bluuebunny/crossref_metadata_2025 huggingface dataset:
The persistence of Theileria parva infection in cattle immunized using two stocks which differ in their ability to induce a carrier state: analysis using a novel blood spot PCR assay
Authors: SKILTON R. A. , BISHOP R. P. , KATENDE J. M. , MWAURA S. , MORZARIA S. P.
Published: October 2002

An improved Theileria parva DNA detection assay based on the polymerase chain reaction (PCR) using primers derived from the 104 kDa antigen (p104) gene was developed to detect parasite DNA in blood spots on filter paper. The specificity of the assay was validated using DNA from a wide range of cattle-derived and buffalo-derived stocks of T. parva. DNA of T. annulata, T. buffeli, T. lestoquardi, T. mutans and T. taurotragi was not amplified using the p104 primers. The detection threshold of the assay was ∼1–2 parasites/μl of infected blood. PCR amplification using the p104 primers was applied to sequential samples from groups of cattle experimentally infected with either the T. parva Marikebuni stock that induces a long-term carrier state or the Muguga stock, which does not induce a carrier state. The study extended for up to 487 days post-infection and PCR data from defined time points were compared with parasitological microscopy and serological data, together with xenodiagnosis by experimental application of ticks. Microscopy first detected piroplasms between days 13 and 16 after infection whereas all cattle became PCR +ve between days 9 and 13. Animals infected with the Muguga stock of T. parva had parasite DNA in the peripheral blood, which could be detected by PCR, for between 33 and 129 days post-infection in different animals. By contrast parasite DNA in the blood of cattle infected with the Marikebuni stock could be detected consistently from day 9 up to 487 days, when the study terminated. The data suggest that the nature and persistence of the carrier state may differ markedly between different T. parva parasite stocks.
Population dynamics of untreated Plasmodium falciparum malaria within the adult human host during the expansion phase of the infection
Authors: SIMPSON J. A. , AARONS L. , COLLINS W. E. , JEFFERY G. M. , WHITE N. J.
Published: October 2002

A retrospective analysis was performed of parasite count data recorded from the first 7 days of blood or mosquito transmitted Plasmodium falciparum infections given for the treatment of neurosyphilis in the USA before 1963. The objective of this study was to characterize initial growth dynamics before host defences have significant effects on the infecting parasite population. Of the 328 patients' data available for analysis, 83 were excluded because they had received anti-malarial treatment during the first 7 days of the patent infection. Nonlinear mixed effects modelling was performed to estimate the parameters of interest; ‘parasite multiplication rate per 48 h’ (PMR), and length of the parasite life-cycle (periodicity). The parasitaemia versus time profiles showed great variability between patients. The mean population estimate of ‘PMR’ was approximately 8, and was highly dependent on the P. falciparum ‘strain’. PMR also varied significantly between patients with a 90% prediction interval varying from 5·5 to 12·3-fold. Both intrinsic parasite multiplication rate (an intrinsic virulence determinant), and host susceptibility and defence contribute to expansion of the parasite biomass and thus disease severity in falciparum malaria.
Purification of a 64 kDa antigen from Trypanosoma evansi that exhibits cross-reactivity with Trypanosoma vivax
Authors: UZCANGA G. , MENDOZA M. , ASO P. M. , BUBIS J.
Published: October 2002

Trypanosoma evansi and Trypanosoma vivax are the most extensively distributed trypanosomes responsible for diseases in livestock. Western blot and indirect immunofluorescence assays revealed a high immunological cross-reaction between these two parasites. An antigen with an apparent molecular mass of 64 kDa (p64), which exhibited cross-reactivity with T. vivax, was purified to homogeneity from a Venezuelan isolate of T. evansi. This antigen is glycosylated, contains a glycosyl-phosphatidylinositol anchor and appeared to be localized through the cell except in the nucleus, indicating that it could primarily be confined to the parasite surface. These results, together with its relative abundance and apparent molecular weight, suggest that p64 probably corresponds to the soluble form of a variable surface glycoprotein from T. evansi. Anti-p64 polyclonal antibodies, raised on mice, recognized a 53 kDa polypeptide band from a Venezuelan isolate of T. vivax on Western blots. Additionally, sera obtained from naturally infected animals also recognized p64, suggesting its potential use as a diagnostic reagent. Mild acid treatment only slightly decreased the immunorecognition of p64, suggesting its potential use as a diagnostic reagent. Mild acid treatment only slightly decreased the immunorecognition of p64, demonstrating that another relevant cross-reacting epitope, different than the inositol-1,2-cyclic phosphate of the cross-reacting determinant, must exist in p64. To date, p64 represents the first antigen isolated and partially characterized from T. evansi.
Antibodies induced in mice by a DNA-construct coding for the elastase of Schistosoma mansoni recognize the enzyme in secretions and preacetabular glands of cercariae
Authors: BAHGAT M. , CHLICHLIA K. , SCHIRRMACHER V. , RUPPEL A.
Published: October 2002

A DNA-construct coding for the elastase of the parasite Schistosoma mansoni was prepared from adult S. mansoni worm RNA which was reverse transcribed into cDNA. The gene coding for the elastase was amplified using primers specific for the sequence of cercarial elastase and was cloned into a mammalian expression vector. Expression of the elastase gene at the transcriptional level was achieved for the first time in transfected mammalian cells (COS-7) and was also successful in muscle tissue of mice injected with the DNA-construct. These mice developed antibodies recognizing in Western blots the elastase from cercarial secretions. Also, these antibodies reacted in immunofluorescence tests with the preacetabular glands of cercariae, i.e. the site of origin for elastase. Thus, the DNA-construct induced the expression of elastase in mice and formation of antibodies that recognized the native antigen.
Comparison of European Trichobilharzia species based on ITS1 and ITS2 sequences
Authors: DVOŘÁK J. , VAŇÁČOVÁ š. , HAMPL V. , FLEGR J. , HORÁK P.
Published: October 2002

Schistosomes are parasites of considerable medical and veterinary importance and, therefore, all aspects of their biology have been intensively studied. In contrast, our knowledge of species of the largest genus, Trichobilharzia, is insufficient. Because morphological characterization of Trichobilharzia species provides a limited number of criteria for species determination, molecular data are required. In the present paper, we sequenced internal transcribed spacers ITS1 and ITS2, and 5·8S ribosomal RNA (rRNA) genes of 3 European Trichobilharzia species (T. regenti, T. szidati and T. franki). We showed that ITS1 and ITS2 sequences can be used in species identification. Repetitive elements were found in ITS1 of all 3 Trichobilharzia species; their number and length varied depending on the species. Phylogenetic analysis showed that the visceral T. franki is more related to the nasal T. regenti, than to the visceral T. szidati. The newly designed primer, which is specific for T. regenti, might be used as a tool for diagnosis of this potential pathogen.
To avoid or eliminate: cestode infections in copepods
Authors: VAN DER VEEN I. T. , KURTZ J.
Published: October 2002

The outcome of a parasite infection is the result of the interaction between the host and the parasite. In the system we studied, there are 3 critical stages for the outcome of infection of the (intermediate) host, the copepod Macrocyclops albidus, with the cestode Schistocephalus solidus. During the establishment phase of the parasite, the host may firstly avoid ingesting the parasite and, secondly, may prevent the parasite from entering the body cavity and, thirdly, during the growth phase of the parasite, the host's immune system may eliminate the parasite from the body cavity. We were able to study the growth phase separately from the establishment phase. The establishment phase was influenced by characteristics of the host as well as characteristics of the parasites. Small copepods and males performed poorly; they were more often infected and had a lower survival. Parasites from different sib-groups differed in infectivity. During the growth phase some disappearance of parasites was observed. However, this could not be related to any of the studied characteristics of the host, and the sib-groups of parasites did not seem to differ in their likelihood to disappear. Instead, we suggest that disappearance of parasites, once they have entered the body cavity, may be due to intrinsic mortality of the parasites, independent of the host or the sib-group that the parasites belong to. This indicates that the crucial interactions between host and parasite determining the outcome of infection takes place in the short time-period between ingestion and penetration of the gut-wall.
Migration, site-specificity and development of Benedenia lutjani (Monogenea: Capsalidae) on the surface of its host, Lutjanus carponotatus (Pisces: Lutjanidae)
Authors: WHITTINGTON I. D. , ERNST I.
Published: October 2002

Life-history attributes of the capsalid monogenean Benedenia lutjani, a parasite of Lutjanus carponotatus from the Great Barrier Reef, Queensland, Australia, were investigated from experimental infections. Oncomiracidia of B. lutjani invaded and attached at any site on the fish, but more commonly invaded body surfaces. Immature specimens then migrated to the pelvic fins. Development of the reproductive organs of B. lutjani corresponded with migratory movements on the host. Parasite aggregation on the pelvic fins coincided with the development of functional male reproductive organs and some protandrous worms that possessed a vagina appeared to be inseminated. Migration to, and aggregation on, the branchiostegal membranes (membranous folds posterior to the opercula) coincided with the onset of sexual maturity and commencement of egg production by parasites. The rate of parasite development and the timing of migratory events on the host were influenced by water temperature. All specimens of B. lutjani reached sexual maturity between 12 and 14 days p.i. at 24 °C and between 8 and 10 days p.i. at 27 °C. Anterior hamuli grew continually during a 16-day experiment at 27 °C and 25-day experiment at 23 °C and their length appeared to provide a suitable index to estimate parasite age. The possible adaptive significance of the migratory behaviour, site-specificity and its link with changes in parasite development are discussed.
The osmotic relationship of the swimbladder nematode Anguillicola crassus with seawater eels
Authors: KIRK R. S. , MORRITT D. , LEWIS J. W. , KENNEDY C. R.
Published: October 2002

The study was designed to test the hypothesis that the majority of individuals in a population of Anguillicola crassus can tolerate seawater by osmoconformation with the blood plasma of the eel host. The osmolality of the pseudocoelomic fluid of pre-adult and adult A. crassus was compared to the osmolality of eel plasma after eels were maintained in laboratory freshwater for 2 weeks (short-term transfer) or 3 months (long-term transfer) or in natural seawater for 2 h (acute transfer), 2 weeks or 3 months. The majority of A. crassus (at least 90% of the tested population) osmoconform with their hosts in seawater within ±30 mOsm/kg of host osmolality. Some pre-adults and adults (15–21% of the total population) were unable to withstand osmotic stress resulting in vacuolation of the hypodermis and intestinal wall, and cuticular detachment. The reasons for variation in the tissue tolerance of A. crassus to increased osmolality of host plasma are unknown and are not related to maturity, sex or conditions in the swimbladder. Osmoconformation in the majority of the population, however, enables parasites to survive and reproduce for long periods in seawater eels. The adaptation of A. crassus to its euryhaline host has played an important part in the rapid spread of the swimbladder nematode in populations of the European eel.
Small subunit ribosomal DNA phylogeny of microsporidia that infect Daphnia (Crustacea: Cladocera)
Authors: REFARDT D. , CANNING E. U. , MATHIS A. , CHENEY S. A. , LAFRANCHI-TRISTEM N. J. , EBERT D.
Published: October 2002

Glugoides intestinalis, Microsporidium sp., Ordospora colligata, Gurleya vavrai, Larssonia obtusa and Flabelliforma magnivora are microsporidian parasites of planctonic freshwater crustaceans Daphnia spp. We performed a phylogenetic analysis of the small subunit ribosomal DNA which revealed their positions as polyphyletic. G. intestinalis, Microsporidium sp. and O. colligata, which are horizontally transmitted gut parasites with small spores and low virulence, group with different lineages. G. intestinalis is related to 2 microsporidia infecting lepidopterans and to Vittaforma corneae, which has been described as a human pathogen. It is thought that V. corneae may have an invertebrate as its natural host. Microsporidium sp. is a relative of the genera Enterocytozoon and Nucleospora, pathogens of man and fish respectively. O. colligata is the first species found to be closely related to the genus Encephalitozoon, which is comprised of 3 species that are parasites of homeothermic vertebrates. G. vavrai and L. obtusa are sister taxa that branch close to the Amblyosporidae, the only microsporidia with known intermediate hosts. This finding supports the presumption of secondary hosts for G. vavrai and L. obtusa, as it has not been possible to maintain these species in Daphnia in the laboratory. F. magnivora roots deep at the base of the phylum microsporidia with no close relative found so far.
Detection of eight Cryptosporidium genotypes in surface and waste waters in Europe
Authors: WARD P. I. , DEPLAZES P. , REGLI W. , RINDER H. , MATHIS A.
Published: October 2002

Cryptosporidia are important protozoan parasites of vertebrates, and a number of species and genotypes, with different host ranges, have been described. In this study a protocol was established for the detection and the genetic characterization of Cryptosporidium spp. isolated from various types of surface waters (rivers, creeks, lakes, sewage plant in- and outlets and swimming pools) from the area between Zurich (Switzerland) and Munich (Germany). Cryptosporidium oocysts were isolated by continuous-flow-centrifugation and immunomagnetic separation (IMS). A novel nested PCR combined with direct sequencing of the amplicon which spans a variable region of the 18S rRNA allowed characterization of species and genotypes. Cryptosporidium spp. were detected in 23 of the 68 water samples investigated. Almost half of these isolates represent species and genotypes known to be pathogenic to man, namely C. parvum ‘bovine genotype’ (from 6 samples) and C. parvum ‘human genotype’ (4). Furthermore, we identified C. muris ‘genotype A’ (3), C. muris ‘genotype B’ (6), C. baileyi (1) as well as 3 novel Cryptosporidium genotypes. Our results confirm the ubiquitous presence of Cryptosporidium oocysts in surface waters. The detection of a variety of species and genotypes stresses the importance that molecular characterization is indispensable before drawing conclusions of medical or epidemiological significance.
Mesocestoides corti (syn. M. vogae): modulation of larval motility by neuropeptides, serotonin and acetylcholine
Authors: HRČKOVA G. , VELENBNÝ S. , HALTON D. W. , MAULE A. G.
Published: October 2002

The effect of platyhelminth FaRPs and selected classical neurotransmitters on the motility of intact Mesocestoides corti (syn. M. vogae) tetrathyridial larvae was studied in vitro using a micromotility meter. The effects of the test substances were temperature dependent and these were examined at 4, 23, 30 and 36 °C. At 36 °C all test substances had concentration-dependent excitatory effects, with thresholds for activity of: 100 nM (GNFFRFamide), 10 μM (YIRFamide), 30 μM (GYIRFamide), 100 nM (serotonin) and 100 μM (acetylcholine). At this temperature significant elevation of motility indices (MI) was recorded within 5 min of the addition of peptide or serotonin. The effect of acetylcholine was slower in onset and appeared 15–20 min post-addition. At 30 °C larval motility diminished more rapidly than that recorded at 36 °C, following the addition of 1 mM of each test substance. At 23 °C only serotonin (1 mM) significantly increased the MI, all other test substances having no apparent effect. Larval movement was completely arrested at 4 °C. The results demonstrate for the first time excitatory effects of platyhelminth neuropeptides and acetylcholine on muscle systems in cestode larvae. The fact that the only known cestode FaRP, GNFFRFamide, was more potent than any of the turbellarian FaRPs tested, suggests structural conservation of FaRPs and FaRP receptors within the cestodes.
Comparison of the macroparasite communities of wild and stocked brown trout (Salmo trutta L.) in the west of Ireland
Authors: BYRNE C. J. , HOLLAND C. V. , POOLE R. , KENNEDY C. R.
Published: October 2002

The aim of the present study was to compare the helminth infra and component communities of wild and stocked brown trout in Lough Feeagh, in the west of Ireland, and also to examine the establishment and development of helminth communities in stocked brown trout. Fish were sampled in May, August and November 1997 and 1998 and an additional sample of wild brown trout was examined in April 1997. In total 217 wild trout and 122 stocked trout were examined. The acanthocephalans Acanthocephalus clavula and Pomphorhynchus laevis were the first parasite species to infect stocked trout in May 1997. In May 1998 both acanthocephalan species along with the trout specialists Eubothrium crassum and Crepidostomum farionis were the first to infect trout. Mean species richness values for stocked trout increased from May to November, in 1997 and 1998. For wild trout, mean species richness values increased from April to November, in 1997 and decreased from May to November in 1998. The parasite communities of wild trout were richer than those of stocked trout in May of both years. In August the parasite communities recorded for wild and stocked trout were similar in terms of the number of species present but differed in terms of structure, and in November the parasite communities of stocked trout were richer than those of wild trout.
A model to explain the replacement of Schistosoma intercalatum by Schistosoma haematobium and the hybrid S. intercalatum×S. haematobium in areas of sympatry
Authors: MORAND S. , SOUTHGATE V. R. , JOURDANE J.
Published: October 2002

Numerous hypotheses have been postulated to explain the rapidly changing parasitological situation in Loum, Cameroon as a result of the interaction between Schistosoma haematobium and S. intercalatum. The aim of this study is to test the various hypotheses using a simple mathematical model, incorporating equal and unequal sex ratios of adult schistosomes, recombinations, and levels of compatibility with the intermediate molluscan hosts, B. forskalii and B. truncatus. The model assuming an equal sex ratio does not fit with the existing field data in that it predicts a continued presence of S. intercalatum, S. haematobium and the hybrids. The model assuming a sex bias in favour of males, which reflects the situation usually observed in schistosome populations, predicts the loss S. intercalatum which indeed concurs with the most recent data.
Description of Enteromyxum scophthalmi gen. nov., sp. nov. (Myxozoa), an intestinal parasite of turbot (Scophthalmus maximus L.) using morphological and ribosomal RNA sequence data
Authors: PALENZUELA O. , REDONDO M. J. , ÁLVAREZ-PELLITERO P.
Published: October 2002

A new Myxozoa species causing enteritis and death in cultured turbot, Scophthalmus maximus, is described at light and electron microscope levels. In addition, small subunit ribosomal RNA gene sequences (SSU rDNA) from the new species and from similar myxozoans were obtained and used for phylogenetic inference, as complementary criteria to resolve its taxonomic classification. The new parasite is closely related to Myxidium leei, another enteric histozoic species from marine fish. However, the ascription of M. leei to the genus Myxidium was based on weak morphological evidence and is not supported by our rDNA data analysis. A close relationship with Zschokkella, the other morphologically related myxozoan genus is also not supported. The combined morphological and molecular study results in the establishment of the new genus Enteromyxum to accommodate the new species E. scophthalmi, and the former M. leei, which is transferred to the new genus as Enteromyxum leei (Diamant, Lom & Dyková 1994) n. comb. This genus of marine, histozoic and enteric myxozoans includes significant parasite species for marine finfish culture.
Proteins and proteinases in the in vitro released products (IVRP) of the tissue-invasive and lung-dwelling larvae of the pentastomid Porocephalus crotali
Authors: BUCKLE A. C. , KNOX D. P. , RILEY J.
Published: October 2002

Pentastomids are arthropod-like parasites which inhabit the respiratory tract of tetrapods and, despite being haematophagous, cause little or no visible pathology. Nymphs (or larvae), belonging to the advanced genus Porocephalus, encyst in the tissues of rodent intermediate hosts and migrate from this site to the lung following ingestion of the intermediate host. During migration, several moults occur and instars encounter a variety of tissue barriers and environmental cues. It was therefore relevant to define the proteins and proteinases released by the different instars during this migration as they are likely to be essential for tissue penetration, feeding and immune evasion. In vitro released proteins (IVRP), commonly termed ES, were defined on the basis of molecular size and immune recognition by naturally infected rodent intermediate hosts. In addition, proteinases present in IVRP were characterized using gelatin-substrate gels and protein degradation assays. These studies showed that the protein profile is subtly different when IVRP from different instars is compared. In addition, IVRP from each instar contained metallo-proteinases with proteolysis at 48 kDa dominating in all stages. However, other higher molecular weight activities were, to an extent, released in a stage-specific manner. These proteinases degraded haemoglobin and fibrinogen as well as structural proteins such as collagen and fibronectin, suggesting roles in bloodmeal digestion and tissue penetration. Immunoglobulin digestion was not demonstrated.
The health state of the eel swimbladder as a measure of parasite pressure by Anguillicola crassus
Authors: LEFEBVRE F. , CONTOURNET P. , CRIVELLI A. J.
Published: October 2002

We have developed an index based on macroscopic criteria to easily assess the health state of the eel swimbladder as a result of infection by the nematode Anguillicola crassus. In the sampling area (brackish lagoons of the French Mediterranean coast), 92% of the host sample (1251 eels covering all size classes) showed pathological signs of infection. The general trend was for increasing damage as eel size increased, thus suggesting accumulation of pathological effects. We also revealed a non-linear relationship between the swimbladder index and the abundance of living worms. In particular, we showed that severely damaged swimbladders harboured very few living nematodes. We argue that the swimbladder degenerative index more closely reflects the parasite pressure than does classic parasite count. We found seasonal variation in the swimbladder index, with maximum damage occurring in July and thereafter a trend for healthy individuals. We discuss the possibility that the seasonal decrease in the swimbladder index could reflect the death of the more severely affected individuals during the warmest months.
Dietary pectin, but not cellulose, influences Heligmosomoides polygyrus (Nematoda) reproduction and intestinal morphology in the mouse
Authors: SUN Y. , KOSKI K. G. , WYKES L. J. , SCOTT M. E.
Published: October 2002

Dietary texture has been reported to influence parasite establishment and survival, but to what degree this relationship is modified by either the type or quantity of dietary fibre is unknown. Using a 2×4 factorial design, we explored the relationship between fibre type (soluble = pectin vs insoluble = cellulose) and fibre quantity (0, 5, 10 and 20% by dry weight) on parasitic outcomes in BALB/c mice infected with 100 Heligmosomoides polygyrus (Nematoda) larvae. Pectin, but not cellulose, exerted a significant effect on parasite egg production. Following in vitro culture of female worms, increasing levels of dietary pectin were associated with increasing release of eggs. Yet this pattern was not observed in vivo, where per capita egg production peaked at the 10% pectin concentration, but was very low in mice fed 20% pectin. Parasite establishment was elevated in mice fed 20% pectin, but was unaffected by cellulose concentration. Neither type nor quantity of fibre affected H. polygyrus survival or spatial distribution along the gastrointestinal tract. To what degree differences in parasite establishment and reproduction could be attributed to the marked effects of pectin on gut morphology (increased intestinal length, villus length, mucosa thickness and villus/crypt ratio) requires further exploration. Our data indicate that cellulose is preferable to pectin as the source of fibre for experimental diets as cellulose did not affect H. polygyrus establishment, reproduction or survival during a 4-week primary infection.
Receptor–ligand interactions and cellular signalling at the host–parasite interface
Authors: YOSHINO T. P. , BOYLE J. P. , HUMPHRIES J. E.
Published: October 2002

Although the effects of trematode infection on snail host physiology or host responses on parasite development have been well described in the literature, very little is known regarding the underlying mechanisms and specific molecules responsible for mediating those effects. It is presumed that many host–parasite interactions are communicated through receptor-mediated events, in particular those involving haemocytic immune responses to invading parasites, larval motility and migration through host tissues, and larval acquisition of host molecules either as nutrients or critical developmental factors. The intent of this chapter is to review current knowledge of molecules (both receptors and their ligands or counter-receptors) involved in molecular communication at the interface between larval trematodes, especially the mother or primary sporocyst stage, and host cells/tissues in intimate proximity to developing larvae. Information to date suggests that the molecular exchange at this interface is a highly complex and dynamic process, and appears to be regulated in specific cases. Topics discussed will focus on snail cell receptor interactions with the sporocyst tegument and its secretions, host cell–cell and cell–substrate adhesion receptors and their related signal transduction pathways, and sporocyst tegumental surface receptors and ligands involved in the binding of soluble host molecules.
A perspective on the ecology of trematode communities in snails
Authors: ESCH G. W. , CURTIS L. A. , BARGER M. A.
Published: October 2002

This paper presents a perspective on the ecology of trematodes in snail hosts based on recent evidence. Because flukes use snails almost obligatorily as first intermediate hosts, we highlight the role of gastropods as keystone species for trematodes and their communities. After reviewing recent developments in the transmission of trematodes to and from snails, we discuss trematode communities within individual snails (infracommunities) and in snail populations (component communities). Results garnered using various protocols at the infracommunity level are reviewed. The few data available, all from marine systems, indicate that low colonization rates characterize infracommunities, suggesting that trematode infracommunities tend to be isolationist in character rather than interactive. The variety of trematode species present in a component community seems to be determined by spatial overlap of definitive hosts. Relative abundance of species in a component community shows little dependence on negative interspecific interactions at the level of the infracommunity. Temporal aspects of trematode communities are related to the life history of the host snail. The component communities of long-lived snails (mostly marine) integrate many infection episodes whereas shorter-lived snails (mostly freshwater) acquire new component communities each time host cohorts turnover.
Schistosoma mansoni and Biomphalaria: past history and future trends
Authors: MORGAN J. A. T. , DEJONG R. J. , SNYDER S. D. , MKOJI G. M. , LOKER E. S.
Published: October 2002

Schistosoma mansoni is one of the most abundant infectious agents of humankind. Its widespread distribution is permitted by the broad geographic range of susceptible species of the freshwater snail genus Biomphalaria that serve as obligatory hosts for its larval stages. Molecular phylogenetic studies suggest that Schistosoma originated in Asia, and that a pulmonate-transmitted progenitor colonized Africa and gave rise to both terminal-spined and lateral-spined egg species groups, the latter containing S. mansoni. Schistosoma mansoni likely appeared only after the trans-Atlantic dispersal of Biomphalaria from the Neotropics to Africa, an event that, based on the present African fossil record, occurred only 2–5 million years ago. This parasite became abundant in tropical Africa and then entered the New World with the slave trade. It prospered in the Neotropics because a remarkably susceptible and productive host, B. glabrata, was widely distributed there. Indeed, a snail similar to B. glabrata may have given rise to the African species of Biomphalaria. Schistosoma mansoni has since spread into other Neotropical Biomphalaria species and mammalian hosts. The distribution of S. mansoni is in a state of flux. In Egypt, S. mansoni has nearly completely replaced S. haematobium in the Nile Delta, and has spread to other regions of the country. A susceptible host snail, B. straminea, has been introduced into Asia and there is evidence of S. mansoni transmission in Nepal. Dam and barrage construction has lead to an epidemic of S. mansoni in Senegal, and the parasite continues its spread in Brazil. Because of competition with introduced aquatic species and environmental changes, B. glabrata and consequently S. mansoni have become less abundant on the Caribbean islands. Control of S. mansoni using praziquantel and oxamniquine has reduced global prevalence but control is difficult to sustain, and S. mansoni can develop tolerance/resistance to praziquantel, raising concerns about its future efficacy. Because of legitimate environmental concerns, snail control is unlikely to be an option in future control efforts. Global warming will impact the distribution of Biomphalaria and S. mansoni, but the magnitude and nature of the effects are poorly understood.
Genetic structure in natural populations of flukes and snails: a practical approach and review
Authors: JARNE P. , THÉRON A.
Published: October 2002

Several aspects of the coevolutionary dynamics in host-parasite systems may be better quantified based on analyses of population structure using neutral genetic markers. This includes, for example, the migration rates of hosts and parasites. In this respect, the current situation, especially in fluke-snail systems is unsatisfactory, since basic population genetics data are lacking and the appropriate methodology has rarely been used. After reviewing the forces acting on population structure (e.g. genetic drift or the mating system) and how they can be analysed in models of structured populations, we propose a simplified, indicative framework for conducting analyses of population structure in hosts and parasites. This includes consideration of markers, sampling, data analysis, comparison of structure in hosts and parasites and use of external data (e.g. from population dynamics). We then focus on flukes and snails, highlighting important biological traits with regard to population structure. The few available studies indicate that asexual amplification of flukes within snails strongly influences adult flukes populations. They also show that the genetic structure among populations in strongly affected by traits in other than snails (e.g. definitive host dispersal behaviour), as snails populations have limited migration. Finally more studies would allow us to deepen our current understanding of selective interference between flukes and snails (e.g. manipulation of host mating system by parasites), and evaluate how this affect population structure at neutral markers.
The relationship between Schistosoma mansoni and Biomphalaria glabrata: genetic and molecular approaches
Authors: LEWIS F. A. , PATTERSON C. N. , KNIGHT M. , RICHARDS C. S.
Published: October 2002

Biomphalaria glabrata is a major intermediate host for the helminth parasite Schistosoma mansoni. Beginning in the mid-20th century, studies were carried out with this snail species to identify the immunological and genetic components that might be involved in controlling schistosome development. A number of genetically well-defined snail stocks were derived as a direct result of these studies and have since played major roles in helping investigators to identify important cellular and humoral components in the snail/schistosome relationship. This review will explore the historical development of these stocks and describe some of the major advances in several areas of medical malacology that have been made possible by their use.
Snail–trematode life history interactions: past trends and future directions
Authors: SORENSEN R. E. , MINCHELLA D. J.
Published: October 2002

Life history traits expressed by organisms vary due to ecological and evolutionary constraints imposed by their current environmental conditions and genetic heritage. Trematodes often alter the life history of their host snails by inducing parasitic castration. Our understanding of the variables that influence the resulting changes in host growth, fecundity and survivorship is insufficient to confidently predict specific outcomes of novel snail–trematode combinations. In a literature review of the last 30 years, we found 41 publications examining various life history characteristics of trematode-infected snails. These publications reported 113 different field and laboratory experiments involving 30 snail species and 39 trematode species and provided a data set for assessing factors that potentially affect life history outcomes. Analysis of the diverse responses across various snail–trematode systems and experimental conditions teased out general patterns for the expression of host growth, fecundity and survival. These were used to address existing hypotheses and develop several new ones relating the response of snail-trematode interactions to environmental and genetic factors. Finally, we propose directions for future experiments that will better assess the ecological and evolutionary factors influencing snail life history responses to trematode parasitism.
The relationship between parasitological status and humoral responses to Loa loa antigens in the Mandrillus sphinx model after immunization with irradiated L3 and infection with normal L3
Authors: AKUE J. P. , DUBREUIL G. , MOUKANA H.
Published: October 2002

In order to identify antigens associated with protection and those associated with active infection, the humoral immune response of 6 Mandrillus sphinx immunized with 150 irradiated L3 and challenged with 100 normal L3 of Loa loa or 6 animals infected with 100 L3 were compared. The plasma of these animals was analysed by Western blot using adult, Mf and L3 antigens. Several antigens with molecular weights varying from 120 kDa to 13 kDa were recognized by the plasma of all animals. It was shown that early recognition of microfilarial antigens with molecular weights of 97, 68, 45 and 33 kDa correlated with the amicrofilaraemic state. A total of 83% of animals with circulating microfilariae had antibodies against the microfilariae 21 kDa antigen. Furthermore, the antibodies against the 21 kDa appeared 1 month before detection of microfilariae in the peripheral blood of 80% of these animals, and declined when animals became amicrofilaraemic. In contrast, when L3 antigen was used, a molecule with a relative molecular weight of 20 kDa was recognized by antibodies of the only animal which remained amicrofilaraemic for 1 year after immunization with irradiated L3. These results suggest that the microfilarial molecule of 21 kDa may be useful as a marker of Loa loa patent infection, whereas the 97, 68, 45 and 33 kDa molecules of microfilariae and the L3 molecule of 20 kDa may be associated with resistance against Loa loa.
Acquired immunity to Trichuris suis infection in pigs
Authors: PEDERSEN S. , SAEED I.
Published: October 2002

Strong resistance to reinfection developed in pigs as a result of trickle inoculations with Trichuris suis (250 infective eggs twice weekly for 4 weeks). At challenge (4000 eggs) 8 weeks after the last trickle inoculation, we observed a 96% reduction in the mean number of established challenge worms in immunized (TRI/CHA) compared with non-immunized controls (CON/CHA) (74 v. 1753; P = 0·004). Moreover, the total faecal egg excretion was significantly lower in immunized pigs compared with controls (P = 0·0003). The trickle inoculations depressed pig weight gains over the 8-week course of immunization (P = 0·042). It was observed that a small number of pigs developed a weaker level of resistance, reflecting the importance of genetic determinants. The relevance of these data to the population biology of porcine and human whipworm infections is discussed.
Isolation and characterization of the Golgi complex of the protozoan Trypanosoma cruzi
Authors: MORGADO-DÍAZ J. A. , NAKAMURA C. V. , AGRELLOS O. A. , DIAS W. B. , PREVIATO J. O. , MENDONÇA-PREVIATO L. , DE SOUZA W.
Published: October 2002

In this study the Golgi complex of the epimastigote forms of Trypanosoma cruzi were isolated and characterized. Using well-controlled sonication to rupture the cells and centrifugation on a discontinuous sucrose density gradient, a highly enriched Golgi fraction was obtained. The Golgi fraction contained most of the β-galactosyltransferase (β-Gal transferase) and UDP-N-acetyl-glucosamine: polypeptide-α-N-acetyl-glucosaminyltransferase (O-α-GlcNAc transferase) activities with minimal contamination of other organelles, as observed by enzymatic assays and electron microscopy analysis. To characterize the Golgi from T. cruzi cells further, it was incubated with a monoclonal antibody against a 58 kDa protein involved in the association of the Golgi complex with microtubules in mammalian cells. Immunofluorescence microscopy showed that the 58 kDa protein is localized in the T. cruzi Golgi region, a result confirmed by high resolution scanning electron microscopy immunocytochemistry. Thus, our results show, for the first time, that the β-Gal transferase, the O-α-GlcNAc transferase and the 58 kDa protein are present in the Golgi complex of T. cruzi and are novel biochemical markers which can be used in the characterization of this organelle in T. cruzi.
Different response of satellite cells in the kinetics of myogenic regulatory factors and ultrastructural pathology after Trichinella spiralis and T. pseudospiralis infection
Authors: WU Z. , MATSUO A. , NAKADA T. , NAGANO I. , TAKAHASHI Y.
Published: October 2002

Infection of an intracellular parasitic nematode, Trichinella spiralis, resulted in severe damage in muscle cells which was followed by activation and proliferation of satellite cells. The repairing process, shortly after the damage, histopathologically resembled those seen after mechanical injury. Resemblance was also true for kinetics of expression of myogenic regulatory factors (MyoD, myogenin and MRF4). The difference resided in the next step where the muscle cell infected with T. spiralis transformed to a unique cell which is parasitologically known as the nurse cell, and the proliferated satellite cells did not differentiate to the muscle cell but to the nurse cell (misdifferentiation). Thus the nurse cell was a fusion of the transformed infected muscle cell and misdifferentiated satellite cells. Infection with another species of Trichinella, T. pseudospiralis, also caused cell damage, but more extensively involving the entire length of the infected muscle cells because no septum was formed to minimize the affected area. Therefore, a large number of satellite cells were activated and proliferated. The myogenic regulatory factors such as MyoD and myogenin were activated for a longer period than in the case with T. spiralis infection. The infected muscle cell transformed to the nurse cell, whose cytoplasm was characterized by extensive smooth endoplasmic reticulum. Satellite cells misdifferentiated to the nurse cell, whose cytoplasm was amorphous, void of distinct cell organelles. The two kinds of cytoplasm did not fuse as examined thus far. Thus infection with T. spiralis and T. pseudospiralis caused misdifferentiation of satellite cells, but in a different way.
Histone-like proteins from fish are lethal to the parasitic dinoflagellate Amyloodinium ocellatum
Authors: NOGA E. J. , FAN Z. , SILPHADUANG U.
Published: October 2002

Antimicrobial proteins were purified from acid extracts of rainbow trout (Oncorhynchus mykiss) and sunshine bass (Morone saxatilis male×M. chrysops female) skin, gill and spleen by reverse-phase HPLC. Mass spectrometry and amino acid sequence data suggest that these proteins are closely related to histone H2B and histone H1 and thus they were designated histone-like proteins (HLPs). These proteins were lethal to Amyloodinium ocellatum, which is one of the most important parasitic agents affecting fish. Antibiotic concentrations as low as 12·5 μg/ml were inhibitory. Activity was directed against the trophont (feeding) stage of the parasite, while the disseminative (dinospore) stage was unaffected. Thus, HLPs act unlike typical drugs used to treat amyloodiniosis, which usually target the dinospore. Both the ability of the parasite to infect host cells, as well as the ability to grow and differentiate after infection were severely inhibited. This is in contrast to magainin 2, which was similarly toxic to both the dinospore and trophont stages. These findings provide further evidence that histone-like proteins may be important defensive molecules in fish.
Effect of benzimidazole under-dosing on the resistant allele frequency in Teladorsagia circumcincta (Nematoda)
Authors: SILVESTRE A. , CABARET J. , HUMBERT J.-F.
Published: October 2002

This experiment was designed to determine the effects of under-dosing on the frequency of benzimidazole resistant allele in the nematode Teladorsagia circumcincta. Fenbendazole (FBZ) was tested at 1/32, 1/16, 1/8 and 1/4 of the recommended dose for sheep (5 mg/kg body weight). The fraction of the susceptible homozygote (SS), susceptible heterozygote (RS) and resistant homozygote (RR) genotypes were compared among FBZ dose groups to evaluate differences between SS and RS genotype selective advantage. Almost all SS genotype worms were eliminated by 1/4 of the FBZ recommended dose, whereas a significant fraction of the RS genotype worms survived treatment. The selective advantage was 4·5 times higher for the RS genotype. This selective advantage was determined at 1/4 of the manufacturer's recommended dose of FBZ. This value should be taken as an indictor of the selective advantage of RS over the SS genotype when lambs are under-dosed. A computer simulation was used to study the putative spread of anthelmintic resistance over a range of RS selective advantages (2, 4·5 and 10-fold), with two average sizes of individual host worm population (20 or 2000 worms/host) and two initial R allele frequencies (0·1% or 1%). In all situations, the lowest selective advantage of the RS genotype over the SS genotype was sufficient to promote the spread of resistance in susceptible populations. When the RS genotype had no selective advantage over the SS genotype, genetic drift almost always led to the loss of the R allele, except in the largest populations (average size = 2000 worms).
Molecular cloning and characterization of a serine proteinase inhibitor from Trichinella spiralis
Authors: NAGANO I. , WU Z. , NAKADA T. , MATSUO A. , TAKAHASHI Y.
Published: October 2002

We produced a recombinant protein from a cDNA library from muscle larvae of Trichinella spiralis which had proteinase inhibitory activity. The predicted amino acid sequence of the clone had an identity of only 30% to the serine proteinase inhibitors (serpins) from Caenorhabditis elegans or Brugia malayi. At the putative reactive region, however, the identity was about 50%. The recombinant protein expressed in Escherichia coli inhibited 82% of the activity of the serine proteinase (trypsin). Stage-specific expression of this protein was suggested from the following experiments. Antibody against the recombinant protein could stain proteins migrating at about 42 kDa (which is the expected size from the sequence) in crude extracts from newborn larvae and 18-day post-infection (p.i.) muscle larvae, but it failed to stain any proteins in crude extracts from 30-day p.i. muscle larvae. Production of mRNA transcript for the serpin gene was restricted largely to the newborn larvae and to 18-day p.i. muscle larvae. The antibody reacted with the stichocytes of the larvae at 18 days p.i., but did not react with the muscle larvae at 24 days and 30 days p.i.
Metronidazole-resistant strains of Trichomonas vaginalis display increased susceptibility to oxygen
Authors: RASOLOSON D. , TOMKOVÁ E. , CAMMACK R. , KULDA J. , TACHEZY J.
Published: October 2002

Susceptibility to oxygen and properties relative to oxygen metabolism were compared in metronidazole-resistant and susceptible strains of Trichomonas vaginalis. The study involved clinical isolates displaying the aerobic type of resistance, as well as resistant strains developed in vitro, both with aerobic (MR-3) and anaerobic (MR-5, MR-100) resistance. Elevated sensitivity to oxygen of the resistant clinical isolates was observed. Progressive increase of susceptibility to oxygen also accompanied in vitro development of resistance. No correlation was found between the activity of NADH oxidase and aerobic resistance, while the in vitro derivative with fully developed anaerobic resistance (MR-100) showed about 50% decrease of NADH oxidase activity. The superoxide dismutase (SOD) activity was elevated in both resistant clinical isolates and in in vitro-developed resistant strains. The changes in levels of ferredoxin were insufficient to support ferredoxin deficiency as a cause of aerobic metronidazole resistance. Western blot analysis and electron paramagnetic resonance spectroscopy of purified hydrogenosomes showed that ferredoxin is expressed in aerobically resistant strains and has intact iron-sulfur clusters. Down-regulation of ferredoxin was demonstrated only in the late phase of development of the anaerobic resistance (MR-100). The results support a link between aerobic resistance and defective oxygen scavenging. The increased levels of intracellular oxygen, beneficial to resistant parasites when they interact with the drug, may have adverse effects on their fitness as shown by their increased sensitivity to oxidative stress.