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closantel resistance in haemonchus contortus from sheep. 19902334373
cryopreservation of some common nematodes of ruminants for up to 11,3 years.infective larvae of selected batched of the following nematode species from sheep and cattle were examined for survival and infectivity (by injection into either the abomasum, the duodenum, or the jugular vein) after having been stored in liquid nitrogen for 103-136 months: haemonchus contortus, haemonchus placei, ostertagia circumcincta, ostertagia ostertagi, marshallagia marshalli, cooperia spp., trichostrongylus axei, trichostrongylus colubriformis, trichostrongylus falculatus, nematodirus sp ...19902338992
a novel approach to the control of anthelmintic-resistant haemonchus contortus in sheep.this paper reports attempts to control a resistant strain of haemonchus contortus on pasture by replacing it with a susceptible strain. by making use of artificially infected donor sheep, six camps (paddocks) were seeded with a resistant field strain of h. contortus until it was confirmed by means of worm-free tracer lambs that the grazing had become infective. thereafter, using donor sheep infected with a susceptible laboratory strain of h. contortus for seeding the pasture, attempts were made ...19902343532
the establishment and development of haemonchus contortus in goats.twelve goats were inoculated with 40,000 third-stage haemonchus contortus larvae and two were killed on each of days 4, 7, 11, 14, 18 and 21 after inoculation (dai). the number of worms that established, and the site of development were recorded. more worms established in the fundic, than in the middle or pyloric thirds of the abomasum. early development occurred within the mucosa; emergence into the lumen started between 7 and 11 days after infection. by 4 dai, all worms had completed the third ...19902343536
effect of selection pressure for thiabendazole resistance on fitness of haemonchus contortus in sheep.a strain of haemonchus contortus showing moderate levels of resistance to thiabendazole (tbz) (egg hatch assay lc50 2.1 microm) was subjected, in alternating sequence, to 5 in vitro and 4 in vivo selections with tbz. this resulted in a significant increase in resistance (egg hatch assay lc50 2.8 microm). the isolates obtained after each combined in vitro and in vivo selection were compared in terms of egg hatch assay, establishment, net egg output, per capita egg output and degree of pathology c ...19902345665
anthelmintic activity of paraherquamide in sheep.paraherquamide, an oxindole alkaloid metabolite of penicillium paraherquei, was tested against the common gastrointestinal nematode species of sheep at 0.25, 0.5, 1.0, and 2.0 mg/kg, per os. it was highly efficacious (greater than or equal to 98% reduction) as a single oral treatment dosages greater than or equal to 0.5 mg/kg against adult haemonchus contortus, ostertagia circumcincta, trichostrongylus axei, trichostrongylus colubriformis and cooperia curticei, and the l4 stage of cooperia spp. ...19902352063
faecal water content and egg survival of goat gastro-intestinal strongyles under dry tropical conditions in guadeloupe.faeces from naturally infected goats were deposited on a natural grassland during the dry season in guadeloupe (french west indies) at different times throughout the day. the grass was either 7 or 20-30 cm tall. after a period of between several hours and 7 days, the number of viable strongyle eggs and the faecal water content were measured. faecal temperature was recorded continuously. faecal temperature was greater than 40 degrees-45 degrees c at midday and dehydration was rapid between 8 a.m. ...19902352914
effect of environmental stimuli on pre-infective and infective stages of haemonchus contortus in the northern united states for the induction of hypobiosis.the effects of both natural and artificial conditioning of pre-infective and infective stages of haemonchus contortus were examined in two studies with 108 crossbred lambs, using an ohio isolate of h. contortus known to exhibit up to 100% winter hypobiosis. the intensity of hypobiosis varied from 0 to 36% in 17 lamb groups given larvae subjected to various temperature and photoperiod conditions. the results in lambs given larvae conditioned for 4-8 weeks were not significantly different from tho ...19902353422
biochemical characterization of cuticle polypeptides from the infective larvae of haemonchus contortus.1. ecdysis of infective haemonchus contortus larvae is effected by the enzymatic degradation of a specialized region of the second molt cuticle containing a biochemically unique polypeptide (mol. wt = 160,000). 2. the 160,000 mol. wt polypeptide and related polypeptides are synthesized at approximately 6 days of larval development. antigenically similar polypeptides occur in other ruminant trichostrongyles. 3. cuticle polypeptides digested during ecdysis differ from second molt cuticle collagens ...19902361368
immune exclusion of haemonchus contortus larvae in the sheep: effects on gastric mucin of immunization, larval challenge and treatment with dexamethasone.the rapid expulsion of the gastric nematode haemonchus contortus from primed sheep is a complex mechanism which probably involves immediate hypersensitivity reactions and mucus. quantitative techniques were employed to determine the content and distribution of mucin in the gastric mucosae of sheep of varying immune status, following a single large challenge with h. contortus. substantial depletion of both neutral and acidic mucin, following challenge, was noted in the gastric mucosae of naive sh ...19902365855
resistance by haemonchus contortus to ivermectin in angora goats. 19902368307
fenbendazole resistance in haemonchus contortus of sheep. 19902368313
[principal helminths of small ruminants in ituri (upper zaire)].from august 1986 to november 1987, about 180 slaughtered sheep and goats were examined at bunia (haut-zaïre) in order to establish the main helminth parasites. seventeen and fifteen species were identified in sheep and goats respectively. the occurrence of stilesia hepatica, oesophagostomum multifoliatum and muellerius capillaris as well as the absence of echinococcus granulosus constituted the original features of this check-list in the area. parasitism the most frequently encountered both in s ...19902369171
the effect of level of nutrition on the development of resistance to haemonchus contortus in sheep.merino wether weaners, 5-months old at the start of the experiment and fed lucerne-based pellets at 600 g per head per day, developed resistance to haemonchus contortus given as a continuous or "trickle" infection at the rate of 500 larvae 3 times per week over a period of 17 weeks. by contrast, the development of resistance was impaired in weaners fed pellets at 400 g per head per day. low food intake and protein-energy deprivation, therefore, have a major effect in impairing the development an ...19902375712
seasonal changes and hypobiosis in haemonchus contortus infection in the west african dwarf sheep and goats in the nigerian derived savanna.a survey was conducted in the nigerian derived savanna (from august 1987 to july 1988) on the seasonal fluctuations in the composition of haemonchus contortus burden of naturally infected west african dwarf sheep and goats. during this period 117 abomasa collected from locally slaughtered animals were processed. male, female as well as immature worms were enumerated. the incidence of haemonchus infection was high (77.8-100%) with no definite seasonal distinction. there was however, a clear seaso ...19902382380
critical controlled test to evaluate resistance of field strains of haemonchus contortus to thiophanate.following reports of suspected gastrointestinal strongylid nematode resistance to thiophanate in sheep and goats at sokoine university of agriculture (sua), tanzania, field strains of haemonchus contortus, one from sua and another from kimamba, tanzania, were selected for a critical controlled test to evaluate the efficacy of thiophanate. the sua h. contortus strain in goats showed a marked resistance to thiophanate at an oral dose of 50 mg kg-1 liveweight (efficacy = 24.1%), while the kimamba h ...19902382387
development and survival of haemonchus contortus larvae on pasture at vom, plateau state, nigeria.the development and survival of the eggs of haemonchus contortus on pasture at vom were studied by depositing faecal pellets on grass plots over a period of 12 months. development and survival to the infective larvae occurred throughout the study except during the dry season months of december to april. more infective larvae were recovered from the herbage in june, july and august than in other months. the survival time of the infective larvae ranged from 2 weeks in october to 10 weeks in june, ...19902382405
molecular cloning and primary sequence of a cysteine protease expressed by haemonchus contortus adult worms.we have cloned cdnas encoding a 35-kilodalton cysteine protease that is a major component of protective extracts isolated from blood-feeding haemonchus contortus adult worms. near full-length cdnas for the protease were isolated by immunoscreening an adult worm cdna expression library with a rabbit antiserum prepared against the protein eluted from preparative sds gels and by rescreening the library with oligonucleotide probes. the protein predicted from the nucleotide sequence of the cdnas and ...19902385265
experimental haemonchus contortus infection in three breeds of sheep.nine- to 10-month-old florida native, st. croix and dorset/rambouillet sheep were infected with haemonchus contortus. the primary infection was terminated by anthelmintic treatment 9 weeks later and animals were then reinfected with h. contortus. dorset/rambouillet sheep showed higher fecal egg counts and decreased packed cell volumes and plasma protein levels compared with the other two breeds during the primary infection. however, no breed differences were found in total worm burdens in either ...19902399644
haemonchus contortus with low inhibited development in sheep from the highveld of zimbabwe.the abomasa of sheep grazing on natural pastures in the highveld of zimbabwe were examined for haemonchus contortus. of 304 abomasa, 213 (70%) harboured h. contortus. the worm burden increased during the rains to reach the peak in february-march. this was followed by a decline with low worm loads throughout the dry season. the fourth stage larvae (l4) accounted for 1-7% of the total h. contortus population, except during july and august when they comprised 22 and 54% of the worm burden, respecti ...19902399655
haemonchus contortus: evidence that the 3a3 collagen gene is a member of an evolutionarily conserved family of nematode cuticle collagens.rabbit antisera were raised against an 18 amino acid-long peptide that corresponds to the predicted sequence of the carboxy-terminal, nontriple helical region of the haemonchus contortus 3a3 collagen gene. this sequence is highly conserved and diagnostic for members of the col-l collagen family, which includes the 3a3 gene. we find that these antisera react predominantly with multiple, high molecular weight (greater than 68 kda) proteins on western blots of whole worm extracts. the number and mo ...19902404780
haemonchus contortus: a simple procedure for purifying surface proteins from third- and fourth-stage larvae.surface proteins were solubilized from exsheathed third (xl3)- and fourth (l4)-stage larvae of haemonchus contortus by a one-step extraction procedure involving brief heat treatment of the worms in the presence of buffer and 100 mm sodium chloride. surface proteins also could be preferentially extracted from xl3s, but not from l4s, by heating the worms briefly in 1% sodium dodecyl sulfate. the major proteins extracted by these procedures were similar in molecular weight to those detected by surf ...19902404783
the distribution and localization of the stage-specific gp31 antigen from infective ostertagia circumcincta larvae.the 31,000 mol. wt glycoprotein (gp31) antigen of infective third-stage (l3) ostertagia circumcincta larvae was shown, by surface labelling experiments and immunofluorescent antibody staining of whole larvae and larval sections, to be distributed internally. when transverse sections of l3 o. circumcincta, taken from the anterior pharyngeal region, were further examined by electron microscopy, after immunogold staining with rabbit anti-gp31 antiserum, the gp31 antigen was found to be specifically ...19901690183
vital staining of glycoprotein secreted by infective third stage larvae of haemonchus contortus prior to exsheathment.staining of infective third stage larvae of haemonchus contortus prior to exsheathment shows that protein is exuded from the head region and spreads between the cuticles and that a carbohydrate-containing substance is also found between the l2 and l3 cuticles throughout, at exactly the same sites in this nematode. this glycoprotein, which is either secreted from the mouth or the amphids or both is exuded whether or not the larvae have been stimulated to exsheath. slight staining was also sometim ...19901699905
effects of plumbagin on development of the parasitic nematodes haemonchus contortus and ascaris suum.1. plumbagin (5-hydroxy,2-methyl-1,4-napthoquinone) inhibited the motility and survival of haemonchus contortus first-stage larvae (l1) with an ed50 of 1 microgram/ml, but was less effective in preventing the development of h. contortus to infective third-stage larvae in a faecal slurry assay. 2. of the structural analogs tested, plumbagin was the most potent in preventing development of l1 followed in decreasing order of potency by 1,4-naphthoquinone, 5-hydroxy-1,4-napthoquinone (juglone) and 1 ...19911687553
a possible role of caesium radiations in the control of propagation of hookworm.faeces charcoal mixtures containing eggs of sheep hookworm, haemonchus contortus were exposed to caesium radiations (23 r to 1656 r) from 1st to 7th day of incubation. each plate was exposed only once. a dose related inhibition of transformation of eggs to infective larvae was observed. the maximum effect was observed on 2nd day of incubation. the radiation has maximum effect on the 1st stage larvae followed by 2nd stage. the 3rd stage or ineffective larvae are relatively resistant to the effect ...19911743750
local eradication of haemonchus contortus using closantel. 19911755790
immunity to haemonchus contortus and the cellular response to helminth antigens in the mammary gland of non-lactating sheep.cellular exudates induced by infusion with helminth antigens were examined in non-lactating mammary glands of ewes immune to infection with the abomasal nematode, haemonchus contortus. secondary immunological responsiveness was expressed in two ways. firstly, antigens from adult h. contortus elicited larger eosinophil-rich cellular exudates in immune compared to non-immune ewes. in this situation, secondary responsiveness in the mammary gland must have been generated through abomasal infection w ...19911757191
effects of cholinergic drugs on longitudinal contraction in levamisole-susceptible and -resistant haemonchus contortus.a novel force transducer was used to measure the effects of cholinergic agonists on longitudinal contraction in haemonchus contortus. drugs were applied to whole worms or injected via a cannula in the pseudocoelomic cavity. a number of agonists, including nicotine and the anthelmintics m-aminolevamisole, levamisole and morantel, caused contractions in whole worms. four- to 25-fold increases in concentration of the active compounds were required to cause contractions in each of two levamisole-res ...19911757196
effects of time of day, season and stratum on haemonchus contortus and haemonchus placei third-stage larvae on irrigated pasture.the effect of time of day, season and stratum of herbage and soil on the availability of haemonchus contortus and haemonchus placei third-stage larvae (l3) on pasture was assessed. feces from infected calves and lambs were placed on pasture plots and samples of upper herbage, lower herbage, mat and soil were collected at five intervals per day throughout the daylight hours on 18 sample days over 12 months. using recovery rate factors derived from a preliminary investigation on the efficacy of la ...19911763493
interaction of parasitism and nutrition and their effects on production and clinical parameters in goats.weaned wether goats (n = 144) approximately 6 months of age were placed in a 2 x 3 factorial design experiment for 5 months to test the main effects and interaction of two levels of nutrition (growth + maintenance, nut1; twice growth + maintenance, nut2) and three levels of haemonchus contortus burden (0, 500 and 2000 larvae administered every 2 weeks: w0, w500 w2000, respectively) on weight, feed intake, level of infection and packed cell volume (pcv). the rationale for the experimental design ...19911763494
[the threat of wide dissemination of anthelmintic resistance by veld ram performance testing units].a veld ram performance testing unit consists of an association of stud or commercial ram breeders, who compare the performance of selected rams under field conditions on common pastures. the best performers are subsequently auctioned at public sales. to date, at least 10 merino veld ram clubs have been established in various centres in south africa. a strain of haemonchus contortus, which was isolated from the pastures of one of these performance testing units, was found to be resistant to iverm ...19911770493
detection of resistance to ivermectin in haemonchus contortus.infective, third-stage (l3) larvae of haemonchus contortus isolates resistant to ivermectin (ivm) show a decreased sensitivity to ivm-induced paralysis in vitro. the inhibition of larval motility by ivm can be detected in l3 larvae incubated in the dark on an agar matrix containing ivm, by the failure of affected larvae to move when stimulated by exposure to light. optimally, avermectin (avm) potency is quantified after three cycles, each involving storage in the dark for 24 h followed by a brie ...19911774112
purified glutathione s-transferases from parasites as candidate protective antigens.glutathione s-transferase (gst) activity was detected in larvae of the australian sheep blowfly lucilia cuprina, and in the nematode haemonchus contortus. a specific inhibitor of the enzyme was shown to affect survival of both species of parasite in vitro. gst from both parasites has been purified and partially characterized. antisera raised to the purified enzymes were shown to inhibit the enzyme activity in vitro. however, the antisera had no effect on the survival of either parasite.19911774119
a study of the mortality and fecundity of haemonchus contortus in sheep following experimental infections.the regulation of the fecundity and mortality of h. contortus in sheep was examined using a series of mathematical models. six-month-old dorset crossbred lambs were infected once only with various doses of infective h. contortus larvae (500-20,000 larvae). parasite mortality was found to be an increasing linear function of the magnitude of the initial infection over the range of doses examined. parasite fecundity was found to remain constant over the intensity and duration of the infection. the ...19911774120
infection of goats with haemonchus contortus and trichostrongylus colubriformis: histopathology and ph changes.two groups of goats were experimentally infected with haemonchus contortus and trichostrongylus colubriformis, and killed at various days after infection (dai). the percentage of worms that established in the abomasum and the small intestine was low. at necropsy, abomasums from infected goats had thickened walls and oedematous folds. at 7 dai there was an initial infiltration of eosinophils and some neutrophils which tend to increase with age of infection. the mean ph of the abomasum in goats in ...19911777801
ultrastructural changes associated with exsheathment of infective juveniles of haemonchus contortus.ultrastructural changes associated with exsheathment of the infective juveniles of haemonchus contortus are described. hyaline ring formation occurs associated with annulations 10 and 20 and consists of the dissolution of the basal zone and the inner electron-dense layer resulting in the rupture of the sheath. these changes are consistent with the action of a protease-exsheathing enzyme. there is a significant reduction associated with exsheathment in the size of the excretory cells and the numb ...19911780179
disposition of oxfendazole in goats and efficacy compared with sheep.the disposition of intraruminally administered oxfendazole (ofz) in goats was studied at 5, 10 and 20 mg kg-1. the area under the plasma concentration with time curve (auc) increased with increasing dose but at a declining rate. auc was lower after intra-abomasal compared with intraruminal administration. ofz was less effective against drug resistant trichostrongylus colubriformis in goats than in sheep but was of similar efficacy against drug resistant haemonchus contortus in both host species. ...19911780578
effect of weaning on antibody responses and nematode parasitism in merino lambs.lambs weaned at eight weeks old were compared with control lambs which remained with their dams; both groups grazed the same pasture. weaning significantly reduced the growth rate, control lambs being, on average, 6 kg heavier than weaned lambs at 15 weeks old. when contamination of pasture with larval parasites was light, both groups of lambs suffered only modest parasitic infections. when lambs were experimentally infected with 5000 haemonchus contortus and 10,000 trichostrongylus colubriformi ...19911788476
production and characterization of monoclonal antibodies against excretory-secretory products of fasciola hepatica.four monoclonal antibodies (mabs) (9.49, 24.27, 46.71 and 179.57) were produced against fasciola hepatica excretory-secretory products. isotype analysis revealed the antibodies to be igm, igg3, igg1, and igm. in immunoblot assays, the mabs recognized different antigenic polypeptides migrating between 29 and 180 kda. specificity of the mabs was evaluated by elisa against antigens of fascioloides magna, anoplocephala magna, stichorchis subtriquetrus, haemonchus contortus, sheep liver extract (sle) ...19911788930
blood gastrin and pepsinogen responses of native village goats in malaysia to infection with haemonchus contortus.blood gastrin and pepsinogen responses of native village goats in malaysia to a single dose of 10,500 infective haemonchus contortus larvae were investigated. both blood values were significantly elevated within a week of infection and exhibited a highly significant correlation during the study. the magnitude of the blood gastrin response was, however, significantly greater than that of pepsinogen during the period that both blood values were elevated. it is suggested that blood gastrin assay ma ...19911796870
[development and survival of haemonchus contortus isolated from sheep on a pasture at bunia (itiri, zaire)].development and survival of haemonchus contortus larvae were studied from december 1987 to november 1988 during three different periods (dry season, first and second rainy seasons) on an experimentally infected pasture at bunia (ituri, zaïre). whatever the season, eggs developed into infective larvae within six days and the largest number of larvae on the herbage occurred between the 12th and the 18th day post deposition. however, the two rainy seasons were the most favourable for transmission b ...19911818364
cloning of a cdna encoding phosphofructokinase from haemonchus contortus.phosphofructokinase (pfk), the key regulatory enzyme in glycolysis, has been cloned from the pathogenic parasitic nematode haemonchus contortus by functional complementation in escherichia coli. an e. coli strain deleted for both pfk loci (strain df1020) was transformed with plasmid dna from a lambda zap ii h. contortus cdna library. two out of 3 x 10(7) transformants were able to grow on minimal medium with mannitol as the sole carbon source. a plasmid, ppfk, containing a 2.7-kb insert, was iso ...19911838137
protective studies in sheep immunized with cuticular collagen proteins and peptides of haemonchus contortus.twenty-eight nonsibling sheep aged approximately 12 months and raised in a helminth-free environment were used in two protection studies. immunizations were conducted by two intramuscular injections 30 days apart with a synthetic 18aa cuticle collagen peptide and native cuticle collagens derived from the third- and fourth-stage larvae of haemonchus contortus. ten days following the last immunization, the sheep were each given 500 infective h. contortus larvae per day for five consecutive days by ...19911852473
beta-tubulin and benzimidazole resistance in the sheep nematode haemonchus contortus.we have compared benzimidazole (bz) susceptible (s) and resistant (r) strains of haemonchus contortus from sheep by two-dimensional polyacrylamide gel electrophoresis (2-d page), western blotting and elisa techniques. the s strain bound more drug per mg protein than the r strain. bz binding could be resolved into high-affinity and low-affinity binding. low-affinity binding in parasite preparations devoid of tubulin was observed, but high-affinity binding occurred only in preparations containing ...19911857382
serum igg response of manchego lambs to infections with haemonchus contortus and preliminary characterization of adult antigens.manchego lambs (16-18 weeks old) were infected with 2500 infective larvae (l3) of haemonchus contortus and challenged 2 months later with 5000 l3. the serum igg anti-haemonchus response was estimated by enzyme-linked immunosorbent assay (elisa) using soluble proteins from adults and l3. previously infected manchego lambs failed to mount a protective immune response against challenge, at least as assessed by faecal egg counts and pre-patency periods. primary infection did not provoke any rise in ...19911858283
changes in liveweight gain and blood constituents in experimental infection of goats with a goat-derived compared with a sheep-derived strain of haemonchus contortus.two groups of goats were experimentally infected with two different strains of haemonchus contortus and compared with the controls. group a animals were infected with a goat-derived strain (gds) while group b animals were infected with a sheep-derived strain (sds). changes in the liveweights and some blood constitutents between the two infected groups were compared. the pathogenic effects of the gds larvae were generally more serious when compared with those of the sds larvae.19911858284
concurrent infections with the ruminant nematodes haemonchus contortus and trichostrongylus colubriformis in jirds, meriones unguiculatus, and use of this model for anthelmintic studies.haemonchus contortus- and trichostrongylus colubriformis-infected jirds (meriones unguiculatus) are useful for anthelmintic studies. with concurrent infections of these parasites established in the jird, questions of not only anthelmintic activity, but to some extent spectrum, could be assessed in a single model system. this report outlines a model using immunosuppressed (0.02% hydrocortisone in feed) jirds concurrently infected with h. contortus and t. colubriformis. immunosuppressed jirds were ...19911865271
interaction of benzimidazole anthelmintics with haemonchus contortus tubulin: binding affinity and anthelmintic efficacy.the ability of various benzimidazoles (bzs) to bind tubulin under different conditions was assessed by determining their ic50 values (the concentration of unlabeled drug required to inhibit 50% of the labeled drug binding), ka (the apparent equilibrium association constant) and bmax (the maximum binding at infinite [bz] = [drug-receptor]). the ability of unlabeled benzimidazoles--fenbendazole, mebendazole (mbz), oxibendazole (obz), albendazole (abz), rycobendazole (albendazole sulfoxide, abzso), ...19911889474
fecundity of gastrointestinal trichostrongylid nematodes of sheep in the field.twenty-two dorset rambouillet lambs were moved to contaminated pasture on apr 1, 1987. at regular intervals thereafter, pairs of lambs were withdrawn and euthanatized. gastrointestinal parasites in the abomasum, small intestine, cecum, and large intestine were removed and counted. the last pair of lambs was euthanatized 8 months after original placement on the contaminated pasture. fecal samples were taken at 3- to 4-week intervals throughout the grazing season and the fecal egg counts were used ...19911892277
periparturient rise in faecal nematode egg counts in west african dwarf sheep in southern ghana in the absence of arrested strongyle larvae.the nematode egg output of two groups of ewes, a pregnant test group (2-3 years of age) mated between march and april and a non-pregnant control group (5-6 years of age) was followed. the worm burdens acquired by worm-free 'tracer' lambs were also followed on the same pasture from march 1988 to february 1989. there was a significant difference (p less than 0.05) in the magnitude of the egg output in the test group compared with the control group. in the test ewes, an initial rise in egg producti ...19911897121
post natal ontogeny of immunological responsiveness in merino sheep.sheep in five age groups (two weeks, 10 weeks, 18 weeks, six months and four years old) were immunised systemically, twice, with ovalbumin or brucella abortus (live or killed) and antibody responses in blood were measured. the animals were also infected with the nematode parasites trichostrongylus colubriformis and haemonchus contortus and faecal egg counts and serum antibody responses to larval antigens were measured. the experiments were designed so that, as far as possible, the effect of age ...19911910202
protective immunity to a blood-feeding nematode (haemonchus contortus) induced by parasite gut antigens.to determine the ability of gut antigens to induce a protective immune response against blood-feeding nematodes, isolated gut antigens were used to immunize goats against haemonchus contortus. immunization-induced antibody responses recognized parasite gut antigens which were associated predominantly with the microvillous membrane region of the parasite gut. antibody from immune serum also recognized seven predominant gut proteins on a western blot (immunoblot). several of these proteins appeare ...19911937800
effectiveness of clean grazing strategies in controlling haemonchus contortus infections in sheep in the united kingdom.the effectiveness of clean grazing systems for controlling the sheep abomasal parasite haemonchus contortus under experimental conditions was monitored for a grazing season in ewes and lambs carrying either benzimidazole-susceptible or resistant populations of the parasite. both preventive and evasive strategies failed to give effective control of h contortus. lambs grazing with ewes that had received no anthelmintic showed clinical signs of haemonchosis by early july. lambs from ewes dosed with ...19911949535
synthesis and biological activity of a series of diaryl-substituted alpha-cyano-beta-hydroxypropenamides, a new class of anthelmintic agents.a series of alpha-cyano-beta-hydroxypropenamides was prepared and tested for anthelmintic activity. alpha-cyano-beta-hydroxy-n-[4- (trifluoromethyl)phenyl]-3-[4-(trifluoromethyl)phenyl]propenamide (1) showed good activity against the nematode nematospirodes dubius in a mixed parasite infection in mice; several of the analogues were also effective against the cestode hymenolepis nana. in sheep trials, 1 caused 100% reduction of the hematophagous nematode haemonchus contortus after a single dose o ...19911956049
non-specific resistance of sheep against haemonchus contortus with freund's complete adjuvant.six groups of four ovines each were injected intraperitoneally with freund's complete adjuvant (fca), at various times before, during, or after infection with 10 000 larvae (l3) of haemonchus contortus per sheep. animals in groups a and b received fca on days 14 and 7, respectively, before infection. ovines in group c were treated with fca on the same day of infection; while sheep in groups d, e, and f were injected with the adjuvant on days 7, 14, and 21, respectively, after infection. signific ...19911956702
effectiveness of strategic anthelmintic dosing in controlling haemonchus contortus infections in sheep in the united kingdom.the strategic use of anthelmintics in the control of infections of haemonchus contortus in ewes and lambs, was investigated in a series of paddock trials. the levels of infection and clinical signs associated with the presence of either benzimidazole-resistant or benzimidazole-susceptible strains of h contortus in lambs were controlled by regular drenching with levamisole or mebendazole, respectively, or by the strategic use of closantel in combination with mebendazole. in the latter case, contr ...19911957469
efficacy of some anthelmintics on an ivermectin-resistant strain of haemonchus contortus in sheep.following evidence of reduced efficacy of ivermectin in a field population of haemonchus contortus in brazil, this strain of the parasite was submitted to a controlled anthelmintic test. eighty worm-free lambs were randomly split into two groups of 40. each lamb in the first group was infected with 5000 third stage larvae (l3) of the ivermectin-resistant strain; the remaining 40 lambs were each infected with 5000 l3 of a h. contortus strain of known susceptibility to the major groups of anthelmi ...19911957487
specific interaction of benzimidazole anthelmintics with tubulin from developing stages of thiabendazole-susceptible and -resistant haemonchus contortus.the low- and high-affinity binding of tritiated benzimidazole anthelmintics (mebendazole and oxibendazole) to tubulin-containing supernatants derived from unembryonated eggs, third stage larvae or adult worms of thiabendazole-susceptible and -resistant strains of haemonchus contortus were examined and compared. the displacement of these radioligands by unlabelled benzimidazoles (mebendazole, fenbendazole, thiabendazole and oxibendazole) also was examined. the binding affinity, k alpha, and maxim ...19911986746
utility of a haemonchus contortus/jird (meriones unguiculatus) model for studying resistance to levamisole.trichostrongylid nematodes of sheep commonly are identified as exhibiting resistance to levamisole. in vitro assays have been developed to study levamisole resistance for haemonchus contortus, but no in vivo model has been identified for this species. to determine the utility of a h. contortus/jird (meriones unguiculatus) model for examining levamisole resistance, immunosuppressed jirds were inoculated with approximately 1,000 exsheathed infective larvae of h. contortus (resistant or susceptible ...19911992099
fecundity of anthelmintic resistant adult haemonchus contortus after exposure to ivermectin or benzimidazoles in vivo.a strain of haemonchus contortus resistant to the benzimidazoles, ivermectin and salicylanilides was used to study the effect of exposure to ivermectin or oxfendazole on the number of eggs produced by adult female parasites. after anthelmintic administration there was a reduction in the faecal egg count of the infected lambs. ivermectin caused a reduction in the number of eggs within adult parasites for up to 72 hours but this returned to higher than pre-treatment levels at 168 hours after treat ...19912034909
secretion and excretion of endogenously synthesized lipids by adult haemonchus contortus in vitro.results of the incorporation of carbon from 14c-glycerol into total, polar and nonpolar lipids in haemonchus contortus (nematoda: trichostrongylidae) reveal that the radioactivity lost into the medium as lipids decreased during the first 3 h of incubation. this was followed by a drastic increase during the 4th h. again, there was a decline by 75% during the 5th h. however, there was a slight increase in the nonpolar lipids during the 5th h.19912050989
effect of development of resistance to benzimidazoles, salicylanilides and ivermectin on the pathogenicity and survival of haemonchus contortus.two groups of six lambs were infected either with an anthelmintic-susceptible strain of haemonchus contortus or with a strain resistant to benzimidazoles, ivermectin and salicylanilides. the pathogenicity of the two strains of parasite was compared by monitoring the development of anaemia, changes in plasma proteins and abomasal damage in the two groups of lambs. there were no significant differences between the groups, suggesting that the development of resistance to several anthelmintics did n ...19912063534
humoral responses in rabbits immunized with two fractions of haemonchus contortus: the antigen specificity of such antibodies.humoral responses were examined in rabbits immunized with either 28-40 kda (fraction 1) or a 19-24 kda (fraction 2) antigenic fraction from soluble antigens (sol l3 ag) from infective larvae (l3) of haemonchus contortus. these fractions were eluted from electrophoretically separated sol l3 ag. immunoblots revealed antibodies to fraction 1 (fr. 1) or fraction 2 (fr. 2) polypeptides as well as to several other molecular weight polypeptides of the sol l3 ag. the latter antibodies were shown by abso ...19921281589
helminths of sheep and goats in desert areas of south-west mauritania (trarza).faecal samples were obtained from sheep and goats before, during and after the rainy season at three locations in south-west mauritania. several animals were also necropsied at the same time. haemonchus contortus was the most prevalent worm. infection by digestive-tract strongyles and strongyloides papillosus was always very light (prevalence less than 20%). sheep were more heavily infected than goats but animals under 1 year of age were not infected by digestive-tract strongyles. it is likely t ...19921295205
comparative neuromuscular blocking actions of levamisole and pyrantel-type anthelmintics on rat and gastrointestinal nematode somatic muscle.the basis for the comparative toxicity to parasitic nematodes and their mammalian hosts of the anthelmintics levamisole, pyrantel, and several related analogs on somatic nicotinic cholinergic transmission was examined. measurements of muscle contractility and membrane potential were made using the isolated hemidiaphragm preparation of the rat and isolated axial muscle segments from the gastrointestinal nematode haemonchus contortus. pyrantel caused a dose- and time-dependent reduction of nerve-e ...19921310165
histoenzymic effects of thiophenate and fenbendazole on the absorptive surfaces of haemonchus contortus.in vitro alterations induced by a 10 micrograms/ml and 50 micrograms/ml dose each of thiophenate and fenbendazole on the absorptive surfaces of haemonchus contortus (nematoda: trichostrongylidae) were studied. the most significant changes were induced in the gut epithelium. alkaline phosphatase and adenosine triphosphatase activities were decreased, succinic dehydrogenase activity was increased, while acid phosphatase and glucose-6-phosphatase were completely lost from the intestinal epithelium ...19921335682
the development and mortality of the free-living stages of haemonchus contortus in laboratory culture.haemonchus contortus eggs were cultured in intact fecal pellets at various temperatures (5-35 degrees c) for 22 days. temperature and relative humidity were kept constant throughout the incubation period. nl larval development occurred at 5 degrees c; peak third-stage larval recovery occurred at 20 degrees c. egg mortality was an age-dependent phenomenon, whereas larval mortality remained constant irrespective of larval age. development was characterized by a minimum development time followed by ...19921399249
response to ivermectin treatment of parasitic stages of haemonchus contortus resistant or susceptible to ivermectin.two groups of 33 helminth-naive lambs were infected with 5,000 l3 of an ivermectin-resistant or -susceptible strain of haemonchus contortus (groups r and s). on days 6, 10, 16, and 21 postinfection, 5 animals from each group were chosen at random and orally treated with 0.2 mg/kg of ivermectin. on each occasion, 2 randomly selected lambs from each group were also killed to determine the number and stage of development of the worms present at the time of treatment. these necropsies revealed that ...19921403434
the interaction of trypanosoma congolense and haemonchus contortus infections in trypanotolerant n'dama cattle.the interactions between trypanosoma congolense and haemonchus contortus infections were studied in n'dama calves. a total of 38 n'dama bulls was divided into four groups and each group infected either with h. contortus 1 week after infection with t. congolense or with t. congolense 4 weeks after infection with h. contortus, or with either infection singly. parasitological (faecal egg counts, parasitaemia), haematological (packed cell volume, white blood cell counts, albumin) and clinical parame ...19921413448
multiple anthelmintic resistance in a field strain of haemonchus contortus in goats. 19921413479
lymphocyte reactivity to antigens of haemonchus contortus in antigen-inoculated and h contortus-naive lambs.lambs were inoculated during either fetal or early neonatal life with antigens of haemonchus contortus (hcag) third-stage larvae, or ovalbumin (ova), or were left untreated. by the time lambs were 4 weeks old, blood lymphocytes from all of them responded to hcag. this was evident in all lambs, regardless of the previous inoculation regimen, although higher response was seen in hcag-inoculated lambs, compared with naive lambs. only lambs inoculated with ova had ova-specific lymphocyte activity. i ...19921416379
a preliminary study of the effect of microclimate on third-stage larvae of haemonchus contortus and haemonchus placei on irrigated pasture.assessments were made on the influence of several microclimatic variables on the availability of third-stage larvae of haemonchus contortus and haemonchus placei on four strata of irrigated kikuyu pasture. three replicates of these pasture samples were collected on 18 sample days over 12 months and the log10 mean counts of the larvae recovered were analysed by a step-wise regression model. predictors for the log counts of the four strata for the two nematode species included relative humidity, i ...19921428508
the influence of challenge dose, duration of immunity, or steroid treatment on mucosal mast cells and on the distribution of sheep mast cell proteinase in haemonchus-infected sheep.the distribution of granule-specific sheep mast cell proteinase (smcp), was assayed by immunocytochemistry and quantified by immunoassay in sheep immune to haemonchus contortus. repeated infection with haemonchus larvae over 10-12 weeks induced a pronounced mucosal mastocytosis, including intraepithelial globule leukocytes (gl), which, 7 days after ceasing this dosing regime, was associated with the inability of incoming larvae to establish within the abomasal mucosa. loss of this resistance, du ...19921437235
isoenzyme analysis of haemonchus contortus resistant or susceptible to ivermectin.three different strains of haemonchus contortus (susceptible to ivermectin, s-ivm; selected for resistance to ivermectin, r-ivm; a multiple resistant strain, i.e. resistant to benzimidazole and ivermectin, r-ivm/sa) were examined for isoenzyme variation by starch gel electrophoresis. using stains for seven enzymes separated in five different buffer systems, no differences in the electrophoretic mobility could be detected between any of the strains. results demonstrate a low level of enzyme varia ...19921441194
characterization of the eggshell of haemonchus contortus--i. structural components.1. by transmission electron microscopy, the eggshell of haemonchus contortus was seen to be similar to previously studied nematodes, with an outer vitelline layer bounded by a trilaminate membrane, a broad medial region, containing chitin, and an electron dense basal region, containing lipid and protein. 2. exposure of haemonchus contortus eggs to proteases resulted in disruption of the shell with removal of components of the outer, medial and basal regions. exposure to chitinase depleted fibril ...19921458842
the kinetics of mebendazole binding to haemonchus contortus tubulin.the kinetics of the binding of mebendazole (mbz) to tubulin from the third-stage (l3) larvae of the parasitic nematode, haemonchus contortus, have been characterized. in partially purified preparations, the association of [3h]mbz to nematode tubulin was rapid, k1 = (2.6 +/- 0.3) x 10(5) m-1 min-1, but dissociation was slow, k-1 = (1.58 +/- 0.02) x 10(-3) min-1. the affinity constant (k(a)) for the interaction, determined by the ratio k1/k-1, was (1.6 +/- 0.2) x 10(8) m-1. similar results were ob ...19921459788
selection of merino sheep for increased and decreased resistance to haemonchus contortus: peri-parturient effects on faecal egg counts.peri-parturient worm egg counts were compared in 395 merino ewes bred for either increased (irh) or decreased (drh) resistance to haemonchus contortus, or from an unselected control flock (ch). following a 10 month period with no anthelmintic treatment, a rise in egg counts began about 4 weeks before parturition and continued into lactation. at all stages, egg counts were significantly lower in irh ewes, even those failing to conceive. before lambing, irh ewes averaged 263 epg, compared with 111 ...19921459789
interaction of parasitism and nutrition in goats: effects on haematological parameters, correlations, and other statistical associations.weaned wether goats (n = 144) approximately 6 months of age were placed in a 2 x 3 factorial experiment to test the effects and interaction of two levels of nutrition (growth+maintenance, nut1; and twice growth+maintenance, nut2) and three levels of haemonchus contortus burden (0, 500, and 2000 larvae administered every 2 weeks; w0, w500, and w2000, respectively) on packed cell volume, red blood cell count, total serum protein and leukocytes. the statistical analysis revealed clear and proportio ...19921466129
immune response of clun forest sheep to vaccination with membrane glycoproteins from haemonchus contortus.clun forest lambs were injected with a fraction containing integral membrane glycoproteins derived from the intestinal microvilli of haemonchus contortus in two equal doses of 0.5, 5, 50 or 500 micrograms protein and then challenged with 10,000 infective larvae. the time-course of serum specific antibody responses were determined. compared to the adjuvant control group, the animals injected with 1000 micrograms protein were better than 84% protected and those injected with 100 micrograms, better ...19921470484
isolation of putative cysteine protease genes of ostertagia ostertagi.recombinant phage containing putative ostertagia ostertagi cysteine protease genes have been isolated from a lambda embl-3:genomic dna library using a haemonchus contortus cathepsin b-like cysteine protease cdna as hybridization probe. restriction enzyme maps of the phages suggest that they identify at least 3 genes, 2 of which appear to be linked in tandem. the complete nucleotide sequence of one gene, cp-1, was determined. the cp-1 gene appears to be organized into 12 exons than span 4.5 kb of ...19921475000
cloning of a cdna encoding alpha-tubulin from haemonchus contortus. 19921484557
comparison of an indirect haemagglutination assay and an elisa for diagnosing fasciola hepatica in experimentally and naturally infected sheep.an enzyme-linked immunosorbent assay (elisa) with somatic (s) or excretory-secretory antigens (es) was compared with an indirect haemagglutination assay (iha) for ability to detect antibodies against fasciola hepatica in sheep. the specificity of both assays was determined by testing sera collected from sheep experimentally or naturally mono-infected with fasciola hepatica, haemonchus contortus, ostertagia circumcincta, cooperia curticei, taenia ovis, eimeria spp., trichostrongylus vitrinus, tri ...19921485406
haemonchus contortus resistance to ivermectin and netobimin in brazilian sheep.suffolk, texel, hampshire down and ile de france sheep from the municipalities of porto amazonas, piraquara and araucaria in the state of paraná, and bagé in the state of rio grande do sul were brought to sobral, state of ceará, to be used in a cross-breeding project. on arrival they had clinical signs of nematode parasitosis, and one suffolk female died. the animals were treated orally with ivermectin (0.2 mg kg-1) and fifteen days later with netobimin (20.0 mg kg-1). neither drug reduced the e ...19921485411
gastrointestinal helminths and lungworms of french dairy goats: prevalence and geographical distribution in poitou-charentes.a study was conducted on 81 dairy-goat farms in western france. faecal samples were collected once and 31 culled goats were necropsied in order to assess their gastrointestinal and respiratory helminth species, their prevalences and the intensities of infection as well as their geographical distribution in six subregions of the surveyed area. fifteen species of helminth were recovered. the most frequent were muellerius capillaris, trichostrongylus colubriformis and teladorsagia circumcincta with ...19921494857
evaluation of ivermectin against experimental infections of haemonchus contortus and trichostrongylus colubriformis in goats.fourteen nematode parasite-naïve kids were given a mixed larval inoculum (approximately 17,250 infective larvae) via stomach tube. twenty-two days after infection, the kids were randomly assigned to control and treatment groups of seven animals each. mean eggs per gram for control and treatment groups were 4304 and 5315, respectively. kids in the treatment group were given ivermectin (0.2 mg kg-1) administered by subcutaneous injection. at necropsy, the mean numbers of haemonchus contortus and t ...19921496785
fibrinogen-degrading proteins from haemonchus contortus used to vaccinate sheep.sixteen nonsibling sheep, approximately 12 months old, that were raised in a helminth-free environment, were used for 2 protection studies 6 months apart. sheep were vaccinated weekly for 5 weeks by im injection of fibrinogen-degrading proteins derived from the intestinal tract of adult haemonchus contortus. ten days after the last vaccination, sheep were given 2,500 infective h contortus larvae by intraruminal injection. vaccinated sheep produced specific antibodies, and were protected from the ...19921497200
anthelmintic activity of dioxapyrrolomycin.dioxapyrrolomycin, pyrrolomycin c, pyrrolomycin d, and piericidin c2 produced by uc 11065 were evaluated as anthelmintics. assays used to examine these compounds included effects on the free-living nematode caenorhabditis elegans, ability to clear target nematodes (haemonchus contortus and trichostrongylus colubriformis) from jirds, and clearance of haemonchus contortus from lambs. a crude extract of uc 11065 containing dioxapyrrolomycin, pyrrolomycin c, pyrrolomycin d, and piericidin c2 was act ...19921500366
resistance of st. croix lambs to haemonchus contortus in experimentally and naturally acquired infections.parasitological and immunological parameters of experimental or naturally acquired infections with haemonchus contortus were compared in st. croix and dorset lambs. in experimental infections, st. croix lambs developed significantly greater levels of resistance to h. contortus, following primary exposure, as compared with dorset lambs. this resistance was influenced both by age and by prior exposure to parasites. in grazing experiments on h. contortus-infected pasture, st. croix lambs shed signi ...19921502784
efficacy of moxidectin against an ivermectin-resistant strain of haemonchus contortus in sheep.the efficacy of moxidectin was determined against ivermectin-susceptible and resistant strains of haemonchus contortus. at the onset of the trial, 40 lambs were each infected with 5000 third stage larvae of one of two strains of haemonchus contortus. the lambs were randomly sorted into eight treatment groups 28 days post-infection and were treated as follows: group 1, susceptible strain with no treatment; group 2, resistant strain with no treatment; group 3, susceptible strain treated with 0.2 m ...19921502793
comparison of anthelmintic control programs for sheep in virginia.haemonchus contortus is the most serious parasitic problem encountered by sheep producers in southwestern virginia. four anthelmintic control programs for grazing lambs were tested. group tr received monthly sc injections of ivermectin (200 micrograms/kg of body weight). group si received the same dose of ivermectin at 0, 3, 6, 9, and 12 weeks after the start of the grazing season. group sl was given levamisole (8 mg/kg, po) 0, 3, 6, 9, and 12 weeks after the start of the grazing season, and gro ...19921506250
efficacy of moxidectin, nemadectin and ivermectin against an ivermectin-resistant strain of haemonchus contortus in sheep.the efficacies of ivermectin, nemadectin and moxidectin were evaluated when administered orally to lambs infected with either a susceptible laboratory strain of haemonchus contortus or a strain reported to be resistant to ivermectin. groups of 24 dorset cross cheviot cross suffolk lambs were infected with either the susceptible or resistant strain of h contortus and allocated to treatment groups according to their faecal egg counts 27 days after infection. one day later the lambs were dosed oral ...19921514227
controlled tests on activity of contemporary parasiticides on natural infections of helminths in lambs, with emphasis on strains of haemonchus contortus isolated in 1955.ten controlled tests were done between 1972 and 1989, in lambs on pasture, evaluating activity of fenbendazole (fbz; 5 mg/kg of body weight), oxfendazole (ofz; 3.5 and 10 mg/kg), oxibendazole (obz; 10 mg/kg), pyrantel pamoate (prt; 25 mg of base/kg), and thiabendazole (tbz; 44 and 50 mg/kg) against natural infections of helminths, with emphasis on 2 strains (a and b) of haemonchus contortus. strain a was phenothiazine-susceptible and strain b was phenothiazine-resistant when isolated in 1955. fo ...19921539921
interaction between the nematode-destroying fungus arthrobotrys robusta (hyphomycetales) and haemonchus contortus infective larvae in vitro.in an in vitro trial, the effect of the nematode-destroying fungus arthrobotrys robusta on haemonchus contortus infective larvae was evaluated in petri dishes containing corn meal agar. after seven days incubation at 25 degrees c, 92.33% (+/- 4.1) predation was recorded.19921561755
levamisole-resistant haemonchus contortus in goats. 19921566537
localization of immunoglobulin-containing cells in the abomasum of sheep following infection with haemonchus contortus.abomasal cannulation followed by serial collection of biopsies was used to study the kinetics of appearance of iga-, igg1-, igg2- and igm-containing cells in the abomasum of sheep following infection with haemonchus contortus. very few immunoglobulin-containing cells (icc) were found in the abomasum of sheep before infection. following h. contortus infection, there were increased numbers of icc in the submucosa of the abomasum. seven days after infection, the numbers of iga-, igg1- and igm-conta ...19921570678
cloning and sequence comparisons of four distinct cysteine proteases expressed by haemonchus contortus adult worms.three new members of a developmentally regulated cysteine protease gene family of the parasitic nematode haemonchus contortus have been isolated and characterized. one of the new genes, ac-3, was found to be linked in tandem to the previously characterized ac-2 gene. nucleotide sequence analyses revealed that the first 90 amino acids of ac-3 are organized into four exons, similar to the situation in ac-2. a cdna that appears to be a near full-length copy of the ac-3 gene was isolated using the p ...19921574079
gut-specific and developmental expression of a caenorhabditis elegans cysteine protease gene.a caenorhabditis elegans cysteine protease gene fragment, amplified by pcr using conserved eukaryotic protease gene sequences as primers, was used as a probe to isolate cdna and genomic clones. the genomic clone, which had a coding sequence of 987 bp interrupted by 2 small introns, was physically mapped to the middle of linkage group v. the predicted amino acid sequence of the mature c. elegans cysteine protease was homologous to those of other eukaryotic cysteine proteases, particularly to that ...19921574082
effects of dietary molybdenum on nematode and host during haemonchus contortus infection in lambs.the addition of molybdenum (0.05 mmol kg-1 dry-matter) to the diet of lambs given a trickle infection of haemonchus contortus larvae (500 third stage larvae d-1 over six weeks) reduced mean faecal egg counts (epg) from 3952 to 2312 +/- 402 by 32 days (p less than 0.02) and greatly reduced the mean number of worms recovered from the abomasum 14 days after infection ceased (907 compared with 4167: p less than 0.01). infection reduced haemoglobin concentrations less in lambs given molybdenum althou ...19921585080
a comparison of superoxide dismutase (sod, ec:1.15.1.1) distribution in gastro-intestinal nematodes.an examination of the distribution of superoxide dismutase (sod) activities in whole worm homogenates from six gastro-intestinal nematodes, at different life-cycle stages, demonstrated that the third larval stages of each species contained notably more activity than the corresponding adults. significant sod activities were detected in culture fluids following in vitro maintenance of third and fourth larval stage and adult trichostrongylus vitrinus and teladorsagia circumcincta (formerly ostertag ...19921587685
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