| selection for a strain of haemonchus contortus that exhibits periparturient egg rise in sheep. | periparturient egg rise (ppr) is a principal means for some nematode parasites to survive over winter and to provide transmission of infective larvae from ewes to lambs during the spring. routine laboratory propagation techniques probably have selected for those characteristics that would not promote ppr in conventional laboratory strains of haemonchus contortus. an established isolate of h. contortus (bpl) was the source of the initial inoculum to select for a strain that readily exhibits chara ... | 1993 | 8501597 |
| r4, a non-ltr retrotransposon specific to the large subunit rrna genes of nematodes. | a 4.7 kb sequence-specific insertion in the 26s ribosomal rna gene of ascaris lumbricoides, named r4, is shown to be a non-long terminal repeat (non-ltr) retrotransposable element. the r4 element inserts at a site in the large subunit rrna gene which is midway between two other sequence-specific non-ltr retrotransposable elements, r1 and r2, found in most insect species. based on the structure of its open reading frame and the sequence of its reverse transcriptase domain, r4 elements do not appe ... | 1995 | 8524653 |
| amplification and characterization of cysteine proteinase genes from nematodes. | in order to isolate proteinase genes from parasitic nematodes by polymerase chain reaction (pcr) techniques, we employed a pair of consensus oligonucleotide primers designed to anneal to the active site cysteine (primer ncpc) and asparagine (primer ncpn) coding regions of cysteine proteinases. the primers were biased toward the nucleotide and codon usages of cysteine proteinase genes of nematodes and were based on the consensus nucleotide sequences flanking the active site residues of genes from ... | 1995 | 8525283 |
| experimental study of survival strategy of haemonchus contortus in sheep during the dry season in desert areas of the mauritania. | the survival of the most common worm of sheep and goats of desert areas, haemonchus contortus, during the dry season is of the utmost importance. it may be achieved through long survival of adult worms that may preserve their ability to excrete viable eggs or to inhibited development in host and survival as a larval stage. twelve lambs were experimentally infected with larvae obtained at the end of the rainy season. the resulting adult worms were able to survive and maintain their ability to pro ... | 1995 | 8544042 |
| the effect of molybdenum and sulphur on anthelmintic resistant haemonchus contortus in sheep. | | 1995 | 8544158 |
| the persistence of the efficacy of injectable or oral moxidectin against teladorsagia, haemonchus and trichostrongylus species in experimentally infected sheep. | the persistence of the efficacy of moxidectin was evaluated against experimental gastrointestinal nematode infections in 55 lambs randomly allocated to 11 equal groups and infected on day 0. moxidectin 1 per cent injectable solution was administered at a dose rate of 0.2 mg moxidectin/kg bodyweight to five of the groups on days -42, -35, -28, -21 and -14; five other groups were treated with moxidectin 0.1 per cent oral drench at the same dose rate on days -35, -28, -21, -14 and -7, and the 11th ... | 1995 | 8545937 |
| isolation of af2 (kheylrfamide) from caenorhabditis elegans: evidence for the presence of more than one fmrfamide-related peptide-encoding gene. | numerous fmrfamide-related peptides (farps) have been isolated and sequenced from extracts of free-living and parasitic nematodes. the most abundant farp identified in ethanolic/methanolic extracts of the parasitic forms, ascaris suum and haemonchus contortus and from the free-living nematode, panagrellus redivivus, was kheylrfamide (af2). analysis of the nucleotide sequences of cloned farp-precursor genes from c. elegans and, more recently, caenorhabditis vulgaris identified a series of related ... | 1995 | 8554607 |
| actin isoforms in the parasitic nematode haemonchus contortus. | actin proteins in the parasitic nematode haemonchus contortus were partially purified by a new method based on precipitation with podophyllotoxin and dimethylsulfoxide. two-dimensional gel electrophoresis of partially purified actin proteins revealed differences in isoform composition between adults and third-stage larvae. the significance of this finding is possibly related to the existence of differential functional or developmental characteristics between these two life-cycle stages. | 1995 | 8570588 |
| heat-shock and stress response of the parasitic nematode haemonchus contortus. | before and after a stress treatment, larval stages and adult worms of haemonchus contortus were tested for the induction and expression of heat-shock proteins (hsps) using immunoblot analysis with hsp70-and hsp65-specific monoclonal antibodies. stress treatment or heat shock did not alter the signals obtained with these antibodies, but the amount of hsp70 differed between the successive stages. in addition, the different stages were metabolically labeled with [35s]-methionine during a temperatur ... | 1995 | 8570590 |
| [anthelmintics resistance in gastrointestinal nematodes in domestic animals]. | in belgium benzimidazole resistance has been reported in 28% of the sheep farms and 29 to 50% of the studs. in several member states of the european union the prevalence of anthelmintic resistance (ar) is even higher than in belgium, although ar is nearly absent in some countries of southern europe. ar is particularly widespread in certain nematodes of sheep, goats and horses in europe, whereas only sporadic cases of ar have been reported in helminths of cattle. in belgium only one case of ar ha ... | 1995 | 8571668 |
| humoral and cellular responses following local immunization with a surface antigen of the gastrointestinal parasite haemonchus contortus. | a purified, larval specific antigen of the abomasal parasite haemonchus contortus was used to immunize sheep. in an attempt to induce a local immune response in the abomasum, the antigen was injected twice into the abomasal wall after one peripheral immunization. serum antibody responses were boosted by each intra-abomasal immunization but not by the challenge infection given 3.5 weeks after the last immunization. examination of the specific antibody secreting cells (asc) recirculating in the pe ... | 1995 | 8578690 |
| moisture and temperature requirements in faeces for the development of free-living stages of gastrointestinal nematodes of sheep, cattle and deer. | isolates from eight gastrointestinal nematode species parasitic in sheep, cattle and deer were maintained in sheep, to provide eggs in similar faecal environments and to compare temperature and moisture requirements for their development. faecal cultures were processed at different temperatures (for four species) and moisture contents (for the eight species). at 60% of faecal moisture content (fmc), maximal rates of development (expressed as l3/100 hatchable eggs estimated by an extraction techn ... | 1995 | 8583130 |
| microclimatic effect on vertical migration of haemonchus contortus and haemonchus placei third-stage larvae on irrigated kikuyu pasture. | the influence of microclimate on numbers of third-state larvae of haemonchus contortus and haemonchus placei in four strata of irrigated kikuyu pasture was assessed. on 36 different, interspersed days three replicates of pasture samples were collected on three occasions per day from 1990-1992 for larval recovery and the log10 mean counts of the larvae recovered were analysed by use of anova models. because the ground-surface area from which herbage was collected was standardized, estimated larva ... | 1995 | 8600435 |
| developmentally regulated zinc metalloproteinases from third- and fourth-stage larvae of the ovine nematode haemonchus contortus. | parasitic third-stage larvae of the sheep abomasal nematode haemonchus contortus develop and molt in vitro to the fourth stage (l4) in 48-72 hr, at which time they begin feeding. coincident with the third molt, larvae begin to secrete significant amounts of protein into culture fluids, including a zinc metalloproteinase. this culture-derived zinc metalloproteinase differs from a previously described metalloproteinase from infective third-stage larvae (l3[2m]), which mediates the ecdysis process. ... | 1996 | 8604083 |
| p-azidosalicyl-5-amino-6-phenoxybenzimidazole photolabels the n-terminal 63-103 amino acids of haemonchus contortus beta-tubulin 1. | benzimidazoles (bz) are broad spectrum anthelmintics thought to exert their effects by interacting with and disrupting the functions of microtubules. however, direct biochemical evidence for binding between bz and tubulin has not been shown nor is it known what sequences in tubulin interact with bz. in this study, a photoactive analogue of 2-acetamido-5-(3-aminophenoxy)benzimidaz ole that has biological activity similar to other benzimidazoles was synthesized and used to photoaffinity label cell ... | 1996 | 8621485 |
| viability of infective larvae of haemonchus contortus, ostertagia ostertagi, and trichostrongylus colubriformis following exsheathment by various techniques. | various techniques were examined to determine optimum conditions for exsheathing infective larvae of 3 important ruminant parasites (haemonchus contortus, ostertagia ostertagi, and trichostrongylus colubriformis). in repeated experiments, aliquots of 10(5)-10(6) infective larvae, 1-2 mo old, of each parasite were incubated in each of 4 exsheathing media (distilled water, earle's balanced salt solution + carbon dioxide, nematode washing buffer + carbon dioxide, or sodium hypochlorite) for 1 or 18 ... | 1996 | 8627476 |
| introduction to symposium on recent research on haemonchus contortus. | | 1995 | 8635878 |
| progress on vaccination against haemonchus contortus. | control of haemonchus contortus at present is largely by the use of anthelmintics, assisted in some regions by management programs. widespread development of resistance, particularly in south africa and australia, and concerns associated with the manufacture and use of chemicals have led to increasing interest in vaccination as an alternative means of control. vaccination strategies basically fall into 2 categories, 'hidden' antigens (usually derived from the gastrointestinal tract of the adult ... | 1995 | 8635880 |
| extracellular matrix degradation by haemonchus contortus. | to better understand the in vivo function of secreted cysteine proteases of haemonchus contortus, the ability of live parasites to degrade connective tissue was investigated using [3h]proline-labeled extracellular matrix produced by smooth-muscle cells (r22). the matrix was composed of glycoprotein(s) (34%), elastin (49%), and collagen (15%) in an insoluble, multilayered, cross-linked structure. no degradation of the extracellular matrix by third-stage larvae (l3) (10,000/ml) occurred during 24- ... | 1996 | 8636839 |
| helminth parasites and hypobiosis of nematodes in n'dama cattle during the dry season in the gambia. | three series of necropsies of cattle were performed, corresponding to early dry season, approximately 1 month after the last rains (november, n = 6), mid dry season (february, n = 6) and end dry season (april, n = 3). eggs per gram of faeces (epg) were determined just before necropsy. three trematodes (fasciola gigantica, schistosoma spp. and paramphistomatids) and 11 nematodes were identified from cattle, with the prevalence rate varying from 6.7% to 100%. haemonchus contortus was the most abun ... | 1995 | 8644452 |
| a comparison of the responses to repeated experimental infections with haemonchus contortus among scottish blackface lambs. | twenty helminth-naive scottish blackface lambs were given three infections with 10,000 infective larvae of haemonchus contortus at 8 week intervals. an additional six lambs served as uninfected controls and eight lambs were infectivity controls. the lambs were 7 months old at the start of the infection. four of the 20 lambs developed severe haemonchosis and were put down during the experiment. the remaining 16 lambs plus uninfected controls were necropsied 8 weeks after the third infection. the ... | 1995 | 8644460 |
| influence of soyabean meal supplementation on the resistance of scottish blackface lambs to haemonchosis. | protein supplementation improves the resistance of sheep to haemonchosis. this experiment investigated the scottish blackface breed to establish whether dietary protein supplementation is still beneficial in a genetically resistant breed. lambs were given either a basal diet or a diet supplemented with soyabean meal to give an additional 80 g crude protein kg dry matter-1. the lambs were given an initial loading dose of haemonchus contortus, followed by a trickle infection for 10 weeks. the weig ... | 1996 | 8685535 |
| the prevalence of anthelmintic resistance in nematode parasites of sheep in southern latin america: argentina. | sixty-five sheep farms in the northern provinces of buenos aires, entre rios, corrientes, cordoba and sante fe were used in this survey on anthelmintic resistance. anthelmintic groups tested were the benzimidazoles, levamisole, the combination levamisole + benzimidazole product and the avermectins. the overall level of resistance was 46% of properties, with resistance to the individual drug groups being 40%, 22%, 11% and 6%, respectively. on a large proportion of farms the resistance recorded wa ... | 1996 | 8686164 |
| the prevalence of anthelmintic resistance in nematode parasites of sheep in southern latin america: paraguay. | this survey to detect anthelmintic resistance in nematode parasites of sheep was conducted on 11 farms in the occidental and 26 farms in the oriental regions of paraguay using the faecal egg count reduction test (fecrt). the anthelmintic groups tested were the benzimidazoles, levamisole and avermectins (both oral and injectable). overall the levels of resistance were 73%, 68%, 73% and 47%, respectively. levels of resistance were similar for all three important nematode genera, viz. haemonchus co ... | 1996 | 8686166 |
| potential for misinterpretation of the faecal egg count reduction test for levamisole resistance in gastrointestinal nematodes of sheep. | the faecal egg count reduction test (fecrt) is widely used to assess the presence or absence of levamisole resistance in gastrointestinal nematodes in sheep flocks. however, in a recent study the fecrt appeared to falsely indicate the presence of levamisole resistance. one possible explanation for this result could have been that the anthelmintic failed to completely remove all immature stages of levamisole-susceptible strains, which then developed into egg laying adults and gave misleading resu ... | 1996 | 8686173 |
| characterization of excretory-secretory products from larval stages of haemonchus contortus cultured in vitro. | to determine biochemical changes associated with early parasite development, haemonchus contortus larvae were cultured in vitro to the fourth stage (l4). infective larvae developed from third to fourth stage in 48-96 h. metabolic activity increased following stimulus of infective stages by co2 secretion/excretion of significant amounts of protein into cultures and larval feeding did not occur until larvae had molted to the fourth stage. larval feeding, as monitored by the ability of larvae to in ... | 1996 | 8686175 |
| secretion of anti-parasite substances and leukotrienes from ovine gastrointestinal tissues and isolated mucosal mast cells. | the presence of larval migration inhibitory (lmi) compounds in the gastrointestinal mucus of nematode resistant sheep has been shown previously to be associated with increased numbers of gastrointestinal mucus of nematode resistant sheep has been shown previously to be associated with increased numbers of gastrointestinal mucosal mast cells (mmc) and globule leukocytes (gl). this experiment was designed to determine if lmi compounds were secreted by mmc/gl in response to nematode antigenic chall ... | 1996 | 8690545 |
| haemonchus contortus ga1 antigens: related, phospholipase c-sensitive, apical gut membrane proteins encoded as a polyprotein and released from the nematode during infection. | it was previously shown that the haemonchus contortus apical gut surface proteins p46, p52, and p100 induced protective immunity to challenge infections in goats. here, it is shown that the three proteins are all encoded by a single gene (ga1) and initially expressed in adult parasites as a polyprotein (p100ga1). p46ga1 and p52ga1 are related proteins with 47% sequence identity, including a cysteine-containing region, which appears to confer secondary structure to these proteins, and a region wi ... | 1996 | 8710924 |
| cryopreservation of the first-stage larvae of trichostrongylid nematode parasites. | first stage (l1) larvae of haemonchus contortus, trichostrongylus colubriformis and ostertagia circumcincta can be cryopreserved in the presence of dmso using a two-step freezing protocol involving an initial period at -80 degrees c prior to transfer to liquid nitrogen. thawed l1 larvae continue development in vitro producing third stage (l3) larvae that are infective to sheep when dosed per os. establishment rates for l3 larvae grown from thawed l1 larvae were 40 and 80% for h. contortus and t. ... | 1995 | 8719953 |
| nematode burdens and immunological responses following natural challenge in romney lambs selectively bred for low or high faecal worm egg count. | breeding lines of romney sheep, selected as lambs for consistently low or high faecal nematode egg count (fec) following periods of natural challenge, have been maintained at wallaceville for some years. in order to determine the extent to which fecs in low and high genotypes reflected their ability to resist the establishment of gastro-intestinal nematode burdens, we investigated the infection status and immune responses in 8- to 9-month-old progeny of selected rams from low and high fec breedi ... | 1996 | 8720563 |
| coccidial and helminth infections in goats kept indoors in the netherlands. | an investigation was carried out on coccidial and helminth infections in goats kept indoors on five farms in the netherlands. the goats were individually sampled. coccidial oocysts were identified and nematode eggs counted. larval cultures were made and infective larvae identified to the generic or species level. the goats were divided into three groups according to their age: kids, those weaned but not served, and older goats. oocysts were found in 26 out of 27 kids (96.3%), in 52 out of 55 wea ... | 1996 | 8720569 |
| helminth infections of sheep in north sumatra, indonesia. | gastrointestinal tracts of 73 indigenous sheep were obtained from the medan abattoir in north sumatra, indonesia, and examined for the presence of helminths. a total of 13 species of helminths, eight nematodes, one cestode and four trematodes were encountered. all sheep were infected by more than one species of nematodes. trichostrongylus colubriformis, t. axei and haemonchus contortus were the most common species. the intensity of the nematode infections was very high: the average burden was ov ... | 1996 | 8720574 |
| [epidemiology of gastrointestinal nematodes in small ruminants in the plateau areas in togo]. | post-mortem helminthological examinations were performed in togo on small ruminants of the djallonké breed (59 sheep, 60 goats), revealing the presence of eight gastrointestinal nematode species which were, in decreasing prevalence order, trichostrongylus sp. (t. axei and t. colubriformis) (99%), haemonchus contortus (82%), strongyloides papillosus (67%), cooperia curticei (43%), oesophagostomum columbianum (40%), gaigeria pachyscelis (36%) and trichuris ovis (4%). the average worm burden was 1, ... | 1995 | 8734228 |
| the effect of level of feed intake on the pharmacokinetic disposition and efficacy of ivermectin in sheep. | the kinetic disposition of orally administered [3h]-ivermectin (ivm) was examined in sheep in which the feed intake was maintained at either 800 or 400 g/day. the [3h]-metabolites were almost completely associated with particulate digesta in the rumen. in the low feed intake group the digesta flow was slower than in sheep on high feed intake. this resulted in an extended residence time and greater availability of ivm and its metabolites. the anthelmintic efficacy of ivm was then examined in shee ... | 1996 | 8735414 |
| flow-cytometry analysis of sheep-nematode egg populations. | flow cytometry was applied to the analysis of nematode populations. three strains of haemonchus contortus susceptible or resistant to anthelmintics were studied. eggs were chosen for these analyses. data on light-scatter emissions and native green fluorescence were collected. in addition, the size of the eggs (image analysis), the hatching rate, and the susceptibility to benzimidazoles were measured. the results showed that nematode eggs are a suitable material for multiparametric flow-cytometry ... | 1996 | 8740553 |
| immunisation of sheep with an integral membrane glycoprotein complex of haemonchus contortus and with its major polypeptide components. | sheep were immunised against haemonchus contortus with an integral membrane glycoprotein complex isolated from the intestines of the parasite as antigen. this antigen has been termed haemonchus galactose-containing glycoprotein complex. sodium dodecyl sulphate (sds) polyacrylamide gel analysis has shown that it is composed of several polypeptides but so far these have proved refractory to separation when in the native state. however when dissociated by sds, it was found to be as efficacious as i ... | 1996 | 8745246 |
| alveolar mastocytosis and eosinophilia in lambs with naturally acquired nematode infections of protostrongylus rufescens and haemonchus contortus. | specific-pathogen-free dorset and st. croix lambs were placed on pasture contaminated with haemonchus contortus third stage larvae and slugs carrying third stage larvae of protostrongylus rufescens for an entire grazing season to evaluate breed differences in acquired resistance to these nematodes. lambs were evaluated for clinical signs, clinical pathology and histopathologic lesions associated with these infections. both breeds acquired natural infections with h. contortus and lungworm when al ... | 1995 | 8746699 |
| dietary protein for young grazing sheep: interactions with gastrointestinal parasitism. | effects of protein supplementation and of nematode control on production responses in young grazing sheep and on nematode population dynamics were assessed. young merino wether sheep (n = 270) were allocated to one of three supplementation (su) treatments and one of three regimes of nematode control (drench, dr) in a factorial design. each of the nine treatments was replicated three times in a randomised complete block. animals received no supplement (su0) or were given supplements at a level eq ... | 1995 | 8747911 |
| evidence for multiple anthelmintic resistance in sheep and goats reared under the same management in coastal kenya. | four experiments, two with sheep and two with goats, were carried out to determine the efficacy of ivermectin, fenbendazole, levamisole, closantel and some of their combinations by faecal egg count reduction tests. in the first experiment, injectable ivermectin, oral ivermectin, fenbendazole and levamisole were tested in 6-month-old lambs, and their reduction percentages were 77%, 13%, 42% and 92%, respectively. in the second experiment, with yearling sheep, the reduction percentages were 35% fo ... | 1995 | 8747913 |
| studies on multispecific resistance of gastrointestinal nematodes to benzimidazoles on dairy-goat farms. | multispecific resistance to benzimidazoles was studied in three selected farms. these farms had bred dairy goats for more than 15 years. the helminths were introduced with the goats at the establishment of the farms which afterwards remained isolated. nematode resistance could then be related to their own management practices. faecal egg count tests and egg hatch assays were performed to assess intensity of resistance. the generic (infective larvae in faecal cultures) and specific richness (adul ... | 1995 | 8747916 |
| multiple anthelmintic resistance in haemonchus contortus on a sheep farm in india. | multiple resistance to benzimidazoles (fenbendazole, albendazole and mebendazole) in a strain of haemonchus contortus in sheep was detected on a farm where fenbendazole resistance had already been identified. following a faecal egg count reduction test, this was confirmed by both critical and controlled anthelmintic tests. different groups of sheep infected naturally or given an experimental infection with the fenbendazole-resistant strain were treated with the recommended doses of various anthe ... | 1995 | 8747919 |
| in vitro screening of haemonchus contortus third stage larvae for ivermectin resistance. | the indiscriminate repeated use of ivermectin has resulted in the emergence of ivermectin resistant field strains of haemonchus contortus in sheep in south africa. there is a need for a rapid and cost effective in vitro test to detect such strains. infective h contortus larvae known to be resistant to ivermectin, were incubated in vitro in a diluted concentration of the drug. subsequently their ability to migrate was compared with that of larvae of isolates known to be susceptible to ivermectin. ... | 1996 | 8750685 |
| identification and sequence comparison of a cuticular collagen of brugia pahangi. | the cuticle of filarial nematodes is a specialized extracellular matrix that covers the parasite and protects it from adverse conditions of the environment. as a surface structure it is in direct contact with the host defence mechanisms and therefore plays an important role in the molecular host-parasite relationship. using polyclonal antisera raised against the insoluble components of the cuticle of the adult filarial parasite brugia pahangi, we have isolated cdna clones encoding collagen molec ... | 1996 | 8760314 |
| antigens with application toward immune control of blood-feeding parasitic nematodes. | this review considers progress toward immune control of nematode parasites that feed on mammalian host blood. approaches to identify relevant parasite antigens include use of irradiated larvae, somatic antigens, metabolites, enzymes and gut antigens. because significant immune protection has more recently been achieved using gut antigens of the blood-feeding parasite haemonchus contortus, these antigens are considered in greater detail. issues discussed are implications of gut antigens in immune ... | 1996 | 8762603 |
| lectin staining of trichostrongylid nematode eggs of sheep: rapid identification of haemonchus contortus eggs with peanut agglutinin. | the binding of 10 different lectins to the surface of trichostrongylid nematode eggs of sheep were investigated. osage orange seed agglutinin bound to eggs from haemonchus contortus, ostertagia circumcincta and trichostrongylus colubriformis, jack bean agglutinin to h. contortus and o. circumcincta eggs and peanut agglutinin to h. contortus eggs only. staining of egg mixtures with fluorescein-labelled peanut agglutinin showed that the lectin correctly identified the percentage of h. contortus eg ... | 1996 | 8773534 |
| genetic variability in resistance of creole goats to natural infection with trichostrongylids in guadeloupe. | the objective of this study was to show the existence of genetic variability in resistance of creole goats to natural infection with intestinal nematodes. four successive cohorts of male and female kids were reared from weaning during 9 months in intensive pangola pastures (stocking rate 1.4 t/ha, regrowth of 21 days, 300 kg n/ ha/year of fertilization). all cohorts considered, 203 offsprings from 13 bucks and 149 goats were used in the experiment. animals were treated with an oral dose of iverm ... | 1996 | 8784523 |
| identification and partial purification of a 26 kilodalton antigen of adult haemonchus contortus. | adult h. contortus soluble extracts were fractionated by means of gel filtration (s-200) and anion exchange chromatography (deae-sephacel). fractions from both analyses were checked by elisa and western blotting (wb) with sera from lambs infected with h. contortus, monospecific heterologous sera (anti-trichostrongylus colubriformis and anti-teladorsagia circumcinta) and sera from naturally infected sheep with mixed trichostrongylid infections. high cross reactivity was seen between h. contortus ... | 1996 | 8786222 |
| use of free living stages to study the effects of thiabendazole, levamisole, pyrantel and ivermectin on the fine structure of haemonchus contortus and heligmosomoides polygyrus. | ultrastructural changes induced in vitro by thiabendazole, levamisole, pyrantel and ivermectin in the free living larval stages of two trichostrongyles (heligmosomoides polygyrus and haemonchus contortus) were analysed. the observed damage for each anthelmintic is related to the known mode of action and compared to the damage commonly described in adults. the advantage of using larvae to study the effects of anthelmintics on the fine structure of nematodes rather than adults is described. thiabe ... | 1996 | 8792583 |
| reduction of haemonchus contortus infective larvae by harposporium anguillulae in sheep faecal cultures. | harposporium anguillulae is a common nematophagous fungus which colonizes cattle pats deposited in brachiaria decumbens pasture in brazil. to assess its possible effect on free living stages of trichostrongylid nematodes, the reduction of haemonchus contortus infective stages in sheep faecal culture was evaluated in vitro. addition of 300,000 conidia per gram of faeces caused a reduction of 99.5% compared to the control group. this result indicates that h. anguillulae could be a candidate for th ... | 1996 | 8818730 |
| cross-reactive, stage-specific antigens in the oestridae family. | the larval stages of different economically important oestridae species were studied for their antigenicity and cross reactivity, using elisa and immunoblotting. the immune sera of cattle from algeria, belgium, france and switzerland were compared for their capacity to recognize the stage-specific antigens of their specific parasites hypoderma bovis and h lineatum, originating from different populations. this comparison was extended to other hypoderminae species responsible for economic losses i ... | 1996 | 8822621 |
| carbohydrate epitopes on haemonchus contortus antigens. | extracts of infective larvae and adults of the trichostrongylid haemonchus contortus were studied for the presence of carbohydrate moieties. several different lectin-binding sites were demonstrated in both stages using a panel of nine lectins. the carbohydrate specificity of the lectins used strongly suggests that alpha-d-mannose, alpha-d-glucose, and d-n-acetylglucosamine are the most important carbohydrate epitopes present on h. contortus proteins. thus, n-linked oligosaccharides form the majo ... | 1996 | 8825443 |
| occurrence of anthelmintic resistant nematodes on sheep farms in england and goat farms in england and wales. | a survey in 1992 showed that 44 per cent of the sheep farms tested in the south west and 15 per cent of those in the north east of england had parasitic nematode worm burdens which were resistant to benzimidazole anthelmintics, and that 65 per cent of the non-dairy goat farms tested in england and wales had resistant worms. ostertagia circumcincta was the main species in sheep and haemonchus contortus in goats. the resistance to benzimidazoles was diagnosed by a combination of an egg hatch assay ... | 1996 | 8843638 |
| interaction between fenbendazole and piperonyl butoxide: pharmacokinetic and pharmacodynamic implications. | the effect of the cytochrome p450 inhibitor, piperonyl butoxide on the pharmacokinetics and anthelmintic efficacy of the benzimidazole compound fenbendazole was studied in sheep and goats. pretreatment of goats with the inhibitor caused a greater than three-fold increase in the relative bioavailability of fenbendazole and fenbendazole sulphoxide. a pharmacokinetic dose titration study was carried out in sheep with fenbendazole (5 mg kg-1) and piperonyl butoxide administered orally at 0, 15, 31, ... | 1996 | 8866343 |
| developmentally regulated expression of a haemonchus contortus surface antigen. | all life cycle stages of haemonchus contortus were screened with antibody-secreting cell (asc) probes generated from immune sheep 5 days after a challenge infection. an antigen with an approximate molecular weight of 70-90 kda was found to be predominantly expressed in the 3rd-stage larvae, while a molecule with an approximate molecular weight of 28-31 kda was recognised by the asc-probes in the earlier developmental stages. antisera generated against the purified 70-90 kda molecule and antibodi ... | 1996 | 8875315 |
| development and survival of haemonchus contortus and trichostrongylus sp. on pasture in cameroon. | the development and survival of haemonchus contortus and trichostrongylus sp. on pasture at bamenda, cameroon were studied by spreading faeces containing strongyle eggs from mixed infections on 12 experimental grass plots from april 1988 to march 1989. development of eggs to infective larvae during the rainy season (april to october) took place within one week. the infective larvae of h. contortus survived for 11 +/- 2 weeks (with a range of 7 to 13 weeks) during this period while those of trich ... | 1996 | 8888523 |
| comparative efficacies of closantel, ivermectin, oxfendazole, thiophanate and levamisole against thiabendazole resistant haemonchus contortus in sheep. | forty-nine sheep artificially exposed to a thiabendazole (tbz) resistant isolate of haemonchus contortus were assigned to 7 groups of 7 animals each and used to conduct a controlled anthelmintic trial. one group of sheep served as untreated infected controls and 6 groups were treated as follows: closantel, 5.0 mg kg-1; ivermectin, 0.2 mg kg-1; oxfendazole, 5.0 mg kg-1; thiophanate, 50 mg kg-1, levamisole, 7.5 mgkg-1 and thiabendazole, 66 mg kg-1. eggs per gram of faeces were determined on days 2 ... | 1996 | 8888527 |
| a tandemly repetitive dna sequence is present at diverse locations in the genome of ostertagia circumcincta. | a novel repetitive dna sequence in the sheep parasitic nematode ostertagia circumcincta was cloned and sequenced. this 1.2-kb sequence (oc1b) was not found in the closely related cattle parasite ostertagia ostertagi, nor in the more distantly related sheep parasites haemonchus contortus or trichostronylus colubriformis. sequences similar to oc1b were found at various genomic locations and contained a pair of 33-bp direct repeats. oc1b also contained a single copy of a 218-bp sequence (designated ... | 1996 | 8890746 |
| the role of the sheath in resistance of haemonchus contortus infective-stage larvae to proteolytic digestion. | surface iodinated larvae of haemonchus contortus were incubated in the presence of the fungal protease, proteinase k, and proteolysis quantified by scintillation counting of released radioactivity. no radioactivity was released from live ensheathed infective-stage larvae (l3(2m)). in contrast, 58% of the radioactivity was released from ecdysed, second molt (2m) cuticles (sheaths) of l3(2m) and 48% from live exsheathed third-stage larvae (l3). when l3(2m) larvae were killed by heat (80 degrees c ... | 1996 | 8893481 |
| efficacy of moxidectin 0.5% pour-on against naturally acquired nematode infections in cattle. | the efficacy of 0.5% moxidectin pour-on at two dosages was evaluated in 30 cattle with naturally acquired gastrointestinal nematode infections. the cattle were ranked according to pretreatment fecal egg counts and body weights, and were randomly assigned from replicates to three treatment groups. the mean number of trichostrongyle eggs in pretreatment fecal samples did not differ among the groups. groups i and ii received 0.5% moxidectin pour-on at dosages of 0.25 mg moxidectin per kg body weigh ... | 1996 | 8916402 |
| anthelmintic resistant nematodes in goats in the netherlands. | a suspected case of anthelmintic resistance on a farm with angora and anglo-nubian goats was confirmed in a controlled test. twelve lambs of sheep were infected with larvae cultured from faeces of the goats. the lambs were allocated to four groups: untreated controls and lambs treated 21 days after infection with 5 mg kg-1 oxfendazole, 0.2 mg kg-1 ivermectin or 7.5 mg kg-1 levamisole. the lambs were slaughtered 1 week later and post-mortem worm counts were performed. benzimidazole resistance was ... | 1996 | 8916403 |
| comparison of resistance of four genotypes of rams to experimental infection with haemonchus contortus. | fifty-five rams aged about 18-24 months weighing 30-42 kg were used in this study. ten rams of each of four genotypes, s (sumatra), h1 (50% sumatra-50% virgin island), b1 (50% sumatra-50% barbados blackbelly), e1 (50% sumatra-50% java fat-tail), were infected orally with a newly isolated strain of haemonchus contortus. each animal received 2000 infective larvae 3 times week-1 for 3 weeks, with a total of 18,000 larvae. fifteen rams belonging to sumatra and its crosses with virgin island were use ... | 1996 | 8916407 |
| radiolabelled adult haemonchus contortus obtained from eggs voided in the faeces of a sheep injected with 59fe. | the infective larvae of haemonchus contortus (l3) obtained from an artificially infected sheep injected with 125 microci of 59fe, incorporated the isotope and retained it in sufficient quantities to be detectable by autoradiography in the adult worms which developed. this is apparently the first report of incorporation of 59fe into adult helminths, of which the l3 originated from an animal that was injected with the isotope. | 1996 | 8917865 |
| the immunogenetics of resistance to trichostrongylus colubriformis and haemonchus contortus parasites in sheep. | three possible immunogenetic markers for resistance to intestinal parasites in sheep have been studied. allotypes of the major histocompatibility complex (mhc) of the sheep have been investigated as markers, using serological typing or gene probes, for associations between allotypes and resistance to parasites in selected high responder and low responder lines of sheep. only the serologically-determined class i ovine leucocyte antigen (ola) types sy 1a and sy 1b have been found to be consistentl ... | 1995 | 8920110 |
| management of anthelmintic resistance: inheritance of resistance and selection with persistent drugs. | resistance to the benzimidazole (bz) anthelmintics is inherited as an incomplete dominant/ incomplete recessive trait and is now widespread in populations of gastrointestinal nematode parasites of sheep. unlike benzimidazole resistance, which is common in haemonchus contortus, trichostrongylus colubriformis and ostertagia circumcincta, resistance to levamisole is relatively rare in h. contortus, although common in the other 2 species. one explanation for the slow spread of resistance to levamiso ... | 1996 | 8923146 |
| duration of the persistent activity of moxidectin against haemonchus contortus in sheep. | weaned lambs were infected with haemonchus contortus 35, 28, 21, 14 and 7 days after treatment with moxidectin at 0.2 mg/kg and 35 and 14 days after treatment with ivermectin at the same dose rate. worm counts 14 days after infection showed that moxidectin prevented the establishment of over 99% of infective larvae for 28 days and reduced the establishment rate at 35 days by 96%, relative to ivermectin. there was no difference in the protective efficacy of ivermectin at 14 or 35 days. the persis ... | 1995 | 8929185 |
| response of dorper and red maasai lambs to trickle haemonchus contortus infections. | six-month-old red maasai lambs were more resistant than dorper lambs to repeated infections at one to two week intervals with 1000 haemonchus contortus infective larvae. resistance after infection was assessed by means of faecal egg counts, packed cell volumes, eosinophil counts, total serum protein concentrations and mortality rates. the weight gains of the infected animals were only marginally lower than those of their uninfected controls, most probably because of their significantly higher fe ... | 1996 | 8938850 |
| haemonchus contortus glycoproteins contain n-linked oligosaccharides with novel highly fucosylated core structures. | structural studies on the n-linked oligosaccharides of haemonchus contortus, an economically important nematode that parasitizes domestic ruminants, have revealed core fucosylation of a type not previously observed in any eukaryotic glycoprotein. mass spectrometric analyses were performed on detergent extracts of homogenized adult h. contortus and on purified h11, a glycoprotein isolated from intestinal brush borders which has been previously shown to be an effective vaccine antigen. the major n ... | 1996 | 8940027 |
| prevalence and seasonal changes in the gastro-intestinal helminths of nigerian goats. | a total of 120 gastro-intestinal tracts and 960 faecal samples were examined to assess the prevalence and seasonal changes in the gastro-intestinal helminth parasites of red sokoto (maradi) goats slaughtered at ibadan between may 1991 and april 1992. egg types of strongyles, strongyloides, trichuris, skrjabinema, dicrocoelium and moniezia were encountered in 93%, 83%, 44%, 0.9%, 2.3% and 31% of the faecal samples respectively. however, only strongyle, strongyloides and trichuris eggs occurred in ... | 1996 | 8960229 |
| are the 26-kda somatic and the 24-kda excretory/secretory antigens of haemonchus contortus one and the same? | | 1996 | 8982797 |
| susceptibility of suffolk and gulf coast native suckling lambs to naturally acquired strongylate nematode infection. | three trials compared responses to naturally-acquired strongylate nematode infection between suckling suffolk and gulf coast native (native) lambs which grazed together. in trial 1 (1992), infection in 14 lambs of each breed was monitored from birth to 12 weeks of age using fecal egg count (fec) and blood packed cell volume (pcv). in trial 2 (1993), two age-matched lambs of each breed were sacrificed at seven and ten weeks of age to estimate nematode burdens. in trial 3 (1994), infection in 18 l ... | 1996 | 8983151 |
| cryopreservation of infective larvae of haemonchus contortus. | three freeze protectants were evaluated to preserve h. contortus infective larvae. freezing solutions used: a) saline solution phosphate buffer ph 7.2 (pbs); b) 10% dmso (dimethyl sulphoxide); c) 10% glycerol. fifty thousand infective larvae were put into each of 10 vials per freeze protectant and then stored into liquid nitrogen. results were based on the motility of the larvae under a light microscope at 30, 90, 180, and 360 days of freezing. ten vials of each freeze protectant were removed fr ... | 1996 | 8986110 |
| proteolytic enzymes of infective larvae and adults of trichostrongylus colubriformis and haemonchus contortus. | the aim of this study was to acquire preliminary characterisation of the proteolytic enzymes of trichostrongylus colubriformis and haemonchus contortus so as to obtain a better understanding of the parasites' defence mechanisms against the host immune response. the proteinase band-pattern activity obtained using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (sds-page) showed nine bands in t. colubriformis and h. contortus l3 larvae and four bands in adult t. colubriformis at alkaline ... | 1997 | 9000233 |
| a high efficiency technique for the long-term preservation of infective nematode larvae. | improvements are suggested for the existing long term techniques for the preservation of nematode larvae. haemonchus contortus, teladorsagia circumcincta, trichostrongylus colubriformis and cooperia curticei larvae exsheathed in sodium hypochlorite and then suspended in phosphate buffered saline (pbs ph 7.2) are cooled in the gas over liquid nitrogen at a cooling rate of -1 degree c min-1 down to -50 degrees c. larvae are then stored in liquid nitrogen at -196 degrees c. after warming at 30 degr ... | 1997 | 9008808 |
| efficacy of an albendazole slow-release capsule for the control of susceptible or resistant nematode parasites of dairy goats. | the efficacy of albendazole slow release capsules-asrc- (proftril-captec) on gastro-intestinal nematodes of dairy-goats was assessed both for benzimidazole (bz) susceptible and resistant strains. for bz susceptible strains, the efficacy of asrc, assessed by controlled test, ranged from 92% for trichostrongylus colubriformis to more than 99% for haemonchus contortus on existing worm burdens. the administration of the asrc prevented infection with the same strains for 85 to 91 days post treatment. ... | 1996 | 9017868 |
| fmrfamide-related peptides (farps) in nematodes: occurrence and neuromuscular physiology. | the occurrence of classical neurotransmitter molecules and numerous peptidic messenger molecules in nematode nervous systems indicate that although structurally simple, nematode nervous systems are chemically complex. thus far, studies on one nematode neuropeptide family, namely the fmrfamide-related peptides (farps), have revealed an unexpected variety of neuropeptide structures in both free-living and parasitic species. to date 23 nematode farps have been structurally characterized including 1 ... | 1996 | 9051931 |
| in vitro effects of anthelmintics on the histochemistry of haemonchus contortus and trichuris globulosa. | in vitro incubation of haemonchus contortus (rud., 1803) and trichuris globulosa (v. linstow, 1901) were proformed for 10-12 h in tyrode's solution and 10 and 50 micrograms/ml concentrations each of albendazole (abz), fenbendazole (fbz), thiophenate (tp), dl-tetramisole and oxyclozanide (to), dl-tetramisole hci (tms) and levamisole hci (lms) to study morphological and histochemical alterations. the major structural changes observed after treatment with all the drugs were vacuolation in the intes ... | 1996 | 9060178 |
| genetic resistance of three genotypes of goats to experimental infection with haemonchus contortus. | a total of 46 weaned kids of three genotypes aged about 4-5 months were used to evaluate the effects of trickle infection with a sheep strain of haemonchus contortus. a completely randomized 3 x 2 factorial design was used. factors were genotype (thai native (tn), 75% tn x 25% anglo-nubian (an) and 50% tn x 50% an) and parasite (control and infected). the animals were infected with 750 infective larvae (l3) of h. contortus three times a week for 3 weeks, with a total of 6750 larvae. the experime ... | 1997 | 9066054 |
| peri-parturient rise in faecal strongyle egg counts of different genotypes of sheep in north sumatra, indonesia. | faecal strongyle egg counts were monitored in peri-parturient ewes and dry ewes grazing in a rubber plantation in north sumatra, indonesia. a significant rise in faecal egg counts was observed during the post-parturient period. haemonchus contortus was the dominant species in the faecal cultures of the lactating ewes. the intensity of the peri-parturient rise was affected by the genotype of the sheep, which were the local sumatra and its f1 crosses with st. croix, barbados blackbelly and java fa ... | 1997 | 9066065 |
| protective immunity to the blood-feeding nematode haemonchus contortus induced by vaccination with parasite low molecular weight antigens. | partially purified low molecular weight antigens obtained by gel filtration of whole worm homogenates or total adult excretory-secretory (es) products were tested in a vaccination experiment to determine their ability to induce protective immunity against haemonchus contortus in sheep. sheep were challenged with 20,000 infective 3rd-stage larvae. one animal in the low molecular weight vaccinated group showed no protection against h. contortus, whereas the 4 other sheep in this group showed a mea ... | 1997 | 9075348 |
| cytochrome p450 monooxygenase activity in haemonchus contortus (nematoda). | cytochrome p450 monooxygenase activities towards aldrin and 7-ethoxycoumarin were detected in microsomes prepared from l1 and l3 larvae of haemonchus contortus, and very low levels of activity towards aldrin were detected in adults. larval activities were nadph-dependent, suppressed by carbon monoxide (co) and piperonyl butoxide, and induced (up to 60-fold) by exposure to phenobarbital. different patterns of expression of activities towards the 2 substrates in various life-stages, as well as dif ... | 1997 | 9076527 |
| cortisol as an indicator of severity of parasitic infections of haemonchus contortus in lambs (ovis aries). | two experiments were conducted with lambs to examine the effects of experimental infections of haemonchus contortus on circulating cortisol levels. in both experiments, naive lambs were divided into three groups based on inoculum doses of 0 (control), 2000 (low dose) and 20,000 (high dose) infective larvae. in experiment 1, the lambs were sampled once daily from day 1 post-inoculation (p.i.) until day 39 p.i. lambs from the high-dose group had significantly higher sustained levels of cortisol th ... | 1997 | 9080661 |
| characterization of an acetylcholine receptor gene of haemonchus contortus in relation to levamisole resistance. | the anthelminitic drug levamisole is thought to bind to nicotinic acetylcholine receptors of nematodes. it is possible that resistance to this drug is associated with either a change in binding characteristics or a reduction in the number of nicotinic acetylcholine receptors. therefore, the molecular mechanism of levamisole resistance in the parasitic nematode haemonchus contortus was studied by isolating and characterising cdna clones encoding a putative ligand binding nicotinic acetylcholine r ... | 1997 | 9084038 |
| production of a monoclonal antibody specific for ovine immunoglobulin e and its application to monitor serum ige responses to haemonchus contortus infection. | part of the c epsilon 3-c epsilon 4 region of the ovine immunoglobulin e (ige) gene (nucleotides 1111-1575) was amplified by pcr. the recombinant protein (recige1-2) was expressed in e. coli and both monoclonal and polyclonal antibodies were produced. these antibodies recognized recige1-2 and native ige on western blots and in elisa. the polyclonal serum showed cross-reactivity with other sheep immunoglobulin classes. the monoclonal antibody was specific for ovine ige and goat ige. infection of ... | 1997 | 9107026 |
| molecular cloning and characterisation of a developmentally regulated putative metallopeptidase present in a host protective extract of haemonchus contortus. | antisera from lambs immunised with the haemonchus contortus integral membrane protein complex, haemonchus galactose-containing glycoprotein (h-gal-gp), the lambs being refractory to subsequent challenge, were used to identify several clones from an adult h. contortus lambda gt11 cdna library. using gene-specific oligonucleotide primers in conjunction with primers directed to a conserved nematode spliced leader (sl) sequence and to the polya+ tail of mrna, the remaining 5' and 3' sequences of one ... | 1997 | 9108550 |
| cloning and characterization of a microsomal aminopeptidase from the intestine of the nematode haemonchus contortus. | in order to characterise the integral membrane glycoprotein h11 from the intestinal microvilli of the nematode haemonchus contortus, cdna libraries prepared using mrna from adult worms from the uk and australia were immunoscreened with anti-h11 sera. antibodies affinity purified on the protein expressed by insert dna (295 bp) of a positive clone from a uk library bound specifically to h11. a longer clone (948 bp) was obtained from the australian library by hybridisation. using a primer based on ... | 1997 | 9128148 |
| haemonchus contortus: the uptake and metabolism of closantel. | closantel is an anthelmintic which associates with plasma albumin and is useful for the control of sheep parasites, such as haemonchus contortus, that ingest blood. however, the utility of closantel for parasite control has been threatened by the emergence of resistance. the mechanisms of resistance are unknown. a closantel-resistant and a closantel-susceptible isolate of h. contortus were compared with respect to the distribution and metabolism of closantel. neither strain appeared to metabolis ... | 1997 | 9138034 |
| haemonchus contortus: inter- and intrageographic isolate heterogeneity of proteases in adult worm excretory-secretory products. | | 1997 | 9149245 |
| the in vitro uptake and incorporation of hemoglobin by adult haemonchus-contortus. | the incorporation of radioactivity from [3h]leucine-labeled hemoglobin (hb) into adult haemonchus contortus proteins was investigated. further, the role of previously described cysteine proteases present in intestinal tissue and excretory/secretory products of h. contortus was assessed in the breakdown of hb. a cell lysate preparation (predominantly hb) was obtained from reticulocytes metabolically labeled, in vitro, with [3h]leucine. following 24-h incubation in the presence of [3h]hb, adult h. ... | 1997 | 9187032 |
| how long before resistance makes it impossible to control some field strains of haemonchus contortus in south africa with any of the modern anthelmintics? | this paper describes an exceptional spectrum of multiple anthelmintic resistance in two strains of haemonchus contortus in south africa, one from howick in kwazulu-natal, and the other from badplaas, in mpumalanga. apparently for the first time, a helminth strain is described with resistance to compounds from all five of the modern anthelmintic groups used for nematode control in sheep; also, two strains of h. contortus show resistance to the two substituted phenols, dinitrophenol and nitroxynil ... | 1997 | 9195715 |
| the epidemiology of nematode infections in sheep in a cool tropical environment. | the epidemiology of nematode infections in menz sheep was studied in the highlands of ethiopia at the international livestock research institute (ilri), debre berhan research station, using a series of tracer lambs grazing contaminated pasture for either 4, 16, 32 or 48 weeks from july 1992 to june 1994. the basic nematode seasonal infectivity pattern was expressed in terms of relative numbers of third-stage larvae (l3) available on pasture for different months. data from faecal nematode egg cou ... | 1997 | 9195717 |
| modified plasma and abomasal disposition of albendazole in nematode-infected sheep. | the influence of gastrointestinal nematode infection on the kinetics of albendazole (abz) and its metabolites, albendazole sulphoxide (abzso) and sulphone (abzso2) in plasma and abomasal fluid was investigated in sheep. a micronised suspension of abz was administered intraruminally at 7.5 mg kg-1 to the following groups of sheep: (a) non-parasitised (control); (b) artificially infected with haemonchus contortus; (c) naturally infected with haemonchus contortus and other species of gastrointestin ... | 1997 | 9195734 |
| resistance of four sheep breeds to natural and subsequent artificial haemonchus contortus infection. | the response of red maasai sheep to natural and artificial haemonchus contortus infections was compared with sheep of blackheaded somali, dorper and romney marsh breeds. significant breed differences in egg count, packed cell volume (pcv), and mortality rates showed that the red maasai sheep were more resistant to natural h. contortus infection than sheep from the other three breeds. of the initial groups of 15 wethers of each breed, two animals from each of the dorper and blackheaded somali gro ... | 1997 | 9195736 |
| response to artificial and subsequent natural infection with haemonchus contortus in red maasai and dorper ewes. | maiden red maasai and dorper ewes were kept indoors and artificially infected with a single oral dose of 5000 infective larvae of haemonchus contortus. their faecal egg counts (fec) and packed red cell volumes (pcv) were monitored for 9 weeks. they were then treated with an anthelmintic and turned out to graze together on a pasture contaminated with h. contortus. they grazed this pasture for 14 months and were allowed to mate and lamb. while at pasture the ewes were monitored for fec, pcv and pe ... | 1997 | 9195737 |
| the value of circulating eosinophil count as a selection criteria for resistance of sheep to trichostrongyle parasites. | in merino sheep bred for either increased or decreased resistance to haemonchus contortus, faecal worm egg counts (fec) were lower in the resistant line (6,831 vs 17,645 epg, p < 0.01), and circulating eosinophils (eos) were higher, but not significantly so (3.40 x 10(4) ml(-1) vs 1.40 x 10(4) ml(-1), p = 0.1 1). another flock was artificially infected with trichostrongylus colubriformis and significant genetic variation was found in both fec (heritability 0.40 +/- 0.11) and eos (0.19 +/- 0.08). ... | 1996 | 9198588 |
| influence of organic acid excretion on cuticle ph and drug absorption by haemonchus contortus. | to determine if a cuticle microenvironment ph is maintained by adult haemonchus contortus, organic acid excretion kinetics and absorption kinetics of selected model weak acids and a weak base were measured in incubation media that varied in buffer capacity (0.25-20 mm hepes or 5 mm glycine) and initial ph (7.5 or 3.5). to evaluate the importance of the cuticle as a pathway for organic acid excretion and drug absorption the pharynx was paralyzed with 1 nm ivermectin. h. contortus changed the medi ... | 1996 | 9198593 |
| the effects of closantel treatment on the ultrastructure of haemonchus contortus. | h. contortus were recovered from sheep 0-14 h after intramuscular treatment with closantel. ultrastructural examination revealed that mitochondria were more electron dense and contained swollen cristae compared with untreated controls. following treatment, the basal channels in the intestine became prominent and there was vesicle formation in all organs examined. in contrast, closantel-resistant h. contortus appeared normal after drug treatment. it is likely that closantel affects membrane assoc ... | 1996 | 9198596 |
| beta-tubulin gene polymorphism and benzimidazole resistance in trichostrongylus colubriformis. | the complement of beta-tubulin alleles in trichostrongylus colubriformis populations was examined and found to undergo changes similar to those previously reported for haemonchus contortus following selection for benzimidazole (bz) resistance. genomic dna from bz-resistant and -susceptible strains was probed with a series of overlapping fragments derived from a t. colubriformis beta-tubulin gene. a susceptible population showed a high level of polymorphism (detected as rflps with several enzymes ... | 1996 | 9198600 |
| abomasal nematodes in goats from the subtropical island of grand canary (spain). | the prevalence of gastric nematodes in 151 goats on grand canary island is around 56%, with a mean burden of 691 worms/animal. no significant differences of prevalence and intensity were found between the four isoclimatic areas of the island [dry-desert (dd); dry-steppe (ds); temperate-mild (tm); temperate-cold (tc)]. five nematode species were identified, the most commonly-occurring being teladorsagia circumcincta (observed in 65.8% of parasitized animals) and trichostrongylus axei (51.9%). the ... | 1997 | 9208446 |
| characterization of acetylcholinesterase secreted by the trichostrongyle nematode parasites of ruminants. | acetylcholinesterase (ache) secreted by seven different ruminant trichostrongyles was studied in vitro. ache activity was particularly high (84 and 160 x 10(-3) m.g-1.min-1) in the excretion products of nematodirus spathiger and n battus, moderate (3 and 5 x 10(-3) m.g-1.min-1) for trichostrongylus colubriformis and t vitrinus and low (0.9 x 10(-3) m.g-1.min-1) for teladorsagia circumcincta. no activity was observed with haemonchus contortus and cooperia curticei. at 4 degrees c, 80% of ache act ... | 1997 | 9208448 |
| the repeatability of faecal egg counts in polish wrzosówka sheep. | the number of nematode eggs in the faeces was estimated in polish wrzosówka sheep, in the spring and autumn of 1993 and again in 1994. the sheep had been naturally infected. the dominant species were haemonchus contortus and teladorsagia circumcincta, but trichostrongylus spp., cooperia curticei, nematodirus spp. and chabertia ovina were also present. anthelmintics were not used. egg counts were skewed, with a range of 0-4100 eggs g-1 (epg); most sheep had egg counts below 100 epg. egg counts we ... | 1997 | 9211649 |