bluuebunny/crossref_metadata_2025 huggingface dataset:
Variability in the susceptibility of the fish host, Poecilia reticulata, to infection with Gyrodactylus bullatarudis (Monogenea)
Authors: Madhavi R. , Anderson R. M.
Published: June 2009

Heterogeneity in susceptibility of guppies (Poecilia reticulata) to infection with Gyrodactylus bullatarudis was examined by comparing the establishment, reproduction and survival of the parasite on 4 inbred strains of the fish host following low and high levels of exposure to infection. The 4 strains fell into 2 broad categories of innately ‘resistant’ and ‘susceptible’ fish on the basis of strain differences in (a) the rates of growth and decay of the parasite populations, (b) the proportional occurrence of susceptible and resistant fish within each strain, (c) the average duration of primary infection, and (d) the duration of resistance to reinfection following recovery from a primary exposure. The results suggest genetic control of resistance/susceptibility traits and experiments with hybrids tentatively suggest dominance of resistance over susceptibility. The potential of the guppy – Gyrodactylus laboratory system for the investigation of the role of genetic factors in the study of host–parasite interactions is discussed.
The population dynamics of Lepeophtheirus pectoralis (Müller): seasonal variation in abundance and age structure
Authors: Boxshall G. A.
Published: June 2009

The ectoparasitic copepod Lepeophtheirus pectoralis exhibited a regular annual cycle of abundance on its hosts. Both the incidence and intensity of infection were greatest in August or September and both declined over winter to their minimum values in April. Very similar cycles were observed in both 1972 and 1973. Analysis of the age structure of the parasite population showed that the increase in abundance coincided with the onset of the breeding season. Although females always outnumbered males the sex ratio approached unity during the breeding season, which extended from May to October. Copulating pairs were most commonly observed during this period.

There was a marked bimodal peak of egg production each year, with the first mode occurring around May and the second mode around August or September. This pattern was produced by a system of alternation of generations operating within the parasite population, with a summer type generation (distinguishable by its rapid maturation rate and reduced longevity) alternating with an overwintering type of generation.
Further studies ofSchistosoma mansonicercarial stimulation by crude egg lecithin and other lipids
Authors: Austin F. , Frappaolo P. , Gilbert B. , Landis W. , Rosa M. N. da , Stirewalt M.
Published: June 2009

The stimulus provided to cercariae by the skin fat of their definitive hosts is not the same forSchistosoma mansoniandAustrobilharzia terrigalensis.Cercariae of the former parasite are stimulated by unsaturated fatty acids, those of the latter by cholesterol.

A reinvestigation of the penetration stimulant factors present in crude egg lecithin, which contains both cholesterol and free fatty acids as impurities, has shown that the latter are responsible for the stimulus inS. mansoni.The phospholipid fraction is inactive as is pure cholesterol. A little excitation of cercariae is produced by the monoglyceride fraction. These results fully confirm earlier findings.

Of surface active agents other than lecithin, stimulatory activity was found only in one product which possessed carboxyl groups. Of the C18acids examined, stearic (18:0) is inactive, oleic (18:1) slightly active, linoleic (18:2) and linolenic (18:3) acids highly active. Oleic acid was shown by GC-mass spectrometry to be the most abundant acid in crude egg lecithin and is probably the main penetration stimulus present.
Bloodmeal digestion by strains ofAnopheles stephensiListon (Diptera: Culicidae) of differing susceptibility toPlasmodium falciparum
Authors: Feldmann A. M. , Billingsley P. F. , Savelkoul E.
Published: June 2009

Blood digestion was studied in strains ofAnopheles stephensiwhich had been genetically selected for either refractoriness or susceptibility to infection byPlasmodium falciparum.Females of the refractory Pb3—9a strain ingested more blood than selected (Sda-500) and unselected (Punjab) susceptible females and began to degrade the haemoglobin soon after feeding. In susceptible females, haemoglobin degradation started only after a significant post-feeding lag period. Total protein content of the midgut after the bloodmeal was correspondingly higher for refractory than for susceptible females, but absolute and relative rates of protein degradation were not significantly different between the different mosquito strains. Bloodmeal induction of midgut trypsin activity and the maximal trypsin activity were the same for the different strains. The residual aminopeptidase activity and its relative post-feeding activity (enzyme units per midgut) were significantly higher in refractory females. However, when converting to specific aminopeptidase activity, no differences between strains were evident. The results indicate that both the early initiation of haemoglobin degradation and higher aminopeptidase activity in the Pb3—9a refractory strain are important in the limitation of parasite development within the mosquito midgut, whereas trypsin plays no role in this process.
Characterization ofTrypanosoma congolenseserodemes in stocks isolated from Chipata District, Zambia
Authors: Frame I. A. , Ross C. A. , Luckins A. G.
Published: June 2009

Six stocks ofTrypanosoma congolensewere cloned from 17 stocks isolated from Eastern Zambia and used to initiate insect-formin vitrocultures producing metacyclic trypanosomes. Serological assays were then developed using thesein vitro-derived metacyclics as a reference collection of antigens. Monoclonal antibodies recognized 8 metacyclic variable antigen types (M-VATs) of one stock,T. congolenseTREU 1885, representing 70–80% of that stock's M-VAT repertoire, and in an indirect fluorescent antibody test (IFAT) there were no cross-reactions between them and the metacyclic trypanosomes of the other 5 stocks. Cross-protection assays between the 6 stocks in mice showed that the stocks culturedin vitrowere serologically distinct. In order to facilitate serological typing for serodeme characterization, an IFAT was developed using formalin-fixed metacyclic trypanosomes to identify VAT specific immune responses using 21 day post-infection antisera. The cultured stocks reacted only with their homologous antisera thus confirming the results obtained in the cross-protection assays. No cross-reactions were observed with the 6 cloned stocks and antisera against the 11 stocks ofT. congolenseisolated in the same area at the same time suggesting that these stocks were different from the reference collection of cultured metacyclics. Hence, at least 7 serodemes ofT. congolensehave been identified from the 17 stocks isolated.
Rostellar hook morphology ofEchinococcus granulosus(Batsch, 1786) from natural and experimental Australian hosts, and its implications for strain recognition
Authors: Hobbs R. P. , Lymbery A. J. , Thompson R. C. A.
Published: June 2009

An analysis of the rostellar hooks of Australian isolates ofEchinococcus granulosusrevealed that there was less variation in larval (metacestode) than adult characters and that metacestode characters could be measured directly from adult worms. A factor analysis indicated that two factors, one representing a contrast between number of hooks and their length, and the other representing blade lengths, were sufficient to account for 87.5% of the variance in metacestode hook measurements. These results indicate that rostellar hook morphology is not useful for discriminating strains ofE. granulosusin Australia. The Tasmanian and mainland domestic strains were found to be indistinguishable using rostellar morphology. Although many of the isolates from sylvatic hosts differed from those from domestic hosts, there was not a clear separation as would be expected if two distinct strains existed. Evidence was presented to show that the morphological differences seen in sylvatic hosts could be attributed to host-induced effects, and that the previously accepted existence of two mainland strains should be investigated further.
Anin vivomodel for the study of chemotaxis induced by Schistosomula ofSchistosoma mansoni
Authors: Chao L. P. , Jones J. T. , Kusel J. R.
Published: June 2009

Peritoneal leucocytosis, with an increased percentage of eosinophils, was found in mice which had been infected withSchistosoma mansonifor 7 weeks or longer. Specific IgG against worm and egg antigens increased in peritoneal fluids and their corresponding sera respectively 5 and 7 weeks after infection. An intraperitoneal challenge with schistosomula elicited neutrophilia in all mice regardless of immune status, as well as infiltration of eosinophils and macrophages in infected mice. The secondary eosinophilia occurred in mice previously infected for 1 week or longer, whereas the infiltration of macrophages occurred only after worms from the primary infection had started laying eggs. Unlike the eosinophilia the macrophage response required infection with bisexual populations of cercariae. Injection of previously infected mice withEscherichia, TrichinellaorToxocarafailed to increase the proportions of eosinophils and macrophages. Schistosomula-induced eosinophilia could be elicited in passively sensitized mice. Intraperitoneal injection of PBS extract of adult worms elicited eosinophilia in infected mice and neutrophilia in normal mice. Two chromatographic fractions induced eosinophilia and the third only neutrophilia. The relevance of these observations to host response toS. mansoniinfections is discussed.
An investigation of the prevalence of intestinal parasites in pre-school children in Ghana
Authors: Annan Akweley , Crompton D. W. T. , Walters D. E. , Arnold S. E.
Published: June 2009

Evidence for the presence of 11 intestinal parasites in pre-school children from 4 rural villages in Ghana was obtained from an examination of stool samples. Striking differences were detected between the prevalence of some of the 6 common infections in the 4 villages. The prevalance of Ascaris lumbricoides varied from about 76% in one village (Oshiyie, coastal savanna) to apparently 0% in another (Akuma, forest zone). No differences in prevalence for any infection were observed to be sex dependent. Investigation of the relationship between age of the children and prevalance showed that the degree of prevalence of both A. lumbricoides and Trichuris trichiura had essentially levelled off by the time the children were 4 years old. There was no evidence to suggest that the prevalence of either Entamoeba sp. or spp. or hookworm was approaching a maximum value, even in the oldest children. These trends applied across the villages regardless of the differences in prevalence values for the infections. On average, the children of Oshiyie were found to harbour twice as many infections as the children of the other villages. The investigation of the prevalence data revealed evidence of associations between pairs of infections, particularly those involving hookworm and T. trichiura.
Properties and localization of chitin synthase inAscaris suumeggs
Authors: Dubinský P. , Ryboš M. , Turčeková Ľ.
Published: June 2009

Investigations were carried out into the properties and localization of chitin synthase (EC 2.4.1.16) in connection with the formation ofAscaris suumegg-shells. The chitin synthase of eggs exhibited properties very similar to those found in other chitin-synthesizing organisms. It was stimulated by the presence of ATP, GlcNAc and Mg2+with maximal activity at pH 7·0. In the phase of active chitin synthesis, during formation of the primary shell layers, chitin synthase was bound to the structures of the eggs. On completion of chitin synthesis in the eggs, the amount of the enzyme increased in the soluble fraction. Two forms of chitin synthase have been found in the eggs, namely an inactive (zymogenic) and an active form. Transformation of these two enzyme forms represents a key mechanism in the regulation of chitin synthesis inA. suumeggs.
A method for estimating possible parasite-related host mortality, illustrated using data from Callitetrarhynchus gracilis (Cestoda: Trypanorhyncha) in lizardfish (Saurida spp.)
Authors: Adjei E. L. , Barnes A. , Lester R. J. G.
Published: June 2009

The frequency distribution of parasites in hosts commonly follows a negative binomial or similar distribution. Under certain conditions the magnitude of parasite-associated host mortality can be estimated by comparing the tail of the observed distribution to that of the distribution predicted from the first few points of the data. For the technique to work the following assumptions need to be met: mortality in lightly infected fish must be rare; infection and consequent mortality occur only in fish younger than those sampled; and the frequency distribution of the parasite at the time of infection should conform to a known probability distribution. The method was applied to frequency distributions of blastocysts of Callitetra rhynchus gracilis in 898 Saurida tumbil (Bloch) and 5013 S. undosquamis (Richardson). Parasite-associated mortality in S. tumbil was calculated to be at least 11 % in males and 2% in females. For S. undosquamis, estimated mortality was about 5% in males and 3% in females. The numbers of parasites estimated to produce a 0·5 probability of death, the parasitological equivalent of an LD50 were 3·4 and 5·7 for S. tumbil males and females, and 18 and 3 for S. undosquamis males and females respectively.
Observations on chromosomes and gametogenesis ofTransversotrema patialense(Trematoda)
Authors: Havi R. Mad , Ramanjaneyulu J. V.
Published: June 2009

The karyotype ofTransversotrema patia1enconsists of 10 pairs of chromosomes (2n= 20) of which 5 pairs are metacentrics and 5 pairs are submetacentrics. The chromosomes are large and range in size from 5 to 12 μm. The total chromosome length of the diploid complement is 16783 μm. Stages of spermatogenesis including the two gonial divisions and two reduction divisions leading to production of spermatozoa occur in cercarial embryos inside snail tissue, while the maturation divisions of the ovum occur in eggs freshly liberated by the fluke. The chiasma frequency is high, being 3888/cell and 388/bivalent. Cytological data indicate an independent phylogenetic status for the family Transversotrematidae.
A Gene associated with cell division and drug resistance in Giardia duodenalis
Authors: Upcroft J. A. , Healey A. , Murray D. G. , Boreham P. F. L. , Upcroft P.
Published: June 2009

A 3000 bp cDNA insert (G6/1) from Giardia duodenalis, cloned into Escherichia coli is located on chromosome 3 of Giardia stocks which have 3 chromosomes detectable by field-inversion gel electrophoresis in the range 650–800 kb and on chromosome 3 and/or 4 of stocks with 4 chromosomes in this size range. The loss of this sequence from chromosome 4 but not chromosome 3 was associated with the induction of drug resistance in a previously sensitive laboratory stock. G6/1 appears to represent a single copy gene in Giardia as determined by hybridization of the probe to cleaved genomic DNA. Furthermore, the sequences flanking at least 12 kb of G6/1 are the same when G6/1 appears on both chromosomes 3 and 4. The cDNA encodes a protein associated with the nuclei of trophozoites during some stages of growth of the parasite. In a non-dividing culture, the antigen is associated with the nuclei of about 30% of trophozoites and fewer in a dividing culture. Three Giardia stocks with obvious chromosome rearrangements, which grow poorly and fail to divide normally, apparently lack the DNA sequence G6/1.
Ascaris infections in humans from North America: molecular evidence for cross-infection
Authors: Anderson T. J. C.
Published: June 2009

Cases of human Ascaris infection occur sporadically in areas such as N. America and Western Europe, where this parasite is thought to be non-endemic. Clinical case histories suggest that many of these cases may be cross-infections from pigs. I describe patterns of variation in the ribosomal DNA of Ascaris from 9 such cases. For comparative purposes, I also describe patterns of variation in parasites obtained from pigs and humans from worldwide locations. A Hae III restriction site distinguishes two classes of rDNA repeats; repeats bearing this restriction site were found in > 96% of parasites from pig populations worldwide and in all 9 worms from humans in N. America. In contrast, repeats bearing this restriction site were detected in < 2% of parasites from humans in endemic areas. The molecular data clearly incriminate pigs as the source of infection in the N. American cases. I discuss evolutionary and public health implications of incomplete host fidelity in Ascaris.
Antibodies to the glutamate dehydrogenase ofPlasmodium falciparum
Authors: Ling I. T. , Cooksley S. , Bates P. A. , Hempelmann E. , Wilson R. J. M.
Published: June 2009

Polyclonal antisera raised againstPlasmodium knowlesireacted with (1) NADP-specific glutamate dehydrogenase (GLDH) ofP. knowlesi, (2) GLDH ofP. falciparumand (3) GLDH ofProteus spp. The antisera did not react with NAD(P) GLDH from bovine liver. Polyclonal antisera raised against the GLDH ofProteus spp. cross-reacted with GLDH fromP. falciparum. Monoclonal antibodies (McAbs) obtained from mice immunized with Proteus GLDH were either specific for the bacterial enzyme or cross-reacted withP. falciparumGLDH. The selected McAbs did not react with GLDI-1 fromP. knowlesi,P. chabaudiorP. berghei. The GLDH ofP. falciparumwas shown to be a cytosolic protein (by FAT) with a subunit molecular weight of approximately 49000 Da (by immunoprecipitation) having a pre dominantly hexameric form (by sucrose density gradient). Implications of the conserved sequences of GLDHs and other enzymes are discussed.
Experimental infection ofTribolium confusum(Coleoptera) byHymenolepis diminuta(Cestoda): host fecundity during infection
Authors: Maema Malefane
Published: June 2009

Some effects ofHymenolepis diminutaon the fecundity ofTribolium confusumare described. Host fecundity is observed to be reduced exponentially with increasing parasite burden/host, although there are differences in the ability of individual hosts to respond to parasitism. Of particular interest is the finding that host fecundity is greatly reduced in young beetles on or by day 14 post-infection (p.i.). This age-related reduction in host fecundity is discussed in relation to the population dynamics of this hostr-parasite relationship.
Theileria parva: influence of vector, parasite and host relationships on the epidemiology of theileriosis in southern Africa
Authors: Norval R. A. I. , Lawrence J. A. , Young A. S. , Perry B. D. , Dolan T. T. , Scott J.
Published: June 2009

The protozoan parasite Theileria parva, transmitted by the ixodid tick Rhipicephalus appendiculatus, is the cause of East Coast fever (ECF) and the related syndromes of Corridor disease and January disease in cattle of eastern, central and southern Africa. It is likely that buffalo (Syncerus caffer) are the natural host of T. parva. In eastern and southern Africa, there exist both buffalo-adapted and cattle-adapted T. parva. Disease caused by buffalo-adapted parasites is called Corridor disease, and that caused by cattle-adapted parasites is termed East Coast fever. In eastern Africa, it has been shown experimentally that buffalo-adapted T. parva can, after serial passage in cattle, become adapted to cattle, in which it can then be maintained and cause ECF. This adaptation has been termed transformation. The transformation of buffalo-adapted T. parva to a cattle-adapted parasite has not been reported in southern Africa, and ECF, eradicated from South Africa, Swaziland and southern Mozambique by 1960, has not reappeared in the subcontinent. This paper discusses the possible reasons for this, and hypothesizes that vector population dynamics and the susceptibility of the vector population to infection with T. parva are among the most important factors which influence the expression of ECF as a disease entity, and the likelihood of transformation occurring. It also considers the possibility that disappearance of ECF from southern Africa resulted from the extinction, as a result of vigorous control measures and unfavourable climatic conditions, of non-diapausing populations of R. appendiculatus that may have been introduced from eastern Africa with cattle imported in 1901.
Effects of temperature and host density on the snail-finding capacity of cercariae of Echinostoma caproni (Digenea: Echinostomatidae)
Authors: Meyrowitsch D. , Christensen N. Ø. , Hindsbo O.
Published: June 2009

The effect of temperature (19–36 °C) and snail host density (0.014–10 snails/1) on the snail-finding capacity of Echinostoma caproni cercariae is described. The initial swimming speed increased whereas the length of the infective period decreased with increasing temperature. The combined effect resulted in the E. caproni cercarial snail-finding capacity being temperature independent in the range 19 to 36 °C at a snail density of 0·014 snails/1. A moderate temperature dependency was, however, seen at a lower snail density. The cercarial snail-finding capacity was snail-host density dependent in the density range 0.014 to 1 snail/1. The findings from this study show that a relatively low and biologically realistic snail host density must be used in experimental studies if realistic estimates of the dynamics of cercarial transmission are to be obtained.
Existence of host-related DNA sequences in the schistosome genome
Authors: Iwamura Y. , Irie Y. , Kominami R. , Nara T. , Yasuraoka K.
Published: June 2009

DNA sequences homologous to the mouse intracisternal A particle and endogenous type C retrovirus were detected in the DNAs ofSchistosoma japonicumadults andS. mansonieggs. Furthermore, other kinds of repetitive sequences in the host genome such as mouse type 1 Alu sequence (B1), mouse type 2 Alu sequence (B2) and mo-2 sequence, a mouse mini-satellite, were also detected in the DNAs from adults and eggs ofS. japonicumand eggs ofS. mansoni. Almost all of the sequences described above were absent in the DNAs ofS. mansoniadults. The DNA fingerprints of schistosomes, using the mo-2 sequence, were indistinguishable from each other and resembled those of their murine hosts. Moreover, the mo-2 sequence was hypermethylated in the DNAs of schistosomes and its amount was variable in them. These facts indicate that host-related sequences are actually present in schistosomes and that the mo-2 repetitive sequence exists probably in extra-chromosome.
Partial characterization of 2-β-mercaptoethanol-soluble surface-associated antigens ofOnchocerca volvulus
Authors: Engelbrecht F. , Braun G. , Connor V. , Downham M. , Whitworth J. A. , Taylor D. W.
Published: June 2009

Antigens were extracted from the epicuticle/cuticle of intact femaleOnchocerca volvulususing 2% 2-β-mercaptoethanol and 1% SDS. In Western blot analysis a human infection serum selected for its high antibody titre against whole worm homogenates did not recognize any component solubilized by 1% SDS. However, the same serum did bind at least 7 antigens among the material extracted with 2-β-mercaptoethanol. These antigens have apparent molecular weights (Mr) of: 15 000, 18 000, 28 000, 78 000, 98 000, 120 000 and 200 000. In ELISA using this preparation as target antigen, 151 out of 153 human infection sera gave positive results. AnOnchocerca-specific IgG1 monoclonal antibody, designated Cam1, recognized the 28 000Mrantigen, which is the most prominent antigen detected by Western blot analysis using human infection sera. In ELISA, using material affinity-purified with Cam1 as target antigen, 149 out of 153 human infection sera gave a positive IgG response. From a cDNA library three expressing clones were isolated with a rabbit serum raised against 2-β-mercaptoethanol solubilized material. One of these clones was recognized by the monoclonal antibody Cam1.
Efficacy of treatment of murineSchistosoma mansoniinfections with praziquantel and oxamniquine correlates with infection intensity: role of host antibody
Authors: Fallon P. G. , Hamilton J. V. , Doenhoff M. J.
Published: June 2009

The reduction in worm burden obtained by treatment ofSchistosoma mansoniwith praziquantel and oxamniquine was greater in mice with heavy infections than in relatively lightly infected animals. The reduction in worm burden achieved by each drug correlated with the size of the pre-treatment worm burden (r2= 0·82 and 0·81 for praziquantel and oxamniquine, respectively). Intensity of infection did not affect the degree of tegumental damage and drug-induced antigen exposure on worms recovered soon after treatment with praziquantel. However, praziquantel-treated worms from mice with heavy infections had significantly more murine antibody attached to the treated-worm surface than worms from praziquantel-treated lightly infected mice. Heavily infected mice had greater levels of circulating anti-worm antibodies than lighter infected mice. The correlation between infection intensity and cure rates achieved by praziquantel and oxamniquine may thus be a reflection of the higher litres of relevant antibody in heavily infected mice mediating death of drug-treated worms.
Proteinases releasedin vitroby the parasitic stages ofTeladorsagia circumcincta, an ovine abomasal nematode
Authors: Young C. J. , McKeand J. B. , Knox D. P.
Published: June 2009

Proteinases released duringin vitromaintenance of third (L3) and fourth larval stage (L4) and adultTeladorsagia circumcincta(formerlyOstertagia circumcincta), an ovine abomasal nematode parasite, were characterized on the basis of pH optima, molecular size and specific proteinase inhibitor sensitivity. Enzyme activity was maximal at alkaline pH and stage-specific release was demonstrated. Proteinases released by the adult parasite degraded a variety of protein substrates including plasminogen, albumin and haemoglobin, in a pH-dependent manner. At alkaline pH fibrinogen degradation was restricted to the α and β peptide chains although the γ peptide chain was also degraded at acidic pH. Inhibitor sensitivity studies indicated that degradation was predominantly due to metalloproteinases although aspartyl proteinase activity was indicated at acidic pH.
The distribution and pathobiology ofNeoechinorhynchus cylindratusin the intestine of green sunfish,Lepomis cyanellus
Authors: Adel-Meguid M. , Esch G. W. , Eure H. E.
Published: June 2009

The status of bluegill (Lepomis macrochirus) and green sunfish (Lepomis cyanellus) as homologous hosts for the acanthocephalanNeoechinorhynchus cylindratuswas experimentally determined. It was found that the adult parasite did not establish in bluegills, but that these fish could serve as paratenic host. In contrast, complete growth and development to the adult stage occurred in the green sunfish. When green sunfish were intubated with 10 cystacanths/fish, the parasite exhibited a clear preference for the anterior half of the intestine; when 50 cystacanths/fish were intubated, the parasites showed a preference for the posterior half of the intestine. With repeated exposure of cystacanths, the parasites were distributed throughout the intestine. The extent of histopathology induced byN. cylindratuswas related to the numbers of parasites present. In light infections (10 cystacanths), the parasite penetrated deeply into the intestinal wall and connective tissue developed around the proboscis. In infections with 50 cystacanths, the proboscis penetration was shallow and little if any connective tissue accumulated. There was also an indication that in crowded areas, the parasites appeared to change their sites of attachment frequently. In both heavy and repeated infections, the parasites evoked significant goblet cell hyperplasia and substantial quantities of mucus covered the intestinal wall. It is suggested that the sticky covering and the presumed presence of antibodies in the mucus combined to create a protective barrier thereby reducing the numbers of parasites that could attach and become established.
Development and ultrastructure ofTrachipleistophora hominisn.g., n.sp. afterin vitroisolation from an AIDS patient and inoculation into athymic mice
Authors: Hollister W. S. , Canning E. U. , Weidner E. , Field A. S. , Kench J. , Marriott D. J.
Published: June 2009

Continuous culture was achieved in several cell lines of a microsporidium obtained from the skeletal muscle of an AIDS patient. Development in COS-1 and RK13 cells was prolific. Spores from the original biopsy were also inoculated into athymic mice by i.m. and i.p. routes. Infection was found in several organs as well as in skeletal muscle after a few weeks. All stages were surrounded by an electron-dense surface coat. Meronts had 2–4 nuclei and divided by binary fission. In sporogony the surface coat became separated from the plasma membrane to form a sporophorous vesicle, within which division into sporoblasts was effected by repeated binary fissions. The number of sporoblasts (and later spores) within the sporophorous vesicles varied from 2 to > 32 and the sizes of the vesicles varied, according to the number of spores contained therein, from 5 μm diameter to 14·0 × 11·0 μm. Spores measured 4·0 × 2·4 μm and had a prominent posterior vacuole. The parasite differs from the genusPleistophorain that it does not form multinucleate sporogonial plasmodia and that the sporophorous vesicle enlarges during sporogony and its wall is not a multilayered structure. It is proposed to place it in a new genus and speciesTrachipleistophora hominisn.g., n.sp.
Changes in foraging behaviour during the infective stage of entomopathogenic nematodes
Authors: Lewis E. E. , Selvan S. , Campbell J. F. , Gaugler R.
Published: June 2009

Studies of foraging strategies are often complicated by competing goals of the forager. In contrast, non-feeding infective juvenile entomopathogenic nematodes forage exclusively for a single host. Two questions were posed: (1) what is the relationship between metabolic rate, energy reserves and foraging strategy and (2) when a foraging strategy fails, will an infective-stage parasite switch strategies? Three species of entomopathogenic nematodes were stored in water and changes in their behaviour, metabolic rate, energy reserves, and infectivity were measured throughout the storage period.Steinernema carpocapsaeambushes insect hosts, whereas S.glaseriandHeterorhabditis bacteriophoracruise forage.Steinernema carpocapsaewas least active and had the lowest metabolic rate.Heterorhabditis bacteriophorawas more active and had the highest metabolic rate.Steinernema glaseriwas most active and had an intermediate metabolic rate. Neither cruising species changed foraging strategy.Steinernema carpocapsaedecreased nictation (a behaviour associated with ambushing only) and increased their locomotory rate. Any change in searching strategy occurred without assessment of the profitability or distribution of potential hosts, but the advantage this confers is unknown.
Reduced spatial learning in mice infected with the nematode, Heligmosomoides polygyrus
Authors: Kavaliers M. , Colwell D. D.
Published: June 2009

Parasite modification of host behaviour influences a number of critical responses, but little is known about the effects on host spatial abilities. This study examined the effects of infection with the intestinal trichostrongylid nematode, Heligmosomoides polygyrus, on spatial water maze learning by male laboratory mice, Mus musculus. In this task individual mice had to learn the spatial location of a submerged hidden platform using extramaze visual cues. Determinations of spatial performance were made on day 19 post-infection with mice that had been administered either 50 or 200 infective larvae of H. polygyrus. The infected mice displayed over 1 day of testing (6 blocks of 4 trials) significantly poorer acquisition and retention of the water maze task than either sham-infected or control mice, with mice that had received 200 infective larvae displaying significantly poorer spatial performance than individuals receiving 50 larvae. The decrease in spatial learning occurred in the absence of either any symptoms of illness and malaise, or any evident motor, visual and motivational impairments. It is suggested that in this single host system the parasitic infection-induced decrease in spatial learning arises as a side-effect of the host's immunological and neuromodulatory responses and represents a fitness cost of response to infection.
Damage to malaria-infected erythrocytes following exposure to oxidant-generating systems
Authors: Wozencraft Anne O.
Published: June 2009

A study has been made of the damage incurred by normal andPlasmodium falciparum-infected human erythrocytes following exposure to a variety of oxidant-generating systems. Hydrogen peroxide, produced by the glucose–glucose oxidase system, increased methaemoglobin formation within normal erythrocytes while normal levels of oxyhaemoglobin were maintained. Exposure to products of the xanthine–xanthine oxidase interaction did not have the same effect. Malondialdehyde measurements indicated that the host cell membranes of parasitized cells had undergone lipid peroxidation even before exposure to the oxidant-generating systems. Lipid peroxidation of normal and parasitized cell membranes was increased upon exposure to reagent-grade hydrogen peroxide and alloxan: this increase was not observed following exposure to the two enzyme–substrate systems that generated reactive oxygen intermediates. In addition, the effects of parasitism on intracellular levels of catalase and superoxide dismutase were assessed. Normal and parasitized erythrocytes were found to possess similar levels of these enzymes, which protect against oxidant-induced damage. It was therefore concluded that the increased susceptibility of infected cells to oxidant damage was probably not related to any decrease in the function of these enzymes.
A study on antigen recognition by onchocerciasis patients with different clinical forms of disease
Authors: Lucius R. , Büttner D. W. , Kirsten Christa , Diesfeld H. J.
Published: June 2009

Sera from 40 onchocerciasis patients from the Yemen Arab Republic with either mild localized forms of onchocerciasis, intermediate or severe localized forms of the disease or generalized forms of infection were studies with rspect to their IgG and IgM response againstOnchocerca volvulusantigens. Immunoblotting, performed with SDS–PAGE-separated proteins of femaleO. volvulusand quantified by densitometric scanning, revealed IgG and IgM antibodies against worm components in sera of all patients. Persons with intermediate or severe localized forms of onchocerciasis had a stronger IgG response against more proteins than individuals of the other group. However, some antigens (Mr21, 23, 30, 33 kDa) induced comparable quantities of IgG in all groups. The IgM response of patients with mild localized forms of onchocerciasis was more intensive and directed against more antigensthan in the other groups. No antigens were detected that were recognized only by individuals with low levels of microfilaridermia. In all groups, varying concentrations of antibodies against cuticle, muscle/hypodermis layer and/or uterus of femaleO. volvuluswere detected by the indirect immunofluorescence test using frozen worm sections as antigen. The highest mean antibody titres were found in patients with intermediate and severe localized forms of disease.
Population dynamics in echinococcosis and cysticercosis: mathematical model of the life-cycle of Echinococcus granulosus
Authors: Roberts M. G. , Lawson J. R. , Gemmell M. A.
Published: June 2009

A mathematical model of the life-cycle of Echinococcus granulosus in dogs and sheep in New Zealand is constructed and used to discuss previously published experimental and survey data. The model is then used to describe the dynamics of transmission of the parasite, and the means by which it may be destabilized. It is found that under the conditions that prevailed in New Zealand during the late 1950s, at the time of surveys of this parasite, the dog–sheep life-cycle was not regulated by any effective density-dependent constraint. In contrast there was evidence for an effective acquisition of immunity to reinfection by cattle. The long time to maturity of the cyst in sheep, together with the practice of feeding aged sheep to dogs, provides a time delay in the intermediate host. By comparison, the time to maturity of the adult stage in dogs is short, but it is of sufficient magnitude to be a key factor in the destabilization of the system by a regular dog-dosing programme. The model used to describe the life-cycle is a linear integrodifferential equation of the Volterra type. Such equations are intrinsically unstable in that a small perturbation in parameters can drive a previous equilibrium solution to zero. At the time of the surveys, the value of the basic reproductive rate, R0 was close to 1, and it has since been reduced below 1 by control measures.
Interactions between the plasma proteins ofBiomphalaria glabrata(Gastropoda) and the sporocyst tegument ofSchistosoma mansoni(Trematoda)
Authors: Bayne C. J. , Loker E. S. , Yui Mary A.
Published: June 2009

The tegumental surface ofSchistosoma mansonisporocysts is the site of both nutritive and immunological interactions with haemolymph cells and plasma ofBiomphalaria glabrata, the schistosome intermediate host. Within minutes of being placed in host plasma, sporocysts acquire plasma antigens, and within 3 h host plasma antigens are present on the surface at near steady state. Though a wide variety of peptides is acquired, there is selection. Furthermore, some differences occur in the peptides acquired from the plasma of susceptible and resistant strains of snail. Acquired antigens are rapidly processed, and are predominantly undetectable in tegumental extracts after a few hours. In contrast, rabbit antibody on sporocysts remainsin situfor at least 48 h, so under some conditions there is stable expression of certain tegumental antigenic determinants.These data, obtained using antibodies to snail plasma antigens and to sporocyst tegumental antigens, are discussed in the light of current ideas on the cellular and molecular basis of susceptibility and resistance in this host#parasite system.
Inequalities in the individual reproductive success of parasites
Authors: Dobson A. P.
Published: June 2009

Two simple methods of measuring the levels of inequality in reproductive success of different individuals in parasite populations are presented. These techniques are then applied to a number of sets of data for cestodes and acanthocephalans. The analysis suggests that both population density and host nutrition are important in determining the observed degree of inequality in reproductive success and body size. Cestodes, with a more flexible growth form, are shown to exhibit higher levels of inequality than acanthocephalans. The discussion outlines the evolutionary importance of considering variation in the reproductive success of different individuals.
During canine viscero-cutaneous leishmaniasis the anti-Hsp70 antibodies are specifically elicited by the parasite protein
Authors: Quijada L. , Requena J. M. , Soto M. , Alonso C.
Published: June 2009

ALeishmania infantumcDNA library was screened with sera from dogs with viscero-cutaneous leishmaniasis. Sequence analysis of a positive clone isolated from the library revealed that it coded for the carboxyl-terminal region of a member of the 70-kDa heat-shock protein family. The full-length sequence of theL. infantumhsp70 gene was determined after isolation of genomic clones. This protein shows a high degree of sequence conservation with the homologous protein from other organisms. To test its antigenicity a recombinant Hsp70 protein fused to the maltose-binding protein was produced inEscherichia coliusing the expression vector pMAL-cRI. By FAST-ELISA assays it was observed that while the complete recombinant protein was recognized by 100% of the sera, the 20 carboxyl-terminal amino acids of the protein were only recognized by 30% of those sera. Thus, although a B-cell epitope must be present within the carboxyl terminal end of the protein other antigenic determinant(s) must reside out of this region. The analysis of the cross-reactivity with mouse Hsp70 by Western blotting strongly suggests that the anti-Hsp70 antibodies generated by infection withL. infantumare directed at specific determinants of theL. infantumHsp70. Thus, our results indicate that anti-Hsp70 autoantibodies are not induced duringLeishmaniainfection.
Neutral glycolipids ofSchistosoma mansonias feasible antigens in the detection of schistosomiasis
Authors: Dennis R. D. , Baumeister S. , Lauer G. , Richter R. , Geyer E.
Published: June 2009

The neutral glycolipid fraction from mouse-propagated,Schistosoma mansoniadult worms has been investigated as to its chromatographic and antigenic properties, and whether it fulfills the serodiagnostic antigen requirements of sensitivity and specificity in the detection of schistosomiasis. Serological analyses were performed by thin-layer chromatography immunostaining and ELISA. In the acute-phase form of mouse schistosomiasis, the kinetics of development of neutral glycolipid-specific antibody levels was correlated with the intensity of the initial infection and the response was dominated by IgG, as represented by the subclass IgG1. With the experimental animal helminthiases screened, glycolipid antigenicity fulfilled the fundamental traits for a serodiagnostic reagent. In the chronic-phase form of human schistosomiasis mansoni, neutral glycolipid-specific antibody levels were not correlated with the intensity of infection, as estimated from the faecal content of parasite eggs, whilst the isotypic response was dominated by IgM and IgG, the latter represented primarily by IgG1 and secondarily by IgG3. With other human helminthiases, glycolipid antigenicity was incomplete, in that, the specificity was only partially fulfilled. The reason for this incomplete specificity has been clarified, in part, by the detection of cryptic schistosomiasis infections in the cohorts of African patient sera examined.
AGiardia duodenalisgene encoding a protein with multiple repeats of a toxin homologue
Authors: Chen N. , Upcrofta J. A. , Upcroft P.
Published: June 2009

A gene,CRP136,from the intestinal protozoan parasiteGiardia duodenalis,expressed at a high level in a metronidazole-resistant line, encodes a 136 kDa protein with 23 copies of a 40 amino acid repeat. The protein is cysteine-rich and has the typical membrane-spanning region and CXXC amino acid motifs of a family ofGiardiacysteine-rich surface proteins (CRSPs). The repeat unit inCRP136, shares 57% homology with the gene encoding the precursor of the sarafotoxins, a group of snake toxins from the burrowing adder known to cause symptoms similar to those of humans acutely infected withGiardia.The sarafotoxins are low molecular weight sulphydryl cross-linked peptides which are proteolytically cleaved from a precursor polyprotein.CRP136has homology over the entire length of the sarafotoxin precursor, and the repeats are of the same length. ThusCRP136represents the first evidence for a potentialGiardiatoxin. The genomic copy number ofCRP136appears to be the same in both the parent and drug-resistant lines and expression of this gene, and at least one other, is associated with a conserved partial duplication, but not amplification, of one chromosome.
Transcriptional regulation of Schistosoma mansoni calreticulin: possible role of AP-1
Authors: Khalife J. , Godin C. , Capron A.
Published: June 2009

Little is known about the regulation and control of Schistosoma mansoni gene expression. In order to study such mechanisms a gene reporter expression vector construction, under the control of a promoter region derived from the S. mansoni calreticulin gene was used to transfect the human Jurkat T cell line. The promoter region contains potential TATA and CAAT boxes as well as an AP-1 core element. We show here that transcriptional factors of eucaryotic cells may induce a gene reporter activity under the control of a S. mansoni promoter region. Treatment of stably transfected cells with N-acetyl cysteine (NAC), a well-characterized antioxidant which counteracts the effects of reactive oxygen intermediates, enhanced the AP-1 dependent transactivation. This effect was abolished when the SmCaR promoter region was deleted in the AP-1 site. Electrophoretic Mobility Shift Assays showed that the AP-1 sequence of S. mansoni bound to both S. mansoni extracts and in nuclear extracts from Jurkat cells, thus explaining possible activation of AP-1 by NAC. Finally treatment of S. mansoni schistosomula and adult worms with NAC induced an increased synthesis of calreticulin protein suggesting a possible role of redox mechanisms in the regulation of a calreticulin gene transcription process in S. mansoni.
Computer model of the maintenance and selection of genetic heterogeneity in polygamous helminths
Authors: Saul A.
Published: June 2009

A stochastic simulation model of the transmission and maintenance of genetic heterogeneity in the absence and presence of external selection pressures is presented for polygamous intestinal helminths such as Ascaris. The model assumes that the density distribution of the adult parasites is highly aggregated and that density-dependent effects on fecundity are important. The model gives rise to stable infection rates in the host. Where the parasite population contains genetic heterogeneity, with the exception of stochastic fluctuations which models genetic drift, the ratio of the different alleles remained constant over extended periods of time. This result contrasts with that of an earlier analytical model (Anderson, R. M., May, M. R. & Gutpa S. (1989) Parasitology 99, S59–S79), in which uneven mating probabilities for the different combinations of worm possible in a host was postulated to inevitably lead to fixation of the most abundant allele. New results suggest that in spite of the restricted choice of mating available to a worm in the confines of a host, selection pressure always leads to enrichment of the parasites carrying resistant alleles.
Resistance of glucose-6-phosphate dehydrogenase deficiency to malaria: effects of fava bean hydroxypyrimidine glucosides onPlasmodium falciparumgrowth in culture and on the phagocytosis of infected cells
Authors: Ginsburg H. , Atamna H. , Shalmiev G. , Kanaani J. , Krugliak M.
Published: June 2009

The balanced polymorphism of glucose-6-phosphate dehydrogenase deficiency (G6PD-) is believed to have evolved through the selective pressure of malaria combined with consumption of fava beans. The implicated fava bean constituents are the hydroxypyrimidine glucosides vicine and convicine, which upon hydrolysis of their β-O-glucosidic bond, become potent pro-oxidants. In this work we show that the glucosides inhibit the growth ofPlasmodium falciparum, increase the hexose-monophosphate shunt activity and the phagocytosis of malaria-infected erythrocytes. These activities are exacerbated in the presence of β-glucosidase, implicating their pro-oxidant aglycones in the toxic effect, and are more pronounced in infected G6PD-erythrocytes. These results suggest that G6PD-infected erythrocytes are more susceptible to phagocytic cells, and that fava bean pro-oxidants are more efficiently suppressing parasite propagation in G6PD-erythrocytes, either by directly affecting parasite growth, or by means of enhanced phagocytic elimination of infected cells. The present findings could account for the relative resistance of G6PD-bearers to falciparum malaria, and establish a link between dietary habits and malaria in the selection of the G6PD-genotype.