Paramphistomum daubneyi sp.nov., recovered from Bos taurus in Kenya, East Africa, is described and differentiated from the other species of the genus possessing a Microbothrium type of genital atrium.

Lymnaea truncatula Müller was infected experimentally with miracidia of P. daubneyi and the development in the snail host is briefly described.

Classical transmitters are present in all phyla that have been studied; however, our detailed understanding of the process of neurotransmission in these phyla is patchy and has centred on those neurotransmitter receptor mechanisms which are amenable to study with the tools available at the time, for example, high-affinity ligands, tissues with high density of receptor protein, suitable electrophysio-logical recording systems. Studies also clearly show that many neurones exhibit co-localization of classical transmitters and neuropeptides. However, the physiological implications of this co-localization have yet to be elucidated in the vast majority of examples.

The application of molecular biological techniques to the study of neurotransmitter receptors (to date mainly in vertebrates) is contributing to our understanding of the evolution of these proteins. Striking similarities in the structure of ligand-gated receptors have been revealed. Thus, although ligand-gated receptors differ markedly in terms of the endogenous ligands they recognize and the ion channels that they gate, the structural similarities suggest a strong evolutionary relationship. Pharmacological differences also exist between receptors that recognize the same neurotransmitter but in different phyla, and this may also be exploited to further the understanding of structure-function relationships for receptors. Thus, for instance, some invertebrate GABA receptors are similar to mammalian GABAa receptors but lack a modulatory site operated by benzodiazepines. Knowledge of the structure and subunit composition of these receptors and comparison with those that have already been elucidated for the mammalian nervous system might indicate the functional importance of certain amino acid residues or receptor subunits. These differences could also be exploited in the development of new agents to control agrochemical pests and parasites of medical importance.

The study of the pharmacology of receptor proteins for neurotransmitters in invertebrates, together with the application of biochemical and molecular biological techniques to elucidate the structure of these molecules, is now gathering momentum. For certain receptors, e.g. the nicotinic receptor, we can expect to have fundamental information on the function of this receptor at the molecular level in both invertebrates and vertebrates in the near future.

Latent infection from Toxoplasma gondii (T. gondii) is widespread worldwide and has been associated with cognitive deficits in some but not all animal models and in humans. We tested the hypothesis that latent toxoplasmosis is associated with decreased cognitive function in a large cross-sectional dataset, the National Health and Nutrition Examination Survey (NHANES). There were 4178 participants aged 20–59 years, of whom 19·1% had IgG antibodies against T. gondii. Two ordinary least squares (OLS) regression models adjusted for the NHANES complex sampling design and weighted to represent the US population were estimated for simple reaction time, processing speed and short-term memory or attention. The first model included only main effects of latent toxoplasmosis and demographic control variables, and the second added interaction terms between latent toxoplasmosis and the poverty-to-income ratio (PIR), educational attainment and race-ethnicity. We also used multivariate models to assess all three cognitive outcomes in the same model. Although the models evaluating main effects only demonstrated no association between latent toxoplasmosis and the cognitive outcomes, significant interactions between latent toxoplasmosis and the PIR, between latent toxoplasmosis and educational attainment, and between latent toxoplasmosis and race-ethnicity indicated that latent toxoplasmosis may adversely affect cognitive function in certain groups.

We present the first parasitological, molecular and longitudinal analysis of an isolated outbreak of malaria. This outbreak occurred on Santiago Island (Republic of Cabo Verde), a region where malaria is hypoendemic and controlled, and thus the population is considered non-immune. Blood samples were collected from the inhabitants over 1 month and during cross-sectional surveys in the following year. The presence and nature of the parasites was determined by PCR. Plasmodium falciparum was the only species detected. Genetic analysis revealed that the circulating parasites were genetically homogeneous, and probably clonal. Gametocytes were found throughout this period. Our data suggest that this represented a focal outbreak, resulting in the infection of at least 40% of the villagers with a clonal parasite line. Thus, P. falciparum infections can persist for at least 1 year in a substantial proportion (10%) of the hosts. Implications for malaria control and the interpretation of epidemiological data are discussed.

In non-permanent parasites the separation from the host should take place in suitable habitats that allow the continuation of their life cycle. Furthermore, detachment strategies determine the parasites' dispersal capability, a characteristic on which epidemiological dynamics and the evolution of host specificity centre. In this study we experimentally investigate in the laboratory how 2 congeneric tick species, with contrasting habitat requirements, time detachment from one of their current songbird hosts (Parus major). Ixodes arboricola is a nidicolous tick, infesting bats and birds breeding or roosting in tree holes. Ixodes ricinus is a non-nidicolous generalist that parasitizes mammals, birds and even reptiles. We experimentally infested full-grown great tits, P. major, and found that I. arboricola detaches during the night, the moment when P. major sleeps in tree holes. In contrast, I. ricinus detaches during the day, the moment when birds are most active. In addition we found that all I. ricinus immatures left the birds within 5.5 days, while in I. arboricola the detachment time was long (up to 20 days) and highly variable. We discuss these findings with respect to their implications on the ticks' dispersal capability and host specificity.

Nucleoside triphosphate diphosphohydrolases (NTPDases, GDA1_CD39 protein superfamily) play a diverse range of roles in a number of eukaryotic organisms. In humans NTPDases function in regulating the inflammatory and immune responses, control of vascular haemostasis and purine salvage. In yeast NTPDases are thought to function primarily in the Golgi, crucially involved in nucleotide sugar transport into the Golgi apparatus and subsequent protein glycosylation. Although rare in bacteria, in Legionella pneumophila secreted NTPDases function as virulence factors. In the last 2 decades it has become clear that a large number of parasites encode putative NTPDases, and the functions of a number of these have been investigated. In this review, the available evidence for NTPDases in parasites and the role of these NTPDases is summarized and discussed. Furthermore, the processes by which NTPDases could function in pathogenesis, purine salvage, thromboregulation, inflammation and glycoconjugate formation are considered, and the data supporting such putative roles reviewed. Potential future research directions to further clarify the role and importance of NTPDases in parasites are proposed. An attempt is also made to clarify the nomenclature used in the parasite field for the GDA1_CD39 protein superfamily, and a uniform system suggested.

Haem from host erythrocyte (RBC) haemoglobin is polymerized in the digestive organelle of Plasmodium falciparum to haemozoin (HZ), a crystalline, insoluble substance. Human monocytes avidly ingest HZ that persists undigested for long periods of time, and generates potent bioactive lipid peroxide derivatives. Protein kinase C, an effector of signal transduction, phagolysosome formation and acidification, is inhibited in HZ-fed monocytes. Inability to digest HZ might derive from impairment in phagolysosome formation or acidification. Time-course and extent of HZ phagocytosis and acidification of phagolysosomes were studied by quantitative confocal microscopy. From 180 min until 72 h after the start of phagocytosis approximately 75–79% of the monocytes contained massive amounts of HZ. Coincidence between red (HZ) and green (acidic organelles) fluorescent compartments was very high. Confocal images showed that at 30–60 min after the start of phagocytosis, HZ was preferentially present as separated particles, with full co-localization of red and green fluorescence. Later on HZ-laden phagolysosomes tended to fuse together. In conclusion, phagolysosome formation and acidification were normal in HZ-fed monocytes during the 72-h observation time. The presence of HZ in the phagolysosome, the site of antigen processing, may offer a physical link with immunodepression in malaria.

Chagas disease and sleeping sickness are neglected tropical diseases closely related to poverty, for which the development of plant-derived treatments has not been a promising prospect. Thus, we systematicaly review the preclinical in vivo evidence on the applicability of plant-based products in the treatment of Trypanosoma cruzi and Trypanosoma brucei infections. Characteristics such as disease models, treatments, toxicological safety and methodological bias were analysed. We recovered 66 full text articles from 16 countries investigating 91 plant species. The disease models and treatments were highly variable. Most studies used native (n = 36, 54·54%) or exotic (n = 30, 45·46%) plants with ethnodirected indication (n = 45, 68·18%) for trypanosomiasis treatment. Complete phytochemical screening and toxicity assays were reported in only 15 (22·73%) and 32 (48·49%) studies, respectively. The currently available preclinical evidence is at high risk of bias. The absence of or incomplete characterization of animal models, treatment protocols, and phytochemical/toxicity analyses impaired the internal validity of the individual studies. Contradictory results of a same plant species compromise the external validity of the evidence, making it difficult determine the effectiveness, safety and biotechnological potential of plant-derived products in the development of new anti-infective agents to treat T. cruzi and T. brucei infections.

Introduction. Palaeozoic calcareous sponges (stromatoporoids) are common bio-constructing fossils; they are sometimes found in association with helicoidal structures of unknown biological affinities. The interaction between the tube-forming organisms has usually been classified as commensalism. Methods. About 260 stromatoporoid skeletons from the Middle Devonian (Givetian) of the Mont d'Haurs section near Givet (Champagne-Ardenne, France) were thin-sectioned and analysed under transmitted light. Results. Approximately 10% of the examined stromatoporoids (mainly belonging to the genera Actinostroma, Stromatopora and Stromatoporella) contain tubes classified as Torquaysalpinx sp. The Torquaysalpinx organisms penetrated the skeletons of stromatoporoids in vivo (as evidenced by skeletal overgrowths); around the infesting organisms, growth bands are bent down. Conclusion. Diminished growth rates around the infesting organism demonstrate a negative influence on the host, similar to that seen in the modern demosponge–polychaete association of Verongia–Haplosyllis. This is demonstrated by changes in growth bands. As in the above-mentioned association, the endosymbiont might have been feeding directly upon the tissues of the host. The Torquaysalpinx organisms were gaining habitat and possibly also food resources – for them this interaction was clearly positive. This long-term association can therefore be classified as parasitism. This is the first evidence for parasitism in Palaeozoic sponges.

1. Diapause in Lucilia sericata is caused by unfavourable conditions during the larval or prepupal period.

2. Diapausing prepupae usually contain a higher proportion of dry matter than do normal individuals.

3. Diapause occurs because the corpus allatum (Weismann's ring) is not producing the necessary hormone.

4. Diapause is ended when prepupae are removed from sand to empty tubes. Probably the corpus allatum is stimulated by a nervous reaction; the reaction is not due to an increase in the rate of metabolism.

5. Low temperatures (5° C.) do not affect the hormone, but high ones (35–37° C.) destroy it.

6. Prepupae of Lucilia sericata have salivary glands which are dilated to nearly a quarter the body size. The contents serve as a store of water during diapause.

7. Diapausing prepupae after desiccation drink water and return to their original body weight. The water increases the volume of blood in circulation, and the blood controls the size of the adult produced.

8. Diapause in nature enables the species to survive unfavourable conditions.

At concentrations ranging from 0·1 to 10·0 mg/l, copper and zinc reduced both the longevity and infectivity of Echinoparyphium recurvatum cercariae. Concentrations of 10·0 mg/l copper and zinc in hard water reduced the time to 50% mortality of cercariae from 30·5 h to 8·5 h and 15·5 h respectively. Copper-induced effects upon cercarial infectivity were particularly severe and exposures of cercariae to 0·5 mg/l of this metal for as little as 15 min caused significant reductions in their ability to infect molluscan 2nd intermediate hosts. Water hardness had a marked influence on copper toxicity but had a much lower effect on the toxicity of zinc. Metal concentrations found to exert a profound influence on parasite transmission in the present laboratory-based study have been found to occur in natural, albeit polluted, freshwater habitats.

Twenty-seven stocks of Nannomonas trypanosomes isolated from livestock in 1982 on a ranch at Kilifi on the Kenyan coast were characterized by isoenzyme electrophoresis and by the abilities of the parasite's DNA to hybridize to two repetitive sequence DNA probes. Allthe Kilifi stocks which were examined had isoenzyme patterns which were markedly different from the 75 patterns previously described from 78 stocks of Trypanosoma congolense. On average only 15% of the enzyme bands present in the Kilifi stocks were present in those stocks of T. congolense which had previously been surveyed for isoenzymes. The DNA from all the Kilifi stocks which had been examined for isoenzymes hybridized with only the repetitive sequence probe isolated from a clone of a Kilifi stock. In contrast, the DNA from all 27 Kilifi stocks failed to hybridize with a repetitive sequence probe isolated from a clone from a different stock of T. congolense. Thus, the trypanosomes in all the Kilifi stocks examined were both phenotypically and genotypically discrete. These genetically discrete trypanosomes have also been detected in 2 stocks isolated from livestock from another location on the Kenyan coast. The results show that there is a wide range of genetic heterogeneity within the trypanosomes currently classified as T. congolense. We suggest that the limits of this genetic heterogeneity could represent incipient speciation.

A study of neutralization reaction of trypanosomes with immune sera made against them is recorded, together with a description of the technique.

Neutralizing antibody appears in rabbits infected with T. brucei 5 days after infection and reaches its peak (1/320) within 28 days.

The same titre of neutralizing antibody can be produced in rabbits by a series of injections of dead formalized trypanosomes.

Antibody titres persist at high levels for a longer period in animals infected and subsequently treated than in animals immunized with dead trypanosomes.

Neutralizing antibody can be demonstrated in infected guinea-pigs but on a much lower level than in rabbits. Mice and rats infected with T. brucei and not treated failed to show demonstrable neutralizing antibody.

Mice infected with T. brucei can be protected from infection by inoculation at the same time, or even 1 hr. later, with 0·5 ml. of antiserum showing a high level of neutralizing antibody.

Mice inoculated with the same antiserum showed passive immunity lasting for 10 days.

The evidence that T. brucei ‘O‘ after passages through rabbits failed to be neutralized by homologous or heterologous sera which, on the other hand, were able to neutralize the parent strain, suggests that strains after passage through rabbits were not genetic variants, but developed a protective mechanism against immune bodies.

In vitro excretory/secretory products of 4-week (immature) and 8- week-old (mature) Fasciola hepatica parasites, derived from rats, were injected together with adjuvant into naive rats and mice. Resistance to infection was assessed in rats by counting adults in the bile ducts at 9 weeks, or in mice by recording deaths after oral challenge with a high dose of viable metacercariae. Exposure of rats to excretory/secretory products of immature F. hepatica conferred a significant degree of resistance which was comparable to the level of resistance induced following oral administration of a low number of metacercariae. No protection against infection was seen in rats injected with excretory/secretory products from mature, bile duct-derived worms. In mice, no obvious mouse strain variation in susceptibility to first infection existed and hypothymic nude mice were as susceptible to infection as intact mice. As determined by protection against death, vaccination with excretory/secretory products derived from immature P. hepatica was without effect in mice. It is concluded that ‘host protective antigens’, at least for rats, were present in the excretory/secretory products of immature F. hepatica larvae.

Adult Onchocerca volvulus worms obtained by enzyme digestion from nodules of infected Mexicans were radio-isotope labelled by the chloramine-T or Bolton–Hunter methods. No antigenic determinants were detected in extracts of worms labelled by the chloramine-T method but 3 antigens were detected in extracts of the Bolton–Hunter labelled worms. Two were present in such small amounts that it was impractical to investigate them further, but a major component of mol. wt 20 kDa was purified by gel filtration and used in a serological survey of inhabitants of villages in Southern Mexico. Using the 20 kDa antigen, which is superficially located on both sexes of O. volvulus, sera from both non-endemic and endemic regions were analysed by radio-immunoprecipitation of this antigen. In Southern Mexico, the average sensitivity of the test was 92%, and the specificity 98%. Whilst the 20 kDa antigen did not detect antibodies in the sera of Trinidadians infected with Wuncheria bancrofti or Mansonella ozzardi, this antigen detected high levels of antibodies in Indians exposed to W. bancrofti.

Upon infection with a pathogen, eukaryotic cells can undergo programmed cell death as an ultimate response. Therefore, modulation of apoptosis is often a prerequisite to establish a host-pathogen relationship. Some pathogens kill macrophages by inducing apoptosis and thus overcome the microbicidal arsenal of the phagocyte. Apoptotic macrophages, on the other hand, can elicit an inflammation by secretion of proinflammatory cytokines. Shigella flexneri, the aetiological agent of bacillary dysentery, induces apoptosis in macrophages which, in agony, specifically release mature interleukin-1β (IL-1β). This cytokine attracts neutrophils (PMN) to the site of infection resulting in the massive colonic inflammation characteristic of bacillary dysentery. Shigellosis represents a paradigm of a proinflammatory apoptosis in a bacterial infection. The molecular link between apoptosis and inflammation is interleukin-1β converting enzyme (ICE) which is activated during macrophage apoptosis and binds to IpaB, a secreted Shigella protein.

The aim of this study was to assess the seroprevalence of the Toxoplasma gondii parasite in pork produced in France, and to determine infection risk factors. An innovative survey was designed based on annual numbers of slaughtered pigs from intensive and outdoor farms in France. A total of 1549 samples of cardiac fluids were collected from pig hearts to determine seroprevalence using a Modified Agglutination Test. Of those, 160 hearts were bio-assayed in mice to isolate live parasites. The overall seroprevalence among fattening pigs was 2·9%. The adjusted seroprevalence in pigs from intensive farms was 3·0%; the highest in sows (13·4%); 2·9% in fattening pigs and 2·6% in piglets. Adjusted seroprevalence in fattening animals from outdoor farms was 6·3%. Strains were isolated from 41 animals and all were genotyped by Restriction Fragment Length Polymorphism as type II. Risk-factor analysis showed that the risk of infection was more than three times higher for outdoor pigs, and that sows’ risk was almost five times higher than that of fattening animals. This study provides further evidence of extensive pork infection with T. gondii regardless of breeding systems, indicating that farm conditions are still insufficient to guarantee ‘Toxoplasma-free pork’.

Salivarian trypanosomes pose a substantial threat to livestock, but their full diversity is not known. To survey trypanosomes carried by tsetse in Tanzania, DNA samples from infected proboscides of Glossina pallidipes and G. swynnertoni were identified using fluorescent fragment length barcoding (FFLB), which discriminates species by size polymorphisms in multiple regions of the ribosomal RNA locus. FFLB identified the trypanosomes in 65 of 105 (61·9%) infected proboscides, revealing 9 mixed infections. Of 7 different FFLB profiles, 2 were similar but not identical to reference West African Trypanosoma vivax; 5 other profiles belonged to known species also identified in fly midguts. Phylogenetic analysis of the glycosomal glyceraldehyde phosphate dehydrogenase gene revealed that the Tanzanian T. vivax samples fell into 2 distinct groups, both outside the main clade of African and South American T. vivax. These new T. vivax genotypes were common and widespread in tsetse in Tanzania. The T. brucei-like trypanosome previously described from tsetse midguts was also found in 2 proboscides, demonstrating a salivarian transmission route. Investigation of mammalian host range and pathogenicity will reveal the importance of these new trypanosomes for the epidemiology and control of animal trypanosomiasis in East Africa.

Dactylogyrus (Monogenea) species were studied on the gills of roach (Rutilus rutilus) from a total of 293 fish in 3 interconnected lakes in Central Finland. One of the lakes is eutrophic and polluted by a paper and pulp mill, one is eutrophic and one is oligotrophic. Nine Dactylogyrus species were found. The structure of the monogenean communities was analysed at the component and infracommunity level and the Dactylogyrus fauna of the lakes was compared. Although it was found that the component communities tended to be very similar there were also differences. The abundance and diversity were highest in the polluted lake; the infracommunities of this lake were considerably more often dominated by Dactylogyrus micracanthus and the similarities between the infracommunities were higher within the lakes than between the lakes. It is suggested that these differences are due to the differing water quality of the lakes. The nature of the monogenean community, its possible interactivity, is also discussed.