bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental amoebiasis and the development of anti-amoebic compounds
Authors: Neal R. A.
Published: June 2009

In the ideal situation, the development of new amoebicides, or more accurately anti-amoebic compounds which are compounds with activity againstEntamoeba histolytica, should initially proceed with the study of parasite-specific metabolic pathways and their inhibition, followed by whole parasitein vitrostudies, experimentalin vivomodels and finally clinical trial. However, there are considerable gaps in our knowledge which will be discussed below, and consequently many investigators consider that empirically selected compounds should be tested experimentally in addition to specifically designed compounds. Before clinical trials can begin, extensive examination of the candidate amoebicide in experimental animals is required in order to investigate possible toxicological hazards.

In addition to inhibiting the amoebic parasite, the drug has to reach the parasite in several different sites in the body, thus there is also a problem of pharmacokinetics and distribution. Prior to the discovery of the nitroimidazole class of amoebicides, the multi-site attack was solved by the use of several drugs, sometimes in sequence during the treatment of an individual case (Powell, 1972). The discovery of the nitroimidazole class of compound changed the situation dramatically and these have shown a clinical and parasitological effect against extra-intestinal and intestinal wall infections. The effect on intralumenal infection (that is mildly symptomatic or asymptomatic infections) of the large intestine is, however, less certain (Finegold, 1977; Spillman, Ayala & Sanchez, 1976).

Although the treatment of amoebiasis appears to be satisfactory at the present time, it is difficult to predict problems which might arise in the future, and therefore it is valuable to continue the pre-clinical development, especially the investigation of parasite metabolism, in order to define parasite-specific points of chemotherapeutic attack.

The chemotherapy of amoebiasis was reviewed comprehensively by Woolf (1963, 1965). The present account of the development of amoebicides therefore starts from the Woolfe reviews.
Development of Plasmodium berghei ookinetes in the midgut of Anopheles atroparvus mosquitoes and in vitro
Authors: Janse C. J. , Rouwenhorst R. J. , Van Der Klooster P. F. J. , Van Der Kaay H. J. , Overdulve J. P.
Published: June 2009

Plasmodium berghei ookinete formation in vitro and within the midgut of susceptible Anopheles atroparvus were compared. No significant morphological differences were seen, except that in vitro development was more synchronized and less degenerating forms occurred. In vitro ookinete yields were 4–31 times higher and less variable than those in vivo. Mosquitoes of a susceptible and of a refractory line of A. atroparvus were simultaneously fed on the same host or via a membrane with the same suspension of in vitro-formed mature ookinetes. Up to 100% of mosquitoes of the susceptible line produced oocysts, mostly in high numbers, whereas infection rates and numbers of oocysts produced in mosquitoes of the refractory line were lower and much more so after host feeding than after membrane feeding of mature ookinetes, indicating that refractoriness does not depend on a single process of inhibition.
The influence of a chronic subclinical infection ofTrichostrongylus colubriformison gastrointestinal motility and digesta flow in sheep
Authors: Gregory P. C. , Wenham G. , Poppi D. , Coop R. L. , MacRae J. C. , Miller S. J.
Published: June 2009

The influence of a chronic subclinicael infection ofTrichostrongylus colubriformis, 2500 larvae/day for 12 weeks, on gastrointestinal motility and digesta flow was studied in 12 sheep suppliedad libitumwith food and water. Motility was recorded by X-radiography and electromyography from chronically implanted electrodes;abomasal volume and outflow were estimated by dilution of CrEDTA; small intestinal transit time was estimated by passage of Phenol Red. The findings were compared with measurements made prior to infection at restricted food intake and reported separately. The first effects of infection were seen after 3–4 weeks. No animal developed diarrhoea, but food intake was progressively reduced. Small intestinal transit time, abomasal volume and half-time of marker dilution increased while abomasal outflow decreased during infection. These changes occurred both in absolute terms and when compared with values predicted from the observed level of food intake. As the animals became resistant to the parasites abomasal volume and digesta flow returned towards control values (weeks 10–12). The migrating myoelectric complex (MMC) was disrupted in only one sheep, and only transiently. In all sheep the frequency of the MMC was increased during infection and there was a progressive inhibition of abomasal, duodenal and jejunal motility. X-radiography showed there was prolonged pooling of digesta in the proximal small intestine which was cleared only at the phase of regular spiking activity. Two sheep given an anthelmintic drench recovered normal motility and clearance of digesta. It is concluded that subclinical infection of sheep with T.colubriformisalters the normal pattern of gastrointestinal motility in the absence of any diarrhoea, and causes inhibition of abomasal and proximal small intestinal motility and digesta flow. The increased frequency of MMCs helps to maintain digesta flow through the proximal small intestine.
Echinococcus granulosus: specificity of amino acid transport systems in protoscoleces
Authors: Jeffs S. A. , Arme C.
Published: June 2009

Protoscoleces ofEchinococcus granulosusabsorb the l-amino acids proline, methionine, leucine, alanine, serine, phenylalanine, lysine and glutamic acid by a combination of mediated transport and diffusion. All eight amino acids were accumulated against a concentration gradient. Comparison ofKtandVmaxvalues suggests that a low affinity for a particular compound is compensated for by a relatively larger number of transport sites for that compound. Four systems serve for the transport of the eight substrates studied: 2 for neutral (EgNl, EgN2) and 1 each for acidic (EgA) and basic (EgB) amino acids. All eight amino acids are incorporated into protein to varying degrees and substantial portions of absorbed l-alanine and l-methionine are metabolized into other compounds.
The epidemiology ofOstertagia ostertagiand other gastrointestinal nematodes of cattle in Louisiana
Authors: Williams J. C. , Knox J. W. , Marbury K. S. , Kimball M. D. , Baumann B. A. , Snider T. G.
Published: June 2009

The epidemiology ofOstertagia ostertagiand other gastrointestinal nematodes in yearling beef cattle was examined in each of 2 successive years. During each year 50 head of newly weaned beef calves were given a single dose of thiabendazole and then placed on experimental pastures. Twenty-four of the animals were designated for monthly slaughter (n= 2) and analysis of worm population characteristics and 25 were designated for blood and faecal collection and for weighing. Parasite-free tracer calves were grazed alongside the yearling cattle each month (n= 2) throughout the 2 years and were also slaughtered for analysis of worm populations. Faecal egg counts, plasma pepsinogen determinations, herbage larval counts, and animal liveweight changes were recorded monthly. Results of this work substantiated previous observations on seasonal changes of populations of the different nematode genera, but greater continuity and definition of patterns was possible in the present work.Ostertagia ostertagiwas the predominant nematode present. While minimal numbers of inhibited larvae were observed from autumn into winter, most of the population was adult at this time. Acquisition of inhibition-prone larvae begins in late winter and peak numbers are acquired between March and June. Little transmission ofO. ostertagioccurs between June and September.Trichostrongylus axeihad a similar seasonal prevalence toO. ostertagi.A major difference in the 2 years was in the pattern of maturation of inhibited larvae. This occurred early, during May 1981, following below average temperatures in May and above average rainfall in May and June. Overt type II disease was not associated with a smaller level of maturation in autumn 1981. In contrast, maturation of large burdens of inhibited larvae did not occur until autumn 1982 following a protracted period of dry and hot weather from spring. Acute type II disease was observed in autumn 1982. Reasons for the differences in maturation pattern, based on worm counts from yearling cattle and tracer calves and association of these with faecal egg counts, herbage larval counts, clinical condition, and liveweight changes are discussed.
The relationship between the density of Fasciola hepatica miracidia and the net rate of miracidial infections in Lymnaea truncatula
Authors: Smith G.
Published: June 2009

Experimental studies on the dynamics of infection of Lymnaea truncatula by the miracidia of Fasciola hepatica show that there is a linear relationship between the net rate of attachment of miracidia to snail epithelium and the density of infective stages. The probability of a snail remaining uninfected after exposure to a single miracidium varies with the size class of the snail. Under the conditions of the experiment (temperature, 15° C; exposure period, 30 min; water volume, 8 ml), the probability was 0·46–0·48, 0·27–0·26 and 0·13–0·19 for snail size classes, 0·5–2·9, 3·0-5·9 and 6·0-8·9 mm respectively.
Detection of circulating trypanosomal antigens by double antibody ELISA using antibodies to procyclic trypanosomes
Authors: Liu M. K. , Pearson T. W.
Published: June 2009

A double antibody sandwich ELISA technique has been developed for detection of antigens of African trypanosomes present in the sera of infected mammals. The assay uses a high titre, high affinity rabbit antiserum made to purified membranes of procyclic trypanosomes as ‘capture’ reagent and a mixture of three biotin-labelled trypanosome-specific monoclonal antibodies as detecting reagent. The monoclonal antibodies were chosen on the basis of their specificity for surface membrane antigens ofTrypanosoma bruceispp., the relative abundance and solubility of their specific antigen in aqueous solvents (including serum), and the fact that each monoclonal antibody binds to distinct epitopes on the same antigen molecule. Thus, antigen capture from serum and subsequent detection was achieved using as little as 10 ng/ml of whole trypanosome lysate, or the equivalent of 5000 trypanosomes/ml when solubilized material was added to normal serum in an artificial system. Using the optimized assay, antigen was detected in the sera of trypanosome-infected mice as early as 2 days after infection withT. b. rhodesiense.The results indicate that the assay allows detection of low concentrations of specific membrane antigens ofT. bruceispp. of African trypanosomes and thus may have immunodiagnostic utility.
Evidence for predisposition in humans to infection with Ascaris, hookworm, Enterobius and Trichuris in a South Indian fishing community
Authors: Haswell-Elkins M. R. , Elkins D. B. , Anderson R. M.
Published: June 2009

Studies of patterns of reinfection with four species of intestinal nematodes (Ascaris, hookworm, Trichuris and Enterobius) in 174 individual patients following chemotherapeutic treatment revealed statistical evidence for predisposition to heavy or light infection (relative to the average level in the overall population). Analyses of associations between the abundances of the four species of nematodes within a combined sample of 525 worm burdens showed significant correlations between 5 out of the 6 possible pair-wise comparisons between species. The relevance of these results to the design of control programmes based on chemotherapeutic application is discussed.
The regulation ofOstertagia ostertagipopulations in calves: the effect of past and current experience of infection on proportional establishment and parasite survival
Authors: Grenfell B. T. , Smith G. , Anderson R. M.
Published: June 2009

A mathematical model of the parasitic phase of the life-cycle ofOstertagia ostertagiin calves is described. The model is used in the re-analysis of previously published data from a long-term trickle infection experiment in which groups of calves were infected daily with graded doses of 3rd-stage (L3) larvae. The results of the analysis are consistent with the hypothesis that the observed changes in the intensity of infection in the calves were the result of a decline in the proportional establishment of ingested L3 larvae, and a rise in the death rate of the 5th-stage worms as the duration of exposure to infection increased. The proportion of ingested L3 larvae that become established in the mucosa can be described as an exponential decay function of the duration of the infection. Within the range of trickle intensities investigated, the function appears to vary independently of the level of exposure to infection. In contrast, the rate of mortality of the 5th-stage worms appears to be an increasing linear function of the total cumulative number of 3rd-stage larvae administered.
The regulation ofOstertagia ostertagipopulations in calves: density-dependent control of fecundity
Authors: Smith G. , Grenfell B. T. , Anderson R. M.
Published: June 2009

The decline in faecal egg counts, characteristic of calves which have been experimentally infected withOstertagia ostertagi, is analysed using a mathematical model in which parasite fecundity is assumed to be an inverse function of both the duration and intensity of infection. The model incorporates a description of the frequency distribution of mature parasites between hosts (which is less over-dispersed than is usual for many other helminth infections). The model provides a good overall description of the decline in faecal egg production observed during trickle and single infection experiments. The main discrepancy between a comparison of the model predictions and the results of the most detailed available series of trickle infection experiments occurs at the initial peak of egg production. The magnitude of this difference appears to be related to the worm burden at the peak of egg production. The possible mechanisms underlying density-dependent regulation of the fecundity ofO. ostertagiaare discussed.
Population biology ofOstertagia ostertagiand anthelmintic strategies against ostertagiasis in calves
Authors: Smith G. , Grenfell B. T. , Anderson R. M. , Beddington J.
Published: June 2009

Five chemoprophylactic or chemotherapeutic strategies against bovine ostertagiasis are compared using a mathematical model of the population biology ofOstertagia ostertagi. The model offers a means of screening novel strategies prior to their further investigation in the field. Under conditions of climate and management typical of many regions in Northern temperate Europe, the model indicates that all of the tested prophylactic strategies will result in a profound reduction in the intensity of infection in grazing beef calves when compared with an untreated control group or the simple therapeutic protocol. Not all of those strategies which caused diminution in the scale of the midsummer rise in pasture larval contamination resulted in progressively less contaminated pastures in subsequent years. Moreover, the reproductive potential of the parasite is so great that the principal advantage of the ‘pasture cleaning’ effect that is the consequence of some protocols is not that the pasture may eventually be used to graze untreated calves but that the treated animals are subjected to a progressively smaller parasitic challenge with the concomitant pay-off in production gains.
Questions in digenean systematics and evolution
Authors: Gibson D. I.
Published: June 2009

Since the work of Dujardin (1845), attempts have been made to decipher acceptable divisions of the trematode groups at higher taxonomic levels, and yet there is still no generally accepted classification of the higher taxa of the Trematoda as there are for other groups of parasitic worms, such as the Monogenea, Cestoda, Nematoda and Acanthocephala. Why is it that workers with a wide knowledge of trematode systematics, such as Dollfus, Stunkard, Manter and especially Yamaguti, have felt unable or unwilling to comment in detail upon the phylogenetic relationships within the group at higher taxonomic levels? One of the main reasons for this state of affairs lies in the fact that, generally speaking, the group is not easily split into major subgroups by obvious, non-homoplasious morphological characters. Early attempts at division, based upon sucker arrangements, i.e. monostome, distome, amphistome and gasterostome, are not satisfactory, as distomes form the vast majority of the Digenea and both monostomes and amphistomes are certainly polyphyletic. In addition, the picture within the Digenea is complicated by the group's complex life-history patterns. Whereas early classifications all tended to be based upon adult (marital) morphology, life-history patterns are given great weight by workers such as Pearson (1972) and Bozhkov (1982). The cercarial morphology is considered the dominant feature in the classification of the group presented by La Rue (1957) and is emphasized in the phylogenetic relationships between the subgroups recognized by Cable (1974). Odening (1961), following an earlier suggestion of Lebour (1912), presented a classification, the major divisions of which were based upon the daughter-parthenita (i.e. the redia or daughter-sporocyst), a stance which he later found untenable (Odening, 1974). Consequently, the wealth of conflicting data from these and other sources has deterred the presentation both of classifications and speculations on evolutionary relationships. The classification of Odening (1974) and the recent cladistic analysis of Brooks, O'Grady & Glen (1985b) utilized data from all of the life-history stages. As the classification of Brooks et al. (1985b) is the most recent, and readily available in English, it must be a serious contender in terms of general acceptance. If it is accepted, then one would hope that this will be on its merits rather than because of its availability or the lack of viable alternatives; but, as discussed below, it is easy to find fault with this classification when it and its premises are examined in detail.
Eimeria tenellasporozoites: the method of excystation affects the surface membrane proteins
Authors: Wisher M. H. , Rose M. E.
Published: June 2009

Eimerian sporozoites can be recovered from intestinal washings after oral administration of oocysts to chickens but suspensions of sporozoites are usually prepared in the laboratory by incubation of sporocysts or fractured oocystsin vitro, at body temperatures, with relatively high concentrations of trypsin and bile salts. Since these agents affect membrane structure, the surface membrane of proteins ofEimeria tenellasporozoites excystedin vivoandin vitrohave been compared. Surface radio-iodination followed by sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS–PAGE) showed that more125I was incorporated into polypeptides on sporozoites excystedin vivothan on sporozoites excystedin vitro. The125I-polypeptide profile of sporozoites excystedin vivowas more resistant to subsequent incubation with pure trypsin than that of sporozoites excystedin vitro, but incubation with bile salts resulted in the loss of some iodinated polypeptides from both preparations of iodinated sporozoites. Reaction with combinations of crude trypsin and bile salts led to the lysis of sporozoites. The method of excystation had no effect on the reaction of convalescent chicken serum with Western blots of sporozoites but the results of immunofluorescent staining carried out with mouse monoclonal antibodies indicated that the structure of the cell surface was altered and some antigenic determinants were lost from sporozoites excystedin vitro. In contrast, neither the infectivity of sporozoites determinedin vivo, nor their invasion of cultured cells was changed by the method of excystation.
Measurement of malarial infectivity of human populations to mosquitoes in the Madang area, Papua New Guinea
Authors: Graves P. M. , Burkot T. R. , Carter R. , Cattani J. A. , Lagog M. , Parker J. , Brabin B. J. , Gibson F. D. , Bradley D. J. , Alpers M. P.
Published: June 2009

The proportion of blood meals taken on humans which are infectious to mosquitoes in the Madang area, Papua New Guinea was estimated by two methods. In the first, laboratory rearedAnopheles farautiwere fed on individuals of all ages at village surveys. The results showed that 3·8% of people were infectious and that the mean percentage of mosquitoes which became infected by feeding on these people was 37·9%. From the average proportion of mosquitoes infected, the probability that a mosquito feeding on a human would pick up infection was 0·013±0·005. In the second approach mosquitoes were fed on identifiedPlasmodium falciparum, P. vivaxandP. malariaegametocyte carriers. The results indicated that 46% of gametocyte carriers were infectious and that the mean probability of a mosquito becoming infected after feeding on a gametocyte carrier was 0·151±0·029. Gametocyte prevalence rates in all ages measured over 18 months in three villages averaged 3·3%P. falciparum, 4·0%P. vivaxand 0·7%P. malariae, totalling 8·0±0·7%. Combining gametocyte prevalence rates with the probability of a mosquito becoming infected from a gametocyte carrier, the probability of a mosquito becoming infected following a blood meal on a member of the human population was estimated to be 0·012±0·003.
Expression of circumsporozoite proteins revealedin situin the mosquito stages ofPlasmodium bergheiby the Lowicryl-immunogold technique
Authors: Hamilton A. J. , Davies C. S. , Sinden R. E.
Published: June 2009

A monoclonal antibody against the circumsporozoite proteins of thePlasmodium bergheisporozoite was used to trace the synthesis and expression of these proteins, via the Lowicryl immunogold technique, within the developing oocyst. The proteins were detected on the endoplasmic reticulum of the oocyst and were present in the sporozoite membranes at the point of their formation.
The tylenchid (Nematoda) egg shell: formation of the egg shell in Meloidogyne javanica
Authors: McClure Michael A. , Bird A. F.
Published: June 2009

Oogonia of Meloidogyne javanica are radially arranged around a central rachis to which they are attached by cytoplasmic bridges. As the oocytes mature the rachis disappears and the oocytes pass through the oviduct in tandem. The oviduct-spermatotheca valve is constructed of two rows of tightly packed cells of which there are four per row. The nuclei of these cells are large and contain balloon-shaped cytoplasmic invaginations. The spermatotheca is characterized by microtubules which extend to its lumen and by invaginations of plasmalemma. Cells of the distal uterine region contain large intracytoplasmic spaces bordered by endoplasmic reticulum whereas proximal uterine cells have dense cytoplasm and large areas of compact endoplasmic reticulum. Egg-shell formation begins in the spermatotheca with the modification of the oolemma to form the vitelline layer. The chitinous layer begins in the distal portion of the uterus and appears to originate from the egg. Proline-containing protein is incorporated into the chitinous and lipid layers as the egg passes through the mid-region of the uterus and formation of the lipid layer in this region completes egg development.
Immune expulsion ofTrichuris murisfrom resistant mice: suppression by irradiation and restoration by transfer of lymphoid cells
Authors: Wakelin D. , Selby Gwendoline R.
Published: June 2009

Lethal irradiation (850 rads) of mice made resistant toTrichuris murismarkedly depressed their ability to expel a challenge infection. Expulsion was restored within 7–10 days when MLNC from uninfected mice were transferred on the day of infection, but no significant restoration was evident after transfer of immune serum. Transfer of BM alone had no restorative effect within 10 days and no synergism was seen when both BM and MLNC were transferred. MLNC from uninfected donors did not restore challenge expulsion when transfer was delayed until day 7 and the mice were killed 3 days later, although MLNC from resistant donors were effective within this time. When irradiated mice were given BM and the challenge infection allowed to continue for 15 days expulsion was restored, as it was when challenge was delayed for 7 days after BM transfer in thymectomized mice. The results confirm that expulsion ofT. murisinvolves both antibody-mediated and lymphoid cell-mediated phases and offer no evidence for the involvement of other cell types.
Some observations on egg production and autoreinfection ofReighardia sternae(Diesing, 1864), a pentastomid parasite of the herring gull
Authors: Banaja A. A. , James J. L. , Riley J.
Published: June 2009

Egg production byReighardia sternae, implanted at various stages of maturity into the interclavicular air sacs of captive gulls, is described.

Females produce only 2900 eggs per lifetime over a short patent period of 1–3 days. The problem of a direct life-cycle in relation to this unusually low fecundity is discussed, and speculation is advanced concerning a possible parasitic behavioural trait which could facilitate direct transmission. The hazards of the latter are also offset by auto-reinfection.
Immunity to Hymenolepis diminuta: unresponsiveness of the athymic nude mouse to infection
Authors: Bland P. W.
Published: June 2009

Male and female congenitally athymic nude (nu/nu) mice infected with a single cysticercoid of Hymenolepis diminuta at 6 weeks of age retain the infection for at least 33 days. In the males of their phenotypically normal litter-mates, however, a single cysticercoid infection establishes and grows but is expelled between days 11 and 17. The unresponsiveness of the nude mouse to single H. diminuta infection is evidence that the immune rejection from normal mice is thymus-dependent.
The occurrence of Eimeria marsica in the domestic sheep in England and Wales
Authors: Norton C. C. , Catchpole Janet
Published: June 2009

Eimeria marsica Restani 1971 is re-described from oocysts recovered in pure culture from experimentally infected coccidia-free lambs. The ellipsoidal oocysts, which measure 19·1 x 131 μm, possess an inconspicuous micropylar cap. The prepatent period varies from 14–16 days. E. marsica is recorded for the first time from sheep in England.
Eimeria tenella, E. acervulina and E. maxima: studies on the development of resistance to diclazuril and other anticoccidial drugs in the chicken
Authors: Chapman H. D.
Published: June 2009

Resistance to diclazuril was induced by 10 passages of the Houghton strains of Eimeria acervulina and E. tenella in chickens given progressively greater concentrations of the drug. This resistance was, however, not complete since the drug retained some efficacy against the drug-passaged lines. Attempts to passage the Houghton strain of E. maxima in birds medicated with concentrations of diclazuril greater than 0·016 parts per million (ppm) were unsuccessful and after 10 passages at this concentration resistance had not developed. Resistance to methyl benzoquate developed after 6 passages of E. tenella in medicated chickens but resistance to amprolium was only partial after 10 passages. The pathogenicity of diclazuril- and amprolium-resistant lines of E. tenella was lower than that of the parental line. Diclazuril was effective against lines of E. tenella resistant to amprolium, arprinocid, clopidol, dinitolmide, halofuginone, methyl benzoquate, monensin and robenidine.
Cercarial emergence of Proterometra macrostoma and P. edneyi (Digenea: Azygiidae): contrasting responses to light: dark cycling
Authors: Lewis M. C. , Welsford I. G. , Uglem G. L.
Published: June 2009

Proterometra macrostoma and P. edneyi infect the same snail host, Goniobasis semicarinata, but different fish hosts in their life-cycles. Cercariae of P. macrostoma complete development in sunfish, those of P. edneyi in darters; fish become infected when they ingest free-swimming cercariae as ‘prey’. Laboratory and field experiments were designed to test the hypothesis that light: dark (L: D) cycling regulates emergence of both species. Under L: D cycling conditions, P. macrostoma emerged in the dark and P. edneyi in the light. These emergence patterns resulted from differential sensitivity to light and dark. In the laboratory and field, reversing the light and dark periods resulted in corresponding alterations in emergence patterns of both species. Both species emerged in constant light and constant dark, but their emergence patterns were altered. Emergence patterns may represent adaptations that make the cercariae more susceptible to ‘predation’ by their respective fish hosts.
Developmental changes in proteins and glycoproteins revealed by direct radio-iodination of viableTaenia saginatalarvae
Authors: Joshua G. W. P. , Harrison L. J. S. , Sewell M. M. H.
Published: June 2009

Direct surface I radio-isotope labelling techniques and SDS—PAGE analysis were used to compare the proteins and lentil—lectin adherent glycoproteins of the bovine stage of viableTaenia saginatalarvae at three points in their development, the invasive oncospheres, immature (4-week-old) and mature (12 to 16-week-old) cysticerci. Some proteins and glycoproteins were present on all three of the ages of the parasite examined but there were also distinct age-specific proteins and glycoproteins detected on oncospheres and 4-week-old cysticerci and a marked difference between the protein/glycoprotein profiles of the parasite was apparent at these earlier stages of development and the mature cysticerci. The latter were characterized by the presence of high, 160–200 kDa molecular weight, lysine rich, glycoproteins, whereas small 16 and 18 kDa glycoproteins and a reduction-sensitive 23 kDa glycoprotein were first detected on 4-week-old immature cysticerci. Antigenic characterization of the isotope-labelled proteins and glycoproteins by immunoprecipitation against a panel of clinically defined bovine sera combined with SDS–PAGE analysis indicated that relatively few proteins were precipitated by sera fromT. saginata-infected cattle as compared to the glycoproteins. However, both protein and glycoprotein antigens of possible protective and/or diagnostic significance were identified from oncospheres and cysticerci.
Antibody responses of rodents to a tegument membrane preparation from adultSchistosoma mansoni
Authors: Roberts Shirley M. , Boot C. , Wilson R. A.
Published: June 2009

A preparation highly enriched in tegument membranes from adult worms has been used to probe rodent responses to schistosome surface antigens. All exposure regimes in mice stimulated levels of anti-tegument IgG, measurable by ELISA. Plateau levels of circulating antibody attained were similar after mixed-sex and male-only infections, and vaccination with tegument membranes. Female-only infections and exposure to irradiated cercariae stimulated lower levels of anti-tegument antibody. Responses in rats were similar, but occurred more rapidly, probably due to the large initial parasite exposure. Although both mice and rats could be stimulated to produce high levels of anti-tegument antibody by multiple vaccination, consistent protection against a challenge was not obtained. Paradoxically, rats and mice vaccinated with irradiated cercariae developed low levels of antibody to tegument membrane antigens but were highly resistant to challenge. It was concluded that, in the range of sera examined, antibody responses to schistosome tegument membranes did not correlate with the immune status of the host.
A comparative evaluation of snail sampling and cercariometry to detect Schistosoma mansoni transmission in a large-scale, longitudinal field-study in Machakos, Kenya
Authors: Ouma J. H. , Sturrock R. F. , Klumpp R. K. , Kariuki H. C.
Published: June 2009

In an operational Schistosoma mansoni field-study in an area of about 20 km (population approximately 8000), transmission detection by simple snail sampling was compared with cercariometry. Between 1985 and 1987, 62 field sites were sampled at fortnightly intervals. Of a total of 2758 field observations, 89.8% gave full snail data; 64.4% full cercarial data; and 61.7% complete data for both methods. The complete data sets showed significant but not strong correlations between Biomphalaria pfeifferi (total and infected with S. mansoni or other trematodes) and cercarial (S. mansoni and non-human) recoveries. Non-human (but not S. mansoni) cercarial recovery decreased with deteriorating cercariometry filter quality. Both snail and cercarial recoveries diminished significantly with increasing water flows at the time of collection. Many samples yielded infected snails or cercariae, but not both, and neither method detected significantly more transmission sites. The method of choice for detecting transmission in a large-scale field-study depends on logistical and financial considerations. Relatively simple snail sampling allows quick, cheap and widespread data collection adequate for most purposes but more complicated cercariometry is still valuable for specific, small-scale studies.
A preliminary assessment of the feasibility of evaluating promising antifilarials in vitro against adult Onchocerca volvulus
Authors: Comley J. C. W. , Szopa T. M. , Strote G. , Buttner M. , Darge K. , Buttner W.
Published: June 2009

The suitability of motility indices and tetrazolium-based colorimetric assays for the determination of the viability of adult Onchocerca volvulus after in vitro exposure to potential macrofilaricides has been examined. Experimentation showed that both techniques could be applied to adult O. volvulus, although the variability between individual worms necessitated the use of large experimental groups. The potential of using cut anterior tips of female O. volvulus for screening was also investigated. These were shown to give reasonably consistent motility indices, and drug effects were discernible even after 72 h in vitro culture. Application of these viability criteria to studies on the short-term in vitro survival of intact male and female O. volvulus incubated in Eagles MEM plus serum, under 5% CO2 in air, showed this medium to be suboptimal with a greater than 50 % loss of worm viability within 144 h of nodulectomy. Males isolated by the collagenase technique were shown to be significantly less viable than dissected males, by both motility indices and tetrazolium reduction. The results highlight the need to use either dissected males, or in the case of females, the need to minimize exposure to collagenase solution. A possible mechanism for selecting a more uniformly viable female worm population is discussed. Examination of the in vitro effects of CGP 20376 using these viability criteria/assay systems showed some delayed suppression of worm motility, but after 120 h in vitro CGP 20376 was not macrofilaricidal against male or female O. volvulus. Male worms were also implanted subcutaneously into gerbils. Treatment of these animals with CGP 20376, with autopsy 2 weeks later, resulted in a small macrofilaricidal effect (28% worm death). Some reduction in the motility of living worms recovered from CGP 20376-treated gerbils was also evident. Good survival of control worms recovered 2 weeks post-implantation suggests that male O. volvulus might survive longer subcutaneously. The prospects for undertaking meaningful drug evaluations against O. volvulus in vitro (and in vivo in rodents) is therefore promising, but because of parasite availability will probably be limited to those compounds which have shown potential in other filarial test systems.
The epidemiology of multiple-clone Plasmodium falciparum infections in Gambian patients
Authors: Conway D. J. , Greenwood B. M. , McBride J. S.
Published: June 2009

The occurrence of multiple-clone Plasmodium falciparum haploid blood-stage infections is a pre-requisite for cross-fertilization and genetic exchange at the diploid stage in the mosquito. Using monoclonal antibodies against 3 polymorphic blood-stage antigens, a method of two-colour differential immunofluorescence allowed the resolution of between 1 and 4 clones/isolate. A mean of 2 P. falciparum clones was detected in the blood of malaria patients in The Gambia. The mean number of clones/patient showed no correlation with age, parasitaemia, or disease severity. There was a slight difference in mean number between sample periods, probably reflecting temporal differences in transmission intensity. A statistical analysis of 2-locus genetic diversity of clones within isolates concludes that not all multiple-clone infections result from superinfection, but that some are due to single multiple-clone inoculations.
Proliferation ofToxoplasma gondiiin human neutrophilsin vitro
Authors: Nakao M. , Konishi E.
Published: June 2009

Human neutrophils were infected with tachyzoites ofToxoplasma gondii in vitro. Infection rates after 1 h of incubation were 38·6–52·0% and 16·0–25·8% in the presence or absence of specific antibody respectively. Apparently, neutrophils killed tachyzoites 18 h after infection in the presence of antibody, whereas tachyzoites proliferated in 25·0–35·0% of infected neutrophils in the absence of antibody. Total tachyzoite counts 18 h after infection were approximately 4 times as high as those 1 h after infection in the absence of antibody and complement. Complement also enhanced phagocytosis and killing of tachyzoites by neutrophils, but the effects were less than that of antibody. Superoxide anion was produced intensively within 1 h after infection, depending on the presence of antibody or complement. Neutrophils seem to be responsible for dissemination of tachyzoites in the host during the initial phase ofToxoplasmainfection until antibody is produced.
Neutrophil chemotactic factors secreted fromToxoplasma gondii
Authors: Nakao M. , Konishi E.
Published: June 2009

Neutrophil chemotactic activity was detected in the fluid ofToxoplasma gondiicultures by the agarose plate and the Boyden chamber methods.Toxoplasmaculture fluid was obtained by incubating the tachyzoites at 37 °C in a 5% CO2atmosphere for 6 h in Dulbecco's modified Eagle's minimum essential medium containing 10% heat-inactivated foetal calf serum. Soluble extracts from tachyzoites had negligible activity, indicating that the chemotactic factors were metabolites secreted from tachyzoites. The chemotactic activity inToxoplasmaculture fluid depended on the number of tachyzoites and the period of incubation. The substances responsible for neutrophil chemotaxis were two heat-labile peptides with estimatedMr4·5 and 14 kDa with N-terminal groups free.
The magnitude and kinetics of delayed-type hypersensitivity responses in mice vaccinated with irradiated cercariae ofSchistosoma mansoni
Authors: Ratcliffe E. C. , Wilson R. A.
Published: June 2009

A footpad assay was used to measure the DTH of mice to soluble worm antigens (SWAP), and to living day 7 lung schistosomula, following vaccination and challenge infections withSchistosoma mansoni. DTH to SWAP was first observed on day 10, and reached its maximum on day 17 post-vaccination. Treatment of mice with anti-CD4 antibody on the 3 days prior to footpad challenge completely abrogated this response. Reactivity to living parasites was of a lower order than that to SWAP; it also peaked earlier, on day 10 post-vaccination. By day 35, responsiveness to both sets of antigens had declined almost to control levels. There was no correlation between the level of DTH to living schistosomula, at any time, and the degree of resistance subsequently developed. Percutaneous challenge of vaccinated mice was followed by a resurgence of reactivity to SWAP. This secondary response occurred more rapidly than the primary response, peaking on day 7 post-challenge, and was of a similar magnitude. We were unable to detect a similar recall of DTH to living schistosomula, possibly because the assay was insufficiently sensitive. We conclude that the intensity and kinetics of DTH responsiveness are crucial features of the irradiated vaccine model, and suggest that further investigation of cell-mediated immune reactions, particularly those occurring in the lungs, is vital to a better understanding of events underlying the development and expression of immunity.
The role of positive and negative interspecific associations in the organization of communities of intestinal helminths of bats
Authors: Lotz J. M. , Font W. F.
Published: June 2009

Twelve populations of bats were examined to determine the extent of interspecific associations in determining the species richness of intestinal helminth infracommunities. The pool of helminth species which was available to individual bats ranged from 2 to 21. The ‘summed binomial’ distribution was determined to underlie the host frequency distribution of the number of helminth species per host. Overall covariation in occurrences of species in replicated communities can be detected by testing for the equality of the observed variance of the host frequency distribution to the variance expected when species are allocated to hosts at random. Where statistically significant the covariance was indicative of a majority of positive rather than negative interspecific associations. As the mean number of species per host in a host population increases not only does the number of positive associations increase but so does the proportion of species pairs which exhibit positive associations. Although there is an increase in the proportion of species pairs which exhibit positive associations as the number of species increases, the magnitude of the associations (as indicated by the mean positive or the mean negative pairwise covariances) does not. Therefore, we concluded that positive interactions are more common than negative interactions in determining the species richness of helminth infracommunities of bats. Further, positive associations become even more important as the community becomes more complex. However, the increased importance is derived from the number rather than the strength of the associations.
Transfer ofEimeria apionodesfrom wood mice (Apodemus sylvaticus) to laboratory mice (Mus musculus)
Authors: Ibrahim S. A. M. , Nowell F.
Published: June 2009

Transfer ofEimeria apionodesfrom wood mice directly into untreated laboratory mice was unsuccessful but transfer into corticosteroid-treated animals produced an oocyst output, about 1000 times less than that observed from wood mice after a similar inoculum. Repeated passage through corticosteroid-treated laboratory mice resulted in a line adapted to survival in untreated animals. This line was compared with the parent strain maintained in wood mice and some features of the oocyst output patterns, notably the pre-patent period, appeared to be controlled by the host species. The oocyst production of each population was higher in the host species to which it was adapted than in the other host species (P> 0·001). Once adapted to laboratory mice, the line produced insignificantly different levels of oocysts in corticosteroid-treated and untreated animals (P> 0·05).
The purification, characterization, serological activity and hepatotoxic properties of two cationic glycoproteins (α1and ω1) fromSchistosoma mansonieggs
Authors: Dunne D. W. , Jones F. M. , Doenhoff M. J.
Published: June 2009

T cell-deprived mice acutely infected withS. mansonisuffer microvesicular hepatocyte damage which is not seen in infected, immunological intact animals. A cationic fraction (CEF6) of the PBS-soluble portion ofS. mansonieggs (SEA) induces antibodies which, on passive transfer, prevent hepatocyte damage. CEF6 contains 2 antigens, ω1and α1, and has also been shown to be a useful serodiagnostic reagent. This paper describes the purification and characterization of the 2 antigens present in CEF6. ω1is a monomeric glycoprotein with a pI > 9·0 and a molecular weight of 31 kDa. α1consists of two immunologically cross-reactive dimers, 41 and 36 kDa in non-reducing conditions, each of which consists of one unique and one common glycoprotein subcomponent. In ELISA with mouse and human infection sera ω1is shown to beS. mansonispecific and is better able to distinguishS. mansoniinfections from other schistosome infections than are unfractionated SEA, CEF6 or α1. Passive transfer of monospecific anti-ω1sera intoS. mansoniinfected, T cell-deprived mice completely prevented the occurrence of microvesicular hepatocyte damage in these animals. Monospecific anti-α1serum had no hepatoprotective capacity.
Relations between resistance to chloroquine and acidification of endocytic vesicle of Plasmodium berghei
Authors: Mahmalgi J. , Veignie E. , Prensier G. , Moreau S.
Published: June 2009

In order to visualize low-pH compartments of Plasmodium berghei strains we have used a basic congener of dinitrophenol, 3-(2,4-dinitroanilino)-3'-amino-N-methyldipropylamine (DAMP) which concentrates in acidic compartments, and can be detected by immunocytochemistry with anti-dinitrophenol antibodies. We have demonstrated that in a P. berghei chloroquine-sensitive strain (N strain), DAMP accumulates in the endocytic vacuoles where haemoglobin degradation is occurring. These compartments which have recently been shown to concentrate 4-aminoquinoline drugs (Moreau, Prensier, Maalla & Fortier, 1986) have an acidic pH. Conversely DAMP was found scattered all over the cytoplasm in a P. berghei chloroquine-resistant strain; the same phenomenon was previously observed (Moreau et al. 1986) in the localization of a 4-aminoquinoline on this same strain. Monensin-induced swelling of acidic compartments (Boss & Morre, 1984) was used as a complementary method for the determination of low-pH compartments on P. berghei strains. All the data reported here suggest that chloroquine resistance in P. berghei RC may be related to an impairment in the acidification of endocytic vesicles.
Egg production inBrugia pahangi(Nematoda: Filarioidea)
Authors: Delves C. J. , Rees H. H. , Howells R. E.
Published: June 2009

Oogenesis inBrugia pahangihas been studied by means of the aceto-orcein chromosomal squash technique and light-microscope autoradiography. The use of colchicine has demonstrated a 2–3 mm terminal germinative zone within the ovary, in which continuous and rapid mitotic division of germ cells occurs. In 80% of the gonads, oocytes within a 1–2 mm length of the ovary proximal to the germinative zone were at the prophase of meiosis I. Primary oocytes with markedly less condensed chromatin, apparently interphase cells, were observed in the corresponding region of the ovary in the remaining 20% of material examined. A cyclical or phased development of primary oocytes is suggested. Autoradiographic studies, concerned with the incorporation of [5-3H]uridine into germ cells ofB. pahangi in vitro, further suggest that the onset of meiotic prophase is associated with the initiation of high RNA synthetic activity. Following meiotic prophase, oocytes complete meiosis I before entering a period of growth during which the chromatin material is decondensed. Recondensation of chromosomes prior to meiosis II is only observed after fertilization within the seminal receptacle. On completion of meiosis II, with the extrusion of a polar body, the haploid chromosome complement of the female unites with that of the male, re-establishing the diploid number of the zygote (2n= 10).