bluuebunny/crossref_metadata_2025 huggingface dataset:
Fasciola hepatica and lymnaeid snails occurring at very high altitude in South America
Authors: MAS-COMA S. , FUNATSU I. R. , BARGUES M. D.
Published: October 2002

Fascioliasis due to the digenean species Fasciola hepatica has recently proved to be an important public health problem, with human cases reported in countries of the five continents, including severe symptoms and pathology, with singular epidemiological characteristics, and presenting human endemic areas ranging from hypo- to hyperendemic. One of the singular epidemiological characteristics of human fascioliasis is the link of the hyperendemic areas to very high altitude regions, at least in South America. The Northern Bolivian Altiplano, located at very high altitude (3800–4100 m), presents the highest prevalences and intensities of human fascioliasis known. Sequences of the internal transcribed spacers ITS-1 and ITS-2 of the nuclear ribosomal DNA of Altiplanic Fasciola hepatica and the intermediate snail host Lymnaea truncatula suggest that both were recently introduced from Europe. Studies were undertaken to understand how the liver fluke and its lymnaeid snail host adapted to the extreme environmental conditions of the high altitude and succeeded in giving rise to high infection rates. In experimental infections of Altiplanic lymnaeids carried out with liver fluke isolates from Altiplanic sheep and cattle, the following aspects were studied: miracidium development inside the egg, infectivity of miracidia, prepatent period, shedding period, chronobiology of cercarial emergence, number of cercariae shed by individual snails, survival of molluscs at the beginning of the shedding process, survival of infected snails after the end of the shedding period and longevity of shedding and non-shedding snails. When comparing the development characteristics of European F. hepatica and L. truncatula, a longer cercarial shedding period and a higher cercarial production were observed, both aspects related to a greater survival capacity of the infected lymnaeid snails from the Altiplano. These differences would appear to favour transmission and may be interpreted as strategies associated with adaptation to high altitude conditions.
Interactions between intermediate snail hosts of the genus Bulinus and schistosomes of the Schistosoma haematobium group
Authors: ROLLINSON D. , STOTHARD J. R. , SOUTHGATE V. R.
Published: October 2002

Within each of the four species groups of Bulinus there are species that act as intermediate hosts for one or more of the seven species of schistosomes in the Schistosoma haematobium group, which includes the important human pathogens S. haematobium and S. intercalatum. Bulinus species have an extensive distribution throughout much of Africa and some surrounding islands including Madagascar, parts of the Middle East and the Mediterranean region. Considerable variation in intermediate host specificity can be found and differences in compatibility between snail and parasite can be observed over small geographical areas. Molecular studies for detection of genetic variation and the discrimination of Bulinus species are reviewed and two novel assays, allele-specific amplification (ASA) and SNaPshot™, are introduced and shown to be of value for detecting nucleotide changes in characterized genes such as cytochrome oxidase 1. The value and complexity of compatibility studies is illustrated by case studies of S. haematobium transmission. In Senegal, where B. globosus, B. umbilicatus, B. truncatus and B. senegalensis may act as intermediate hosts, distinct differences have been observed in the infectivity of different isolates of S. haematobium. In Zanzibar, molecular characterization studies to discriminate between B. globosus and B. nasutus have been essential to elucidate the roles of snails in transmission. B. globosus is an intermediate host on Unguja and Pemba. Further studies are required to establish the intermediate hosts in the coastal areas of East Africa. Biological factors central to the transmission of schistosomes, including cercarial emergence rhythms and interactions with other parasites and abiotic factors including temperature, rainfall, water velocity, desiccation and salinity are shown to impact on the intermediate host-parasite relationship.
Genetic variability and molecular identification of Brazilian Biomphalaria species (Mollusca: Planorbidae)
Authors: CARVALHO O. S. , CALDEIRA R. L. , SIMPSON A. J. G. , VIDIGAL T. H. D. A.
Published: October 2002

Freshwater snails belonging to the genus Biomphalaria are intermediate hosts of the trematode Schistosoma mansoni in the Neotropical region and Africa. In Brazil, one subspecies and ten species of Biomphalaria have been identified: B. glabrata, B. tenagophila, B. straminea, B. occidentalis, B. peregrina, B. kuhniana, B. schrammi, B. amazonica, B. oligoza, B. intermedia and B.t. guaibensis. However, only the first three species are found naturally infected with S. mansoni. The classical identification of these planorbids is based on comparison of morphological characteristics of the shell and male and female reproductive organs, which is greatly complicated by the extensive intra-specific variation. Several molecular techniques have been used in studies on the identification, genetic structure as well as phylogenetic relationships between these groups of organisms. Using the randomly amplified polymorphic DNAs (RAPD) analysis we demonstrated that B. glabrata exhibits a remarkable degree of intra-specific polymorphism. Thus, the genetics of the snail host may be more important to the epidemiology of schistosomiasis than those of the parasite itself. Using the simple sequence repeat anchored polymerase chain reaction (SSR-PCR) in intra-populational and intra-specific studies we have demonstrated that snails belonging to the B. straminea complex (B. straminea, B. kuhniana and B. intermedia) clearly presented higher heterogeneity. Using the low stringency polymerase chain reaction (LS-PCR) technique we were able to separate B. glabrata from B. tenagophila and B. tenagophila from B. occidentalis. To separate all Brazilian Biomphalaria species we used the restriction fragment length polymorphism (PCR-RFLP) of the internal transcribed spacer region (ITS) of the DNA gene. The method also proved to be efficient for the specific identification of DNA extracted from snail eggs. Recently we have sequenced the ITS2 region for phylogenetic studies of all Biomphalaria snails from Brazil.
Coevolution and compatibility in the snail–schistosome system
Authors: WEBSTER J. P. , DAVIES C. M.
Published: October 2002

In stark contrast to the huge body of theoretical work on the importance of hosts and parasites as selective agents acting on each other, until recently, little systematic empirical investigation of this issue has been attempted. Research on snail–schistosome interactions have, therefore, the potential for making an important contribution to the study of coevolution or reciprocal adaptation. This may be particularly pertinent since snail–schistosomes represent an indirectly transmitted macroparasite system, so often overlooked amongst both theoretical and empirical studies. Here we review ideas and experiments on snail–schistosome interactions, with particular emphasis on those that may have relevance to the potential coevolution between host resistance and parasite infectivity and virulence. We commence with an introduction and definition of the general concepts, before going into detail of some specific studies to illustrate these: evidence of snail–schistosome coevolutionary process in the field; evidence of coevolutionary processes in the laboratory; a general assessment of the applicability of coevolutionary models in snail–schistosome interactions; and finishing with a section on conclusions and areas for further study.
The effect of parasite dose on disease severity in the rodent malaria Plasmodium chabaudi
Authors: TIMMS R. , COLEGRAVE N. , CHAN B. H. K. , READ A. F.
Published: October 2002

Experiments were designed to look at the relationship between infective dose and disease severity using 2 clones of Plasmodium chabaudi that differ in virulence. We asked whether there were dose–severity relationships, whether clone differences in virulence were maintained over a range of doses, and whether disease severity could be accounted for by parasite dynamics. Groups of mice were infected with parasite doses differing by an order of magnitude, ranging from 100 to 1×108 parasites. Infective dose affected the probability of death, but only with the more virulent clone. Dose also affected morbidity. For both clones, higher doses induced greater anaemia. Larger doses caused greater weight loss, but only for infections with the more virulent clone. Here, for a given dose, mice lost a fixed amount of weight, irrespective of their initial weight. Larger doses induced earlier mortality and morbidity than did lower dose treatments. Finally, dose affected parasite dynamics, with earlier and higher peak parasite densities in larger dose infections. All these effects were small relative to clone differences in disease severity, which were apparent across the range of doses. Dose effects were manifested through the timing and/or magnitude of peak parasite densities, broadly supporting the idea that dose affects disease severity by altering the time the host has to control parasite densities and ameliorate the effects of parasites. We discuss the possible efficacy of intervention strategies aimed at reducing human disease severity by reducing infective parasite dose.
Interferon-gamma-induced apoptosis in host cells infected with Neospora caninum
Authors: NISHIKAWA Y. , MISHIMA M. , NAGASAWA H. , IGARASHI I. , FUJISAKI K. , OTSUKA H. , MIKAMI T.
Published: October 2002

Interferon-gamma (IFN-γ) has a crucial role for host defence against parasite infection. It is not clear, however, how IFN-γ affects the parasite-infected host cells. The effect of IFN-γ on Neospora caninum-infected cells was investigated in murine fibroblasts and canine kidney cells in vitro. In the presence of IFN-γ, the viability of the infected host cell was decreased and apoptotic cell death occurred, as analysed by DNA stainings with propidium iodide and a terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labelling (TUNEL) and DNA fragmentation. The percentage of apoptotic cells depended on the dose of IFN-γ. Flow cytometric analysis indicated a significant increase of FasL expression on the IFN-γ-treated cells following N. caninum infection. Moreover, IFN-γ treatment down-regulated Bcl-2 expression in the cells cultured with N. caninum while parasite infection up-regulated Bcl-2 expression. The present study suggests that the IFN-γ induced increases of FasL expression and down-regulated Bcl-2 expression in N. caninum-infected cells are associated with apoptosis in vitro.
Investigations of intermediate host specificity help to elucidate the taxonomic status of Trichobilharzia ocellata (Digenea: Schistosomatidae)
Authors: KOCK S.
Published: October 2002

The avian schistosomatid Trichobilharzia ocellata plays an important role as causative agent of cercarial dermatitis of humans in Europe. In order to improve the taxonomic knowledge on this parasite, studies of miracidial chemo-orientation as well as experimental infections of different snail species were conducted using strains of T. ocellata and T. franki. Both schistosomes exhibited a high intermediate host specificity. The miracidia clearly preferred the SCW (snail-conditioned water) of the respective natural intermediate host to SCW of other sympatric snail species. T. ocellata proved to be capable of infecting Lymnaea stagnalis and Stagnicola palustris, but could not develop in Radix ovata or R. auricularia. T. franki established an infection in specimens of R. auricularia and R. ovata, but not in L. stagnalis or S. palustris. The results imply that the intermediate host spectrum of T. ocellata is limited to L. stagnalis and S. palustris. Findings of T. ocellata (or Cercaria ocellata) that originated from snails of the genus Radix are likely to have actually belonged to species such as T. franki or T. regenti. The assumption that T. szidati is synonymous to T. ocellata is also discussed.
Trematode infection and the distribution and dynamics of parthenogenetic snail populations
Authors: LIVELY C. M.
Published: October 2002

According to the Red Queen hypothesis for sex, cross-fertilization should be positively associated with the probability of exposure (risk) to virulent parasites. Unfortunately, risk is difficult to measure in the wild, and prevalence of infection is often substituted for risk. Here I suggest that prevalence of infection may not generally suffice as a surrogate for risk, since the Red Queen model can make opposite predictions depending on the distribution of risk in the wild. Specifically, the results of a matching-alleles model suggest that asexual populations should be more infected than sexual populations, when (1) the variance in risk among populations is small, and (2) the mean risk of exposure to parasites is near the point where selection switches to favouring sex over asex. If, however, the variance in risk among populations is large, sexual reproduction should be positively associated with the prevalence of infection. In addition, the coefficient of variation for reproductive mode should increase sharply at the switch point. In light of these results, I re-evaluated data from two studies on the distribution of males in 95 populations of a freshwater snail (Potamopyrgus antipodarum). Populations of these snails are often mixtures of sexual and asexual individuals, and the frequency of males is correlated with the frequency of sexual females in the population. The results show a large, highly skewed variance among populations for prevalence of infection by larval trematodes. The results also show a positive, significant relationship between prevalence of infection and the frequency of males, with a sharp increase in the coefficient of variation at intermediate prevalence. In addition, experimental studies suggest that some of the necessary conditions of the Red Queen hypothesis are also met in this system. Specifically, the most common trematode infecting these snails is (1) adapted to infecting local host populations of the snail, and is (2) more infective to clones that were common in the recent past. It is too early to know if the parasite theory is sufficient to explain the widespread distribution of sex. I suggest that the theory is not sufficient, but that parasites in combination with mutation accumulation in clonal lines may explain the maintenance of sex in species that occasionally produce apomictic mutants.
Seasonality in the transmission of schistosomiasis and in populations of its snail intermediate hosts in and around a sugar irrigation scheme at Richard Toll, Senegal
Authors: STURROCK R. F. , DIAW O.-T. , TALLA I. , NIANG M. , PIAU J.-P. , CAPRON A.
Published: October 2002

Irrigation for intensive sugar cultivation started in the early 1980s at Richard Toll, some 100 km from the mouth of the Senegal River. Infections with Schistosoma mansoni were first seen in late 1988. This study records quantitative snail surveys for over 3 years from 1992 at sites representing different habitats in and around the irrigation scheme. Populations of both Biomphalaria pfeifferi (the intermediate host of S. mansoni) and Bulinus spp. (mainly B. truncatus, the local host of S. bovis) peaked in late ‘spring' or early ‘summer', depending on the habitat, and then remained low until the following ‘spring'. B. pfeifferi favoured smaller, man-made habitats with most transmission between May and August each year. The less abundant Bulinus spp. favoured larger natural and man-made habitats with most S. bovis transmission between April and July. S. mansoni infections were more, but S. bovis infections were less abundant than other trematodes in their respective snail hosts. Ecological changes in the early 1980s due to sugar irrigation pre-dated similar, more widespread changes in the late 1980s when the completion of dams across the Senegal River prevented seasonal rain fed floods and sea water intrusion. S. mansoni has since spread rapidly around Richard Toll. The incompatibility of the local S. haematobium strains with the dominant bulinid snails has so far prevented an epidemic of urinary schistosomiasis at Richard Toll, but the invasion of similar downstream habitats by susceptible B. globosus is worrying. The principal control measure, chemotherapy, given in the ‘winter' would minimise the rate of reinfection. It could be reinforced by judicious mollusciciding within the sugar irrigation scheme but not elsewhere.
Mechanisms of molluscan host resistance and of parasite strategies for survival
Authors: BAYNE C. J. , HAHN U. K. , BENDER R. C.
Published: October 2002

In parallel with massive research efforts in human schistosomiasis over the past 30 years, persistent efforts have been made to understand the basis for compatibility and incompatibility in molluscan schistosomiasis. Snail plasma contains molecules that are toxic to trematodes, but these seem to kill only species that never parasitize the mollusc used as the source of plasma. A sporocyst will be killed actively by haemocytes alone if they are from a snail that is resistant to the trematode. Oxygen-dependent killing mechanisms play a major role. Enzymes such as NADPH oxidase, superoxide dismutase, myeloperoxidase and nitric oxide synthase are critical components of the putative killing pathways. Metabolic intermediates such as hydrogen peroxide and nitric oxide appear to be more important against trematodes than the shorter-lived intermediates that are more important in anti-microbial defences. Products secreted by trematode larvae influence the physiology of snail haemocytes, implying active counter-defences mounted by the parasite, but these remain largely unexplored. A possible molecular basis for the susceptibility/resistance dichotomy in molluscan schistosomiasis is suggested to be deficient forms of enzymes in the respiratory burst pathway, and a selective disadvantage for schistosome resistance is an integral component of this model.
Multiple strategies of schistosomes to meet their requirements in the intermediate snail host
Authors: de JONG-BRINK M. , BERGAMIN-SASSEN M. , SOLIS SOTO M.
Published: October 2002

The results of the studies on our model combination Trichobilharzia ocellata–Lymnaea stagnalis, presented in this review, lead to the conclusion that schistosomes use multiple strategies to reach their goals, i.e. to propagate and to continue their life cycle. They have to escape from being attacked by the internal defence system (IDS) of the snail host and to profoundly affect the host's energy flow, of which reproduction and growth are the main determinants, for their own benefit. These physiological changes they establish mainly by interfering with the two regulatory systems in the snail host, the IDS and the neuroendocrine system (NES). Moreover, these two regulatory systems clearly interact with each other. Parasitic E/S products affect the host's IDS both in a direct and an indirect way. The neuropeptides or neuropeptide-like substances that are secreted by parasite glands into the host directly suppress haemocyte activity in the snail. The indirect effects include effects of (1) peptides from connective tissue cells and (2) neuropeptides from NES and/or IDS. Parasitic E/S products also induce the effects on energy flow in the host. These E/S products act either directly on a target, as shown for the inhibiting effect of the parasite on the development of the male copulation organ, or on the NES regulating reproductive activity, e.g. on gene expression. Indirect effects of E/S products on the NES (hormone-receptor interaction, electrical activity) are mediated by a factor from connective tissue cells, presumably belonging to the IDS. The physiological changes in the snail host are obviously of vital importance for the parasites, since they make use of different strategies to bring them about.
Evidence for translational selection in codon usage in Echinococcus spp.
Authors: FERNÁNDEZ V. , ZAVALA A. , MUSTO H.
Published: October 2002

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.
Novel Plasmodium falciparum clones and rising clone multiplicities are associated with the increase in malaria morbidity in Ghanaian children during the transition into the high transmission season
Authors: OFOSU-OKYERE A. , MACKINNON M. J. , SOWA M. P. K. , KORAM K. A. , NKRUMAH F. , OSEI Y. D. , HILL W. G. , WILSON M. D. , ARNOT D. E.
Published: October 2002

A survey of Plasmodium falciparum infection and clone multiplicity in Ghanaian children was carried out to study the effect of the onset of the malaria transmission season on disease incidence. Fortnightly blood samples were collected from 40 children living in the rural town of Dodowa, between February and August 1998. P. falciparum parasite densities were calculated and PCR genotyping was carried out using the polymorphic MSP-1 and MSP-2 genes as target loci for the estimation of the number of parasite clones in each sample. The average clone number was estimated using maximum likelihood techniques and the minimum number of clones per patient was analysed for the effects of age, sex, season, minimum number of clones per child, level of parasitaemia and parasite genotype. The statistical analysis indicated that the more clones a child carried, the more likely they were to have a clinical malaria episode. This was true after adjusting for age and season effects and for the measured circulating parasitaemia. The probability of clinical disease also increased if the MSP-1 MAD 20 and the MSP-2 FC 27 alleles were present. This longitudinal analysis thus indicates that the probability of a Ghanaian child having a symptomatic malaria episode is positively associated with both increasing numbers and novel types of P. falciparum clones.
Molecular approaches in the study of Biomphalaria glabrata – Schistosoma mansoni interactions: linkage analysis and gene expression profiling
Authors: JONES C. S. , LOCKYER A. E. , ROLLINSON D. , NOBLE L. R.
Published: October 2002

Gene mapping and the generation of linkage groups are fundamental to an understanding of the organization and relationships of genes and marker sequences, providing a framework with which to investigate their association with traits of interest. The abundance of techniques available for generating polymorphic molecular markers, and recent advances in high throughput screening, have allowed the extension of map analysis to the tropical freshwater snail Biomphalaria glabrata, an important intermediate host for Schistosoma mansoni. Direct comparison of gene expression by differential display screening, without prior identification of candidate genes, can be combined with mapping to quantify the involvement of specific sequences in the schistosome resistance response, and other important host–parasite interactions. Here we discuss the application of current and emergent technologies to gene characterization and linkage analysis in snail–schistosome interactions. Preliminary results from the analysis of comparative gene expression in resistant and susceptible snails are also presented.
A stochastic model for the aggregation of Onchocerca volvulus in nodules
Authors: DUERR H. P. , DIETZ K. , BÜTTNER D. W. , SCHULZ-KEY H.
Published: October 2002

A model is presented which describes the aggregation of female Onchocerca volvulus in nodules and their distribution in the human population. The basic model is based on a single parameter, the formation probability q, which represents the probability with which incoming larvae form a new nodule. This parameter describes parasite behaviour which cannot easily be recognized in available data without modelling. The estimate for the average formation probability of μq = 0.39 suggests an attraction of the invading infective larvae to already existing nodules or resident worms with probability 0.61. No significant difference in μq was found between the forest and savanna parasite strains. The model can be used inversely to estimate the worm burden of persons from palpation data. The observed variance in the number of nodules per person requires the assumption of a variance-increasing mechanism which was implemented by heterogeneity within the host population (extended model with 2 parameters). Possible reasons for this heterogeneity are presented and its implications concerning the reproductive biology of the parasite are discussed.
Horizontal and vertical transmission of mouse class I MHC sequence in Schistosoma mansoni
Authors: IMASE A. , KOBAYASHI K. , OHMAE H. , MATSUDA H. , IWAMURA Y.
Published: October 2002

The mouse major histocompatibility complex (MHC) class I sequence was detected in 8-week-old Schistosoma mansoni by in situ polymerase chain reaction (in situ PCR). The signals to the mouse class I MHC sequence were observed in the nuclei of the mesenchymal and reproductive cells of S. mansoni. Signals were also observed in the cytoplasm of the tegumental tubercles. This finding suggested the possibility of MHC gene transfer from the host to schistosomes. Furthermore, the class I MHC sequence was detected in the DNA extracted from the cercariae of S. mansoni by nested PCR. Neither the nucleotide sequence of class I MHC detected in adult worm DNA nor that of class I MHC detected in the host (mouse) DNA was identical with that of class I MHC detected in the cercarial DNA. From the data we assumed that S. mansoni may have retained their own mouse class I MHC sequence in their genome throughout their life-cycle.
Contributions to and review of dicrocoeliosis, with special reference to the intermediate hosts of Dicrocoelium dendriticum
Authors: MANGA-GONZÁLEZ M. Y. , GONZÁLEZ-LANZA C. , CABANAS E. , CAMPO R.
Published: October 2002

An epidemiological study on dicrocoeliosis caused by Dicrocoelium dendriticum was carried out on sheep, molluscs and ants in the mountains of León province (NW Spain) between 1987–1991. The results concerning the intermediate hosts and a review of some aspects of dicrocoeliosis are summarized. Mollusc collection for the helminthological study was random throughout the study area at fortnightly intervals. Twenty-nine Gastropoda species were identified. D. dendriticum infection was only detected in 2·98% of the 2084 Helicella itala examined and in 1·06% of 852 H. corderoi. The highest infection prevalence was detected in H. itala in September and in H. corderoi in February. Daughter sporocysts with well-developed cercariae predominated in spring and autumn. Infection prevalence increased with mollusc age and size. Ants were collected from anthills or plants to which they were attached. The behaviour of ants in tetania was followed. Twenty-one Formicidae species were identified, but only the following harboured D. dendriticum: Formica cunicularia (1158 examined specimens, 0·69% infection prevalence, 2–56 metacercariae per ant); F. sanguinea (234, 1·28%, 2–63); F. nigricans (1770, 4·97%, 1–186); F. rufibarbis (288, 6·59%, 2–107). In a flat area close to León town, 95·39% of the 2085 F. rufibarbis specimens collected in tetania contained metacercariae (1–240) in the abdomen. These were used for parasite characterization by isoelectric focusing and to infect lambs and hamsters. Only one brainworm per ant was found.
Phagocytosis of malarial pigment haemozoin by human monocytes: a confocal microscopy study
Authors: SCHWARZER E. , BELLOMO G. , GIRIBALDI G. , ULLIERS D. , ARESE P.
Published: October 2002

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.
The human isolate of Brachiola algerae (Phylum Microspora): development in SCID mice and description of its fine structure features
Authors: KOUDELA B. , VISVESVARA G. , MOURA H. , VÁVRA J.
Published: October 2002

Ocular, peroral, intraperitoneal, intramuscular, and subcutaneous inoculation of severe combined immunodeficient (SCID) mice with spores of the human isolate (CDC: V404) of Brachiola algerae (syn. Nosema algerae) (Phylum Microspora) revealed that the microsporidium develops in viscera of the immunodeficient mouse host, but only after the ocular administration of spores. It is hypothesized that the physico-chemical milieu of the conjunctiva and cornea helped to adapt the originally ‘poikilothermic microsporidian’ to the conditions within the homoiothermic organism. Ocular application of spores caused no clinical signs of disease at the application site. However, severe infection in the liver was found 60 days after infection, manifested as hepatosplenomegaly and multifocal miliary necroses and granulomas containing parasites. No microsporidia were found in any other tissues. Transmission electron microscopy revealed characteristic tubulovesicular ‘secretory materials’ on the plasma membrane of all developmental stages of B. algerae except sporoblasts and spores. These formations increase the parasite surface and allow more efficient metabolic communication of the parasite with the host cell. It is hypothesized that the presence of these structures is a factor helping the parasite to grow in a variety of hosts and tissues. Ultrastructural characters support the likelihood that B. algerae and B. vesicularum are conspecific, and that there exists a relationship between species of the genera Brachiola and Anncaliia.
Morphometric correlates of host specificity in Dactylogyrus species (Monogenea) parasites of European Cyprinid fish
Authors: SIMKOVÁ A. , DESDEVISES Y. , GELNAR M. , MORAND S.
Published: October 2002

We test the hypothesis that living on larger fish may impose constraints, i.e. the need to develop large attachment organs, related to the necessity to remain attached on large gills. For this, we compiled data on body size and morphometric measurements of attachment organs of 44 Dactylogyrus species (ectoparasites with direct life-cycle) from 19 cyprinid species. Nineteen dactylogyrid species were considered as specialists (infecting only 1 host species) and 25 as generalists (infecting more than 1 species). The lack of phylogenetic information lead us to perform comparative analyses using raw values and independent contrasts obtained by random phylogenies. Our results show that rich parasite communities are formed by specialists and generalists whereas poor communities are composed mainly of generalist parasites. Moreover, specialists are found on larger hosts, which may reflect a specialization on a predictable resource, as larger fish live longer and offer large gills for parasite colonization. Parasite specialization is shown to be linked with adaptation of attachment organs to their fish hosts. Two morphometric variables of the attachment organ, the total length of anchor and length of base of anchor, were positively correlated with host length for specialists.
Fructosamine concentration and resistance to natural, predominantly Teladorsagia circumcincta infection
Authors: STEAR M. J. , ECKERSALL P. D. , GRAHAM P. A. , McKELLAR Q. A. , MITCHELL S. , BISHOP S. C.
Published: October 2002

Fructosamine concentrations reflect protein status and because infection with Teladorsagia circumcincta can induce a relative protein deficiency, we examined the usefulness of fructosamine concentrations as markers of the intensity of infection in naturally infected lambs. Fructosamine concentration was a heritable trait and variation in fructosamine concerntrations was associated with differences in body weight, and a variety of parasitological variables; animals with increased fructosamine concentrations grew more quickly, had increased faecal egg counts in one of the three study years, had decreased pepsinogen concentrations and decreased IgA activity against 4th-stage larvae of T. circumcincta. Fructosamine concentrations were also associated with variation in the subsequent acquisition of nematodes and in the length of adult female T. circumcincta; lambs with increased fructosamine concentrations had fewer nematodes but the mean length of adult female T. circumcincta was longer. Therefore fructosamine concentrations are potentially useful indicators of the severity of nematode infection and may predict magnitude of subsequent infection.
Coccidiosis in the European badger, Meles meles in Wytham Woods: infection and consequences for growth and survival
Authors: NEWMAN C. , MACDONALD D. W. , ANWAR M. A.
Published: October 2002

In total 1502 faecal samples were collected from a population of European badgers (Meles meles) between 1992 and 1995 at Wytham Woods, Oxfordshire, UK. Two coccidia species, Eimeria melis and Isospora melis, were identified. Cubs showed a marked seasonal pattern of infection with E. melis, with infection occurring at significantly higher intensity and prevalence than in adults. There was preliminary evidence to suggest that infantile coccidiosis in badgers may be associated with impaired growth and increased mortality.
Parasite richness and abundance in insular and mainland feral cats: insularity or density?
Authors: FROMONT E. , MORVILLIERS L. , ARTOIS M. , PONTIER D.
Published: October 2002

Hosts living on islands carry few parasite species, and the prevalence and intensity of directly transmitted parasites are often higher in insular than in mainland populations. However, it is unclear whether density or other features of insular populations can be responsible for the pattern observed. We compared the parasite richness, prevalence and intensity of parasites between 2 feral populations of cats living either at low density on an island (Kerguelen) or at high density on the mainland (Lyon). Parasite richness was higher in Lyon than in Kerguelen, where only Toxocara cati was found. T. cati egg prevalence was higher in Kerguelen (71·1%) than in Lyon (58·0%). Because cat density cannot explain this pattern, we propose that the low number of parasite species, the diet and/or immunity of cats act to increase prevalence in Kerguelen. Moreover, prevalence, intensity and variance-to-mean ratio increased with age and body mass in Kerguelen whereas, in Lyon, prevalence decreased with age and body mass. We hypothesize that the pattern of exposure differs between populations, and that density-dependent parasite mortality is lower in Kerguelen than in Lyon. We discuss the consequences concerning the influence of parasites on insular host populations.
Identification of some heat-induced genes ofTrichinella spiralis
Authors: MAK C. H. , SUN K. W. , KO R. C.
Published: October 2002

Three heat-induced genes of the infective-stage larvae ofTrichinella spiraliswere successfully identified by the suppression subtractive hybridization (SSH) technique. As indicated by reverse Northern blotting, 19 of 25 clones were scored as differentially transcribed in the heat-shocked infective-stage larvae. The sequencing data showed the presence of 12 different genes. Three were homologous to histone H3, histone H2B and translationally controlled tumour protein (TCTP). A 0.6 kb cDNA of histone H3 was generated by the RACE method and sequenced. It contained an open reading frame of 136 amino acids that demonstrated 94% identity with genes fromDrosophila hydei. Semi-quantitative RT-PCR indicated that after heat-shock treatment, the expression levels of histone H3, histone H2B and TCTP increased 4.8, 27 and 5.7-fold, respectively. Northern analysis confirmed the upregulation of histone H3, histone H2B and TCTP transcripts. The upregulation of these genes during stress conditions has not been reported in parasitic organisms. The stress proteins may play an active role to sustain the parasite after exposure to hostile host factors.
Programmed cell death in a human intestinal parasite,Blastocystis hominis
Authors: NASIRUDEEN A. M. A. , TAN K. S. W. , SINGH M. , YAP E. H.
Published: October 2002

Although programmed cell death (PCD) has been associated with multicellular organisms, there have been more reports of its presence in some protozoans. Our study shows the existence of PCD in an intestinal protozoan,Blastocystis hominis. Light and electron microscopy, biochemical and flow cytometry studies showed apoptosis-like death inB. hominiscells exposed to a cytotoxic monoclonal antibody (MAb 1D5).B. hominiscells displayed key morphological and biochemical features of apoptosis, namely, nuclear condensation andin situfragmentation, reduced cytoplasmic volume, some externalization of phosphatidylserine and maintenance of plasma membrane integrity. No oligonucleosomal DNA laddering was observed in gel electrophoresis. This study supports earlier observations that the cellular machinery that is required to carry out PCD may have existed before the advent of multicellularity. Our study also ascribes a novel function for theB. hominiscentral vacuole in apoptosis; it acts as a repository where apoptotic bodies are stored before being released into the extracellular space.
Plasmodium falciparum: linkage disequilibrium between loci in chromosomes 7 and 5 and chloroquine selective pressure in Northern Nigeria
Authors: ADAGU I. S. , WARHURST D. C.
Published: October 2002

In view of the recent discovery (Molecular Cell6, 861–871) of a (Lys76Thr) codon change in genepfcrton chromosome 7 which determinesin vitrochloroquine resistance inPlasmodium falciparum, we have re-examined samples taken before treatment in our study in Zaria, Northern Nigeria (Parasitology119, 343–348). Drug resistance was present in 5/5 cases where thepfcrt76Thr codon change was seen (100% positive predictive value). Drug sensitivity was found in 26/28 cases where the change was absent (93% negative predictive value). Allelepfcrt76Thr showed strong linkage disequilibrium withpfmdr1Tyr86 on chromosome 5, more complete than that betweenpfcrtandcg2alleles situated between recombination cross-over points on chromosome 7. Physical linkage ofcg2withpfcrtmay account for linkage disequilibrium between their alleles but in the case of genespfmdr1andpfcrt, on different chromosomes, it is likely that this is maintained epistatically through the selective pressure of chloroquine.
Eel parasite diversity and intermediate host abundance in the River Rhine, Germany
Authors: SURES B. , STREIT B.
Published: October 2002

European eels (Anguilla anguilla) from 2 sampling sites on the Rhine river (near Karlsruhe and near Worms) were investigated with respect to their parasite communities. Nine different metazoan species were found to live in and on the eels. The highest number of species was recorded from the intestine, which contained up to 6 different helminths. Among these, acanthocephalans were the most prevalent worms with the eel-specific parasite Paratenuisentis ambiguus as the dominant species of the intestinal component communities at both sites. Comparing the intestinal parasites from eels caught near Karlsruhe with those from Worms, the acanthocephalans showed a significantly lower abundance at Worms. A significantly lower mean number of intestinal helminth species as well as a significantly lower Brillouin's Index was found at Worms compared with Karlsruhe. This difference could be related to the abundance of the respective intermediate crustacean hosts. At the sampling site Worms the amphipod Corophium curvispinum was the dominant crustacean. Additionally, only the isopod Jaera istri and the amphipod Dikerogammarus villosus were found. All these crustacean species have only recently colonized the Rhine river system via the Main-Danube canal, built in the early 1990s. They are not known to act as intermediate hosts for any of the acanthocephalans found in the eels. The site near Karlsruhe exhibited a higher crustacean diversity, including Asellus aquaticus and different species of the genus Gammarus, which are all known intermediate hosts for the acanthocephalans found. Therefore, changes of eel parasite diversity can be correlated with the appearance of invading crustacean species (neozoans).
Light microscopical structure and ultrastructure of a Besnoitia sp. in the naturally infected lizard Ameiva ameiva (Teiidae) from north Brazil, and in experimentally infected mice
Authors: PAPERNA I. , LAINSON R.
Published: October 2002

A Besnoitia species of the teiid lizard Ameiva ameiva (L.), from north Brazil was established in laboratory mice and hamster by the intraperitoneal inoculation of bradyzoites in the tissue cysts. In the lizards all the cyst wall layers were closely apposed. In the mice the layers of the wall were distinguishable, and ultrastructurally the inner cytoplasmic layer contained either a tight network of endoplasmic reticulum or packed mitochondria or both. These components were less frequent or sparse in the inner cytoplasmic layer of cysts in the lizard. The only animals available for experiments in attempts to indicate the definitive host of the parasite were 3 kittens of the domestic cat and a juvenile specimen of the snake Boa constrictor raised in captivity. No evidence of infection could be detected in these animals after feeding them with the tissues of mice harbouring cysts with very large number of bradyzoites.
Molecular evolution of freshwater snail intermediate hosts within the Bulinus forskalii group
Authors: JONES C. S. , ROLLINSON D. , MIMPFOUNDI R. , OUMA J. , KARIUKI H. C. , NOBLE L. R.
Published: October 2002

Freshwater snails of the Bulinus forskalii group are one of four Bulinus species complexes responsible for the transmission of schistosomes in Africa and adjacent regions. The species status of these conchologically variable and widely distributed planorbids remains unclear, and parasite compatibility varies considerably amongst the eleven taxa defined, making unambiguous identification and differentiation important prerequisites for determining their distributions and evolutionary relationships. Random Amplified Polymorphic DNA (RAPD) analyses were used to investigate relationships between taxa, with particular emphasis on Central and West African representatives. RAPD-derived phylogenies were compared with those from other independent molecular markers, including partial sequences of mitochondrial cytochrome oxidase subunit I (COI) gene, and the nuclear ribosomal RNA internal transcribed spacer 1 region (ITS1). The phylogenetic reconstructions from the three approaches were essentially congruent, in that all methods of analysis gave unstable tree topologies or largely unresolved branches. There were large sequence divergence estimates between species, with few characters useful for determining relationships between species and limited within species differentiation. Nuclear and mtDNA sequence data from Central and East African representatives of the pan-African B. forskalii showed little evidence of geographical structuring. Despite the unresolved structure within the phylogenies, specimens from the same species clustered together indicating that all methods were capable of differentiating taxa but could not establish the inter-specific relationships with confidence. The limited genetic variation displayed by B. forskalii, and the evolution and speciose nature of the group, are discussed in the context of the increasingly arid climate of the late Miocene and early Pliocene of Africa.
The interaction between the gelatin-binding domain of fibronectin and the attachment ofPasteuria penetransendospores to nematode cuticle
Authors: MOHAN S. , FOULD S. , DAVIES K. G.
Published: October 2002

Pasteuria penetransis a Gram-positive endospore-producing bacterium that is a parasite of root-knot nematodes. Attachment of endospores to the cuticle of the nematode is the first stage in the infection process. Western blot analysis with monoclonal and polyclonal antibodies that recognize the 30 kDa heparin-binding domain (HBD) and the 45 kDa gelatin-binding domain (GBD) fragments of human fibronectin (Fn) revealed a series of polypeptides of approximately 40, 45 and 55 kDa present in crude cuticle extracts ofMeloidogyne javanica2nd-stage juveniles. The results suggest that the structure of the nematode fibronectin is different to the fibronectins so far characterized. Pre-treatment of endospores ofPasteuriawith either the HBD or the GBD was found to inhibit binding to the nematode cuticle. The larger GBD fragment was the most effective at blocking adhesion. Pre-treatment of the GBD fragment with gelatin prevented the GBD fragment from inhibiting endospore attachment to the nematode cuticle.
In vitrocultivation ofAnisakis simplex:pepsin increases survival and moulting from fourth larval to adult stage
Authors: IGLESIAS L. , VALERO A. , BENÍTEZ R. , ADROHER F. J.
Published: October 2002

This paper describes thein vitrocultivation of the 3rd-larval stage (L3) ofAnisakis simplexto adulthood in a much simpler and easier to prepare medium than those described to date. The adult males obtained are between 3.8 and 6.5 cm long and the females between 4.5 and 8.0 cm. Some individually cultivated females laid eggs which had an average size of 44.4×50.5 μm. The culture conditions were as follows: medium RPMI-1640 supplemented with 20% heat-inactivated fetal bovine serum and 1% commercial pepsin, at pH 4.0 and a temperature of 37 °C, and in air atmosphere with 5% CO2. The pepsin was found to be the key to the success of the culture. The average survival of the worms in the culture increased from 50 to 88 days, due to the fact that the survival of the adults practically doubled (increasing by 1.9 times). Furthermore, the number of worms that completed the 4th moulting (M4) increased by 4.2 times, from 22.9 to 95.6%. This culture medium may facilitate, due to its simplicity, the study of anisakids, or at least ofA. simplex,constituting another step towards achieving a completein vitrolife-cycle for these parasites.