bluuebunny/crossref_metadata_2025 huggingface dataset:
Chickens and pigs as transport hosts forAscaris,TrichurisandOesophagostomumeggs
Authors: OLSEN A. , PERMIN A. , ROEPSTORFF A.
Published: October 2002

Ten chickens and 2 pigs were fed non-embryonated eggs ofAscaris suum,Trichuris suisandOesophagostomum dentatum. Each chicken was fed approximately 15000 eggs of each parasite species while approximately 300000 eggs were given to each of the pigs. After passage in chickens 8.3% ofO. dentatumeggs were recovered in faeces compared to 61.1% and 41.6% ofA. suumandT. suiseggs, respectively. After passage in pigs the percentages were 38.4%, 49.1% and 30.3%, respectively. After embryonation in the laboratory, 1000 eggs of each parasite species having passed through chickens or pigs or having been kept in the laboratory as controls were fed to groups of 6 pigs to check the infectivity. The number ofA. suumrecovered from pigs was similar in the 3 groups with 34.0, 52.8 and 41.8%, respectively. The recovery ofT. suisin the pig passage group was 54.0% which was significantly lower than the recovery in the chicken passage group (81.8%) and the laboratory group (88.0%). The number ofO. dentatumrecovered was not significantly different among the 3 experimental groups, the percentage recovery being 30.5, 9.2 and 28.5%, respectively. One explanation for the lower infectivity ofT. suisin the pig passage group may be that the eggs have been sublethally damaged through their passage. The results demonstrate that chickens and pigs can act as transport hosts forA. suum, T. suisandO. dentatum, and it is highly probable that these domestic animals are able to act also as transport hosts for the human parasite equivalents. This will have important consequences for the environmental and behavioural strategies in human helminth control programmes.
DNA-binding activity in the excretory–secretory products ofTrichinella pseudospiralis(Nematoda: Trichinelloidea)
Authors: MAK C. H. , KO R. C.
Published: October 2002

A novel DNA-binding peptide ofMr∼30 kDa was documented for the first time in the excretory–secretory (E–S) products of the infective-stage larvae ofTrichinella pseudospiralis.Larvae recovered from muscles of infected mice were maintained for 48 h in DMEM medium. E–S products of worms extracted from the medium were analysed for DNA-binding activity by the electrophoretic mobility shift assay (EMSA). Multiple DNA-protein complexes were detected. A comparison of theMrof proteins in the complexes indicated that they could bind to the target DNA as a dimer, tetramer or multiples of tetramers. Site selection and competition analysis showed that the binding has a low specificity. A (G/C-rich)-gap-(G/T-rich)-DNA sequence pattern was extracted from a pool of degenerate PCR fragments binding to the E–S products. Results of immunoprecipitation and electrophoretic mobility supershift assay confirmed the authenticity of the DNA-binding protein as an E–S product.
Anti-SAG1 peptide antibodies inhibit the penetration ofToxoplasma gondiitachyzoites into enterocyte cell lines
Authors: VELGE-ROUSSEL F. , DIMIER-POISSON I. , BUZONI-GATEL D. , BOUT D.
Published: October 2002

The initial attachment ofToxoplasmatachyzoites to the target host cell is an important event in the life-cycle of the parasite and a critical stage in infection. Previous studies have shown that polyclonal antibodies directed against the major surface antigen ofToxoplasma gondii(SAG1) inhibit the infection of enterocyte cell lines. Here, we demonstrate that antibodies raised against a central peptide (V41T) of SAG1 and the SAG1 protein itself are able to inhibit the infection of various cell lines by the tachyzoites. Antibodies directed against SAG1 peptides were used to define a site on the SAG1 antigen that interacts with the host cell. The epitope carried by V41T was identified on the tachyzoite surface by immunofluorescence. The peptide sequence seems to be conserved in all the members of the SAG1 Related Sequence family (SRS). Using undifferentiated and differentiated Caco-2 cells, we found that tachyzoites enter preferentially via the basolateral side of the cell. These findings highlight the role of the SRS family members in the mediation of host cell invasion.
The effect of dietary carbohydrates with different digestibility on the populations ofOesophagostomum dentatumin the intestinal tract of pigs
Authors: PETKEVIČIUS S. , BACH KNUDSEN K. E. , NANSEN P. , MURRELL K. D.
Published: October 2002

An experiment was undertaken to study the effect of dietary carbohydrates with different digestibility on the populations ofOesophagostomum dentatumin the intestinal tract of pigs. Sixty-four worm-free pigs from a specific pathogen-free farm were randomly divided into 8 equal groups. The animals in 4 groups were assigned to a diet with partially undegradable carbohydrates (diet 1), while the pigs in the 4 remaining groups were given a diet with fermentable carbohydrates (diet 2). Diet 1 was comprised of barley flour, oat husk meal, soybean meal, vitamins and minerals and diet 2 of barley flour, inulin and sugar beet fibre, soybean meal, vitamins and minerals. The pigs in 6 of the groups (n= 48) were inoculated with 6000 infective larvae ofO. dentatum. To determineO. dentatumpopulations at the early stage of infection, 16 pigs were slaughtered 3 weeks p.i., while the remaining 4 groups continued on the diets for a further 9 weeks after which they were slaughtered. In a diet cross-over experiment 6 weeks after inoculation, 8 pigs changed from diet 1 to diet 2 (diet 1>diet 2), and 8 pigs from diet 2 to diet 1 (diet 2>diet 1). The results showed that partially undegradable carbohydrates provided favourable conditions not only for parasite establishment and sustainability, but also for already establishedO. dentatuminfection while, in contrast, the diet composed of highly degradable carbohydrates decreased worm establishment, size and female fecundity. The implications for pastured pigs or pigs fed different complex carbohydrate diets is discussed.
Cloning and characterization of a muscle isoform of a Na,K-ATPase alpha subunit (SNaK1) fromSchistosoma mansoni
Authors: SKELLY P. J. , DOUGAN P. M. , MAULE A. , DAY T. A. , SHOEMAKER C. B.
Published: October 2002

A cDNA encoding a Na,K-ATPase alpha subunit homologue, designated SNaK1, was isolated from an adult cDNA library ofSchistosoma mansoni. The 3.8 kb DNA contained a 3021 bp open reading frame potentially encoding a 1007 amino acid protein that had anMrof 111817 and a pI of 5.48. Homology searches for SNaK1 revealed approximately 70% sequence identity with a variety of Na,K-ATPases from evolutionarily diverse organisms. SNaK1 is predicted to contain 10 transmembrane regions typical of this protein family as well as other conserved domains, such as the phosphorylation site and ATP binding domain. Antibodies raised against an amino terminal peptide detected the protein in membrane preparations of eggs, cercariae and adult males and females, suggesting a general role for SNaK1. The mobility of the protein differed in various life-stages suggestive of post-transcriptional or post-translational modification. Immunolocalization of SNaK1 in sections of adult worms using epifluorescence and electron microscopy, revealed antibody labelling in the subtegumental and peripheral layers. Strong staining was discernible in the peripheral muscle band indicating that SNaK1 plays a central role in muscle contraction in adult parasites and may be the primary target of ouabain action. Staining was also detected in the secretory bodies in sections of ducts in this region and over the RER of the presumed gastrodermis. Immunogold labelling was also localized over neuronal vesicles in axons associated with the peripheral muscle layer.
A novel method for the isolation of gastro-intestinal nematode eggs that allows automated analysis of digital images of egg preparations and high throughput screening
Authors: MES T. H. M. , PLOEGER H. W. , TERLOU M. , KOOYMAN F. N. J. , VAN DER PLOEG M. P. J. , EYSKER M.
Published: October 2002

A simple and robust method for the isolation of gastro-intestinal nematode eggs from faeces is described that uses both salt- and sugar solutions for flotation. Application of this ‘salt–sugar’; isolation method to large numbers of faecal samples of adult dairy cows indicates a 3- or 4-fold reduction in the proportion of e.p.g.-negative cows relative to studies that used other techniques for egg isolation. The procedure detects more eggs than the Wisconsin flotation method in replicate samples and in spiked egg-free faeces. The number of recovered eggs in spiked faecal samples is linear over a range of egg concentrations, and the transparent faecal preparations that result from the protocol can be stored as digital images which can be used as input for an efficient automated egg-counting procedure. The increased rate of processing of faeces combined with the large reduction of the percentage of e.p.g.-negative cows allows more accurate analysis of large numbers of adult or resistant animals for studies of nematode parasitism.
Addition of hypoxanthine to culture media allows in vitro cultivation of Babesia bovis and B. bigemina at reduced serum concentrations
Authors: NEVES L. , CROSS H. F. , LOUREIRO L. , AKÇA A. , HOMMEL M. , TREES A. J.
Published: October 2002

The microaerophilous stationary phase system (MASP) was introduced in 1980 and successfully used as a standard technique for Babesia bovis and B. bigemina in vitro culture. The percentage of serum in the medium and the dependence on specific serum donors have been recognized as important constraints both for immunochemical studies and for the logistics of culture routine. In the present study the supplementation of RPMI 1640 with hypoxanthine at a concentration between 50 and 200 μM has enabled patterns of growth of B. bovis and B. bigemina to be achieved comparable to the standard technique with a simultaneous reduction of serum concentration from 40% to 5%. With hypoxanthine-supplemented medium it was possible to either replace the bovine serum from a specific donor with horse serum or use commercial adult bovine serum or foetal calf serum at 10%. When the serum replacement media Albumax II and GF21 were used, the growth of both B. bovis and B. bigemina markedly decreased after 3×72 h cycles. However, when these species were cultivated in culture flasks previously coated with cells from a murine peritoneal lavage, continuous parasite growth was achieved.
The impact of season and vegetation on the survival and development of Oesophagostomum dentatum larvae in pasture plots
Authors: KRAGLUND H.-O. , ROEPSTORFF A. , GRØNVOLD J.
Published: October 2002

Pats of pig faeces containing known numbers of Oesophagostomum dentatum eggs were placed on plots with bare soil, short or tall herbage on 8 occasions during 1 year. The number of eggs and larvae and the relative distribution of larvae in faeces, soil and herbage was monitored for 1 year after deposition. On 2 occasions soil from 8 selected plots was given to pigs, which were later slaughtered and examined for the presence of adult O. dentatum. Less than 1% of the deposited eggs could be recovered as infective larvae. The highest recoveries were generally made on tall herbage plots. The majority of infective larvae was found within the faecal pats, which indicates that infective O. dentatum larvae, to a large extent, do not disperse onto the herbage or into soil. The infective larval stage was reached only when the mean temperature in the weeks post-deposition was above 10 °C. This stage was reached within 1 week when the mean weekly temperature was above 13 °C. After the winter period no infective larvae could be recovered from any plots and no parasitic worms could be isolated from pigs fed soil from 8 selected plots.
Long-term dynamics ofLigula intestinalisand roachRutilus rutilus: a study of three epizootic cycles over thirty-one years
Authors: KENNEDY C. R. , SHEARS P. C. , SHEARS J. A.
Published: October 2002

Data are presented on 2 full epizootic cycles and the start of a third ofLigula intestinalisin roachRutilus rutilusin a small lake, and the relationships of these cycles to the densities of rudd,Scardinius erythrophthalmus, and Great Crested Grebes,Podiceps cristatus, over 31 years. The parasite was introduced to the lake byP. cristatusin 1973 at a time when the roach population had increased in response to eutrophication to a level at which individual fish growth was stunted and the hithero dominant rudd population had declined in numbers as a consequence of inter-specific competition with roach.Ligulaprevalence peaked at 28% in only 2 years: thereafter parasite-induced host mortality caused a decline in the roach population, releasing fish from stunting and allowing the rudd population to recover. The consequent improved growth of roach individuals and their short life-span reducedLigulatransmission rates and prevalence levels declined to approximately 1% althoughLigulanevertheless persisted for a further 10 years. Following a massive winter-kill of the fish populations in 1984–1985, fish andLigulanumbers declined to barely detectable levels and the parasite disappeared from samples. Rudd recovered first, then roach and interspecific competition again led to a decline in rudd numbers. This increase in roach numbers led to a decrease in roach growth rates, which coincided with the re-colonization of the lake byLigula. This second epizootic ofLigulapeaked within 2 years in 1991–1992, when up to 78% of roach were infected with a maximum abundance of 2.2 parasites and intensity of 21 parasites. Heavy parasite-induced mortality of roach led to a decline in numbers, an improvement in individual growth rate and a reduction ofLigulatransmission rates such that the epizootic died out in 1996. Similar conditions of roach numbers and growth prevailed at the start of a third cycle in 1998. The course of events over the second cycle was so similar to that of the first that it confirms the interpretations of that cycle. Comparison with other localities shows that epizootics ofLigulaalways coincide with rapid increases in roach numbers, for whatever cause, and stunted growth, which together attract piscivorous birds. At the start of a cycleLigulais a major determinant of the population dynamics of the roach, but at the end of the cycle the fish population dynamics determine those of the parasite. The cycles are not regulated and the roach–Ligulasystem is inherently unstable.
Kinetics of Trypanosoma cruzi infection in guinea-pigs, with special reference to the involvement of epidermal Langerhans' cells in the induction of immunity
Authors: NARGIS M. , CHISTY M. M. , IHAMA Y. , SATO H. , INABA T. , KAMIYA H.
Published: October 2002

Several studies have confirmed that epidermal Langerhans' cells (LC) play a central role in the induction of skin-related immunological events. In order to assess the role of LC in Chagas' disease, guinea-pigs were infected intradermally with Trypanosoma cruzi, sacrificed at different time-points, and their tissues were processed for routine histology, electron microscopy and immunohistochemistry. Parasitaemia was observed earliest at day 6 p.i. with 2 peaks at days 9 and 28, and disappeared on day 56 p.i. Parasite-specific serum IgG and IgM were first detected on day 12 p.i. The level of IgG gradually increased by day 84 p.i. All the infected guinea-pigs showed significant alterations in the distribution and morphology of epidermal LC during parasitaemia. The number of LC had significantly decreased in the epidermis by day 3 p.i., only returning to normal levels by day 56 p.i., although the number of LC in the underlying dermis increased concomitantly. Parasites were carried to the regional lymph node, where clustering of parasite-laden dendritic cells (DC) with lymphocytes was seen by electron microscopy. This evidence suggests that LC might be involved in antigen presentation in Chagas' disease.
Amplified fragment length polymorphism (AFLP) protocol for genotyping the malarial parasite Plasmodium falciparum
Authors: RUBIO J. M. , BERZOSA P. J. , BENITO A.
Published: October 2002

We have established an amplified fragment length polymorphism (AFLP) protocol for identifying anonymous polymorphic loci of the malarial parasite, Plasmodium falciparum. The method consists of the following steps (i) digestion and ligation in one reaction; (ii) selective fluorescence forward primers labelled; (iii) PCR products resolved in polyacrylamide gels using the ABIPRISMTM 377 XL DNA sequencer and, (iv) the use of GenescanTM software to size the fragments. This standardized protocol distinguished between 2 standard reference clones of P. falciparum from West African and Southeast Asian and 2 Central African isolates from patients with clinical malaria. The AFLP protocol resulted in evenly distributed and reproducible band patterns for amplified fragments ranking from 163 to 489 bp long ±0·5 S.D. The primer Tru ACA labelled with the phosphoramidite 6-carboxifluorescein (FAM-blue) was easy to interpret, with a maximum of 53 bands per clone and of 81 per isolate (mixed falciparum populations) whereas the primer Tru AG labelled with the hexachlorinated analogue (HEX-green) showed a less clear pattern of bands and reproducibility than Tru ACA.
Echinococcus granulosus: intraspecific genetic variation assessed by a DNA repetitive element
Authors: ROSENZVIT M. C. , CANOVA S. G. , KAMENETZKY L. , GUARNERA E. A.
Published: October 2002

A 186 bp Echinococcus granulosus-specific repetitive element, TREg, was used to assess genetic variation between strains. In G7 genotype (pig strain) it has the characteristics of a satellite DNA element with a copy number of 23000 per haploid genome. Analysis, by sequencing of TREg monomers, showed a great degree of identity within them. In the G1 genotype (common sheep strain) TREg-like repetitive elements were found in an interspersed distribution throughout the genome and in only 120 copies. The sequences of these monomers showed a great degree of variation between them and with TREg of G7 origin. The G6 genotype (camel strain) showed a pattern of distribution and copy number similar to the G7 genotype, and the G2 genotype (Tasmanian sheep strain) similar to the G1 genotype. Isolates from the G5 (cattle strain) and G4 (horse strain) genotypes also showed unique hybridization patterns in Southern blot experiments. The genomic plasticity of E. granulosus, which may have important consequences in the epidemiology and control of cystic hydatid disease is reflected in the results of this work.
Helminths of the sand lizard, Lacerta agilis (Reptilia, Lacertidae), in the Palaearctic: faunal diversity and spatial patterns of variation in the composition and structure of component communities
Authors: SHARPILO V. P. , BISERKOV V. , KOSTADINOVA A. , BEHNKE J. M. , KUZMIN Y. I.
Published: October 2002

We studied variation in the structure of component communities of helminths in sand lizards, Lacerta agilis, from 30 localities in the Ukraine and Bulgaria. Thirty-five separate samples of lizards, with a total of 661 completely censused infracommunities, yielded 30 helminth species (4 cestodes, 10 trematodes, 3 acanthocephalans and 13 nematodes). In its range within the Ukraine, L. agilis serves as the final host for 13 species of which only 3 (S. lacertae, S. hoffmanni and P. molini) can be considered as lizard specialists. A characteristic feature of these helminth component communities was the large proportion of heteroxeneous helminth species for which L. agilis serves as paratenic host. Sand lizards in the meadow steppeland zone were primarily parasitized by larval helminths that represented a major proportion of the total number of all worms recovered while those sampled in the grassland/forest transition zone were characterized by substantially higher proportions of adult helminths using lizards as final hosts. However, L. agilis was parasitized by a much higher proportion of lizard specialists in the ‘typical' habitats of the meadow steppeland zone as opposed to those located in ‘marginal' habitats in the grassland/forest transition zone, where helminths were shared to a greater extent with amphibian hosts.
Testosterone increases the transmission potential of tick-borne parasites
Authors: HUGHES V. L. , RANDOLPH S. E.
Published: October 2002

Using laboratory-bred natural rodent hosts that had been castrated and then implanted with either testosterone or inert oil, we have shown that testosterone causes prolonged and more intense infections of a tick-borne piroplasm, Babesia microti. This will result in more ticks becoming infected while feeding. Sexually active male rodents with high testosterone levels are also known to show increased locomotory activity and reduced innate and acquired resistance to tick feeding, so that more ticks are likely to be picked up and then fed successfully by these hosts. As a result, the transmission potential of B. microti is significantly increased via hosts with high rather than low testosterone levels. It is argued that testosterone helps to generate the observed aggregated distributions of parasites amongst their hosts, which also enhances parasite persistence.
Variation in the helminth community structure in bank voles (Clethrionomys glareolus) from three comparable localities in the Mazury Lake District region of Poland
Authors: BEHNKE J. M. , BARNARD C. J. , BAJER A. , BRAY D. , DINMORE J. , FRAKE K. , OSMOND J. , RACE T. , SINSKI E.
Published: October 2002

We tested the null hypothesis that populations of hosts trapped in isolated neighbouring locations showing comparable habitat quality, should support similar helminth parasite communities. The study was undertaken in a 2-week period in late summer in NE Poland in a single year, thereby eliminating seasonal and between-year variation in parasite burdens. A total of 139 Clethrionomys glareolus (bank vole) were sampled from 3 forest sites of similar habitat quality. Total species richness was 11 (6 nematodes and 5 cestodes) with 85·6% of the voles carrying at least 1 species and an overall mean species richness of 1·4. At the component community level, the fewest species of helminths were recorded from site 2 (n = 6, compared with 9 at each of the other sites), but site 3 had the lowest Berger-Parker Dominance Index and the highest Simpson's Index of Diversity. At the infracommunity level, site 3 had the highest mean no. of helminth species/vole, the highest mean Brillouin's Index of Diversity but the lowest mean no. of helminths/vole. Voles from sites 1 and 3 differed in the nematodes that were most common (site 1, Heligmosomum mixtum – 95%; site 3, Heligmosomoides glareoli – 79·3%). At site 2 no species exceeded 50% but prevalence of Syphacia petrusewiczi was higher than at the other sites. The prevalence of cestodes was too low to test reliably (12·9%), but the highest prevalence of adult cestodes was recorded at site 1 (22·5% compared with 4·9 and 1·7% for sites 2 and 3 respectively). Host sex did not influence infection, but mean species richness increased with age. The different sites were responsible for most of the variation in our data, and the intrinsic factors (sex and age) were less important in shaping the component community structure of helminths. We conclude that even locations in relative close proximity to one another (13–25 km), selected on the basis of similar habitat quality, have rodent populations that differ in their helminth parasite communities, although for reasons other than the factors quantified in the present study.
Identification and characterization of an excretory–secretory product from Giardia lamblia
Authors: KAUR H. , GHOSH S. , SAMRA H. , VINAYAK V. K. , GANGULY N. K.
Published: October 2002

A 58 kDa excretory–secretory product (ESP) of Giardia lamblia has been characterized. The ESP was purified over 508-fold by a combination of ammonium sulphate precipitation and sequential chromatography on affinity matrix and a gel filtration column. The homogeneity of the purified protein was established by sodium dodecyl sulphate polyacrylamide gel electrophoresis (Mr, 58 kDa) and analytical isoelectrophoresis (pI 4·75). The purified protein was recognized by the pooled sera of G. lamblia-positive patients as well as an antiserum raised against crude Giardia extract, thus indicating it to be an immunodominant parasite product. The ESP was found to agglutinate rabbit erythrocytes. The haemagglutinating activity of this protein was inhibited strongly by thyroglobulin, fetuin, asialofetuin and monosialoganglioside but not by simple sugars. The purified protein was characterized immunochemically and was found to be heat stable as well as protease sensitive. Lectin-binding studies of the purified ESP and its sensitivity to periodic-acid silver staining as well as to metaperiodate treatment clearly indicated its glycoprotein nature. The major localization site of the ESP was found to be on the surface of the parasite as revealed by flow cytometric analysis. Further, this glycoprotein induced fluid accumulation in ligated rabbit ileal loops and revealed a positive skin permeability reaction in the rabbit.
The parasite Lernaeocera branchialis on caged cod: infection pattern is caused by differences in host susceptibility
Authors: LYSNE D. A. , SKORPING A.
Published: October 2002

Variation in host susceptibility causes significant differences in infection rates between hosts living in a semi-natural situation. Such knowledge has implications for population dynamics and evolutionary models of host–parasite interactions as well as for estimations of parasite abundance. Infection rates by Lernaeocera branchialis (L.) were measured through time and space on caged Atlantic cod (Gadus morhua L.). One group of hosts, identified by their infection history, developed significantly higher infection rates than the others. These were fish which had been infected previously, but had lost their infection. Differences between groups were consistent through both time and space. Two types of cod seem to have been present in the caged population; a small group of inherently susceptible fish, which were infected, and reinfected if the parasite was lost, and another group of resistant hosts with a small chance of becoming infected.
Survival, feeding and embryo development of Gyrodactylus gasterostei (Monogenea: Gyrodactylidae)
Authors: CABLE J. , TINSLEY R. C. , HARRIS P. D.
Published: October 2002

Viviparous gyrodactylid monogeneans which are detached from their host may form an important source of infection in fish communities. This is particularly significant for these ectoparasites which have no specific free-living stage and where transmission usually occurs through transfer of adult parasites when fish come into close contact. In this study, in vitro survival of Gyrodactylus gasterostei was correlated with changes in tissue ultrastructure of parents and their embryos during detachment and following return to a host. At 10 °C, detached worms survived for up to 89 h (50% survival = 20 h) with mortality influenced by both age-independent and age-dependent factors. The gastrodermis of attached, fed parasites is syncytial and contains a variety of vesicles and feeding vacuoles. However, following detachment and starvation, degenerative changes occur within the gastrodermis, eventually leading to marked damage to the embryo/s. When starved worms reattached to a fish, they began browsing on host epithelial cells within 1 min and ultrastructural evidence for phagocytic activity in the gastrodermis was detected after 5 min. Putative waste vacuoles increased in abundance after 5–30 min on the new host, coinciding with the reappearance of electron-dense vesicles and possibly indicating completion of the first intracellular cycle of digestion. Parental feeding directly influenced the normal cyclical maturation and regression of the uterine lining between births. In extreme cases, starvation led to detached parasites (6·1%) aborting their embryos. However, even short periods off the host influenced development and survival of embryos, suggesting that temporary interruption of nutrient flow to the embryo can significantly affect gyrodactylid reproductive rates.
Mixed strain schistosome infections of snails and the evolution of parasite virulence
Authors: DAVIES C. M. , FAIRBROTHER E. , WEBSTER J. P.
Published: October 2002

Mathematical models often propose that within-host competition between parasites can be a major factor in the evolution of increased parasite virulence. Kin selection predicts that as the coefficient of relatedness between infecting parasites decreases, the benefits of competition to individual genotypes increases. Thus where parasites can adjust their behaviour in response to current conditions, higher virulence is predicted in multiple genotype infections. There is limited experimental data, however, regarding the effects of mixed strain infections on host and parasite fitness. We investigated, for a snail–schistosome system, whether a conditional increase in replication rates occurred in mixed genotype infections and resulted in increased virulence. Four groups of Biomphalaria glabrata snails were exposed to 1 or 2 laboratory strains of Schistosoma mansoni. Mixed genotype infections were observed to be more virulent than single genotype infections, in terms of reductions in host reproductive success and survival. Parasite reproductive rate was also increased in mixed strain groups. Reduced host reproductive success was suggested to be directly due to the genetic heterogeneity of the parasitic infections resulting in increased host defence costs. Reduced host survival was consistent with an adaptive conditional parasite response.
Immune modulation by fish kinetoplastid parasites: a role for nitric oxide
Authors: SAEIJ J. P. J. , VAN MUISWINKEL W. B. , GROENEVELD A. , WIEGERTJES G. F.
Published: October 2002

Trypanoplasma borreli and Trypanosoma carassii are kinetoplastid parasites infecting cyprinid fish. We investigated the role of nitric oxide (NO) in immune modulation during T. borreli and T. carassii infection of carp. Phagocytic cells from different organs produced NO and serum nitrate levels increased, demonstrating that T. borreli activates NO production in vivo. In contrast, T. carassii did not induce NO production in vivo and inhibited LPS-induced NO production in vitro. Production of NO was detrimental to the host as T. borreli-infected carp treated with the inducible NO synthase inhibitor aminoguanidine had a higher survival than infected control carp. This detrimental effect can be explained (in part) by the toxicity of NO to cells in vitro as NO inhibited the proliferative response of blood and spleen leukocytes. Head-kidney phagocytes were resistant to the immunosuppressive effects of NO in vitro. The NO-inducing activity of T. borreli may be an adaptation developed to ensure survival and immune evasion in the fish host. Apparently, T. carassii has adopted another strategy by deactivating specific functions of phagocytes. Both strategies may ensure long-term survival of the parasite.
A previously unclassified trypanosomatid responsible for human cutaneous lesions in Martinique (French West Indies) is the most divergent member of the genus Leishmania ss
Authors: NOYES H. , PRATLONG F. , CHANCE M. , ELLIS J. , LANOTTE G. , DEDET J.-P.
Published: October 2002

Two cases of skin lesions similar to those caused by Leishmania parasites have been reported from Martinique. Parasites isolated from these lesions were unlike Leishmania reference strains by isoenzyme analysis and electron microscopy and were assumed to be monoxenous trypanosomatids which normally only infect invertebrates. Both strains have now been retyped by isoenzyme analysis and found to be identical to each other and distantly related to all other Leishmania species. The sequence of the 18S ribosomal RNA gene and partial sequences of the DNA polymerase alpha and RNA polymerase II largest subunit genes were obtained. These sequences indicated that the Martinique parasites clustered with L. enriettii and were basal to all other euleishmania. However, support for both the position basal to all euleishmania and the clustering with L. enriettii was low. The Martinique parasites may cluster with L.(Leishmania) or L.(Viannia) or form a novel clade within the euleishmania either with or without L. enriettii.
Deep divergence among subgenera of Gyrodactylus inferred from rDNA ITS region
Authors: ZIĘTARA M. S. , HUYSE T. , LUMME J. , VOLCKAERT F. A.
Published: October 2002

This paper adds new insight to a molecular phylogeny of Gyrodactylus, based on a complete sequence of the ITS rDNA region of 4 subgenera and a more detailed molecular analysis. We propose a hierarchical approach in elucidating the phylogeny of this species-rich genus. A total of 37 sequences (915–1239 bp) from 10 representative species from 4 out of 6 subgenera, as defined by Malmberg (1970), are included in the analysis. Genetic differences observed at the 5.8S locus provide objective criteria to separate (sub)genera, while deep genetic differences of the spacers form a sound basis for species-specific identification. We demonstrate that each Gyrodactylus subgenus possesses a unique sequence of the 5.8S gene. Thus, there is concordance between the 5.8S gene and the excretory system used by Malmberg (1970) as a diagnostic character of subgenus status. At the species level, there is a discrepancy between morphological and molecular variation. Whereas the morphological variation, expressed in the shape and size of the attachment apparatus, is very low, the molecular variation, expressed at the ITS1 and ITS2 regions, is very high. This can be attributed either to the fast evolving ITS region or to the fact that the genus consists of groups of a higher taxonomic level than previously recognized. Perspectives and limitations of using the ITS rDNA region for a molecular phylogeny of this genus are discussed.
Characterization of a cytosolic aminopeptidase from Encephalitozoon intestinalis
Authors: MILLERSHIP J. J. , CHAPPELL C. L. , OKHUYSEN P. C. , SNOWDEN K. F.
Published: October 2002

Aminopeptidase activity was detected in Encephalitozoon intestinalis using a fluorometric assay. The aminopeptidase was capable of hydrolysing different amino acids bound to 7-amino-4-trifluoromethyl coumarin, with maximal activity against the amino acid, leucine. Aminopeptidase activity was localized in E. intestinalis spores and in intracellular stages. Enzymatic activity was inhibited by the traditional aminopeptidase inhibitors, bestatin and its analogue, nitrobestatin. Inhibition with the chelating agents, EDTA and 1,10-phenanthroline, suggested that the enzyme activity belongs to the metalloaminopeptidase class. Subcellular fractionation demonstrated that maximal enzyme activity was localized in the cytosolic fraction. Direct fluorogenic substrate analysis by native polyacrylamide gel electrophoresis estimated a molecular weight of 70·8 kDa. Direct fluorogenic analysis by polyacrylamide ampholyte gel electrophoresis indicated an isoelectric point of 4·8. The enzyme was both heat (>37 °C) and cold (<0 °C) labile with an optimal activity at pH 7·2. This is the first report characterizing a cytosolic aminopeptidase in microsporidia.
Mathematical modelling of malaria chemotherapy: combining artesunate and mefloquine
Authors: HOSHEN M. B. , STEIN W. D. , GINSBURG H.
Published: October 2002

Clinical data on the use of artesunate combined with mefloquine in a variety of treatment regimens and parasite loads in Thailand were modelled on the basis of experimentally determined pharmacokinetic data. The model assumed no pharmacodynamic interaction between artesunate and mefloquine, but that the parasites were already resistant to mefloquine. Predictions of the model accorded well with the data. In particular, in accordance with clinical observations, the model showed that monotherapy with either drug failed to cure at moderate parasitaemia, yet such patients could be treated effectively with the combination of 3 days of artesunate + mefloquine. For high levels of parasitaemia, 5 days of artesunate+mefloquine were needed. Simulations were also performed for situations of lower resistance to mefloquine and for the immune human populations found in Africa. The importance of mathematical modelling of combination therapy is borne out by this study and suggests its wider application for other drug combinations.
Does fertilization in the filarial nematode Dirofilaria immitis occur through endocytosis of spermatozoa?
Authors: SACCHI L. , CORONA S. , CASIRAGHI M. , BANDI C.
Published: October 2002

Information on the ultrastructural details of fertilization in filarial nematodes are still unavailable. Here we report new data on this process in Dirofilaria immits, the heartworm of dogs and cats. Electron microscopy allowed us to observe oocytes engulfing spermatozoa through an endocytosis-like process. We also observed spermatozoa inside the oocytes which still possessed their plasma membrane and which were clearly enveloped by a further membrane, likely derived from the endocytosis process. At this stage, at the interface between the sperm membrane and the endocytotic membrane (vacuolar space), we observed flocculent material in the proximity of the membranous organelles (MOs) of the sperm. In the proximity of the MOs, we also observed the enlargement of the vacuolar space. Other images showed the dissolution of the sperm membrane, and the release of nuclear masses and organelles in the egg cytoplasm. We did not observe the fusion of lysosomes to the endocytotic vacuoles. In addition, the lysis of the sperm organelles has never been observed inside the vacuoles containing the whole sperm. Thus we suggest that the degradation of the endocytotic and sperm plasma membranes is determined by material released by the MOs. Since we did not observe the entry of sperm into the oocytes by other mechanisms, we also suggest that endocytosis is the normal process used by the spermatozoon to get into the egg cytoplasm in D. immitis. Finally, during our observations of the seminal receptacle we did not observe any structure in the spermatozoa which could be interpreted as an intracellular bacterium. This is consistent with previous results indicating that the bacterium Wolbachia in filarial nematodes is not transmitted through the sperm.
Complete mitochondrial genomes confirm the distinctiveness of the horse-dog and sheep-dog strains of Echinococcus granulosus
Authors: LE T. H. , PEARSON M. S. , BLAIR D. , DAI N. , ZHANG L. H. , MCMANUS D. P.
Published: October 2002

Unlike other members of the genus, Echinococcus granulosus is known to exhibit considerable levels of variation in biology, physiology and molecular genetics. Indeed, some of the taxa regarded as ‘genotypes’ within E. granulosus might be sufficiently distinct as to merit specific status. Here, complete mitochondrial genomes are presented of 2 genotypes of E. granulosus (G1–sheep-dog strain: G4–horse-dog strain) and of another taeniid cestode, Taenia crassiceps. These genomes are characterized and compared with those of Echinococcus multilocularis and Hymenolepis diminuta. Genomes of all the species are very similar in structure, length and base-composition. Pairwise comparisons of concatenated protein-coding genes indicate that the G1 and G4 genotypes of E. granulosus are almost as distant from each other as each is from a distinct species, E. multilocularis. Sequences for the variable genes atp6 and nad3 were obtained from additional genotypes of E. granulosus, from E. vogeli and E. oligarthrus. Again, pairwise comparisons showed the distinctiveness of the G1 and G4 genotypes. Phylogenetic analyses of concatenated atp6, nad1 (partial) and cox1 (partial) genes from E. multilocularis, E. vogeli, E. oligarthrus, 5 genotypes of E. granulosus, and using T. crassiceps as an outgroup, yielded the same results. We conclude that the sheep-dog and horse-dog strains of E. granulosus should be regarded as distinct at the specific level.
The effect of an experimental infection of the nematode Heterakis gallinarum on hand-reared grey partridges Perdix perdix
Authors: SAGE R. B. , WOODBURN M. I. A. , DAVIS C. , AEBISCHER N. J.
Published: October 2002

We compared 26 hand-reared grey partridges given an experimental infection of the caecal nematode Heterakis gallinarum with 26 uninfected ones. Under laboratory conditions after 91 days, there were no measurable clinical effects of the infection. We found no effect of treatment on the amount of food eaten or on caecal dropping production. However, treated birds, in particular females, developed slightly lower body mass (around 2%) compared to the controls. At post-mortem examination, we found a positive relationship between breast muscle mass and the number of worms collected from the caeca of treated birds. Treated birds with no worms when examined had smaller breast muscle mass (4·6%) compared to the uninfected control birds. These results are largely different to those found in a similar study that documented significant negative impacts on most of these factors in 8 infected birds compared to 6 controls. Its findings were used in a published model to support a hypothesis that H. gallinarum maintained in the environment by common pheasants, the primary host for this worm, could negatively affect wild grey partridge productivity and survival. In the same model our data would not support this hypothesis. Possible explanations for the different results from the 2 experiments are discussed. Together they suggest that only in certain, as yet unidentified circumstances, could experimental H. gallinarum infections have deleterious effects on hand-reared grey partridges.
Characterization and immunolocalization of a main proteinaceous component of the cell wall of the protozoan parasite Perkinsus atlanticus
Authors: MONTES J. F. , DURFORT M. , LLADÓ A. , GARCÍA-VALERO J.
Published: October 2002

Described in the present study is a major component of the cell wall of 2 of the most pathogenic parasites of molluscs, Perkinsus atlanticus and P. marinus. The component is a high molecular weight protein (233 kDa), which we have named PWP-1 (for Perkinsus wall protein-1). Western blots, using a polyclonal serum generated against purified PWP-1 from P. atlanticus, revealed that this protein is expressed by all walled developmental stages of this protozoon. By means of immunogold electron microscopy, labelling for PWP-1 was strong and specifically associated with the cell wall. The label density and distribution pattern was quite different between trophozoites and prezoosporangia. With regard to the structural organization of this protein, PWP-1 is disulphide-linked to other cell wall components and released from the cell wall only following treatment with a sulphydryl agent. We also report that PWP-1 is a trypsin-resistant protein, both in its native and heat-denatured conformation. In addition, results from the N-terminal microsequence of this protein allow us to define PWP-1 as a novel cell wall protein. Overall, our findings strongly suggest that PWP-1 plays a key role in the organization of the cell wall of these protozoa, promoting their survival.
The parasite-induced surfacing behaviour in the cockle Austrovenus stutchburyi: a test of an alternative hypothesis and identification of potential mechanisms
Authors: MOURITSEN K. N.
Published: October 2002

The New Zealand cockle Austrovenus stutchburyi, whose foot is commonly infected by the digenean trematode Curtuteria australis (Echinostomatidae), is often found heavily infected and unable to burrow on the sediment surface of tidal flats. This has been interpreted as a Curtuteria-manipulation with the purpose of increasing the transmission of the parasite to shorebirds acting as final hosts. Using a field-experimental approach the alternative hypothesis was tested, that surface-dwelling cockles, caught on the surface for other reasons than parasites, accumulate larval C. australis at a higher rate than buried cockles. During the 3-month experiment, larval trematodes accumulated with a rate of approximately 0·5 metacercariae/day in both surface and buried cockles. The result strengthens the manipulation hypothesis indirectly by rejecting the alternative hypothesis. The metacercariae were unevenly distributed along the cockle-foot, with about 4 times as many cysts being found in the tip than in either the mid or hind part of the foot. In light of existing knowledge of the burrowing behaviour and apparatus in bivalves, and a negative relationship between foot mobility and infection intensity, it is suggested that C. australis manipulates its host through a mechanical obstruction of foot muscles and the dynamic hydrostatic skeleton, both necessary for successful burrowing.
The role of promastigote secretory gel in the origin and transmission of the infective stage of Leishmania mexicana by the sandfly Lutzomyia longipalpis
Authors: ROGERS M. E. , CHANCE M. L. , BATES P. A.
Published: October 2002

Transmission of leishmaniasis is effected by a specific developmental stage, the metacyclic promastigote. The precursors of metacyclic promastigotes were a distinct subpopulation of parasites, identified for the first time as a new stage in the life-cycle and named leptomonad promastigotes. Microdissection of infected sandflies into 4 midgut regions and foregut allowed precursor-product relationships to be established for amastigote-procyclic promastigote, procyclic-nectomonad promastigote, nectomonad-leptomonad promastigote and leptomonad-metacyclic promastigote developmental switches. Metacyclic promastigotes occurred mainly in the thoracic midgut and cardia, coincident with the accumulation of a promastigote secretory gel (PSG) plug in these anterior regions. The gel-like plug was isolated from flies with mature infections and found to contain predominantly leptomonad promastigotes. The PSG plug also contained the majority (75%) of the total metacyclic promastigote population in the sandflies, which were concentrated at the anterior pole. The PSG plug was found to be the main site of metacyclogenesis, and acted as a reservoir of leptomonad promastigotes from which metacyclic forms differentiated and migrated forward to promote the infective potential of the fly. The PSG plug occluded and distorted the midgut, forcing the stomodeal valve open and affecting the feeding success of the sandflies, such that they experienced difficulty in taking a full meal. Collectively, these data support the role of the PSG in the transmission of leishmaniasis, by conditioning the midgut environment for metacyclogenesis and altering the feeding ability of infected sandflies.