The abundant cell-surface lipophosphoglycan (LPG) of Leishmania parasites plays a central role throughout the eukaryote’s life cycle. A number of LPG-defective mutants and their complementing genes have been isolated and have proven invaluable in assessing the importance of LPG and related glycoconjugates in parasite virulence. While ricin agglutination selection protocols frequently result in lpg- mutants, one L. donovani variant we isolated, named JABBA, was found to be lpg+. Procyclic (logarithmic) JABBA expresses significant amounts of a large-sized LPG, larger than observed from procyclic wild-type but similar in size to LPG from wild-type from metacyclic (stationary) phase. Structural analysis of the LPG from logarithmically-grown JABBA by capillary electrophoresis protocols revealed that it averaged 30 repeat units composed of the unsubstituted Gal(β1,4)Man(α1)-PO4 typical of wild-type L. donovani. Analysis of JABBA LPG caps indicated that 20% are the disaccharide Glc(β1,2)Man, trisaccharide Gal(β1,4)[Glc(β1,2)]Man, and tetrasaccharide Gal(β1,4)[Glc(β1,2)Man(α1,2)]Man in addition to wild-type Gal(β1,4)Man and Man(α1,2)Man and Gal(β1,4)[Man(α1,2)]Man terminating caps, These glucose containing isoforms were absent in stationary parasites. Consistent with these structural observations, analyses of the relevant glycosyltransferases in JABBA microsomes involved in LPG biosynthesis showed a two-fold increase in elongating mannosylphosphoryltransferase activity and up-regulation of a β-glucosyltransferase activity. The β-glucosyltransferase in both JABBA and wild-type in vitro produced a β-glucosidase sensitive and β-galactosidase sensitive trisaccharide, indicative of the mannose of repeating units and caps being used in substrate, novel in comparison to other Leishmania species. Furthermore, the caps of JABBA LPG are cryptic in presentation as shown by the loss of binding by the lectins ricin, peanut agglutinin and concanavalin A and reduced accessibility of the terminal galactose residues to oxidation by galactose oxidase. These results indicate that LPG from JABBA is intriguingly similar to the larger LPG in wild-type parasites that arises following the differentiation of the non-infectious procyclic promastigotes to infectious, metacyclic forms, and has a unique β-glucosyltransferase not active in vivo in wild-type parasites.

A study has been carried out to investigate some aspects of the feeding and digestion of the parasitic copepod Lepeophtheirus salmonis (Kreyer, 1837), a serious pathogen of wild and farmed marine salmonids. The alimentary canal consists of a cuticularised foregut and hindgut and a midgut, the latter comprising most of the length of the alimentary canal. It consisted of an anterior diverticulum, and anterior midgut, mid midgut and posterior midgut. All the midgut is lined in the luminal side with a monolayer of digestive epithelium. The latter is supported by a porous basal membrane. Mesenteries suspend the gut in the haemocoel and attach to the basal membrane by means of extensions of their cytoplasm that interlock with the pores of the basal membrane and are intimately associated with the cellular basal membrane of the enterocytes. Four types of cells could be recognised ultrastructurally and were named according a widely accepted nomenclature for the types of digestive epithelial cells found in decapod crustaceans. R-cells were the most abundant type and were believed to be involved in the absorption of nutrients, storage of lipids and probably excretion of waste material. Once the R-cells have finished their useful life, it is proposed that they finally die after passing through a stage, called A-cell stage, comparable to apoptosis or programmed cell death, after which the A-cell is finally sloughed off the epithelium and discarded in the faeces. F-cells constituted the second cell type, in charge probably of the secretion of digestive enzymes. Once this stage is finished, F-cells are believed to transform into the third type of cells, the B-cells, which engage in intracellular digestion of nutrients. At the end of their useful life they are sloughed off the epithelium. The last cell type, the E-cells, are believed to be embryonic cells that differentiate either into R- or F-cells. A revised mode of feeding is proposed, in which the louse scoops up strips of host skin epithelium of relatively constant size and shape, by means of the structures associated with the mouth cone. Analysis of the gut contents and the faecal pellets revealed that the main food item was host skin epithelium. The feeding activity usually reaches the dermal layer, suggested by the common occurrence of host melanin in the gut and in the faecal pellets. Two types of faecal pellets were found. The first type was a cylindrical one which was made of the ingested host's epithelial cells with little signs of having being digested. Cylindrical pellets could be clear or dark depending on the amount of host melanin present in them. The second type of pellet was a tape- or ribbon-like gelatinous pellet produced mainly when the lice were not eating (as during starvation) or sometimes associated to the end of the cylindrical pellets. Pellets were always surrounded by a delicate peritrophic envelope composed of several peritrophic membranes. Blood was believed to be another important food item. Blood feeding was commonly associated with the production of lipids in the R-cells and it is proposed (but not confirmed) that this alternative food item could be associated with some physiological process that requires lipogenesis, like vitellogenesis. A method for manually feeding the lice was devised. Salmon blood and milk were fed in this way. No sign of digestion of these food items was observed suggesting that possibly an endogenous factor different from the presence of food in the gut is necessary to trigger the digestive process. An analysis of type of gut contents, peritrophic membranes and cell type occurrences during a digestive period was carried out. The results suggested that some digestive processes take place preferentially in one or another gut region. Mid and posterior midgut are probably associated with the production of faecal pellets, production of digestive enzymes, intracellular digestion and excretion of waste materials judging by the higher occurrence of peritrophic membranes, B- and A-cells in these regions. Absorption of nutrients probably takes place throughout the midgut. The morphological changes in the topography shown by the midgut epithelium suggest that it is a very active and plastic tissue. The results of this study were discussed and compared with similar studies of other crustaceans, including other parasitic and free living copepod species. Suggestions were made of the implications of the present findings in the search for a control method for this parasite.

Magistro baigiamajame darbe aprašomi Radviliškio rajone auginamų kiaulių užsikrėtimo virškinimo trakto helmintais intensyvumas priklausomai nuo fermos dydžio ir gyvulio amžiaus. Nustatytas kiaulių užsikrėtimas Ascaris suum, Oesophagostomum spp, Strongyloideas spp. helmintais ir Eimeria spp. pirmuonimis. Literatūros apžvalgoje aprašomas šių parazitų vystymasis, klinika, patogenezė ir epizootiniai duomenys. Tyrimams mėginiai buvo imami Radviliškio rajone esančiuose smulkių kiaulių augintojų ūkiuose ir vidutinio stambumo kiaulių komplekse. Tyrimo laikotarpiu buvo paimti 57 mėginiai iš penkių skirtingų smulkių kiaulių augintojų ir 42 mėginiai iš kiaulių komplekso. Mėginiai ištirti LSMU VA Užkrečiamųjų ligų katedros Parazitologijos laboratorijoje. Kiaulės pagal amžių buvo suskirstytos į grupes: 0 – 3 mėn., 4 – 5 mėn., 6 – 8 mėn., 9 – 11 mėn., paršavedės ir kuiliai. Tyrimai buvo atliekami modifikuotu MacMaster metodu. Aukščiausias užsikrėtimas virškinimo trakto parazitais nustatytas Radviliškio rajone esančiuose smulkiuose kiaulių ūkiuose ir teigiamų atvejų skaičius juose siekė 89 proc. Tuo tarpu vidutinio didumo kiaulių komplekse užsikrėtimas siekė 31 proc. Dažniausiai pasireiškę virškinimo trakto parazitai tiek smulkių ūkių, tiek komplekso mėginiuose buvo Oesophagostomum spp. ir A. suum. Be to, nustatyti sporadiniai Strongyloides spp. ir Eimeria spp. užsikrėtimų atvejai. Oesophagostomum spp. ir Ascaris suum skirtingose kiaulių grupėse didžiausias užsikrėtimas buvo paršavedžių... [toliau žr. visą tekstą] / The research project presented in the thesis was designed to investigate the intensity of gastrointestinal parasite infection in pigs in district of Radviliškis caused by Ascaris suum, Oesophagostomum spp, Strongyloideas spp. and Eimeria spp. depending on the size of farm and age of the animal. In addition, the development cycles of these parasites, clinic, pathogenesis and epidemiological data are described. During the study, 57 samples from 5 different small pig farmers and 42 samples from the medium size pig farm were collected. All samples were examined at Laboratory of Parasitology, Department of Infectious Diseases, Veterinary Academy, Lithuanian University of health Sciences. Pigs were divided according age and sex into 0 – 3 months, 4 – 5 months, 6 – 8 months, 9 – 11 months, sows and boars groups. The samples were examined by modified MacMaster technique. The highest level (89%) of gastrointestinal parasites infection was registered in small pig farms. However, the level of infection in the medium size pig farm was significantly lower i.e. 31%. In our study Oesophagostomum spp. and A. suum were highly distributed and Strongyloides spp. and Eimeria spp were found only as sporadic infection. Most intensive infection level of Oesophagostomum spp. and A. suum was registered in sows, 6 – 8 months and 9 – 11 months pigs. Furthermore, the sporadical cases of infection with Eimeria spp. was found in 4 – 5 months and 6 – 8 months pigs and Strongyloides spp cases in... [to full text]

Anthelmintic resistance is a major problem in livestock, and while it has been slower to emerge in cattle, there are reports of its occurrence. Three broad-spectrum anthelmintics are available for use, and one mechanism of resistance that is common to all is target site alteration. Glutamate-gated chloride channels (GluCls) are an important target for macrocyclic lactone anthelmintics (MLs), while beta-tubulin represents the benzimidazole (BZ) target. The objectives of this thesis were to determine whether GluCls are involved in ML resistance in the cattle parasite Cooperia oncophora , and whether beta-tubulin is involved in BZ and ML resistance. Two isolates of C. oncophora were used. In a fecal egg-count reduction test, ivermectin was found to be 100% effective against one isolate (IVS), and only 77.8% effective against the second isolate (IVR). Two full-length GluCl cDNAs, encoding GluClalpha3 and beta subunits, were cloned. These subunits share high sequence identity with similar GluCl subunits from Haemonchus contortus and Caenorhabditis elegans. Genetic variability analysis of the two genes showed significant differences in allele frequencies between IVS and IVR worms at the GluClalpha3 gene, but not the GluClbeta gene, suggesting that the GluClalpha3 gene is involved in ivermectin resistance. Sequencing of full-length GluCl subunit cDNAs from IVS and IVR worms revealed the presence of mutations in the N-terminal domains. Mutations in the GluClalpha3 caused modest but significant reductions in glutamate, ivermectin and moxidectin sensitivity, while mutations in the GluClbeta abolished glutamate sensitivity. Of the three mutations identified in the IVR GluClalpha3, the L256F mutation accounted for the difference in glutamate and ivermectin response between IVS and IVR GluClalpha3 channels. Two beta-tubulin isotypes cloned from C. oncophora were found to share a high homology with beta-tubulin isotypes from other trichostrongylids. Gen

In mice infected with 10$ sp4$ Giardia muris cysts, a peak lymphocyte proliferation in the spleen and Peyer's patches in response to Giardia extract occurred during the elimination and latent phases, respectively. This shows that the Peyer's patch cells are more responsive than the spleen to Giardia infection. Th2-type cytokines produced by Peyer's patch cells may play a protective role during the latent and acute phases. Th1-type cytokines may contribute to this production during the elimination phase. Cytokine production in response to Giardia extract in vitro was observed in mice immunized with this extract, but not in control mice. Therefore, Giardia antigen can induce cytokine production in vitro in a specific manner.

The American kestrel (Falco sparverius) - Trichinella pseudospiralis host-parasite association was used as a model to study the effect of infection on (1) mate choice of female kestrels and (2) competitive abilities of male kestrels. In 34 choice tests, female selection of infected or uninfected males was random. Male competitive abilities was assessed by observing interactions between infected and uninfected individuals in a pen with a caged female and a single nest box. In 8 of 11 trials, uninfected males spent more time in the section closest to the female than their infected rivals, and performed more chases, attacks, and displacements than the latter. These results suggest that variation in male quality is determined in part by resistance to parasitism and can affect competition for nesting territories. Females may not have evolved mechanisms to detect parasitized males because these males are unlikely to outcompete uninfected males when territories are in limited supply.

The effects of food availability and selective control of late instar larvae of Aedes aegypti on preimago population structure, mortality, adult abundance, sex ratios, and size of females were examined. Food availability i an important factor in determining preimago population structure and mortality. At optimal food availability more adults emerged, females were larger and in higher proportions than at suboptimal food availability. The effects of selective control on preimago population structure and post treatment larval mortality differed with food availability. At suboptimal food availability the type of control applied had a significant effect. Simulated pathogen-induced mortality resulted in a shift of the population to late instars and temporarily reduced density dependent mortality. The findings suggest that although both pathogens and predators reduce intraspecific competition by directly killing competitors, pathogens also provide an influx of food. Compensatory mortality may result from a reduction of intraspecific competition caused by biocontrol agents.

Interactions among zinc deficiency, energy restriction, immunity and Heligmosomoides polygyrus (Nematoda) infection in mice were investigated. Mice were fed zinc-sufficient (Zn+: 60mg zinc/kg diet), zinc-deficient (Zn$-$: 0.75 mg/kg) or pair-fed (PF) diets. Liver and serum zinc concentrations were reduced in Zn$-$ mice, but zinc content of worms was unaffected by host diet. Both zinc deficiency and energy restriction accelerated worm maturation during a primary infection, but zinc deficiency caused stunting of female worms. Energy restriction led to a anteriorad distribution of worms along the intestine whereas zinc deficiency led to a posteriorad distribution. Enhanced parasite survival in Zn$-$ and PF mice was associated with a decreased immune response in both primary and challenge infections. In the primary infection, spleen cell production of interleukin-4 (IL-4) and interferon-gamma (IFN-$ gamma$), peripheral eosinophilia and serum levels of IgE and IgG1 were reduced by zinc deficiency, whereas the reduced delayed type hypersensitivity (DTH) response and impaired interleukin-5 (IL-5) production were attributed to energy restriction. In the challenge infection, reduced antibody levels (total IgE and IgG1, parasite-specific IgG1 and IgG3) and eosinophilia were attributed to zinc deficiency whereas the higher worm numbers were attributed to a combined effect of zinc deficiency and energy restriction. Although the absolute number of spleen cells was reduced in both Zn$-$ and PF mice, neither deficiency altered the proportion of the cell subpopulations. In vitro functional assays in response to parasite antigen (Ag) revealed that T cell proliferation was reduced by a direct effect of zinc deficiency on T cells, and by the effects of energy restriction on antigen presenting cells (APC). Impaired cytokine production in Zn$-$ mice was more complex. Zinc deficiency reduced T cell function (IL-4 production), energy restriction decreased T cell (IFN-$ gamma$ productio

This study investigated the predatory behaviour of kestrels on insect prey in a modified open-field arena, and assessed the effects of T. pseudospiralis infections on the sequence of predatory behaviours, hunting efficiency and choice of hunting method of the birds. Choice of hunting method in kestrels was related to their appraise energy expenditure and relative success. Hunting from a perch was more common, presumably less strenuous and more successful than hunting afoot. Hunting prey confined to the vertical walls of the arena was considered more strenuous and was less successful than hunting freely-roaming ground prey. Infection with T. pseudospiralis did not affect attack rate or hunting success but altered the manner in which prey were taken. Thus, the frequency of strikes performed in level flight declined, and birds tended to hunt more on foot. In flight, the frequency of wing beats and the horizontal distance travelled to regain the elevated perch increased. Concordance was found between intensity of infection and magnitude of change in body weight and flight activities. (Abstract shortened by UMI.)

Both major histocompatibility genes (MHC) and infection have been shown to influence urinary odours in mice, and mice may use MHC-associated odours to detect kin for the purpose of choosing communal nesting partners, or to avoid mating with close relatives. Additionally, mice may use infection-related odours to avoid mating with sick individuals or those genetically susceptible to infection. I tested the above theories using urine as the source of odour. In a series of odour preference experiments, employing two MHC-congenic strains of mice (B10 and B10.Q), I tested the proposition that females prefer MHC-similar female odours when choosing female relatives as nesting partners, and that females prefer MHC-disparate male odours for the purpose of disassoratative mating. I found that females did not display a preference for MHC-similar female odours or MHC-disparate male odours. However, when B10.Q male urine donors were infected with 100 L3 larvae of Heligmosomoides polygyrus (Nematoda), both strains of female displayed a significant preference for the odours of uninfected B10 males. To determine whether female odour preference for uninfected males extended to actual mate choice, I subsequently examined female mate choice in a controlled setting. Using CD-1 outbred mice, I found that females preferred to mate with uninfected males over males subclinically infected with 200 L3 of H. polygyrus , as evidenced by first ejaculation preferences. In this experiment, males were tethered, and as such, male dominance interactions were prevented. Thus, in the final experiment, to assess whether male dominance interactions influenced female mate choice, in addition to infection, I tested female mate choice in a seminatural setting, which allowed for social interactions to occur. In this study, paternity was ascertained through DNA analysis and the resulting data indicated that neither male dominance status nor infection had a substantial impact on fema / Overall, the data do not support the theory that MHC-based preferences occur through urinary odours. However, the results do substantiate previous findings regarding female preferences for the odours of uninfected males. Furthermore, data from the controlled mate choice assay indicate that female odour preference for uninfected males extends to actual mate choice. Conversely, in the seminatural setting neither dominance nor infection prevailed as factors driving female mate choice. I suggest that this may be a consequence of the structural complexity of my arenas.