bluuebunny/crossref_metadata_2025 huggingface dataset:
A study on snail location by Fasciola hepatica using radioisotopically labelled miracidia
Authors: Nansen Peter , Frandsen Flemming , Christensen Niels Ørnbjerg
Published: June 2009

A number of common freshwater molluscs were exposed to Fasciola hepatica miracidia labelled in vivo with radioselenium. Radioactivity was rapidly incorporated in all lymnaeid species tested (L. auricularia, L. columella, L. glabra, L. natalensis, L. palustris, L. pereger, L. stagnalis, L. tomentosa and L. truncatula) whereas no radioactivity could be demonstrated in non-lymnaeid pulmonate species (Aplexa hypnorum, Physa acuta, Physafontinalis, Anisus vortex, Gyraulus albus and Planorbis planorbis) or in the prosobranchs Valvata cristata and Valvata piscinalis. However, the prosobranchs Bithynia leachii, Bithynia tentaculata and Potamopyrgus jenkinsi showed a slow but significant uptake of radioactivity which was presumably explained by uptake of labelled miracidia through a ‘filter-feeding] mechanism. Sphaerium corneum, a true filter-feeder, showed a similar course of uptake of radioactivity.
Phosphoglucomutase polymorphism in the tick Ixodes ricinus
Authors: Healy J. A.
Published: June 2009

Ten variants of phosphoglucomutase were detected by starch-gel electrophoresis in extracts of the tick Ixodes ricinus. Agreement of phenotype frequencies with those predicted by the Hardy–Weinberg model indicated that the enzyme is coded by a single gene locus (Pgm) at which 10 alleles are segregating. Allelic proportions in 5 Irish tick samples indicated that both spatial and temporal genetic differentiation exist. It is suggested that this polymorphism may be of use as a marker for studying the relationships of I. ricinus populations in Europe, as well as in taxonomic studies. A hypothesis is advanced which offers a possible adaptive explanation of the very high Pgm heterozygosity in tick populations. It is suggested that if kinetic differences exist between the various enzyme variants, the polymorphism may act to maintain an array of individuals in each population with varying developmental rates and longevities. Such a genetic strategy could be one factor which determines that the host-infesting seasons are spread over several months, thus ensuring maximum feeding and reproductive rates in each population.
Plasmodium knowlesi in the marmoset (Callithrix jacchus)
Authors: Langhorne J. , Cohen S.
Published: June 2009

Common marmosets were shown to be susceptible to Plasmodium knowlesi malaria. The morphology of the parasite was indistinguishable from that observed in the natural host (Macaca fascicularis) and the common laboratory model (Macaca mulatta). A differential susceptibility to P. knowlesi was observed in the 8 marmosets studied. Multiplication rates of parasites were variable over 24 h periods. Five animals died of a fulminating infection within 12–17 days after challenge. Three animals recovered spontaneously from infection and were subsequently resistant to challenge with homologous and heterologous variants and strains of P. knowlesi. This resistance was maintained for intervals up to 100 days between challenge infections.
Aldose reductase and sorbitol dehydrogenase in the muscle ofAscaris suum(Nematoda)
Authors: Goil M. M. , Harpur R. P.
Published: June 2009

The muscle ofAscaris suumcontains sorbitol dehydrogenase [EC 1.1.1. 14] and the apparentKmvalues indicate that the enzymefavours fructose formation. Aldose reductase [EC 1.1.1.21] is also present and like the mammalian enzyme it has a very high apparentKmfor glucose. Possible functions of the sorbitol pathway inAscarismuscle are discussed.
Amino acids ofDiclidophora merlangi(Monogenea)
Authors: Arme C. , Whyte A.
Published: June 2009

The level of free amino acids inDiclidophora merlangiis high, comprising over 500 μmoles/g ethanol extracted dry weight. A single amino acid, proline, constitutes some 70% of the total pool. Analysis of parasite protein and host blood and mucus revealed low proline levels, suggesting that the high free pool content was not related to a requirement for protein synthesis or to its abundance in the diet of the worm. Experiments revealed that proline was not involved specifically in osmoregulation, and the reasons for the large amounts present inDiclidophoraremain unknown.
Enzyme variation in T. brucei ssp. II. Evidence for T. b. rhodesiense being a set of variants of T. b. brucei
Authors: Tait A. , Barry J. D. , Wink R. , Sanderson A. , Crowe J. S.
Published: June 2009

A collection of stocks of Trypanosoma brucei rhodesiense isolated in Kenya have been examined for electrophoretic variation in 20 enzymes. The results obtained have been analysed in order to determine whether these trypanosomes are diploid and undergo mating and to determine the genetic distance between T. b. rhodesiense, T. b. brucei and T. b. gambiense. The enzyme electrophoretic markers were further used in experiments involving cyclically transmitted mixtures of stocks aimed at detecting genetic exchange in the laboratory. No genetic exchange was detected. Two novel features of the enzyme electro phoretic results were found. Firstly, the stocks of T. b. rhodesiense were considerably more homogeneous than equivalent collections of stocks of T. b. brucei and secondly, all the stocks examined were heterozygous for two alleles of alkaline phosphatase and showed an excess of heterozygotes at the phosphoglucomutase locus. The degree to which these features are typical of T. b. rhodesiense has been examined in relation to previously published data. The results obtained strongly support the view that T. b. rhodesiense is a set of variants of T. b. brucei rather than a subspecies and a working hypothesis as to the relationship between T. b. brucei and T. b. rhodesiense is proposed to explain the enzyme electrophoretic data obtained.
Energy metabolism in the developing larval stages of Ancylostoma tubaeforme and Haemonchus contortus: glycolytic and tncarboxylic acid cycle enzymes
Authors: Onwuliri C. O. E.
Published: June 2009

The activities of glycolytic and related enzymes and the tricarboxylic acid cycle enzymes were measured in freshly isolated 1st- (Li), 2nd- (L2) and 3rd-stage (L3) larvae of bothAncylostoma tubaeformeandHaemonchus contortus. All enzymes of the glycolytic pathway were present in all developmental stages of both strongylid nematodes although higher levels of activities were obtained in the pre-infective 1st- and 2nd-stage larvae than in the infective 3rd stage. However, the pre-infective larvae contained lower levels of pyruvate kinase (PK) than the infective larvae. Consequently, the pyruvate kinase to phosphoenolpyruvate carboxykinase (PEPCK) ratios were 0·23 and 0·26 for the L1s and L2s forA. tubaeformeand 0·36 and 0·21 for those ofH. contortusrespectively. High levels of activity of glucose-6-phosphate dehydrogenase obtained in the bacteriophagous pre-infective larvae were consistent with high rates of morphogenesis and substrate synthesis characteristic of the pre-infective stages. All the tricarboxylic acid cycle enzymes were present in the infective larvae of both nematodes while in the pre-infective Li and L2 stages, the enzymes at the beginning of the cycle, namely aconitate hydratase and NAD-linked isocitrate dehydrogenase, were not detected. A scheme was proposed for the energy metabolism of these developing larvae. In this scheme, the pre-infective larvae were shown to operate an anaerobic metabolic pathway involving the carboxylation of phosphoenolpyruvate (PEP) by phosphoenolpyru vate carboxykinase (PEPCK) to form oxaloacetate (OAA), whereas in the infective larvae the metabolic pathway favouring the direct dephosphorylation of PEP, as in vertebrate tissues, was followed.
Further observations on immunization of sheep against Schistosoma mansoni and S. bovis using irradiation -attenuated schistosomula of homologous and heterologous species
Authors: Bickle Q. D. , Taylor M. G. , James E. R. , Nelson G. S. , Hussein M. F. , Andrews B. J. , Dobinson A. R. , Marshall T. F. de C.
Published: June 2009

This paper describes further characteristics of the immunization of sheep against schistosomes using live, irradiated schistosomula. Sheep immunized with a non-virulent strain of Schistosoma mattheei were protected against a more virulent strain of the same species for over a year. As there was no evidence that the irradiated parasites were able to persist this long, it was concluded that the vaccine had induced a sterile resistance. Heterologous vaccination, using irradiated S. mattheei schistosomula to immunize against S. bovis or irradiated S. mansoni schistosomula to immunize against S. mattheei, failed to induce any protection.
Ultrastructural immunocytochemical localization of two hydatid fluid antigens (antigen 5 and antigen B) in the brood capsules and protoscoleces of ovine and equine Echinococcus granulosus and E. multilocularis
Authors: Davies Caroline , Rickard M. D. , Bout D. T. , Smyth J. P.
Published: June 2009

The unlabelled antibody method was used in the ultrastructural localization of two hydatid fluid antigens, antigen 5 and antigen B, in brood capsules and protoscoleces of Echinococcus granulosus and E. multilocularis. Antigen 5 was found in the parenchyma cells of the protoscolex and brood capsule wall and to a lesser extent in the walls of the flame cells and collecting ducts of the excretory system and in the surrounding interstitial material. It is suggested that, while some excretion of this antigen may occur from the protoscolex, it could also be liberated into the cystic cavity by degeneration of protoscoleces and parenchymal cells of the brood capsule wall. Antigen B was found mainly in the distal cytoplasm and perinuclear cytoplasm of the tegument anterior to the suckers. It is apparently secreted to the outside and was present in the brood capsule contents; it adheres to the anterior surface and the posterior periodic acid–Schiff (PAS)-positive glycocalyx of the protoscolex and to the inner surface of the brood capsule wall. The protoscolex tegument posterior to the suckers was negative. The parenchyma cells of the protoscolex and brood capsule wall were also positive although the intensity of the reaction product was variable.
Variations in the water content of the larvae ofNematodirus battusduring the hatching process
Authors: Parkin J. T.
Published: June 2009

During a series of experiments on the ecology ofNematodirus battusobservations were made on the uptake of water by eggs containing third-stage larvae. It was found that, as they approached hatching, the water content of the larvae increased markedly, then fell immediately after they escaped from the shell. The method of measuring the water content, using interferometry, is also described.
Observations on the bionomics of Pseudolynchia canariensis (Diptera: Hippoboscidae)
Authors: Klei Thomas R. , Degiusti Dominic L.
Published: June 2009

Host suitability, reproduction, effects of temperature on reproduction and pupal development, effects of humidity on pupal development and the effects of photoperoid on puparial deposition, pupal development and adult emergence were studied in a laboratory colony of Pseudolynchia canariensis. Flies were observed to lack strong host specificity. Puparia were produced at regular 24 h intervals by flies maintained at 30 °C, averaging 8·8 puparia per female. Optimum temperature for colony maintenance was observed to range between 26·6 and 30·0 °C. Temperatures of 13 and 37 °C were lethal to pupae. Humidity and photoperiod did not markedly affect pupal development. Puparial deposition and adult emergence occurred only during the photoperiod.
The number and morphology of trypanosomes in the blood and lymph of rats infected with Trypanosoma brucei and T. congolense
Authors: Ssenyonga G. S. Z. , Adam Katherine M. G.
Published: June 2009

The thoracic lymph duct of rats infected with Trypanosoma brucei and with T. congolense was cannulated at different stages of infection. Trypanosomes were always present in the lymph of rats infected with T. brucei, whereas they were absent or very scarce in the lymph of rats infected with T. congolense. There were greater fluctuations in the numbers of trypanosomes in the blood than in the lymph. The intra- and extravascular populations of T. brucei differed: stumpy forms were present only in blood; dividing forms were usually more numerous in lymph.
Schistosoma mansoni from naturally infected Rattus rattus in Guadeloupe: identification, prevalence and enzyme polymorphism
Authors: Rollinson D. , Imbert-Establet Danièle , Ross G. C.
Published: June 2009

An enzymatic comparison has been made between isolates of Schistosoma mansoni from rats and humans in Guadeloupe and a Burundi isolate of S. rodhaini. Analyses of LDH, MDH, AcP, PGM, GPI, G6PDH and HK by isoelectric focusing provided no evidence for the involvement of S. rodhaini in the recent evolution of the schistosomes currently endemic in Guadeloupe. No distinction could be made between murine and human isolates of S. mansoni and it is suggested that murine schistosomiasis should not therefore be ignored in control programmes. Rattus rattus were captured at seven sites around the island; of 142 examined, 48 were positive for schistosomes. Differences in prevalence between habitats were marked and only small changes in prevalence were observed in localities sampled in 1982 and 1983. Animals with the greatest worm burdens were associated with areas of high prevalence, and age-related changes in worm burden were observed. Two alleles, a and b, at the MDH-1 locus of S. mansoni from rats were identified. Differences in the overall frequencies of these alleles were observed for schistosomes from different localities. Allelic frequences representative of schistosomes from rats at four localities were stable from 1982 to 1983. The majority of positive animals, even those with light worm burdens, were found to be infected with a number of different schistosome genotypes.
Lipid metabolism in golden hamsters infected with plerocercoids ofSpirometra erinacei(Cestoda: Pseudophyllidea)
Authors: Tsuboi T. , Hirai K.
Published: June 2009

Golden hamsters infected withSpirometra erinaceiplerocercoids develop a hypertriglyceridaemia characterized by an increase in very low-density lipoprotein. Acyl-CoA synthetase activity, the rate of fatty acid synthesis in the liver and triglyceride production studies showed that the activation and synthesis of fatty acid and production of triglyceride in plerocercoidinfected hamsters were not significantly different from the controls. Lipase activity in post-heparin plasma was found to be suppressed in plerocercoid-infected golden hamsters. The presence of plerocercoids also resulted in a significant reduction in serum thyroxine, but the hypertriglyceridaemia associated with plerocercoid infection was not reversed by injecting the infected hamsters with 2 μg/ day doses of L-thyroxine. The levels of serum immunoreactive insulin in plerocercoid-infected hamsters were not significantly different from the controls. We conclude that the hypertriglyceridaemia, associated with plerocercoid infection in hamsters, results predominantly from a suppression of triglyceride degradation, and that the suppression of lipase activity is probably not the result of hypothyroidism or the lack of insulin, but the result of secretion of growth hormone-like substances.
Serial passage of Eimeria tenella and E. necatrix in turkey embryos
Authors: Kogut M. H. , Gore T. C. , Long P. L.
Published: June 2009

The serial passage of 3 strains of Eimeria from the chicken in embryonating turkey embryos is reported here. All 3 strains increased their reproduction in turkey embryos; reproduction being equal to or better than the same lines maintained in chicken embryos. Pathogenicity and immunogenicity trials conducted in chickens using these 3 strains of Eimeria showed that all 3 turkey embryo-adapted lines were significantly less pathogenic than the parent lines. Only 1 of the lines (E. tenella (PS) turkey embryo-adapted) maintained its immunogenic potential
Ultrastructural observations on oogenesis and shell formation in Gyrinicola batrachiensis (Walton, 1929) (Nematoda: Oxyurida)
Authors: Adamson M. L.
Published: June 2009

Individual females of Gyrinicola batrachiensis produce 2 types of eggs: thin-shelled auto-infective eggs are produced in the ventral horn of the reproductive tract and thick-shelled eggs (transmission agents) are produced in the dorsal horn. Fine structure of oogenesis and egg-shell formation in the 2 horns of the reproductive tract were studied and compared. Early stages of oogenesis were similar in both horns but mature oocytes differed considerably. Those in the dorsal horn were larger than those in the ventral horn; they contained large numbers of lipid droplets, peripheral patches of glycogen and several types of cytoplasmic granules presumably acting as yolk or playing a role in shell formation. Mature oocytes in the ventral horn contained large amounts of glycogen, relatively few lipid droplets and large multivesicular bodies. Four shell layers formed around ova in the dorsal horn: a vitelline layer, a lipid layer, a chitinous layer and an outer protein coat similar to that described in other oxyurids. Only the vitelline layer formed around thin-shelled eggs. Thick-shelled eggs did not embryonate in utero but thin-shelled eggs nearest the vagina contained larvae. The first moult in eggs of G. batrachiensis was described in a previous communication and it is suggested here that the thin fibrous layer loosely applied to the cuticle of infective larvae in thin-shelled eggs is the moulted 2nd-stage cuticle.
Central nervous system involvement in goats undergoing primary infections withTrypanosoma bruceiand relapse infections after chemotherapy
Authors: Whitelaw D. D. , Moulton J. E. , Morrison W. I. , Murray M.
Published: June 2009

Relapse of infection after trypanocidal drug treatment of trypanosome infections is normally attributed to drug resistance on the part of the parasite, under-dosage of the drug, or reinfection of the host. We have demonstrated relapse infections in goats arising from none of these. Fourteen goats infected withTrypanosoma bruceisuffered severe illness and 3 died within 45 days. Despite treatment with the trypanocidal drug Berenil, a 4th goat died 2 days later. Recovery of the remainder followed chemotherapy, and in 2 goats, necropsiecl 45 days after treatment, no trypanosomes or abnormalities were detected. However 2–3 months after Berenil chemotherapy, despite trypanosomes being undetectable in the blood during the intervening period, infections in 4 of the remaining 8 animals relapsed. At all stages of the primary and relapse infections, trypanosomes isolated from the blood of the goats were completely susceptible to Berenil when tested in mice, as were parasites isolated from cerebrospinal fluid and brain tissue at necropsy. At the time of treatment, only minimal cellular infiltration was found in the central nervous system (CNS), but death from the relapse infection was associated with a very severe meningoencephalitis. We conclude that the relapse infections were caused by the re-emergence of trypanosornes from the CNS, where sequestered parasites were inaccessible to the trypanocidal effects of the drug.
Resistance following drug attenuation (Ro 11–3128 or oxamniquine) of earlySchistosoma mansoniinfections in mice
Authors: Bickle Q. D. , Andrews B. J.
Published: June 2009

A single dose of Ro 11–3128 was found to be 98–100% effective againstSchistosoma mansoniinfections at intervals of 3 h to 15 days following infection, and apparently killed the schistosomula stages soon after administration, thus allowing an assessment of the immunizing potential of progressive larval stages. Following infection with 500 unirradiated cercariae, optimum resistance was manifest by groups drug-treated at 48–96 h (60–75%). Significantly lower levels of resistance occurred with early (3 h) or later (6–15 day) treatments. Superimposition of an infection treated at 15 days on a prior infection which had been treated at 2 days did not reduce the level of resistance caused by the latter, indicating that the infection plus delayed treatment had not induced suppression. Thus the peak resistance manifest during the 48–96 h period may reflect optimum expression of protective antigens. Comparison of irradiated (20 krad.) with unirradiated infections showed that, when drug-terminated 24, 48 or 96 h post-infection, irradiated cercariae induced significantly less resistance than unirradiated cercariae, perhaps indicating a delayed appearance of protective antigens following radiation treatment.
Phagocytosis of microvilli of the metacestode ofHymenolepis diminutabyTenebrio molitorhaemocytes
Authors: Richards K.Sylvia , Arme C.
Published: June 2009

A limited number of metacestodes ofHymenolepis diminutafromTenebrio molitorhad host plasmatocytes and cell debris of coagulocyte origin associated with the microvillar surface. There was evidence of phagocytosis of microvilli by plasmatocytes, involving clathrin-like endocytotic vesicles. In contrast to these otherwise ‘normal’ cysticercoids, occasional batches were ‘sticky’ and, on flushing into saline, rapidly developed large bladders possibly associated with osmotic stress. In addition, numerous small surface blebs were present. These ‘surface-stressed’ cysticercoids also had host plasmatocytes and cell debris associated with the bladder bases and the blebs, and phagocytosis of microvilli was observed. In no case had precipitation of haemolymph, melanization or encapsulation (features typical of the insect immune response) occurred. The possibility that the limited host response indicates a spatially restricted impairment of the surface compatibility of the parasite, and thus insufficient to elicit the full immune response, is discussed.
Potential of ear tags impregnated with acaricides for control of the brown ear tick (Rhipicephalus appendiculatus) infesting cattle
Authors: Young A. S. , De Castro J. J. , Burns Casey , Murphy D. L.
Published: June 2009

Plastic ear tags impregnated with acaricides (synthetic pyrethroids; fenvalerate, 10% (w/w); fenpropathrin, 10% (w/w); fiuvalinate, 10% (w/w); and permethrin, 8% (w/w)) were evaluated for the control of Rhipicephalus appendiculatus infesting cattle in the laboratory and field in Kenya. These controlled release devices gave excellent control of R. appendiculatus for over 20 weeks on cattle in the laboratory where they were housed mostly indoors. Fluvalinate-impregnated tags gave consistently the most rapid control of ticks, but all of the tags normally prevented feeding of the ticks on the ears of cattle. Under field conditions in the Trans-Mara Division of Kenya, excellent control of R. appendiculatus naturally infested cattle was obtained by fluvalinate-impregnated tags followed by fenpropathrin. Less impressive control was obtained by fenvalerate- and permethrin-impregnated tags, but this control was more effective than immersion of cattle in toxaphene. In contrast to the laboratory experiments, the effect of the tags on R. appendiculatus infestation waned by 58 days after application. The potential of synthetic pyrethroid-impregnated tags for the control of ticks infesting cattle in Africa was demonstrated, but a more prolonged release of the active ingredients at an effective level in the field and, in some cases, a more robust tag design will have to be achieved before tick control with impregnated tags becomes a practical proposition.
Two new species of Lepeophtheirus (Copepoda: Caligidae) parasitic on fishes from southern California waters
Authors: Dojiri Masahiro
Published: June 2009

Two new species of Lepeophtheirus are described and illustrated based on a collection from the Orange County sewer outfall, California. They are: L. remiopsis sp.nov. from the branchial cavities and external body surfaces of Parophrys vetulus Girard, Hippoglossina stomata Eigenmann & Eigenmann, Pleuronichthys verticalis (Jordan & Gilbert), Chitonotus pugetensis (Steindachner), and Porichthys notatus (Girard); and L. rotundipes sp.nov. from the external body surfaces and occasionally the gill cavities of Scorpaena guttata (Girard) and Citharichthys stigmaeus Jordan & Gilbert.
Bovine trypanosomiasis: the red cell kinetics of Ndama and Zebu cattle infected withTrypanosoma congolense
Authors: Dargie J. D. , Murray P. K. , Murray Max , Grimshaw W. R. T. , McIntyre W. I. M.
Published: June 2009

The responses of susceptible Ndama and Zebu cattle to needle challenge withTrypanosoma congolensewere followed using parasitological, haematological and radio-isotopic methods and compared with those of corresponding uninfected animals. In both breeds, infection became patent at the same time but peak parasitaemias were significantly lower, were attained later and were of short duration in the Ndama. All infected animals became anaemic, the severity of which correlated with the level and duration of parasitaemia. However, even when parasites could no longer be detected in the blood, packed cell volumes showed little tendency to recover. The anaemia was due to increased intravascular red cell destruction and was more pronounced in the Zebu. Haemodilution was not a feature. Increased red cell synthesis occurred in infected animals of both breeds but particularly in the Zebu; this accounted for the capacity to maintain packed cell volume levels following the initial drop associated with parasitaemia. However, in most cases red cell synthesis was less than expected from the degree of anaemia, suggesting impairment of bone marrow function. Measurement of red cell iron utilization indicated that this was due to defective iron re-utilization from degraded red cells arising from reticulo-endothelial blockade. It is concluded that the anaemia in this disease and its underlying processes are broadly in line with the number of parasites in the blood and that the superior resistance of the Ndama cattle lies in their ability to control parasitaemia rather than their capacity to mount a more efficient erythropoietic response.
In vitrovariation of glycogen content in three sheep nematodes
Authors: Premvati G. , Chopra Ashok K.
Published: June 2009

In vitrovariation of glycogen content under aerobic conditions was measured on fresh weight basis in 3 sheep nematodes inhabiting different niches;Haemonchus contortus, Oesophagostomum columbianumandTrichuris ovis. The parasites were separated into species and then sexes and starved for varying periods of time up to 24 h in glucose-free physiological saline. The differences between females and males and among the species with respect to glycogen content and its rate of change with time are discussed.
Evidence for genetic diversity in Trypanosoma (Nannomonas) congolense
Authors: Majiva P. A. O. , Hamers R. , Van Meirvenne N. , Matthyssens G.
Published: June 2009

Genetic proximity between two karyotypic groups of Trypanosoma congolense was investigated using as hybridization probes: (i) total genomic DNA, (ii) a 35 nucleotide long synthetic oligonucleotide, and (iii) non-variant antigen type (non-VAT) specific complementary DNAs. The phylogenetic relationship between Trypanosoma brucei and T. evansi, both of which are accepted species in the subgenus Trypanozoon, was used as a reference to assess the phylogenetic proximity of the two groups of T. congolense. Results indicate that some morphologically indistinguishable T. congolense populations differ in a variety of molecular and genetic properties: molecular karyotypes, majority of the DNA sequences, and the restriction enzyme sites in the genomic environments of various conserved genes. The implications of these findings for trypanosome evolution and T. congolense epidemiology are discussed.
Identification of non-cross-reacting antigens ofOnchocerca volvuluswith lymphatic filariasis serum pools
Authors: Lobos E. , Weiss N.
Published: June 2009

Onchocerca volvulusproteins labelled with125I were immunoprecipitated with onchocerciasis and lymphatic filariasis human serum pools in order to differentiate between cross-reacting and non-cross-reacting antigens. Analysis of the immunoprecipitates by two-dimensional gel electrophoresis revealed that all high molecular weight (Mr)O. volvulusantigens cross-reacted with the lymphatic filariasis serum pools. We observed, however, that at least 80. volvulusantigens were specifically immunoprecipitated only by the onchocerciasis serum pools, with Mrranging from 20000 up to 43000 Daltons. These results suggest that the lower MrO. volvulusantigens are more species specific than the other antigens. The significance of these findings for the immunodiagnosis of onchocerciasis is discussed.
Gametocytogenesis of Plasmodium falciparum in vitro: an electron microscopic study
Authors: Sinden R. E.
Published: June 2009

Plasmodium falciparum was grown in vitro in blood taken from naturally infected Gambian patients, and the development of the cultured sexual parasites was studied by light and electron microscopy. The young (Stage II and III) female gametocytes undergo a single cryptomitotic nuclear division. This division immediately follows the S phase which Sinden & Smalley (1979) have demonstrated in the Stage I and II gametocytes of both sexes. The male gametocytes, by contrast, do not undergo mitosis during their maturation period in the erythrocyte and thus remain polyploid. Hence the cell cycles of the male and female gametocytes differ significantly. The ultrastructural basis of the characteristic changes in shape of the developing gametocyte are shown to be due to the assembly and subsequent loss of components of the sub-pellicular membranous and microtubular cytoskeleton. Stage I–III gametocytes synthesize numerous ribosomes and endoplasmic reticulum. This correlates with the active synthesis of RNA and protein in these young parasites (Sinden & Smalley, 1979). The marked reduction in macromolecular synthesis in the mature parasites is paralleled by a reduction in cytoplasmic ribosome density in the male gametocyte only. In the female, however, this reduction in activity is correlated with the appearance of a nucleolus. These changes suggest that different mechanisms are being used to control RNA synthesis in the two sexes of gametocyte.
Studies on the relationship between the survival of Schistosoma mansoni larvae in mice and the degree of resistance produced
Authors: Bickle Q. D.
Published: June 2009

These studies were aimed at giving a clearer idea of the source of the antigens responsible for the induction of resistance by larval schistosomes. Firstly, the resistance induced by radiation-attenuated (20 krad.) infections was compared with that induced by the larval phase of unirradiated infections. The superiority of the irradiated larvae was demonstrated by infecting mice with 500 female cercariae which were either unirradiated or irradiated, and challenging them 3 weeks later with male cercariae. At perfusion, when primary and challenge worms could be distinguished by sex, significantly greater resistance was demonstrated in the groups vaccinated with irradiated larvae (56 cf. 31% and 48 cf. 26% in two experiments). Secondly, in order to establish how long immunizing larvae need to survive to stimulate optimum resistance, mice were either treated with schistosomulicidal drugs or had the site of infection excised at various intervals post-vaccination. Treatment or excision at up to 24 h did not result in significant resistance to challenge (6–16%). Similar treatments at 1 week did not prevent significant resistance developing (26–37%) but the levels of resistance were significantly lower than those manifest by vaccinated, untreated mice (51–71%). It is concluded that the immunizing larvae need to persist for between 1 and 2 weeks in order to stimulate optimum protection and that antigens released during protracted survival and/or death of the larvae in either the skin or the lungs are probably key factors in the induction of resistance.
Aspects of helminth metabolism
Authors: Ward P. F. V.
Published: June 2009

‘Each organism must be examined as a biochemical entity before any reasonable understanding of helminth metabolism can be attained’ (Saz, 1969).
Prevalence of schistosome infections within molluscan populations: observed patterns and theoretical predictions
Authors: Anderson R. M. , May R. M.
Published: June 2009

The paper draws together a large and scattered body of empirical evidence concerning the prevalence of snail infection with schistosome parasites in field situations, the duration of the latent period of infection in snails (and its dependence on temperature), and the mortality rates of infected and uninfected snails in field and laboratory conditions. A review and synthesis of quantitative data on the population biology of schistosome infections within the molluscan host is attempted and observed patterns of infection are compared with predictions of a schistosomiasis model developed by May (1977) which incorporates differential snail mortality (between infected and uninfected snails) and latent periods of infection. It is suggested that the low levels of prevalence within snail populations in endemic areas of schistosomiasis are closely associated with high rates of infected snail mortality and the duration of the latent period of infection within the mollusc. In certain instances, the expected life-span of an infected snail may be less than the duration of the latent period of infection. Such patterns generate very low levels of parasite prevalence. A new age prevalence model for schistosome infections within snail populations is developed and its predictions compared with observed patterns.

The implications of this study of observed and predicted patterns of snail infection within molluscan populations are discussed in relation to the overall transmission dynamics of schistosomiasis.
Quantitative studies on the transmission ofParahistomonas wenrichiby ova ofHeterakis gallinarum
Authors: Fine Paul E. M.
Published: June 2009

Three groups of chickens were fed small numbers of ova (3, 5 or 9 ova per bird) ofHeterakis gallinarumin a quantitative study of the transovarial transmission ofParahistomonas wenrichiby the nematode. Subsequent incidence rates ofParahistomonasinfections in recipient birds were analysed according to the methods of Chiang & Reeves (1962). The results indicated that at least 25 % ofHeterakisova, passed in the faeces of birds with concomitantParahistomonasinfection, carried the protozoon. The appearance ofParahistomonasin a bird which retained all its challenge nematodes indicated that the protozoon can be released by living worms. Data on the pre-patent periods ofParahistomonasinfections are consistent with a hypothesis that the protozoon is typically released at the time of the final (fourth) moult of the nematode.
The problem of drug resistance in malaria
Authors: Peters W.
Published: June 2009

The resistance in human malaria is mainly of practical importance in relation to Plasmodium falciparum. Strains resistant not only to chloroquine but also to dihydrofolate reductase inhibitors, and even to potentiating combinations of these with sulphonamides or sulphones, are appearing in an ever increasing geographical area which now includes tropical Africa and India. Few new drugs are available or foreseen for the near future, mefloquine and artemisinine being the leading contenders. It is vital that all measures possible should be taken to protect such new compounds, their deployment in the form of judiciously selected combinations with other antimalarials being an essential procedure that should be followed. Drugs in new chemical classes and with different modes of action are still urgently needed. Reliance should not be placed on drugs alone to control malaria on a community basis.
Genetic control of liability to infection with Nematospiroides dubius in mice: direct and correlated responses to selection of mice for faecal parasite egg count
Authors: Brindley P. J. , Dobson C.
Published: June 2009

Mice selected as liable (L) and refractory (R) over 10 generations voided significantly more and less Nematospiroides dubius eggs compared with randomly mated (Rd) mice after primary infection with 100 larvae. Strong positive correlation was found between the numbers of N. dubius eggs in mouse faeces and the numbers of adult N. dubius recovered from mice culled from the R, Rd and L colonies. Selection limit based on a faecal e.p.g. was reached in the L mice after 9 generations whereas the faecal N. dubius e.p.g. voided by the R mice continued to decline throughout selection. In contrast, no change in worm numbers was found in L or R mice after 6 generations. The refractory state of the trait, liability to infection with N. dubius, was inherited as a dominant character with a realized heritability value of ~ 0∣2. Differential correlated responses from N. dubius infectivity compared with N. dubius fecundity and growth indicated murine genetic control of this trait by 2 major genetic units. In general, there were negative phenotypic and genetic correlations between the faecal N. dubius e.p.g. of mice and murine morphological conformation, but positive correlations between the faecal N. dubius e.p.g. of selected mice and establishment, growth and fecundity of N. dubius populations in these mice. There was little correlation between the faecal N. dubius e.p.g. after primary infection and anti-N. dubius antibody titres and parasite female/male sex-ratio.
Endotube–brush border complexes dissected from the intestines of Haemonchus contortus and Ancylostoma caninum
Authors: Munn E. A. , Greenwood C. A.
Published: June 2009

A procedure for the blunt dissection of the syncytial intestine of Haemonchus contortus to separate the endotube–brush border complex is described. A similar complex can be obtained from the partially cellular intestine of Ancylostoma caninum. The structural features of the complexes from the two sources are compared. The main differences are in the retention of terminal bars by the endotube from A. caninum and in the extent and organization of the microfilaments associated with the basal side of the endotubes.
Effects of parasitization by the insect parasite Hyposoter exiguae on the growth, development and physiology of its host Trichoplusia ni
Authors: Thompson S. N.
Published: June 2009

The weight gain and growth rate of Trichoplusia ni larvae were severely depressed following parasitization by the insect parasite, Hyposoter exiguae. The development of the host was also delayed and juvenile hormone esterase activity present at the normal time of moulting was absent in parasitized insects. Similar effects on growth and development were achieved by rearing host insects on nutrient-deficient media. Accompanying the above effects of parasitization were alterations in dry/wet weight ratio and host haemolymph osmolality. Parasitization resulted in immediate increases in the concentrations of haemolymph non-glycogen carbohydrate (composed of trehalose, maltose and glucose) and protein. The concentration of fat body glycogen also increased following parasitization. In contrast, the concentration of haemolymph non-glycogen carbohydrate and protein, as well as fat body glycogen, decreased in nutrient-deprived larvae. The significance of the above results as they relate to the insect parasite–host relationship is discussed.
Infrequency of gross skin lesions among Panamanian forest mammals with cutaneous leishmaniasis
Authors: Herrer Aristides , Christensen Howard A.
Published: June 2009

Natural leishmanial infections among feral mammals in the Republic of Panama were studied in relation to gross skin alterations. Three dermatotropic species of Leishmania, L. braziliensis, L. mexicana and L. hertigi, isolated from 230 sylvatic animals of 5 mammalian orders were involved. In 205 (89%) of the cases there were no gross skin alterations. Cryptic infections of all three leishmanial species among wild animals were confirmed by culture and hamster inoculation. This type of infection was always present in the sloths, Choloepus hoffmanni and Bradypus infusatcus, infected with L. braziliensis and in the porcupine, Coendou rothschildi, infected with L. hertigi. Suggestive skin alterations were encountered in 10 (4%) of infected animals. Only 15 (7%) of infected animals exhibited typical leishmanial lesions. It was possible to correlate skin depigmentation with the course of leishmanial infection in one animal, a young kinkajou, Potos flavus.
Suppression of expulsion ofAspiculuris tetrapterain hydrocortisone and methotrexate treated mice
Authors: Behnke Jerzy M.
Published: June 2009

Hydrocortisone treated male and female mice, given a primary infection withAspiculuris tetraptera, did not reject the worms during the third week of infection. Mice given hydrocortisone during the first week of infection had elevated worm burdens on day 10, suggesting that some worm loss was encountered during the anterior migration in control mice. Furthermore, this temporary period of treatment was sufficient totally to suppress rejection and to allow the parasite to persist until day 28. Methotrexate also significantly delayed rejection, but larval growth was retarded in treated mice. These results, it is suggested, add strength to the hypothesis that the loss ofA. tetrapterain a primary infection in mice, is an immunological phenomenon.
An experimental study of the survival characteristics, activity and energy reserves of the hexacanths of Hymenolepis diminuta
Authors: Anderson R. M. , Lethbridge R. C.
Published: June 2009

Similar survival characteristics were demonstrated for hexacanths of Hymenolepis diminuta incubated in Tyrode's solution with or without a glucose supplement (0–50 mg/ml).

The survival rate of hexacanths in all media tested was shown to be age-dependent and led to a maximum life-span of approximately 11 h.

The amount of energy reserves, as measured by microdensitometric determinations of PAS + material, declined rapidly in time to a plateau at approximately 8 h. Residual PAS + matter present beyond that period was interpreted as structural and thus non-utilizable material.

The rate of activity as measured by hook movements declined more rapidly, and continuous hook cycles were rarely observed after 2 h and ceased after 4 h. A close correlation was demonstrated between the decline in PAS + material and the total number of hook cycles completed per unit of time.

The quantitative results on survival, energy reserves and activity are discussed in relation to the penetration of hexacanths into the haemocoele of the intermediate host.
Pathologically induced alterations in the dimensions of the hepatic portal vasculature of mice infected with Schistosoma mansoni
Authors: McHugh S. M. , Coulson Patricia S. , Wilson R. A.
Published: June 2009

Alterations in the hepatic portal vasculature of NMRI mice infected with Schistosoma mansoni were assessed using a microsphere injection technique. The accumulation of eggs in the livers of infected mice and the development of portal hypertension were closely related to the worm pair burden during the first 15 weeks of infection. Individual variation between mice harbouring identical patent worm pair burdens was partially explained by the reduced fecundity of females from sexually biased infections. As eggs accumulated in the liver and portal hypertension increased, the number of injected microspheres escaping from the hepatic portal system rose in rank order of diameter from 9 μm through 15 μm and 25 μm to 50 μm. There was a strong correlation between the numbers of parasite eggs in the lungs and injected microspheres recovered from the lungs. The pattern of detection of microspheres in the lungs indicated a progressive increase in diameter of intra-hepatic porta-systemic connexions, followed by development of large-bore extra-hepatic collateral vessels. An accurate temporal profile of the pathological state of the host and the extent of collateral vessel formation was obtained. Injection of 141Ce-labelled microspheres demonstrated that the arterial supply to all organs of the body was affected by alterations in the micro-vasculature of the liver and lungs.
Theoretical basis for the use of pathogens as biological control agents of pest species
Authors: Anderson R. M.
Published: June 2009

The population dynamics of insect–pathogen interactions are examined with the aid of simple mathematical models. Three concepts of central importance to the interpretation of population behaviour are discussed, namely the ability of the pathogen to persist within its host population, the ability to regulate and depress host population abundance, and the ability to induce non-seasonal cyclic changes in host density. The selection of pathogen species or strains to depress pest population growth is discussed and the optimal characteristics are shown to be intermediate pathogencity combined with an ability to reduce infected host reproduction, high transmission efficiency, including elements of vertical as well as horizontal transmission stages. When the pathogen plays a significant role in the regulation of host population growth, it is argued that many insect–pathogen interactions will exhibit non-seasonal oscilations in host and pathogen abundance. Mathematical models are used to explore the patterns of population behaviour that result from the continual introduction of a pathogen into a target pest population. It is shown that there exists a critical introdution rate, above which the eradication of the pest is theoretically possible. Significant reductions in pest population abundance will not occur until the introduction rate approaches this critical value, whereupon the oscillatory behaviour of the interaction between host and pathogen population will be suppressed.

A general dicussion is given of the problems arising from the combined use of chemical agents and pathogens for the control of pest species, and the evolutionary pressures acting on host and pathogen populations.
Trematodes: antagonism between species and sterilizing effects on snails in biological control
Authors: Combes Claude
Published: June 2009

There are two ways in which trematodes can be used in the control of other trematodes which transmit diseases of medical or veterinary importance. Either they can interfere with the reproductive capacity of the host species of snails, or they can exert an antagonistic effect against the larval stages of the target trematode species inside the snail. Often the two effects act together.

There are six essential criteria for the selection of a suitable species of snail for control: (1) complete and permanent sterilizing effect; (2) clear dominance over target trematodes; (3) strong infectivity to molluscs of all ages; (4) high egg productivity in the definitive host; (5) lack of pathogenicity towards man and domestic animals; (6) ease and low cost of maintenance of the life-cycle.

Various field trials are discussed and it is considered that trematode species producing rediae are usually dominant over those producing only sporocysts (such as the schistosomes). Most species used in control trials to date have belonged to the family Echinostomatidae as they have rediae, and eggs that can be produced in large numbers in a laboratory host such as the rat.

The mathematical basis and feasibility of control schemes are discussed and it is concluded that much more information is necessary before their potential can be evaluated.