinants were lost from sporozoites excysted in vitro. In contrast, neither the infectivity of sporozoites determined in vivo, nor their invasion of cultured cells was changed by the method of excystation.

It has recently been shown (Gibbs, 1950), in the case of Crithidia familiaris, parasitic in the digestive tract of Cenaeus carnifex (Hemiptera), that resistant, infective bodies are produced in the hind-gut by an unequal division leptomonads. One of the two daughter-cells fails to grow a flagellum but remains attachedm, by a thread, to the flagellum of the other. Laterm the non-flagellate body becomes more compact in form and finnaly becomes invested in a tough, protective periplast. It then becomes detached from the parent flagellate. Large numbers of these bodies are scattered in the faeces, and it has been shown that they are capable of infecting fresh insects when ingested. The purpose of the attachment of the non-motile, immature infective body to an active flagellate is apparently to prevent its being prematurely swept from the gut.

Predicting how elevated temperatures from climate change alter host–parasite interactions requires understandings of how warming affects host susceptibility and parasite virulence. Here, the effect of elevated water temperature and parasite exposure level was tested on parasite prevalence, abundance and burden, and on fish growth, using Pomphorhynchus laevis and its fish host Squalius cephalus. At 60 days post-exposure, prevalence was higher at the elevated temperature (22 °C) than ambient temperature (18 °C), with infections achieved at considerably lower levels of exposure. Whilst parasite number was significantly higher in infected fish at 22 °C, both mean parasite weight and parasite burden was significantly higher at 18 °C. There were, however, no significant relationships between fish growth rate and temperature, parasite exposure, and the infection parameters. Thus, whilst elevated temperature significantly influenced parasite infection rates, it also impacted parasite development rates, suggesting warming could have complex implications for parasite dynamics and host resistance.

1. Large numbers of Plagiorchis (M.) megalorchis n.nom. were found in the intestine of four turkey poults of a total of thirteen which had died on a farm in Radnorshire. Presumably the presence of the parasites was the cause of death.

2. The anatomy of the adult worm is described.

3. The first intermediate host of the parasite is Lymnaea pereger, and the second intermediate host any of the following species of insect larvae: Chironomus riparius Meigen, Culicoides stigma Meigen, Culicoides nubeculosus Meigen and Anatopynia (Psectrotanypus) varius Fabr.

4. The larval stages of the worm are described.

5. The life cycle has been demonstrated experimentally by the feeding of insect larvae containing encysted cercariae to turkey poults.

6. The turkey is probably not the normal host of Plagiorchis (M.) megalorchis. It is most likely that it occurs naturally in some species of wild bird, but this is not yet known.

We analysed the intragenomic variation in codon usage in Echinococcus spp. by correspondence analysis. This approach detected a trend among genes which was correlated with expression levels. Among the (presumed) highly expressed sequences we found an increased usage of a subset of codons, almost all of them G- or C- ending. Since an increase in these bases at the synonymous sites is against the mutational bias (these genomes are slightly A+T- rich), we conclude that codon usage in Echinococcus is the result of an equilibrium between compositional pressure and selection, the latter acting at the level of translation, mainly on highly expressed genes. This is the first report where translational selection for codon usage is detected among Platyhelminthes.

Entamoeba histolytica is the protozoan parasite causative of human amoebiasis, disease responsible for 40 000–100 000 deaths annually. The cysteine proteinase-adhesin complex of this parasite (EhCPADH) is a heterodimeric protein formed by a cysteine protease (EhCP112) and an adhesin (EhADH) that plays an important role in the cytopathic mechanism of this parasite. The coding genes for EhCP112 and EhADH are adjacent in the E. histolytica genome, suggesting that their expression may be co-regulated, but this hypothesis has not yet been confirmed. Here, we performed the knockdown of EhCP112 and EhADH using gene-specific short-hairpin RNAs (shRNA), and the effect of these knockdowns on the expression of both complex components as well as on the in vitro and in vivo virulence was analysed. Results showed that the knockdown of one of the EhCPADH components produced a simultaneous downregulation of the other protein. Accordingly, a concomitant reduction in the overall expression of the complex was observed. The downregulation of each component also produced a significant decrease in the in vitro and in vivo virulence of trophozoites. These results demonstrated that the expression of EhCP112 and EhADH is co-regulated and confirmed that the EhCPADH complex plays an important role in E. histolytica virulence.

We address the effect of spatial scale and temporal variation on model generality when forming predictive models for fish assignment using a new data mining approach, Random Forests (RF), to variable biological markers (parasite community data). Models were implemented for a fish host-parasite system sampled along the Mediterranean and Atlantic coasts of Spain and were validated using independent datasets. We considered 2 basic classification problems in evaluating the importance of variations in parasite infracommunities for assignment of individual fish to their populations of origin: multiclass (2–5 population models, using 2 seasonal replicates from each of the populations) and 2-class task (using 4 seasonal replicates from 1 Atlantic and 1 Mediterranean population each). The main results are that (i) RF are well suited for multiclass population assignment using parasite communities in non-migratory fish; (ii) RF provide an efficient means for model cross-validation on the baseline data and this allows sample size limitations in parasite tag studies to be tackled effectively; (iii) the performance of RF is dependent on the complexity and spatial extent/configuration of the problem; and (iv) the development of predictive models is strongly influenced by seasonal change and this stresses the importance of both temporal replication and model validation in parasite tagging studies.

Concanavalin A added to a defined culture medium renders schistosomula more resistant to the lethal effect of antibody plus complement. The Con A dose-dependent acquisition of protection reached a plateau at a concentration of 4 μg Con A/ml. α-Methylmannoside was not able to reverse the Con A-induced protection but excess methylmannoside, added to the incubation medium together with Con A partially prevented the effect of the lectin. Binding of anti-parasite antibody to the schistosomula surface did not change after pre-incubation with Con A. In the presence of puromycin (100 μg/ml) Con A is still able to confer protection. Incorporation of labelled amino acid into the tegumental proteins was not affected by Con A. Furthermore, a progressive reduction of protection was observed as the time of culture preceding Con A addition increased.

The cestodes of lizards have received little recent attention from systematic zoologists. Those inhabiting snakes are much better known than they were a few years ago, thanks to the researches of La Rue (1914) and of Rudin (1917). The cestodes of snakes almost all belong to the family Ichthyotaeniidae (genera Crepidobothrium, Ophiotaenia, Acanthotaenia). Among the lizards also, several species of Acanthotaenia occur in the Monitors (Varanus), and one is recorded in Lialis, one of the Pygopodidae. The Monitors are also the hosts of a remarkable genus of quite a different type—Duthiersia—our knowledge of which has recently been brought up to date by Beddard (1917), and of another genus—Pancerina—of an equally distinct type.

Three new species of cestodes are described. They are: Joyeuxiella paucitestis sp.nov. from the Rusty Spotted Genet, Genetta rubiginosa; Diplopylidium paurodex sp.nov. from the Rusty Spotted Genet, Genetta rubiginosa; Taenia crocutae sp.nov. from the Spotted Hyaena, Crocuta crocuta.

Re-descriptions are given of Joyeuxiella fuhrmanni (Baer, 1924), Fuhrmann, 1935, and Taenia ingwei Ortlepp, 1938, with particular reference to differences between the original descriptions and those based upon the present material.

The rate of new emerging infectious diseases entering the human population has increased over the past century, with pathogens originating from animals or from products of animal origin accounting for the vast majority. Primary risk factors for the emergence and spread of emerging zoonoses include expansion and intensification of animal agriculture and long-distance live animal transport, live animal markets, bushmeat consumption and habitat destruction. Developing effective control strategies is contingent upon the ability to test causative hypotheses of disease transmission within a statistical framework. Broadly speaking, molecular phylogeography offers a framework in which specific hypotheses regarding pathogen gene flow and dispersal within an ecological context can be compared. A number of different methods has been developed for this application. Here, our intent is firstly to discuss the application of a wide variety of statistically based methods (including Bayesian reconstruction, network parsimony analysis and regression) to specific viruses (influenza, salmon anaemia virus, foot and mouth disease and Rift Valley Fever) that have been associated with animal farming/movements; and secondly to place them in the larger framework of the threat of potential zoonotic events as well as the economic and biosecurity implications of pathogen outbreaks among our animal food sources.

The present paper is concerned with the description of six species of gregarines which are all parasites of British earthworms; they are: Apolocystis herculea (Bosanquet, 1894), A. lavernensis sp.nov., A. perfida sp.nov., A. rotaria sp.nov., A. spinosa sp.nov., A. villosa (Hesse, 1909) Cognetti, 1923. The observations upon which these descriptions are based form part of a larger survey of the monocystid fauna of several British earthworm species from the Cardiff area. The methods used are fully described in a previous paper (Rees, 1962).