bluuebunny/crossref_metadata_2025_split huggingface dataset:
Density-dependent processes in the transmission of human onchocerciasis: relationship between the numbers of microfilariae ingested and successful larval development in the simuliid vector
Authors: Basáñez M. G. , Remme J. H. F. , Alley E. S. , Bain O. , Shelley A. J. , Medley G. F. , Anderson R. M. 
Published: June 2009

SUMMARYA previous paper reported that the intake ofOnchocerca volvulusmicrofilariae (mff) by different species ofSimuliumis essentially proportional to the parasite load in the skin of infected carriers. This paper examines the fate of the ingested mff in susceptible vectors to assess the relationship between parasite intake and infective larval output in blackfly species with and without well-developed cibarial armatures. Analysis is based on data from 3 onchocerciasis endemic areas: Guatemala (S. ochraceum s.l.), West Africa (S. damnosum s.l./S. sirbanum) and the Amazonian focus between South Venezuela and Northern Brazil (S. guianenseandS. oyapockense s.l.). The data, which include published and unedited information collected in the field, record experimental studies of parasite uptake by wild flies maintained in captivity until the completion of the extrinsic incubation period. The relationship between L3 output (measured as the mean number of successful larvae/fly or, as the proportion of flies with infective larvae) and average microfilarial intake, was strongly non-linear. This non-linearity was best represented by a sigmoid function in case of armed simuliids (S. ochraceum s.l., S. oyapockense s.l.), or by a hyperbolic expression in that of unarmed flies (S. damnosum s.l., S. guianense). These results are compatible, respectively, with the patterns of ‘initial facilitation’ and ‘limitation’ described in culicid vectors of lymphatic filariases. A maximum mean number of 1–3 L3/fly was observed in all 4 vectors. It is concluded thatO. volvuluslarval development to the infective stage is regulated by density-dependent mechanisms acting at the early phase of microfilarial migration out of the blackfly's bloodmeal. Damage by the bucco-pharyngeal armature may also be density dependent. A hypothesis, based on this density dependence is forwarded to explain initial facilitation, so far only recorded in vectors with well-developed cibarial teeth. Our results provide quantitative support for the conjecture that chemotherapy alone is likely to have a greater impact on reducing onchocerciasis transmission in endemic areas where the main vector has a toothed fore-gut than in foci where the vectors have unarmed cibaria.
The effect of the nematode peptides SDPNFLRFamide (PF1) and SADPNFLRFamide (PF2) on synaptic transmission in the parasitic nematodeAscaris suum
Authors: Holden-Dye L. , Franks C. J. , Williams R. G. , Walker R. J. 
Published: June 2009

SUMMARYThe action of two peptides isolated from the nematodePanagrellus redivivus, PF1 (SDPNFLRFamide) and PF2 (SADPNFLRFamide) have been studied on synaptic transmission in the motornervous system of the parasitic nematodeAscaris suum.Intracellular recordings were made fromAscarissomatic muscle cells and excitatory junction potentials (EJPs) elicited by stimulation of the ventral nerve cord. The EJPs were cholinergic as they were blocked by theAscarisnicotinic receptor antagonist, benzoquinonium. PF1 caused a slow hyperpolarization, similar to the action of this peptide first reported by Bowman, Geary & Thompson (1990) and further characterized by Frankset al.(1994). The hyper-polarization was accompanied by a marked decrease in the amplitude of the EJPs with an EC50of 311 ± 30 nM (n= 5). This inhibition is unlikely to be due to a post-synaptic site of action of the peptide as the muscle cell input conductance was not significantly altered by PF1 and furthermore the response to bath-applied acetylcholine was not inhibited by PF1 at concentrations up to 10μM (n= 6). PF2 also inhibited the EJPs in a similar manner to PF1. These studies indicate that both of the peptides isolated from the free-living nematodePanagrellus redivivushave biological activity in the parasitic nematodeAscaris suum. PF1 and PF2 have inhibitory actions in contrast to the predominantly excitatory actions of theAscarisendogenous peptides AF1 (KNEFIRFamide) and AF2 (KHEYLRFamide). The potent actions of thePanagrellusneuropeptides PF1 and PF2 inAscarissuggest that peptides with a similar or identical sequence may also occur inAscarisand have an inhibitory role in the motornervous system.
The dynamics of nematode infections of farmed ruminants
Authors: Roberts M. G. , Heesterbeek J. A. P. 
Published: June 2009

SUMMARYIn this paper the dynamics and control of nematode parasites of farmed ruminants are discussed via a qualitative analysis of a differential equation model. To achieve this a quantity, ‘the basic reproduction quotient’ (Q0), whose definition coincides with previous definitions ofR0for macroparasites, but extends to models with periodic time-varying transition rates between parasite stages or management interventions, is introduced. This quantity has the usual threshold property: ifQ0is less than one the parasite population cannot maintain itself in the host population, and in the long term becomes extinct; but ifQ0is greater than one the parasite can invade the host population. An alternative quantity,R(E), that is often easier to calculate is also introduced, and shown to have the same threshold property. The use of these two quantities in analysing models for the dynamics of nematodes in complex situations is then demonstrated, with reference to the dynamics of mixed parasite species in one host; the effects of breeding host animals for resistance to parasitism; and the development of parasite strains that are resistant to chemotherapy. Five examples are discussed using parameters for the dynamics of nematode infections in sheep, and some statements on control policies are derived.
Immunoglobulin-G binding proteins in the ixodid ticks, Rhipicephalus appendiculatus, Amblyomma variegatum and Ixodes hexagonus
Authors: Wang H. , Nuttall P. A. 
Published: June 2009

SUMMARYA guinea-pig immunoglobulin-G linked agarose column was used to detect the immunoglobulin-G binding proteins (IGBP) in the ixodid ticks, Rhipicephalus appendiculatus, Amblyomma variegatum and Ixodes hexagonus. IGBPs were found in salivary gland extract (SGE) of the unfed ticks of all 3 species. The sizes of the IGBPs, as determined by SDS–polyacrylamide gel electrophoresis, differed between species. In R. appendiculatus 2 IGBP bands were detected in haemolymph collected from unfed females and males, and an additional 78 kDa IGBP was detected in haemolymph samples of male and female ticks that had fed for 6 days. Although there was no difference in the IGBP profile of SGE derived from unfed male and female R. appendiculatus, 2 new IGBPs were detected in the SGE of the male ticks after they had fed for 6 days. The possible function of IGBP in ticks is discussed.
An immunodominant antigen on theDictyocaulus viviparusL3 sheath surface coat and a related molecule in other strongylid nematodes
Authors: Gilleard J. S. , Duncan J. L. , Tait A. 
Published: June 2009

SUMMARYMonoclonal antibody 2A6 binds to the surface of theDictyocaulus viviparusL3 sheath and identifies a molecule which is highly antigenic in both infected and vaccinated cattle. Immunogold electron microscopy reveals that the antibody binds to a highly stable surface coat overlying the epicuticle of the L3 sheath. The binding to the cuticular surface is stage specific, being restricted to the surface of the L3 sheath, although the antigen can be detected on Western blots of parasite homogenates from the L1 stage. Immunofluorescence on live parasites demonstrates that the antibodies also bind to the L3 sheath surface of many other strongylid nematodes. The antigen detected by 2A6 differs in molecular weight between the species; inD. viviparusthe antigen is poorly resolved between 29 and 40 kDa by SDS-PAGE whereas in nematodes from the family Trichostrongyloidea a single band or doublet of approximately 20 kDa is detected, suggesting that a related molecule is present in these species. Although infection and vaccination withD. viviparuselicits a strong immune response to the L3 sheath antigen this does not appear to be the case following infection with other strongylid nematodes.
Distribution of schistosome genetic diversity within molluscan intermediate hosts
Authors: Minchella D. J. , Sollenberger K. M. , Pereira De Souza C. 
Published: June 2009

SUMMARYNaturally infected Biomphalaria glabrata snails were collected at two sites near Belo Horizonte, Brazil, and Schistosoma mansoni cercariae isolated from single snails were used to infect individual mice. Genetic comparison of single worm DNA was accomplished by hybridization of Southern blots to a polymorphic repetitive DNA element. Genetic profiles of parasite individuals revealed a diverse array of parasite genotypes in naturally infected intermediate hosts. The observed distribution of schistosome genotypes among intermediate hosts indicates that over half of the infected snails harbour multiple miracidia. Snails were more likely to carry multiple infections than expected by chance. This degree of overdispersion combined with high levels of genetic variability facilitates multi-genotype transmission and helps maintain parasite genetic diversity.
The anti-haemostatic strategies of the human hookwormNecator americanus
Authors: Furmidge B. A. , Horn L. A. , Pritchard D. I. 
Published: June 2009

SUMMARYThe human hookwormNecator americanusappears to have evolved a number of complementary strategies to overcome the host's haemostatic processes. These include the inhibition of blood coagulation, platelet aggregation and mediator release, and the secretion of fibrinogenolytic enzymes. These strategies presumably allow the parasite to establish the chronic infections so often documented in human populations.
Insect immunity: early events in the encapsulation process of parasitoid (Leptopilina boulardi) eggs in resistant and susceptible strains of Drosophila
Authors: Russo J. , Dupas S. , Frey F. , Carton Y. , Brehelin M. 
Published: June 2009

SUMMARYEggs of an immune suppressive strain ( = virulent) of the parasitoid Leptopilina boulardi are encapsulated neither in resistant nor in susceptible strains of Drosophila melanogaster but are encapsulated in Drosophila yakuba. Eggs of a non-immune suppressive strain ( = avirulent) of the same parasitoid are encapsulated in a resistant strain of D. melanogaster and in D. yakuba but are not encapsulated in a susceptible strain of D. melanogaster. Egg chorion in the 2 parasitoid strains showed the same morphology and the same modifications after egg laying whatever the host strain. When a capsule is built, a small dotted dense layer was first spread on the chorion, followed by accumulation layers of cells (plasmatocytes and lamellocytes) and lastly necrosis of the inner haemocytes. The encapsulated eggs darken only at the time of necrosis of haemocytes. In susceptible hosts, neither the tiny dense layer nor haemocyte accumulation occured. We concluded that (1) this tiny dense layer was present before the deposition of the first haemocytes, (2) inhibition of deposition of this dense layer was the initial event of the induced immunosupression, (3) haemocytes other than lamellocytes were engaged in caspsule formation, (4) the immunosupressive factors did not target only the lamellocytes but also the plasmatocytes, (5) darkening of the encapsulated eggs was due to cell necrosis rather than to extracellular melanin deposition.
Energy restriction and severe zinc deficiency influence growth, survival and reproduction ofHeligmosomoides polygyrus(Nematoda) during primary and challenge infections in mice
Authors: Shi H. N. , Scott M. E. , Koski K. G. , Boulay M. , Stevenson M. M. 
Published: June 2009

SUMMARYThe objectives of this study were (1) to determine the impact of severe zinc deficiency on the establishment, growth, survival and reproduction ofHeligmosomoides polygyrusin the laboratory mouse, during both primary and challenge infection protocols, and (2) to determine whether the observed effects resulted from zinc deficiencyper se, or from the accompanying energy restriction. Three diet groups were used: zinc-sufficient (Zn+: 60 mg zinc/kg diet), zinc-deficient (Zn·75 mg zinc/kg diet) and energy restricted (ER: 60 mg zinc/kg diet pair fed to Zn−mice). Neither Zn−nor ER influenced the establishment of the parasite during a primary infection. However, both significantly influenced the early development of the parasite. The proportion of adult worms recovered 9 days post-infection (p.i.) was highest in Zn−mice, intermediate in ER mice and lowest in +Zn+mice. Worms were also distributed more distally in the intestine of the Zn−mice and worm survival was highest in Zn−mice, intermediate in ER mice and lowest in Zn+mice at both 4 and 5 weeks p.i. Although the length of female worms was reduced in Zn−mice, neitherper capitafecundity nor egg viability was affected by zinc deficiency. Energy restriction, on the other hand, significantly reduced worm fecundity at 5 weeks post-primary infection, but had no effect on egg viability. Zinc concentration of adultH. polygyruswas similar among dietary groups. The effects of zinc deficiency and energy restriction were also investigated 4 and 5 weeks after a challenge infection. Whereas strong host resistance was evident in Zn+and ER mice, based on comparison of worm numbers between challenged mice and primary infection controls, no evidence of resistance was detected in Zn−mice. As in the primary infection, female worms were shorter in Zn−mice than in ER and Zn+mice, and energy restriction but not zinc deficiency significantly affectedper capitafecundity. However, in contrast to the primary infection, ER mice had elevated rather than reduced fecundity. This study demonstrates a complex interaction between H.polygyrusand zinc and energy restriction, and highlights the importance of controlling for reduced food intake in nutrition–infection studies.
Maximum-likelihood estimates of the mortality and migration rates of the infective larvae ofOstertagia ostertagiandCooperia oncophora
Authors: Grenfell B. T. , Smith G. , Anderson R. M. 
Published: June 2009

SUMMARYWe present an analysis of the survival and migration rates of the infective (L3) stages ofOslertagia ostertagiandCooperia oncophora. Although the majority of laboratory studies show that the survival of the L3stage depends upon temperature, moisture and the age of the larvae, a simple mathematical model of larval demography, in which their mortality and migration rates are held constant, provides as good agreement between observed and predicted larval counts as models in which these rate processes are made explicit functions of larval age and microclimate. Maximum-likelihood estimates of larval mortality rates in the faeces and on the herbage are 0·0284/day and 0·00887/day respectively. The average migration rate from faeces to herbage under temperate Northern European conditions is estimated as 0·00884/day. Finally, we discuss the probable scale of L3larval losses due to desiccation and lavage (active or passsive migration into the soil).
Cuticle production and ecdysis in larval marine ascaridoid nematodes in vitro
Authors: Mercer J. G. , Munn A. E. , Smith J. W. , Rees H. H. 
Published: June 2009

SUMMARYInfective 3rd-stage larvae of three species of marine ascaridoid nematodes, Pseudoterranova (= Phocanema = Porrocaecum = Terranova) decipiens, Anisakis simplex and Phocascaris/Contracaecum sp. were cultured in vitro in 0·9% saline or Medium 199 at 37°C beneath an atmosphere of either air or 95% air:5% CO2 All three species responded to culture at 37°C by producing a new cuticle. The majority of P. decipiens completed ecdysis under all the culture conditions employed. Ecdysis in A. simplex was stimulated by a high concentration of CO2; this effect was particularly noticeable in saline cultures. Both A. simplex and Phocascaris/Contracaecum sp. developed more effectively in a nutrient medium than in saline.
Quinacrine-resistantGiardia duodenalis
Authors: Upcroft J. A. , Campbell R. W. , Upcroft P. 
Published: June 2009

SUMMARYQuinacrine resistance has been induced in 3Giardia duodenalislaboratory stocks and 4 lines resistant to other drugs. The quinacrine-resistant lines were maintained in normally lethal levels of 5 µM quinacrine and some lines are viable in 20 µM levels of the drug. Fluorescence studies indicated that quinacrine was taken up by sensitive cells but was actively excluded from resistant trophozoites. The nuclei were not a site of drug accumulation and no specific fluorescence in the trophozoite could be attributed to any structure. Blebs of concentrated drug appeared prior to disintegration of the membrane of drug-sensitive trophozoites exposed to drug overnight. Parasite lines already resistant to furazolidone adapted more readily to quinacrine exposure than drug-sensitive stocks. This multiple drug resistant phenotype was not as marked with metronidazole-resistant lines.
The impact of ticks onBufo marinusfrom native habitats
Authors: Lampo M. , Bayliss P. 
Published: June 2009

SUMMARYWe analysed the patterns of tick distribution on 2274 adult toads from Venezuela and Brazil, to explore whether these ectoparasites have any impact on the survival ofBufo marinus. A maximum-likelihood analysis showed that aggregation levels of ticks decreased significantly with the mean intensity of infection. This decline could be attributed to a density-dependent reduction of ticks within toads, density-dependent tick-induced toad mortality and/or density-dependent tick-induced changes in toad susceptibility. However, the relationship between the rate of change in tick loads and tick burdens from recaptured toads indicated that neither the loss of ticks within toads nor the toad susceptibility to further infection were dependent upon tick burdens. Therefore, we can indirectly infer that density-dependent tick-induced toad mortality is responsible for the observed decline in aggregation levels with tick age and burdens. On the other hand, a significant negative relationship between tick burdens and the size-specific weight of toads suggested that ticks may also have a significant impact on the patterns of weight deposition of adult toads. This evidence suggests that these ectoparasites may play an important role in regulating the densities ofB. marinusin native habitats.
Ultrastructural localization of Sm28 GST protective antigen inSchistosoma mansoniadult worms
Authors: Liu J. L. , Fontaine J. , Capron A. , Grzych J. M. 
Published: June 2009

SUMMARYThe localization of the 28 kDaSchistosoma mansoniglutathione S-transferase (Sm28 GST) has been investigated using immunohistochemistry and electron microscopy and the results compared with previously published data. This study confirms the wide distribution of this antigen in the parasite. In male and female worms, Sm28 GST is localized in the tegument, the parenchyma, the oesophageal epithelium and in genital organs. Sm28 GST was clearly detected in germinal and sustentacular cells. The decrease of staining intensity during the differentiation of germinal cells suggests a down-regulated expression of the molecule. At the ultrastructural level, this antigen was abundant in nuclei and less present in the cytoplasm. The marked heterogeneity observed in the staining of individual worms indicates that Sm28 GST seems to be closely associated with the parasite’s metabolism. The results are discussed in relation to the biological and protective functions of the protein.
Characterization of intestinally active proteinases of cystnematodes
Authors: Lilley C. J. , Urwin P. E. , McPherson M. J. , Atkinson H. J. 
Published: June 2009

SUMMARYCryostat sections of juvenile and adult female stages of the soybean cyst-nematode,Heterodera glycines, were incubated with 4 different naphthylamide-linked peptide substrates to localize and characterize proteinase activity within the animal. Detected activity was restricted to the intestine and 2 distinct classes of proteinase were identified on the basis of substrate specificity and sensitivity to plant proteinase inhibitors. A cathepsin L-like cysteine proteinase activity capable of hydrolysing the synthetic substrates Z-Ala-Arg-Arg-MNA and Z-Phe-Arg-MNA but not Z-Arg-Arg-MNA or L-Arg-NA was inhibited by an engineered variant of a cysteine proteinase inhibitor from rice (Oc-IδD86). The cleavage of Z-Phe-Arg-MNA was sensitive to inhibition by a combination of Oc-IδD86 and cowpea trypsin inhibitor (CpTI). Degenerate oligonucleotide primers were used to amplify fragments of cysteine proteinase genes from 2 cyst-nematodes,H. glycinesandGlobodera pallida. Comparison of theH. glycinesfragment with known genes established highest homology to cathepsin L-like genes. In contrast, the amplifiedG. pallidafragment displayed greatest homology to cathepsin B-like genes fromCaenorhabditis elegans.
Do three-spined sticklebacks avoid consuming copepods, the first intermediate host ofSchistocephalus solidus? — an experimental analysis of behavioural resistance
Authors: Wedekind C. , Milinski M. 
Published: June 2009

SUMMARYMany parasites that use intermediate hosts are transmitted to the next host through predation. If the next host's fitness is strongly reduced by the parasite, it is under selection either to recognize and avoid infected intermediate hosts or to exclude that prey species from its diet when alternative prey are available. We investigated the predator-prey interaction between laboratory bred three-spined sticklebacks (Gasterosteus aculeatus), the second intermediate host of the cestodeSchistocephalus solidus, from 2 parasitized and 1 unparasitized population, and different prey types: infected and uninfected copepods and size-matchedDaphniaas alternative prey. Copepods with infective procercoids were more active, had a lower swimming ability and were easier to catch than uninfected controls. The sticklebacks preferred moving copepods. Therefore parasitized copepods were preferentially attacked and consumed. There was no effect of the sticklebacks' parent population being parasitized or not. The sticklebacks switched fromDaphniato (uninfected) copepods in the course of a hunting sequence; this switch occurred earlier in smaller fish. With this strategy the fish maximized their feeding rate:Daphniawere easier to catch than copepods but increasingly difficult to swallow when the stomach was filling up especially for smaller fish. However, there was no indication that sticklebacks from infected populations either consumedDaphniarather than copepods or switched later in the hunting sequence to consuming copepods than fish from an uninfected population. Thus, sticklebacks did not avoid parasitized prey althoughS. solidususually has a high prevalence and causes a strong fitness reduction in its stickleback host.