bluuebunny/crossref_metadata_2025 huggingface dataset:
A rhoptry antigen ofPlasmodium falciparumis protective inSaimirimonkeys
Authors: Ridley R. G. , Takacs B. , Etlinger H. , Scaife J. G.
Published: June 2009

A non-polymorphic antigen associated with the rhoptry organelles ofPlasmodium falciparumhas been purified by immuno-affinity chromatography. The antigen, RAP-1 (rhoptry associated protein-1). which is defined by monoclonal antibodies which inhibit parasite growthin vitro, is a multi-component antigen consisting of four major proteins of 80, 65, 42 and 40 kDa and two minor proteins of 77 and 70 kDa. These proteins were electro-eluted from preparative sodium dodecyl sulphate polyacrylamide gels and protectedSaimiri sciureusmonkeys from a lethal blood-stage infection ofP. falciparummalaria. Sera from the protected animals recognized only proteins of the RAP-1 antigen when used to probe a Western blot of total parasite protein extract, confirming that RAP-1 is responsible for eliciting the protective immune response.
A confocal scanning laser microscope study of the peptidergic and serotoninergic components of the nervous system in larvalSchistosoma mansoni
Authors: Skuce P. J. , Johnston C. F. , Fairweather I. , Halton D. W. , Shaw C.
Published: June 2009

The localization and distribution of the serotoninergic and peptidergic elements of the nervous system of larvalSchistosoma mansonihave been investigated using an indirect immunofluorescence technique in conjunction with confocal scanning laser microscopy (CSLM). A range of antisera was used, raised to the biogenic amine, 5-hydroxytryptamine (5-HT, or serotonin), the vertebrate peptides pancreatic polypeptide (PP), peptide YY (PYY) and neuropeptide Y (NPY) and to the native invertebrate peptide, FMRFamide; all these antisera were shown previously to be immunopositive in the adult worm. No immunoreactivity to 5-HT was detected in any of the larval stages, but both miracidia and cercariae were consistently immunoreactive to all 4 peptides. The peptidergic nervous system of the miracidium is relatively simple, taking the form of a central neural mass with associated paired anterior and posterior nerve tracts. The cercarial peptidergic nervous system comprises a central commissure joining paired anterior ganglia, from which emanate paired dorsal and ventral nerve tracts, which terminate at the body/tail junction. The excretory bladder region of the tail is also immunoreactive for the 4 peptides, and a fine pair of nerve tracts extends the length of the tail shaft. Immunoreactive nerve cell bodies are also evident in the midbody region of the intrasprocystic cercariae, these same structures being immunoreactive for the neuronal marker, neurone-specific enolase (NSE). The organization of the larval peptidergic nervous system is compared to that of the cholinergic nervous system and contrasted with the peptidergic system in the adult worm. The absence of immunoreactivity to 5-HT is discussed in relation to the proposed development of the aminergic nervous system upon establishment in the definitive host.
Antigenic variation duringTrypanosoma vivaxinfections of different host species
Authors: Barry J. D.
Published: June 2009

The sequence of appearance of specific lytic activity against more than 20 variable antigen types (VATs) ofTrypanosoma vivaxin the serum of 27 animals belonging to 5 species has been examined. For each host species there was a characteristic course of infection, with differences in height and duration of parasitaemia and in pathogenicity. The sequence of antigenic variation was similar in all host species, with some VATs consistently eliciting response more rapidly than others. The predominant group, comprising VATs which apparently developed within the first 3 weeks, varied in size according to the total number of trypanosomes in the bloodstream within that period, suggesting there is a spectrum, rather than discrete groupings, in the hierarchy of VAT expression. There was very little evidence for differences in appearance of VATs between host species; the only clear example was one VAT which apparently did not develop in one host species. The sequence of antigenic variation inT. vivaxseems to be determined by the parasite rather than the host species.
Variation in susceptibility of inbred lines of chickens to seven species ofEimeria
Authors: Bumstead N. , Millard B. J.
Published: June 2009

The pattern of oocyst production of 8 inbred lines of chickens was compared for each of the 7 species ofEimeriawhich infect this host. Both the overall numbers and the pattern of oocyst production differed in the inbred lines, but there was no evidence of prolonged cycling of schizogenic developmental stages. Comparison of the numbers of oocysts produced by the different lines indicates that there may be common genetic factors affecting susceptibility to 6 of the 7 species. Surprisingly there appears to be an inverse relationship between susceptibility toE. tenellaand susceptibility to the other species: lines which produced most oocysts ofE. tenellaproduced least oocysts of the other species andvice-versa.
Repeated infection of cats withBrugia pahangi: parasitological observations
Authors: Denham D. A. , Medeiros F. , Baldwin C. , Kumar H. , Midwinter I. C. T. , Birch D. W. , Smail A.
Published: June 2009

Cats were repeatedly inoculated with infective larvae ofBrugia pahangi. On parasitological grounds they could be divided into 5 groups. Group I – most cats (some 70%) became microfilaraemic (mf+) and retained high levels of microfilariae (mf) in their blood for over 2 years. In some Group I cats mf counts stabilized at high levels whilst in others mf counts continued to increase. Large numbers of fecund adult worms were recovered from their lymphatics. Adult counts were not made on the cats in the current experiments but over 100 adults have been recovered from ‘super-susceptible’ cats. Large amounts ofB. pahangiadult antigen were consistently present in the serum of all Group I cats. About 30% of cats became amicrofilaraemic (mf–). In these cats the peak mf levels were seldom above 10000 mf/ml. Group II – these cats had less than 10 000 mf/ml and low antigen levels. After more than 1 year of being repeatedly infectedB. pahangiadult antigen slowly declined and eventually could no longer be detected in their serum and the number of mf declined very slowly after the fall in antigen levels. This shows that in Group II cats the adult worms die and as the cats are resistant to the development of the continuing weekly inoculation of L3 no new adults can develop. Group III – these cats became mf – during the first year of infection but remainedB. pahangiantigen-positive for many weeks after this and, at autopsy, had living adults in their lymphatics. Group IV – in these cats there was a sudden decline in the number of mf, usually in the first year and after they have received a relatively small number of re-infections. Circulating adultB. pahangiantigen disappeared from the serum within a short time of the loss of mf and at autopsy no adult female worms were found. Group V – these cats do not become mf+ when infected. These groups are compared to the parasitological groups seen in areas endemic for infection withWuchereria bancrofti.
Tryptophan metabolism and vitamin B6nutritional status in patients with schistosomiasis mansoni and in infected mice
Authors: Njagi E. N. M. , Bender D. A. , Okelo G. B. A.
Published: June 2009

Patients infected withSchistosoma mansonishowed an abnormal response to a test dose of tryptophan, with little increase in the urinary excretion of kynurenine, hydroxykynurenine, xanthurenic and kynurenic acids,N1-methyl nicotinamide, methyl pyridone carboxamide, 5-hydroxytryptamine or 5-hydroxyindoleacetic acid. In contrast to previous reports, this is different from the pattern of tryptophan metabolism seen in vitamin B6deficiency. Furthermore, the patients' plasma concentrations of pyridoxal phosphate were within the reference range, and supplementation for 5 days with 20 mg vitamin B6/day did not affect tryptophan metabolism. Treatment with a single dose of Praziquantel resulted in a substantial restoration of normal tryptophan metabolism. In mice infected withS. mansonithere was a similar impairment of tryptophan metabolism, as shown by considerably reduced formation of14CO2after the administration of a tracer dose of [14C]tryptophan. Again, the administration of vitamin B6supplements did not correct tryptophan metabolism in the mice. Treatment with Praziquantel resulted in substantial restoration of the production of14CO2from [14C]tryptophan. There was no evidence of vitamin B6deficiency (as determined by erythrocyte aspartate aminotransferase activation coefficient) associated with infection in the mice, although there was a redistribution of pyridoxal phosphate between tissues, with a reduction in the concentration of liver, spleen and kidney, and an increase in skeletal muscle.
A model for variations in single and repeated egg counts in schistosoma mansoni infections
Authors: De Vlas S. J. , Gryseels B. , Van Oortmarssen G. J. , Polderman A. M. , Habbema J. D. F.
Published: June 2009

Faecal egg counts are often used to measure Schistosoma mansoni infection, but the considerable variation between successive counts complicates their interpretation. The stochastic model described in this paper gives a description of observed egg counts in a population and can be used as a tool to gain an insight into the underlying worm load distribution. The model distinguishes between two sources of variation in egg counts: (1) variation caused by the difference in worm load between individuals, and (2) the variability of egg counts for an individual with a given worm load. Empirical data, single and repeated measurements, from surveys in five villages in Burundi and Zaire have been used to fit and validate the model. We have discussed possible mechanisms that explain the differences in estimated values between the villages. The model indicates that the expected number of eggs in a stool sample per S. mansoni worm pair is lower than suggested by autopsy data and that, possibly as a consequence of immunity, the inter-individual variation in worm loads decreases with age.
Transport of isometamidium (Samorin) by drug-resistant and drug-sensitiveTrypanosoma congolense
Authors: Sutherland I. A. , Mounsey A. , Holmes P. H.
Published: June 2009

The uptake kinetics of a14C-labelled trypanocidal compound isometamidium chloride (SamorinR, RMB Animal Health Ltd, UK) was measured in drug-resistant and drug-sensitiveTrypanosoma congolense. It was established that drug uptake was significantly more rapid and quantitatively greater in drug-sensitive parasites. There was clear evidence that drug uptake in both the resistant and sensitive trypanosomes was by a specific, receptor-mediated process. This specific drug transport was energy-dependent, being sensitive to metabolic inhibition with SHAM/glycerol. Significant differences in drug transport were observed which could be correlated with resistance to isometamidium. The optimal pH for drug accumulation was lowered in the resistant trypanosomes; this finding, along with an observed change in specificity for the related compound homidium bromide, suggested that the specific receptor for isometamidium is altered in the resistant trypanosomes, possibly resulting in a reduction in drug uptake. In addition to these alterations in drug uptake, efflux of isometamidium also appears to occur in the resistant trypanosomes. Both a reduction in incubation temperature and metabolic inhibition increased the level of trypanosome-associated isometamidium in the resistant parasites. This was in contrast to observations using drug-sensitive parasites. Furthermore, the addition of calcium flux-modulating agents to the incubation medium also resulted in an increase in accumulation by the resistant parasites.
The regulation of malaria parasitaemia: parameter estimates for a population model
Authors: Gravenor M. B. , Mclean A. R. , Kwiatkowski D.
Published: June 2009

Classical studies of non-immune individuals infected with Plasmodium falciparum reveal that the infection may be regulated for long periods at a relatively stable parasite density, despite the enormous growth potential of a parasite that continually replicates within host erythrocytes. This suggests that the parasite population may be controlled by density-dependent mechanisms, and in theory the most obvious of these is competition between parasites for host erythrocytes. Here we evaluate the role of this mechanism in the regulation of parasitaemia, by modelling the basic population interaction between parasites and erythrocytes in a form that allows all the essential parameters to be estimated from clinical data. Our results show that competition cannot account for the total regulation of P. falciparum, but when combined with immune mechanisms it may play a more important role than is generally supposed. Further analysis of the model indicates that in the long term, parasite replication at low parasite densities can contribute significantly to the high degree of anaemia observed in natural infection, a conclusion which is not obvious from simple clinical observation.
Differentiation between human and animal strains ofCryptosporidium parvumusing isoenzyme typing
Authors: Awad-El-Kariem F. M. , Robinson H. A. , Dyson D. A. , Evans D. , Wright S. , Fox M. T. , Mcdonald V.
Published: June 2009

Isoenzyme typing was used to study a number of oocyst isolates ofCryptosporidium parvumfrom different geographical locations and of human or animal origin. All isolates showed identical enzyme motility when glucose phosphate isomerase (GPI; 23 isolates tested) or lactate dehydrogenases (LDH; 20 isolates tested) was assayed. However, two isoenzyme forms were observed with phosphoglucomutase (PGM; 9 animal isolates showed one form, while 8/9 human isolates showed a second form) and hexokinase (HK; 4 human isolates showed one form and 6 animal isolates showed a second form). Thus, PGM and HK each exhibit 2 isoenzymes corresponding to 2 parasite populations associated with separate hosts. The data from this study, plus supportive evidence obtained by different methods and by independent researchers, lend support to the hypothesis that separate cycles of transmission ofC. parvummay exist within human and animal hosts.
Analysis of antigen switching rates inTrypanosoma brucei
Authors: Lamont Gretel S. , Tucker R. S. , Cross G. A. M.
Published: June 2009

Previously quoted figures for the frequency of antigen switching inTrypanosoma bruceiare based on incorrect assumptions. In order to determine the correct switching frequency, an equation was derived that takes the growth rates of the newly expressed antigen types into consideration as well as the proportion of switched trypanosomes and the number of generations since the population was antigenically homogeneous. When this equation was applied to publishedin vitrodata, variable values were obtained for the switching frequency in clonal populations originally expressing one antigen type. The calculated most likely switching frequencies ranged from 1·4×10−7to 3·5×10−6. This variation was probably caused by differences in the growth rates of the new antigen types in the population and failure to detect slow growing variants. To overcome these problems, an experimental procedure was developed to analyse the switching frequencyin vitro. Trypanosomes were cloned and grown in parallel cultures. After an appropriate number of generations, cells expressing the original antigen type were destroyed and, from the proportion of cultures that contained new antigen types, the switching frequency was calculated. The technique minimized subculturing or other procedures that could distort the results. Although the method was optimized for analysing switching frequency, the values differed between experiments, ranging from 2·2×10−7to 2·6×10−6for one variant. Possible causes for the variations in switching frequency are discussed.
The role of serum in leucocyte adherence to the plerocercoid ofLigula intestinalis(Cestoda: Pseudophyllidea)
Authors: Hoole P. , Arme C.
Published: June 2009

The role of serum in the adherence of roach (Rutilus rutilus) leucocytes to the plerocercoid ofLigula intestinalishas been investigatedin vitro. Roach plerocercoids, either untreated, cultured or killed (fixation in 0·5 % buffered glutaraldehyde or heat at 50°C for 45 mm), were exposed to serum and 4×106leucocytes obtained from the pronephros of non-infected roach using a discontinuous Percoll gradient. At normal roach serum (NRoS) dilutions of 1:5000 to 1:100, leucocyte adherence was observed on all living parasites but was negligible in killed parasites or in complement-depleted NRoS assays. The number of adherent cells increased with increasing NRoS concentration. Leucocytes bound more avidly in the presence of heat-inactivated immune serum (hi IRoS); at a serum dilution of 1:5000 the percentage of the parasite surface covered by leucocytes was approximately 3 times greater in hi IRoS than in NRoS. Ultrastructural observations on parasites revealed that plerocercoids exposed to cells and hi IRoS had, in some areas, abnormal inclusions in their tegument and lacked a microthrix border and distal cytoplasm. In addition, the efflux of radioactivity from [14C] cycloleucine-labelled worms was greater in parasites incubated in the presence of hi IRos.
Eimeria tenella: localization of the sporozoites in the caecum of the domestic fowl
Authors: Rose M. E. , Hesketh P.
Published: June 2009

When sporozoites of Eimeria tenella were inoculated into an isolated horn of the bicornuate caecum of the domestic fowl, replicating infections, culminating in the production of oocysts, were found, almost exclusively, in the inoculated horn. In contrast, sporozoites of E. tenella introduced into the bloodstream via a superficial vein induced infections of equivalent intensity in both horns of the caecum. These findings are discussed with reference to (1) the detection (by tissue transfer) of infective sporozoites in samples of cardiac blood and vascular tissues taken within 3 to 18 h of the oral inoculation of oocysts, and (2) the (previously published) observation that the sporozoites of E. tenella are transported from the superficial epithelium of the caecum (site of invasion) to the crypts (site of initial development) within host intra-epithelial lymphocytes. We suggest that a local inflammatory response to the invasion of sporozoites may be responsible for their re-location in proximity to the site of entry. This could act by directing the homing (or retention) of the parasite-bearing lymphocytes, and/or by providing a stimulus for the sporozoite to leave its transporting cell.
Site availability and density-dependent constraints on the acanthocephalan Pomphorhynchus laevis in rainbow trout, Oncorhynchus mykiss (Walbaum)
Authors: Bates R. M. , Kennedy C. R.
Published: June 2009

Threshold density levels were investigated experimentally in rainbow trout, Oncorhynchus mykiss, for the acanthocephalan Pomphorhynchus laevis. Fifty small fish 120–150 mm long were infected with 50 cystacanths each every 4 weeks for 16 weeks, and samples of up to 10 fish examined at 1, 5, 9, 13 and 17 weeks after the original infection. The mean intestinal length was found to have increased significantly over this period, from a mean of 125 to 173 mm and the mean number of parasites recovered increased after each interval of 4 weeks, and significantly from 19·30 to 86·40 per fish over the 17 weeks. The distribution of the parasites in the alimentary tract of O. mykiss was unaltered, indicating that the favourable region for establishment had remained unchanged. The failure to detect any manifestations of competition is discussed, and the relevance of conventional approaches to experimental investigations of both intra- and interspecific competition in fish was queried, and contrasted to the situation in birds and mammals.
The ultrastructure and immunogold labelling of pancreatic polypeptide-immunoreactive cells associated with the egg-forming apparatus of a monogenean parasite, Diclidophora merlangi
Authors: Halton D. W. , Brennan G. P. , Maule A. G. , Shaw C. , Johnston C. F. , Fairweather I.
Published: June 2009

An electron microscopical examination has been made of the fine structure and disposition of pancreatic polypeptide immunoreactive cells associated with the egg-forming apparatus in Diclidophora merlangi. The cell bodies are positioned in the parenchyma surrounding the ootype and taper to axon-like processes that extend to the ootype wall. The terminal regions of these processes branch and anastomose and, in places, the swollen endings or varicosities form synaptic appositions with the muscle fibres in the ootype wall. The cells are characterized by an extensive GER-Golgi system that is involved in the assembly and packaging of dense-cored vesicles. The vesicles accumulate in the axons and terminal varicosities, and their contents were found to be immunoreactive with antisera raised to the C-terminal hexapeptide amide of pancreatic polypeptide. It is concluded that the cells are neurosecretory in appearance and that, functionally, their secretions may serve to regulate ootype motility and thereby help co-ordinate egg production in the worm.
The relationship between worm burden and levels of a circulating antigen (CAA) of five species ofSchistosomain mice
Authors: Agnew A. , Fulford A. J. C. , De Jonge N. , Krijger F. W. , Rodriguez-Chacon M. , Gutsmann V. , Deelder A. M.
Published: June 2009

This study examines the ability of an assay which measures the amount of a schistosome specific antigen (CAA) in the host circulation to reliably reflect relative worm burden. Mice were infected with 5 species of schistosome with a range of infection dose. The levels of serum CAA increased during schistosome maturation. In all species tested CAA levels correlated well with adult worm burden once the parasites achieved sexual maturity and remained relatively stable during the establishment of egg production. The amount of CAA produced varied between species but within each species CAA levels were proportional to worm numbers: no density-dependent effects on CAA levels were observed even when mice carried worm burdens that were very large relative to host size. T-cell deprivation of the host had no effect on the CAA/worm burden relationship in eitherSchistosoma mansoniorS. haematobiuminfections and the CAA equilibrium was unaltered in intact mice when reduction of worm fecundity occurred. These data support the use of the CAA as an accurate and robust estimate of relative schistosome burden in man.
The effects of age, temperature and shadow stimuli on activity patterns of the cercariae of Cryptocotyle lingua (Digenea: Heterophyidae)
Authors: Rea J. G. , Irwin S. W. B.
Published: June 2009

The behaviour of cercariae was recorded on video at 10, 20 and 30 °C and a combination of population and individual behavioural patterns studied. Initially cercarial populations were extremely active, individuals alternating between swimming and sinking behaviour. As they aged the percentage sinking and resting increased resulting in the establishment of a vertical distribution in the water column. An increased environmental temperature reduced the active life-span of the parasites. Over time cercarial swimming rates declined. Swimming rates increased with environmental temperature and as a result of a shadow stimulus. As cercariae aged, the duration of swimming events decreased. Post-stimulation swimming periods were significantly longer than pre-stimulation periods. Pre- and post-stimulation swimming distances also declined with age. Post-stimulation swimming distances were significantly longer than pre-stimulation distances. The sinking rates of cercariae decreased with age while sinking periods and distances increased. Data for proportional time spent swimming and the ratio of sinking to swimming events indicated that as cercariae aged, less time was spent swimming. The frequency of swimming/sinking events declined with age. The implications of this behaviour for dispersal and transmission are discussed.
Comparative analyses of the neuropeptide F (NPF)- and FMRFamide-related peptide (FaRP)-immunoreactivities in Fasciola hepatica and Schistosoma spp
Authors: Marks N. J. , Halton D. W. , Maule A. G. , Brennan G. P. , Shaw C. , Southgate V. R. , Johnston C. F.
Published: June 2009

Immunochemical techniques were used to determine the distribution, chemical characteristics and relative abundance of immunoreactivity (IR) to two native platyhelminth neuropeptides, neuropeptide F (NPF) (Moniezia expansa) and the FMRFamide-related peptide (FaRP), GNFFRFamide, in the trematodes, Fasciola hepatica and Schistosoma mansoni; the larger S. margrebowiei was used in the chemical analysis. Extensive immunostaining for the two peptides was demonstrated throughout the nervous systems of both F. hepatica and S. mansoni, with strong IR also in the innervation of muscular structures, including those associated with the egg-forming apparatus. The patterns of immunostaining were similar to those previously described for the vertebrate neuropeptide Y superfamily of peptides and for FMRFamide. Ultra-structurally, gold labelling of NPF- and GNFFRFamide-IRs was localized exclusively to the contents of secretory vesicles in the axons and somatic cytoplasm of neurones. Double-labelling experiments showed an apparent homogeneity of antigenic sites, in all probability due to the demonstrated cross-reactivity of the FaRP antiserum with NPF. Radio-immunoassay of acid-ethanol extracts of the worms detected 8·3 pmol/g and 4·7 pmol/g equivalents of NPF- and FMRFamide-IRs, respectively, for F. hepatica, and corresponding values of 4·9 pmol/g and 4·3 pmol/g equivalents for S. margrebowiei. Gel-permeation chromatography resolved IR to both peptides in discrete peaks and these eluted in similar positions to synthetic NPF (M. expansa) and GNFFRFamide, respectively.
Genetic characterization ofToxoplasma gondiistrains by random amplified polymorphic DNA polymerase chain reaction
Authors: Guo Z. G. , Johnson A. M.
Published: June 2009

The technique of Random Amplified Polymorphic DNA (RAPD) PCR has been used to detect DNA polymorphisms amongToxoplasma gondiistrains. Seven arbitrary oligonucleotides (10-mer) were used as primers to amplify total genomic DNAs and significant genetic heterogeneity was detected among 11T gondiistrains with different virulence for mice. The polymorphisms observed allowed relationship dendrograms ofT. gondiistrains to be constructed by PHYLIP and PAUP analyses. The genetic relationships of theT. gondiistrains generated by 2 analyses using completely different assumptions were similar. Both analyses revealed 2 groups ofT. gondiistrains, one formed by the 6 virulent strains and the other formed by the 5 avirulent strains. This suggests that the genus Toxoplasma may actually contain 2 groups, correlated with their virulence, which have probably evolved independently following their initial separation. Significant polymorphisms were also detected between 2 different laboratory stocks of theT. gondiiRH strain.
Virulence and transmission modes of two microsporidia inDaphnia magna
Authors: Mangin K. L. , Lipsitch M. , Ebert D.
Published: June 2009

To understand the relationship between mode of transmission and virulence, we investigated 2 microsporidian parasites inDaphnia magnalaboratory populations.Pleistophora intestinalisis only transmitted horizontally, whileTuzetiasp. is transmitted vertically with high efficiency from mothers to parthenogenetic male and female offspring. We were not able to transmitTuzetiahorizontally in the laboratory.Tuzetiareduces host life-time reproductive success and host survival to a much greater extent than doesP. intestinalis.Tuzetia-infected hosts were rapidly outcompeted by uninfected hosts. We suspect thatTuzetiainfections may persist in natural populations by an as yet undiscovered horizontal transmission. It is possible that an alternate host species may be involved. We present a mathematical model to analyse the conditions for the persistence of a parasite with perfect vertical and an additional degree of horizontal transmission. We show that horizontal and vertical transmission contribute additively to a parasite's ability to invade and persist. Since the fitness contribution of horizontal transmission increases with population size, only very low transmission probabilities per host-to-host contact are necessary for the persistence of parasites occurring in large populations such as those commonly found forDaphnia. The detection of such low rates of horizontal transmission appears unlikely under laboratory conditions since the necessary number of host-to-host (or host-to-spore) contacts is not feasible. We review mechanisms that can maintain vertically transmitted parasites in nature.
Differential development and emission ofTheileria parvasporozoites from the salivary gland ofRhipicephalus appendiculatus
Authors: Shaw M. K. , Young A. S.
Published: June 2009

The initiation of feeding of infectedRhipicephalus appendiculatusadults induces the rapid development ofTheileria parvasporoblasts within the salivary gland acini leading to the production of numerous sporozoites which are inoculated into the mammalian host initiating infection. In this study the pattern of development, host cell specificity and emission ofT. parvasporozoites within the salivary glands of heavily infected, 4-day fed adultR. appendiculatusticks was examined. Infected acini were randomly distributed throughout the salivary gland. Sporozoite development within each gland was not synchronized and wide variation in the rate of parasite development, which correlated with the secretory activity of the individual acinus, was observed in all glands examined. Previous studies had shown thatT. parvadeveloped primarily in Type III ‘e’ cells. However, in heavily infected salivary glands sporogony and the emission of mature sporozoites also occurred in ‘c’ cells of Type II acini. Sporozoite emission from infected cells occurred by a process similar to apocrine secretion. The loss of the apical membrane of the infected cell allowed sporozoites free access to the lumen of the acinus and into the collecting ducts of the salivary gland. Sporozoite discharge was gradual since few parasites were found in the acinus valve or in the collecting ducts. Furthermore, the small size of the acinar valve aperature ensures that only small numbers of sporozoites can be released at any one time from an infected acinus.
The kinetics of maturation of trypanosome infections in tsetse
Authors: Dale C. , Welburn S. C. , Maudlin I. , Milligan P. J. M.
Published: June 2009

Estimates of the time delay between the infective bloodmeal and maturation (incubation or maturation time) for 4 trypanosome stocks (2 Trypanozoon and 2 Trypanosoma congolense) show that maturation time in tsetse is not a parasite species-specific constant. The mean incubation time of a Trypanosoma brucei rhodesiense stock (EATRO 2340 – 18 days) was not significantly different from one T. congolense stock (SIKUDA88 – 15·5 days) but was significantly greater than another (1/148 FLY9 – 12·5 days). There was no significant difference in incubation times between male and female Glossina morsitans morsitans for any of the stocks but in both of the Trypanozoon stocks the proportion of female flies producing mature infections was significantly less than in males. However, estimates of gene frequency, assuming a model in which maturation is controlled by an X-linked recessive allele, gave inconsistent results indicating that maturation cannot be controlled by a single sex-linked gene. Maturation was shown to be a tsetse sex-dependent phenomenon in Trypanozoon but not in T. congolense infections. Incubation time was quite variable even for a single trypanosome stock (e.g. standard deviation of 5 days for one Trypanozoon stock); we discuss how this variability can affect disease transmission, and the interpretation of age-prevalence data.
Isolation of Fasciola hepatica haemoglobin
Authors: McGonigle S. , Dalton J. P.
Published: June 2009

A haemoprotein released in vitro by adult Fasciola hepatica was purified by gel filtration chromatography on Sephacryl S-200 and ion-exchange chromatography on DEAE-Sepharose. The molecule, with an apparent molecular weight of > 200 kDa, contains a haem group and has absorption spectra characteristics similar to haemoglobins. N-terminal amino acid sequence analysis revealed no similarity between the F. hepatica haemoglobin and other vertebrate or invertebrate haemoglobins. Antibodies to the haemoglobin molecule can be detected in the sera of F. hepatica-infected bovines as early as 1 week after infection.
Temporal differences in praziquantel- and oxamniquine-induced tegumental damage to adult Schistosoma mansoni: implications for drug-antibody synergy
Authors: Fallon P. G. , Fookes R. E. , Wharton G. A.
Published: June 2009

A temporal study of the effects on the tegument of Schistosoma mansoni adult worm following in vivo praziquantel and oxamniquine treatment was performed. Drug-induced damage to the tegument, exposure of surface antigens and attachment of host antibody occurred rapidly, within 1 h, following praziquantel treatment. Oxamniquine-treated worms required 4–8 days for these effects to be apparent. The 2 drugs differed in the degree and sites of damage on the worm surface. The administration of 2 different polyspecific rabbit sera with drug significantly increased the efficacy of praziquantel when administered with the drug, but not when given 6–9 days after drug treatment. In contrast, only 1 serum was synergistic with oxamniquine when administered with drug and both sera were synergistic when given 6–9 days after drug treatment. The effect of immune killing of drug-treated worms is discussed.
A high prevalence of mixed trypanosome infections in tsetse flies in Sinfra, Côte d'Ivoire, detected by DNA amplification
Authors: Masiga D. K. , McNamara J. J. , Laveissière C. , Truc P. , Gibson W. C.
Published: June 2009

The prevalence of various species and subgroups of trypanosomes in the Sinfra area of C⊚te d'Ivoire was determined using the polymerase chain reaction (PCR). Using this technique to amplify specific satellite DNA targets, it was possible to identify developmental-stage trypanosomes in the midguts and the proboscides of tsetse without expansion of parasite populations. The predominant tsetse species in the area wasGlossina palpalis, whileG. palliceraandG. nigrofuscawere also present. Microscopical examination of 811 non-teneral flies revealed an infection rate of 14% in midguts and/or proboscides. Three subgroups ofTrypanosoma congolense(Savannah, Forest & Kilifi),T. simiae,T.godfreyi, West AfricanT. vivaxandT. bruceissp. were identified using PCR.T. congolenseForest was the most abundant of theNannomonastrypanosomes. Approximately 40% of all infections were mixed, and there was a significantly higher prevalence of apparently matureT. bruceissp. trypanosomes than has previously been reported. The present study demonstrates that PCR facilitates the easy identification of mature trypanosome infections in tsetse, providing a reliable estimation of trypanosomiasis challenge.
Heat shock response ofTrichinella spiralisandT. pseudospiralis
Authors: Ko R. C. , Fan L.
Published: June 2009

Heat shock proteins (HSPs) were documented for the first time in both somatic extracts and excretory/secretory (ES) products of the infective-stage larvae ofTrichinella spiralisandT. pseudospiralis. Larvae recovered from muscles of infected mice were heat shocked at 37, 40, 43 and 45 °C in RPMI 1640 medium containing L-[35S]methionine. Somatic extracts and ES products of heat-shocked worms were then analysed by SDS-PAGE, autoradiography and laser densitometry. Prominent bands of HSPs were observed at 43 °C which is the optimal heat shock temperature. The major HSPs in somatic extracts ofT. spiraliswere 20, 47, 50, 70, 80 and 86 kDa. When the temperature was increased from 37 to 43 °C, the greatest increase in absorbance was observed in HSPs 70 and 86.In vitrotranslation of mRNA in a nuclease-treated rabbit reticulocyte lysate system showed an increase in the synthesis of the 80 kDa protein. This suggests that the production of HSP 80 is regulated at the transcriptional level. The major HSPs in the ES products were 11, 45, 53 and 64 kDa. InT. pseudospiralis, the major HSPs in the somatic extracts were 20, 26, 31, 50, 53, 70, 80 and 86 kDa, and in the ES products, 11, 35, 37, 41 and 64 kDa.
Density-dependent sex ratio in Echinomermella matsi (Nematoda), a parasite of the sea urchin Strongylocentrotus droebachiensis
Authors: Stien A. , Halvorsen O. , Leinaas H. P.
Published: June 2009

We investigated the adult sex ratio in 70 infrapopulations of the nematode Echinomermella matsi, a parasite of the green sea urchin Strongylocentrotus droebachiensis. The adult sex ratio was skewed towards female dominance at low adult intensity and towards male dominance at high adult intensity. We hypothesize that this is due to differences between the sexes in development and mortality rates, or that female recruitment is density dependent. A model with differences between the sexes in developmental and mortality rates may develop the observed sex ratios if the female developmental and mortality rates are several times that of the males. A large difference in developmental rates between the sexes appears unreasonable because the developmental rate for both sexes is low, and the predicted low female life-expectancy is unlikely because the males appear to accumulate in infrapopulations as the females age. Density dependence of female numbers is, however, supported by a significantly lower female recruitment in infrapopulations with old females. We also find that the mean male length is negatively related to measures of crowding, thereby supporting the hypothesis that competition is of importance in E. matsi infrapopulations. A female bias at low intensities of infection, a density dependence in female recruitment and the taxonomic position of E. matsi indicate that sex may be environmentally determined in this nematode.
NADPH diaphorase activity in peptidergic neurones of the parasitic nematode, Ascaris suum
Authors: Bascal Z. A. , Montgomery A. , Holden-Dye L. , Williams R. G. , Thorndyke M. C. , Walker R. J.
Published: June 2009

The histochemical marker for nitric oxide synthase, NADPH diaphorase, is known to co-localize in mammalian neurones with various classical neurotransmitters and neuropeptides. The nervous system of the parasitic nematode Ascaris suum has previously been shown to contain both NADPH diaphorase activity and neuropeptide immunoreactivity. This study examined the possibility that NADPH diaphorase and neuropeptide immunoreactivity may co-exist in the same neurones. Two antisera were used, one raised to KYSALMFamide, a C-terminal synthetic analogue of SALMFamide 1 (GFNSALMFamide), and another that recognizes calcitonin-gene-related peptide (CGRP). We provide evidence that in a distinct subset of neurones in the ventral, dorsal and lateral ganglia NADPH diaphorase staining and SALMFamide- like immunoreactivity are co-localized, suggesting a possible role for nitric oxide in modulating neuropeptide activity in these regions. CGRP-like immunoreactivity was less widely distributed, and was not consistently co-localized with NADPH diaphorase.
An initial characterization of the proteolytic enzymes secreted by the adult stage of the human hookwormNecator americanus
Authors: Brown A. , Burleigh J. M. , Billett E. E. , Pritchard D. I.
Published: June 2009

The proteolytic activities present in adultNecator americanusexcretory–secretory products have been assessed using biologically relevant, naturally occurring substrates (haemoglobin and fibrinogen) and a number of synthetic fluorogenic and chromogenic substrates. One broad peak of activity was observed against haemoglobin in the pH range 5 to 7, with maximum activity at pH 6·6, while fibrinogenolytic activity was shown to be greater at pH 3·5. Inhibition studies against haemoglobin, fibrinogen and synthetic substrates using a battery of appropriate protease inhibitors indicated the presence of a mixture of aspartyl, cysteinyl and serine proteases. Metal ion (Ca2+, Zn2+and Fe2+) stimulation was demonstrated, with stimulation by Zn2+being the most marked. These results are discussed in the context of recent developments in the field of parasite proteolytic enzymes, where they have been suggested as targets for immuno- and chemotherapy.
Host-specific components of the reproductive success of Transversotrema patialense (Digenea: Transversotrematidae)
Authors: Whitfield P. J. , Anderson R. M. , Bundy D. A. P.
Published: June 2009

Using a range of infection techniques, the ability of cercariae of the ectoparasitic digenean Transversotrema patialense to infect 24 species of tropical freshwater fish is examined. Of the 24 species (from 11 families) it is possible to infect 21 (from 8 families) under laboratory conditions. Reproductive success (R) for T. patialense from the cercarial infection process to the production of viable eggs by adult flukes is estimated for infections on two fish hosts, the cyprinid Brwhydanio rerio and the characinid Cheirodon sp. in controlled laboratory conditions. To calculate R, separate estimations of parasite infectivity, survival, fecundity and egg viability were made on populations of both host species. The enhanced reproductive success (R) of T. patialense on Cheirodon sp. is the composite resultant of higher infectivity, lower mean expected adult fluke life-span and higher mean fecundity/surviving worm when compared with infections on B. rerio under identical experimental conditions. Different patterns of egg viability of the two hosts do not materially influence differential reproductive success. A variety of formal techniques for handling the interacting components of reproductive success are described. The relationship between these techniques and the concept of basic reproductive rate, R0 (Macdonald, 1957; Anderson, 1982) is assessed.
Cloning and expression of DiT33 fromDirofilaria immitis: a specific and early marker of heartworm infection
Authors: Hong X. Q. , Mejia J. Santiago , Kumar S. , Perler F. B. , Carlow C. K. S.
Published: June 2009

Dirofilaria immitisis an important filarial parasite of dogs and cats, and a useful model for human filariasis. Current diagnostic tests for heartworm infection in animals rely on the presence of fecund female worms (usually found 6·5 months post-infection or later) and therefore fail to detect pre-patent infections. Putative pepsin inhibitors from 2 filarial parasites of humans namelyOnchocerca volvulus(Ov33, Oc3.6, OvDSB) andBrugia malayi(Bm33), have been shown to be useful in diagnosis of onchocerciasis and lymphatic filariasis, respectively. Previous studies have suggested that a homologue exists inD. immitis(DiT33), which may have potential in diagnosis of heartworm infection. In this study, the isolation and characterization of a cDNA clone encoding DiT33 is described.‡ This cDNA contains 12 bases of the nematode-specific 22 nucleotide spliced leader sequence and encodes a 26·4 kDa-protein with a high level of similarity (87–89%) to other filarial members of the family. DJT33 was over-expressed inE. colias a fusion with the maltose-binding protein and serological analysis was performed using a panel of clinically defined dog sera. The findings of this study indicate that DiT33 is a promising antigen for the early detection ofD. immitisand may be a valuable tool in the control and management of heartworm infection.
The entry ofTheileria parvamerozoites into bovine erythrocytes occurs by a process similar to sporozoite invasion of lymphocytes
Authors: Shaw M. K. , Tilney L. G.
Published: June 2009

The entry ofTheileria parvamerozoites into bovine erythrocytesin vivois described and compared to sporozoite invasion of lymphocytes. Merozoites make initial contact with erythrocytes with any part of their surface and invasion of the host cell does not require the re-orientation of the apical end of the merozoite towards the surface of the erythrocyte. After the initial attachment the merozoite and host cell membranes form a continual close junction with the two apposed membranes separated by a 6–8 nm gap containing moderately dense material. The progressive circumferential ‘zippering’ of these closely apposed membranes leads to the movement of the parasite into the erythrocyte. The newly internalized merozoite which is completely surrounded by the erythrocyte plasma membrane escapes from this enclosing membrane by a process involving the discharge of at least the rhoptries; whether the merozoite also contain other types of secretory organelles (e.g. micronemes, microspheres or dense bodies) remains to be determined. Morphologically, the events involved in merozoite invasion of erythrocytes are almost identical to the process of sporozoite invasion of lymphocytes but differ significantly from the entry process of the invasive stages of other Apicomplexan parasites.
Characterization of fractionatedSchistosoma mansonisoluble adult worm antigens that elicit human cell proliferation and granuloma formationin vitro
Authors: Hirsch C. , Goes A. M.
Published: June 2009

Soluble adult worm antigens (SWAP) ofSchistosoma mansoniwere fractionated by fast protein liquid chromatography (FPLC) system, using Q-Sepharose anion-exchange resin, in order to characterize antigenic fractions that may elicit cell responses in human schistosomiasis. SWAP fractions were eluted by 20 HIM Tris–HCl solution (pH 9·6) with an increasing gradient of 1 M NaCl. The FPLC system was able to resolve 6 fractions, enumerated I to VI, according to the NaCl gradient. The analysis of each fraction on SDS–PAGE showed that fractions I to IV were constituted by multiple protein bands withMrranging from 21 to > 200 kDa. Large amounts of nucleic acids were evidenced in fractions V and VI, as revealed by ethidium bromide staining of agarose electrophoresis gels. Using ELISA, it was shown that sera from chronic schistosomiasis patients contained antibodies that recognized antigens in practically all fractions. Studies were designed to investigate the capacity of these fractions to induce cell proliferation and granuloma formation. It was demonstrated that fraction III stimulated a significant proliferative response of peripheral blood mononuclear cells (PBMC) from chronic schistosomiasis patients. However, fraction III coupled to polyacrylamide beads induced small granuloma formationin vitro, whereas beads coated with fractions I, II and V were able to induce significant granuloma reactions.