The fine structure of the macrogametocyte, macrogamete and the early stages in the formation of the oocyst wall of Eimeria acervulina have been described and compared with other species of Eimeria. It has been shown that type II wall-forming bodies are formed in cisternae of the granular endoplasmic reticulum in association with Golgi complexes. The developing oocyst has been shown to be enclosed by three membranes: the outermost is the original membrane of the merozoite and macrogametocyte; the second membrane appears when the wall-forming bodies are appearing in the cytoplasm of the macrogametocyte and the innermost membrane appears after fertilization. The wall-forming bodies discharge their contents between the innermost membrane and the middle membrane.

We wish to thank Mr P. L. Long for much valuable discussion, Mrs B. Fisher for technical assistance and Mr B. Carter for assistance with the photography.

In recent years, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has emerged as an efficient tool for arthropod identification. Its application for field monitoring of adult mosquitoes was demonstrated, but identification of larvae has been limited to laboratory-reared specimens. Study aim was to test the success of MALDI-TOF MS in correctly identifying mosquito larvae collected in the field. Collections were performed at 13 breeding sites in urban areas of Marseille, a city in the South of France. A total of 559 larvae were collected. Of these, 73 were accurately morphologically identified, with confirmation either by molecular identification (n = 31) or analysis with MALDI-TOF MS (n = 31) and 11 were tested using both methods. The larvae identified belonged to six species including Culiseta longiareolata, Culex pipiens pipiens, Culex hortensis, Aedes albopictus, Ochlerotatus caspius and Anopheles maculipennis. A high intra-species reproducibility and inter-species specificity of whole larva MS spectra was obtained and was independent of breeding site. More than 92% of the remaining 486 larvae were identified in blind tests against the MS spectra database. Identification rates were lower for early and pupal stages, which is attributed to lower protein abundance and metamorphosis, respectively. The suitability of MALDI-TOF MS for mosquito larvae identification from the field has been confirmed.

1. Trypanosomes were found in the blood of thirty-five of seventy-two fish of five genera (chiefly Tilapia spp.) from Lakes Victoria and George, Uganda.

2. The trypanosomes, which were never numerous in the blood, showed two morphological forms—small (22–44μ. long) and large (45–65μ). No significant differences were observed between the trypanosomes from the different species of fish, and all the trypanosomes seen are provisionally identified as Trypanosoma mukasai Hoare, 1932.

3. Crithidia were found in the gut of a glossosiphoniid leech which had been removed from a fish; although suggestive, this cannot be taken as conclusive evidence that leeches of this family are vectors of T. mukasai.

4. The taxonomy of the trypanosomes of African fresh-water fish is reviewed, and it is concluded that only the following species should be regarded as valid at present: T. toddi Bouet, 1909, T. mukasai Hoare, 1932, and T. tobeyi Dias, 1952.

5. Dactylosoma mariae Hoare, 1930, was found in the blood of thirty-six of the seventy-two fish examined. Merozoites, schizonts and gametocytes of this small unpigmented parasite were observed within erythrocytes. No developmental stages were found in certain viscera of two infected fish.

The caecal mucosa of wild young and adult grouse infected naturally with Trichostrongylus tenuis was examined by means of scanning electron microscopy and compared with adult grouse which had been treated with an anthelmintic. The caecal mucosa of young red grouse with low worm burdens possessed longitudinal plicae and exhibited little damage. The caeca from adult grouse, most of which carried high worm burdens, showed a localized depression of plicae and atrophy and cell disruption in areas of nematode aggregation. Caeca from adult birds treated with an anthelmintic showed a similar caecal structure to lightly infected caeca from young birds. It is concluded that the normal functioning of the caeca is probably affected by heavy infections of T. tenuis.

The structure of the sporozoite of Eimeria tenella has been studied with the aid of the electron microscope, using both sectioned fixed material and negatively stained or shadowed whole cells. An apical ring gives rise to a series of 24 fibrils which extend posteriorly under a double bilamellar membrane. Within the apical ring lies a conoid with spirally arranged tubules and an apical pore; under some conditions at least this conoid can be pushed forward beyond the apical ring. Originating within the conoid are a group of club-shaped organelles which extend backwards into the cell to lie among an extensive regular array of micronemes. The nucleus lies between two apparently structureless paranuclear bodies, and scattered throughout the remaining cytoplasm are mitochondria with tubular cristae, oval structures containing amylopectin, occasional lipid droplets, and vesicles containing nondescript material possibly undergoing digestion and which may have a possible connexion with a lateral micropyle.

I am indebted to Mrs Muriel Bentley for much technical collaboration and to Mrs McLaren for making her manuscript available before publication.

Changes in the tegumentary projections of protoscoleces of Echinococcus granulosus, developing within brood capsules, were examined at the ultrastructural level. The original scant covering of spineless, truncated microtriches was supplemented by a population of microvilli covering the entire surface of protoscoleces in the early stages of formation. As differentiation continued, rostellar hooks were formed by enlargement of single large (T 1) microtriches, and normal spined microtriches were produced on the sucker region. These were formed in two ways: by addition of spine material to the truncated microtriches, and de novo followed by up-lifting from the tegumentary surface. A second type of large microthrix (T2) was present in a band immediately below the developing hooks. These microtriches appeared to be formed from a fusion of existing microtriches, but were subsequently lost prior to scolex invagination. The microvilli were also shed from both the sucker and soma regions, to be replaced by microtriches and small blunt elevations respectively.

Sheep infected with Oesophagostomum columbianum showed anorexia, loss of weight, diarrhoea and macroscopically obvious oedema and inflammation of the alimentary tract. Arthus-like lesions caused by the larvae developed particularly in the large intestine.

The gross immunological responses of the sheep were associated with antibodies in greater titre within the mucus of the gut than in the serum. Acquired immunity was manifest through an antibody-antigen reaction which was localized mostly in the large intestine and which involved proliferation of the lymphoid tissue of the gut and an increased synthesis of protein. Lower titres of antibody in serum than in mucus may indicate leakage of antibody away from the gut. The direct effects of antibody were established by the respiratory inhibition of the 3rd-stage larvae. The presence of antibody was associated with particularly high concentrations of β globulin after first and β and γ globulins after second infection. Specific antibody was demonstrated in these protein fractions by blockage of electrophoretic movement by larval antigen in the buffer.

The antibody-antigen reaction may act as a trigger which releases the nonspecific effects of excess mucus production and oedema which causes mechanical dislodgement of the infection. The natural and specific respiratory inhibitory effects of mucus on the worm would facilitate this dislodgement process.

The greatest cellular reactions occurred where there was an active infection. Usually these reactions were associated with oedema, hyperaemia and an increase in the size of the mesenteric lymph nodes.

Muscle cells from adult male Schistosoma mansoni have been isolated using a combination of papain digestions and mechanical dissociation procedures. The muscle fibres isolated in this way lacked nuclei but they did contract and relax in response to high [K+], a response which was blocked in the presence of Co2+. From this we conclude that the isolation procedure yields viable muscle fibres useful for physiological studies. Patch-clamp recordings taken from the isolated fibres show a variety of discrete ionic conductances. In inside-out patches one prominent channel was a Ca2+-activated K+ channel with a conductance of 195 pS and a selectivity greater than 10:1 for K+ over Na+, Cs+ or NH4+. Percentage open time was dependent on [Ca2+] at the intracellular face. With [Ca2+] at 1 μM or greater percentage open time was > 95%; at 0.1 μM it was < 2%. No voltage sensitivity could be detected in the voltage range from –50 to –10 mV membrane potential. Ba2+ (10 mM), but neither tetraethylammonium nor 3,4-diaminopyridine blocked the channel from the intracellular face. This Ca2+-activated K+ channel in the muscle membrane of this acoelomate animal is similar in most respects to the maxi-K+ channels which have been described in a variety of cells from more highly evolved animals.

The life-cycles of the two species of Crepidostomum occurring in a stream in North Wales are investigated. Both species share the same arthropod and definitive hosts, viz. Gammarus pulex and Salmo trutta, respectively, but have different molluscan hosts, viz.: Lymnaea peregra for C. metoecus and Pisidium casertanum for C. farionis.

C. metoecus and C. farionis have annual cycles, hence periodicity of occurrence in their hosts. In C. metoecus the dynamics of occurrence in the three hosts are correlated. The inverse relationship in G. pulex and S. trutta as well as the existence of a time-lag of 3–4 months between the establishment of this worm in G. pulex and in S. trutta are discussed.

Neither premunition nor age-resistance occurs in the parasitization of S. trutta and G. pulex by C. metoecus. The increase in the rate and degree of infestation with the age and length of fish, except in the oldest and longest group, is shown to be due to trophic factors.

C. metoecus is more abundant and widely distributed in the stream than C. farionis. This fact is associated with the occurrence of their molluscan hosts.

Experimental observations were made on the stages in the life-history of C. metoecus, including the mode of emergence of the cercaria, invasion of shrimps and encystment, as well as development of the metacercariae in G. pulex.

More cercariae are shed by day and at higher temperatures, and they live for about 5 days at 8 °C. The metacercaria undergoes considerable development before becoming infective. C. metoecus does extensive damage to L. peregra, has no observed ill-effect on trout, and apparently affects the life-span of shrimps adversely only in cases of very heavy infestations.

The non-parasitization of Cottus gobio by the two flukes is probably due to the prevailing ecological factors.

My thanks are due to Professor H. B. N. Hynes and Dr J. C. Chubb for many helpful criticisms at all stages of this study; to Miss Joan Venn for helping with the sampling programme; and the Commonwealth Scholarship Commission in the United Kingdom for financial support.

1. Three trichomonads have been cultivated and studied, T. hominis, Trichomonas sp. from M. nemestrinus (= R.T. strain), and T. batrachorum from English frogs and toads.

2. A number of strains of T. batrachorum were cultivated over periods varying from two weeks to five months without the appearance of a Eutrichomastix stage.

3. The division process of T. batrachorum has been studied. The new basal fibre arises as an outgrowth from the blepharoplast. The old axostyle is absorbed and new ones are formed from the daughter blepharoplast during the telophase. Six chromosomes appear during the prophase. Spindle fibres do not appear. There is a separation of the daughter blepharoplasts into centro-some and basal granule at the metaphase.

4. Division of T. hominis and Trichomonas sp. from M. nemestrinus is essentially similar to that of T. batrachorum. The number of chromosomes appeared to be five or six. Double individuals were found in the cultures, and in T. hominis individuals containing four or six sets of organellae. Their significance is obscure.

Much of what is currently known of the host-parasite interaction between mice and the parasitic nematode Trichuris muris has come from experiments using a single parasite isolate (E/N). This isolate has been compared with 2 others which, on morphological criteria, belong to the same species. In 3 inbred strains of mouse that show distinct, genetically determined response phenotypes, there was a consistent pattern in terms of parasite survival time regardless of host strain, E/K worms being expelled early, E/N expelled later and S worms very late or not at all. High-responder CBA mice expelled E/K and E/N worms earlier than low-responder C57 B1/10 mice. B10.BR mice were permissive to S isolate infection, mounted a very late response to E/N worms but expelled E/K worms effectively by day 25. The differential response of mice to these isolates provides an experimental system for identifying the basis of variation in this host-parasite relationship.

This work reports a new type of actinospore, Unicapsulactinomyxon, which exhibits a unique morphological characteristic in that it has a single and large polar capsule (9·3×4·1 μm) (which possesses a longitudinally-folded polar filament) instead of the 3 polar capsules previously described for actinosporeans. The spore has a binucleated sporoplasm and 3 valves, each of which forms a long process. The spore has a total length of 241·3 μm. This parasite develops in groups of 8 inside pansporocysts in the coelomic cavity of the polychaete host. Molecular investigations on the SSU rDNA show that the new actinospore type is most closely related to Enteromyxum species (81–84% similarity). A survey of actinospore infections of the marine polychaete Diopatra neapolitana in 2007 and 2009, in the Aveiro Estuary (Portugal), showed an annual prevalence of 1·0% and 0·3%, respectively.

The Apicomplexa is a phylum of parasitic protozoa, which includes the malaria parasite Plasmodium, amongst other species that can devastate human and animal health. The past decade has seen the release of genome sequences for many of the most important apicomplexan species, providing an excellent basis for improving our understanding of their biology. One of the key features of each genome is a unique set of large, variant gene families. Although closely related species share the same families, even different types of malaria parasite have distinct families. In some species they tend to be found at the ends of chromosomes, which may facilitate aspects of gene expression regulation and generation of sequence diversity. In others they are scattered apparently randomly across chromosomes. For some families there is evidence they are involved in antigenic variation, immune regulation and immune evasion. For others there are no known functions. Even where function is unknown these families are most often predicted to be exposed to the host, contain much sequence diversity and evolve rapidly. Based on these properties it is clear that they are at the forefront of host–parasite interactions. In this review I compare and contrast the genomic context, gene structure, gene expression, protein localization and function of these families across different species.

The ookinete is one of the most important stages of Plasmodium development in the mosquito. It is morphologically and biochemically distinct from the earlier sexual stages - gametocytes and zygote, and from the later stages - oocyst and sporozoites. Development to ookinete allows the parasite to escape from the tightly packed blood bolus, to cross the sturdy peritrophic matrix (PM), to be protected from the digestive environment of the midgut lumen, and to invade the gut epithelium. The success of each of these activities may depend on the degree of the biochemical and physical barriers in the mosquito (such as density of blood bolus, thickness of peritrophic matrix, proteolytic activities in the gut lumen etc.) and the ability of the ookinete to overcome these barriers. Ookinete motility, secretion of chitinase, resistance to the digestive enzymes, and recognition/invasion of the midgut epithelium all may play crucial roles in the transformation to oocyst. The overall sporogonic development of Plasmodium, therefore, depends on the results of the two-way manipulations between the parasite and the vector mosquito. Study of ookinete development and of the cellular and biochemical complexities of the mosquito gut may therefore lead to the design of novel strategies to block the transmission of malaria. This article reviews the intricate interactions between the parasite and the mosquito midgut in the context of development and transmission of Plasmodium parasites.

We explored the distribution of Cardicola chaetodontis in chaetodontid fishes from the Great Barrier Reef. We found just four infections of adult worms in 238 individuals of 26 chaetodontid species. By contrast, eggs were present in hearts of 75 fishes (31·5%) and 19 of 26 chaetodontid species (all Chaetodon species). In 10 cases eggs contained moving miracidia; all the others were dead and degenerating. Eggs were sought in the gills of 51 individual fish. There were 17 cases of eggs being present in gills while present in the heart, but also 13 cases where eggs were absent from gills but present in the heart, suggesting that eggs remain longer in heart tissue than in gills. ITS2 rDNA sequences from two adult worms and eggs extracted from gills of five fishes (all different species) were identical to previously reported sequences of C. chaetodontis except for a single base-pair difference in two samples. We conclude that aporocotylid eggs trapped in fish heart tissues may inform understanding of the distributions and host ranges of aporocotylids, especially where adult prevalence is low. The low host-specificity of C. chaetodontis contrasts with higher specificity of trematodes of chaetodontids that have trophic transmission.

Amoebiasis, infection by the protozoan parasite Entamoeba histolytica, remains a global health problem, despite the availability of effective treatment. While improved sanitation could lead to the eradication of this disease, it is unlikely that this will occur worldwide in the foreseeable future; thus alternative measures must be pursued. One approach is to develop a vaccine to prevent this deadly disease. Clinical studies indicate that mucosal immunity may provide some protection against recurrent intestinal infection with E. histolytica, but there is no clear evidence that protective immunity develops after amoebic liver abscess. Over the past decade, progress in vaccine development has been facilitated by new animal models that allow better testing of potential vaccine candidates and the application of recombinant technology to vaccine design. Oral vaccines and DNA-based vaccines have been successfully tested in animals models for immunogenicity and efficacy. There has been significant progress on a number of fronts, but there are unanswered questions regarding the effectiveness of immune responses in preventing disease in man and, as yet, no testing of any of these vaccines in humans has been performed. In addition, there are strong economic barriers to developing an amoebiasis vaccine and questions about how and where an effective vaccine would be utilized.

The sexual life-history traits of Schistosoma mansoni have been reviewed to compare male and female performance and pathogenicity against Biomphalaria glabrata during the life-cycle. A meta-analysis was used on pooled results from different experiments. In most cases, there was no difference between males and females but male cercariae were significantly more infectious than female cercariae. Conversely, cercarial production and cercarial life-span were significantly greater for females than for males; furthermore, females have a tendency to occur in molluscs of larger size. Each difference is discussed and interpreted when possible in terms of male and female differences in transmission strategies. The female strategy may consist of producing many long-living larvae. The male strategy may consist of producing few short-living larvae and would invest in the quality of these larvae instead of their quantity or their life-span.

Fish parasites are used to monitor long-term change in finfish grouper mariculture in Indonesia. A total of 210 Epinephelus fuscoguttatus were sampled in six consecutive years between 2003/04 and 2008/09 and examined for parasites. The fish were obtained from floating net cages of a commercially run mariculture facility that opened in 2001. The fauna was species rich, consisting of ten ecto- and 18 endoparasite species. The ectoparasite diversity and composition was relatively stable, with the monogeneans Pseudorhabdosynochus spp. (83–100% prevalence, Berger-Parker Index of 0·82–0·97) being the predominant taxon. Tetraphyllidean larvae Scolex pleuronectis and the nematodes Terranova sp. and Raphidascaris sp. 1 were highly abundant in 2003/04–2005/06 (max. prevalence S. pleuronectis 40%, Terranova sp. 57%, Raphidascaris sp. 1 100%), and drastically reduced until 2008/09. These parasites together with the prevalence of Trichodina spp., ecto-/endoparasite ratio and endoparasite diversity illustrate a significant change in holding conditions over the years. This can be either referred to a definite change in management methods such as feed use and fish treatment, or a possible transition of a relatively undisturbed marine environment into a more affected habitat. By visualizing all parameters within a single diagram, we demonstrate that fish parasites are useful bioindicators to monitor long-term change in Indonesian grouper mariculture. This also indicates that groupers can be used to monitor environmental change in the wild. Further taxonomic and systematic efforts in less sampled regions significantly contributes to this new application, supporting fish culture and environmental impact monitoring also in other tropical marine habitats.

Chagas disease, which is caused by the parasite Trypanosoma cruzi, affects approximately 7–8 million people in Latin America. The drugs available to treat this disease are ineffective against chronic phase disease and are associated with toxic side effects. Therefore, the development of new compounds that can kill T. cruzi at low concentrations is critically important. Herein, we report the effects of a novel 3-arylideneindolin-2-one that inhibits sirtuins, which are highly conserved proteins that are involved in a variety of physiological processes. The compound KH-TFMDI was tested against the epimastigote, trypomastigote and amastigote forms of T. cruzi, and its effects were evaluated using flow cytometry, light and electron microscopy. KH-TFMDI inhibited the replication of T. cruzi intracellular amastigotes with an IC50 of 0·5±0·2 μm, which is significantly lower than the IC50 of benznidazole. The compound also lysed the highly infectious bloodstream trypomastigotes (BST) with LC50 values of 0·8±0·3 μm at 4 °C and 2·5±1·1 μm at 37 °C. KH-TFMDI inhibited cytokinesis and induced several morphological changes in the parasite, leading to its death by apoptosis and autophagy. This study highlights sirtuins as a potential new target for Chagas disease therapy.

The genus Clinostomum Leidy, 1856 (Digenea: Clinostomidae) has been reported in all ecozones of the world and a clear separation between the species of the ‘Old World’ and ‘New World’ has been recognized based on molecular studies. Recent works on Afrotropical species include redescriptions of C. cutaneum and C. phalacrocoracis, while C. tilapiae has yet to be studied using modern taxonomic approaches. In the present research, morphological redescription of C. tilapiae metacercariae from a new host, Synodontis batensoda sampled at Anambra River Basin, Nigeria, together with molecular analysis of nuclear internal transcribed spacer rDNA and cytochrome c oxidase 1 mtDNA are reported. We also provide morphological and molecular data from four further putative species of Clinostomum (morphotypes 1–4) from different areas of Africa, as well as the first report of C. phalacrocoracis in South Africa.