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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
effect of nilzan and albendazole on the absorptive surfaces of haemonchus contortus (nematoda)--a histoenzymic study.haemonchus contortus, incubated in 10 micrograms/ml and 50 micrograms/ml concentrations of nilzan and albendazole in tyrode solution were stained for histoenzymatic demonstration of various phosphatases, oxido-reductases and esterases. the intestine showed major alterations after drug treatments. the alkaline phosphatases (akpase), adenosine triphosphatase (atpase), glucose-6-phosphatase, succinic dehydrogenase (sdh), glutamate dehydrogenase (gdh), reduced nicotinamide adenine dinucleotide phosp ...19901963279
a membrane associated glutamate binding protein from caenorhabditis elegans and haemonchus contortus.1. a glutamate binding protein has been identified in membrane preparations from the free living nematode, caenorhabditis elegans, and from the parasitic nematode, haemonchus contortus. 2. this putative glutamate receptor was solubilized with 30 mm octyl-b-glucoside and partially purified by anion exchange and gel filtration chromatography. 3. an 80-fold purification with recovery of 75% of the glutamate binding activity was achieved. 4. the soluble c. elegans binding protein displayed a kd for ...19901977551
molecular biology of the cuticle collagen gene families of caenorhabditis elegans and haemonchus contortus. 19901978527
the localization of somatostatin-like immunoreactivity in the alimentary tract of the sheep with observations on the effect of an infection with the parasite haemonchus contortus.cells containing somatostatin immunoreactivity were localized in the alimentary tract of parasite-free sheep by indirect immunocytochemistry, using an antiserum raised to ovine somatostatin. nerve fibres showing somatostatin-like immunoreactivity were identified in the oesophagus, reticulum wall and groove, rumen pillar and wall, omasum sulcus and abomasum. varicose fibres were found in the myenteric plexuses of the duodenum, jejunum, ileum and colon. the greatest distribution of endocrine cells ...19901980195
resistance to benzimidazoles in haemonchus contortus of sheep in tanzania.this study was undertaken to establish whether resistance to benzimidazole anthelmintics was present in gastrointestinal nematodes of sheep and goats at the university farm of sokoine university of agriculture, morogoro, tanzania. groups of lambs were treated with albendazole at 3.8 mg/kg (recommended dose rate), 5.6 mg/kg and 10.0 mg/kg and a fourth group was untreated. seven days after treatment, faecal egg count reductions (fecr) were found to be 94.3%, 97.6% and 99.3% and 14 days after treat ...19901980804
molecular analysis of selection for benzimidazole resistance in the sheep parasite haemonchus contortus.the molecular basis for the resistance of the sheep parasitic nematode haemonchus contortus to the benzimidazole (bz) group of anthelmintics was investigated. three bz-susceptible and three resistant populations from different geographical locations were characterized with respect to the egg-hatch assay with thiabendazole (tbz), mebendazole (mbz) binding tests and restriction fragment length polymorphism (rflp) after southern blotting. cloned h. contortus alpha- and beta-tubulin genes were used ...19901981249
failure of young goats to acquire resistance to haemonchus contortus.two experiments were carried out to investigate the acquisition by goats of resistance to haemonchus contortus. in experiment 1, five saanen wethers reared worm-free and averaging 5 1/2 months of age at the start of the experiment, were dosed with 200 h. contortus infective larvae three times per week for 10 weeks (approximately 23 infective larvae/kg mean initial liveweight/week) and then given anthelmintic treatment. each goat and an equal number of worm-free controls were then challenged with ...198916031502
multigeneric resistance to benzimidazole anthelmintics in sheep.benzimidazole resistance involving several gastrointestinal nematode genera on a single sheep farm in new zealand is reported for the first time. a controlled slaughter trial showed that at the recommended dose rate of 12.5 mg/kg, mebendazole had efficacies of 0, 60, 66, 90, 54 and 38% against haemonchus contortus, ostertagia spp., nematodirus spp., intestinal trichostrongylus spp., strongyloides spp. and oesophagostomum venulosum, respectively. the relevance of such multigeneric resistance to p ...198916031521
parasite-specific t cell responses of sheep following live infection with the gastric nematode haemonchus contortus.helper t cell lines recognizing antigen in the context of mhc class ii molecules were generated from peripheral blood mononuclear cells (pbmc) of sheep undergoing a primary or secondary infection with the nematode parasite haemonchus contortus. the lines were used to identify 15-18, 25-29, 70-80 and greater than 100 kd immunodominant parasite larval antigens fractionated by sds-page under reducing conditions. non-specific mitogenic activity in the antigen fractions was not detected. during prima ...19892479901
effects of the chitin synthesis inhibitor diflubenzuron on development of ascaris suum and haemonchus contortus.the potential of the chitin synthesis inhibitor diflubenzuron (dfb) to alter the development of the parasitic nematodes (ascaris suum and haemonchus contortus was investigated. dfb given orally (10 mg kg-1 per day for 30 days) to sheep inoculated with h. contortus infective larvae did not prevent the establishment of adults or affect fecal egg output. however, there was a significant (greater than 90%) decrease in the number of infective larvae recovered from fecal cultures derived from lambs ha ...19892505433
gastrointestinal nematode infections of goats in a sub-tropical and humid zone of india.twelve hundred and twenty-eight goats (capra hircus l.) from a sub-tropical and humid zone of india were examined for gastrointestinal nematodes. the species encountered in the region were: haemonchus contortus, bunostomum trigonocephalum, oesophagostomum columbianum, trichuris globulosa, o. aspersum, and t. ovis. the overall infection rate was 86.8%. among various species found, h. contortus emerged as the most prevalent, although b. trigonocephalum and o. columbianum were also significantly in ...19892529697
identification and preliminary characterization of cuticular surface proteins of haemonchus contortus.cuticular surface antigens of the xl3 and l4 stages of haemonchus contortus have been studied by surface labeling and immunological techniques. live worms were labeled with 125i and extracted with sodium dodecyl sulfate (sds) followed by sds + 2-mercaptoethanol. the sds-soluble surface proteins of xl3s and l4s were found to consist of relatively few major species. the pattern of labeled polypeptides was distinctive for each developmental stage. these proteins are refractory to digestion by bacte ...19892552312
restriction fragment length patterns of dna from parasitic nematodes of sheep.high molecular weight dna obtained from sheep parasitic nematodes haemonchus contortus, ostertagia circumcincta and trichostrongylus colubriformis, was digested with various restriction endonucleases. digestion with eco r1 produced the most informative pattern of repeat sequence bands. h contortus adult or larval dna produced bands of 2.7, 3.0 and 1.4 kb. o circumcincta adult or larval dna had common 2.7 and 1.4 kb bands with adult specific bands of 2.2 and 0.9 kb and a larval specific 2.08 kb b ...19892564211
effects of exogenous progesterone and/or prolactin on haemonchus contortus infections in ovariectomized ewes.reproduction can alter the course of ovine nematodiasis; fecal nematode egg concentrations often increase near lambing and throughout lactation, a phenomenon referred to as the periparturient rise. to identify the host mechanisms that might link these disparate events, i.e. lactation and the fecundity of gastrointestinal trichostrongyles, ovariectomized ewes were injected daily with progesterone and/or prolactin, or saline. progesterone treatment commenced 20 days before inoculation with haemonc ...19892588470
efficacy of three broad-spectrum anthelmintics against gastrointestinal nematode infections of goats.groups of 10 goats, harbouring both naturally acquired and experimental infections of gastrointestinal nematodes, were drenched with either levamisole (5 mg kg-1), albendazole (3.8 mg kg-1) or parbendazole (15 mg kg-1), or remained untreated. haemonchus contortus was the numerically dominant infection, with strongyloides papillosus, trichostrongylus colubriformis and oesophagostomum columbianum also present. at 5-6 days post-treatment, goats were killed and necropsied. post-mortem worm counts sh ...19892588471
the cuticular proteins from free-living and parasitic stages of haemonchus contortus--i. isolation and partial characterization.1. cuticles were isolated from the adult males, adult females, the second molt (2m) sheath from the infective larvae (l3(2m)), and the parasitic third stage (l3) of the sheep parasite haemonchus contortus by a combination of mechanical disruption and detergent treatment. 2. the 2me soluble cuticular proteins from adult males contained 4 or 5 major protein bands with molecular weights ranging from 100 to 56 kd with the most prominent band at 56 kd. the cuticular proteins from adult females were s ...19892591199
cross-immunity between haemonchus contortus and trichostrongylus colubriformis in sheep.cross-protective immunity between the nematode parasites, haemonchus contortus and trichostrongylus colubriformis, was examined in sheep vaccinated with irradiated larvae of either species. secondary immunological responsiveness stimulated in this manner protected only against challenge infection with the species used for vaccination. significant cross-protective immunity was not observed. titres of serum antibody to an extract of adult but not infective larval t. colubriformis reflected the spe ...19892592138
[the helminth fauna of the gastrointestinal tract of young cattle in northwest germany].ten unmedicated animals of a controlled anthelmintic trial were used to analyse the present gastrointestinal helminth fauna of young cattle from the northwest of germany. this survey done in august revealed ostertagia ostertagi to represent the most prevalent and abundant species followed by cooperia oncophora and nematodirus helvetianus. o. lyrata, o. leptospicularis, c. zurnabada, c. punctata, trichostrongylus axei, haemonchus contortus, bunostomum phlebotomum, capillaria bovis and trichuris d ...19892598802
cuticle collagen genes of haemonchus contortus and caenorhabditis elegans are highly conserved.several genes and partial cdnas encoding cuticle collagens have been isolated from the sheep parasitic nematode haemonchus contortus. dna sequencing and southern blot hybridization studies reveal that h. contortus collagens comprise a large family of related, but non-identical genes. the genes appear to be dispersed throughout the genome. the predominant size of collagen mrna in molting worms was found to be between 1.0 and 1.2 kb. the one complete gene that was sequenced contains two short intr ...19892615789
comparison of three in vitro techniques to estimate benzimidazole resistance in haemonchus contortus of sheep.three in vitro assays to detect benzimidazole resistance, namely, the egg-hatch assay, tubulin-binding assay, and a larval-development assay, were evaluated by estimating the level of benzimidazole resistance in three field isolates of haemonchus contortus compared with a susceptible reference strain. comparisons were also made with estimates of benzimidazole resistance of the three field strains obtained from an in vivo controlled anthelmintic efficacy test. all three in vitro tests showed simi ...19892617826
availability of infective larvae of parasitic nematodes of sheep grazing on kikuyu (pennisetum clandestinum) pastures in the winter rainfall area.thirteen groups of 4 south african mutton merinos grazed for 4 weeks with the flock on kikuyu pastures and were slaughtered for total and differential worm counts at necropsy. subsequently 12 groups of 8 week tracers grazed on the pastures and were killed for worm counts post mortem. the following were present in most sheep: teladorsagia (syn. ostertagia) circumcincta, trichostrongylus axei, trichostrongylus colubriformis, dictyocaulus filaria and oesophagostomum venulosum. haemonchus contortus, ...19892626260
light and scanning electron microscopy of the ecdysis of haemonchus contortus infective larvae.during the second ecdysis of ruminant trichostrongyles, a region of the second molt cuticle is digested by a 44-kda zn-metalloprotease. we have examined this digestion process by light and scanning electron microscopy (sem). the substrate region of the cuticle appeared, during the ecdysis process, as an indented ring at the 20th cuticular annulus coincident with the anterior terminus of the lateral alae. continued digestion of the cuticle resulted in holes in the ring region that expanded until ...19892647956
purification of a 44 kilodalton protease which mediates the ecdysis of infective haemonchus contortus larvae.we have characterized and purified a parasite protease which mediates the ecdysis of haemonchus contortus, and at least several other ruminant trichostrongyles. the protease, with an apparent approximate molecular weight of 44,000, is a zinc metalloprotein which hydrolyzes several large protein substrates in in vitro assays. in vivo and in biological assays on isolated second molt cuticles this protease hydrolyzes a specific circular region of the second stage cuticle which results in removal of ...19892651914
south african field strains of haemonchus contortus resistant to the levamisole/morantel group of anthelmintics.a strain of haemonchus contortus from the pietermaritzburg district of natal was found to be resistant to levamisole (geometric mean efficacy 76.5%), morantel (41.9%), the benzimidazoles (oxfendazole: 33.7%) and rafoxanide (82.0%), but apparently fully susceptible to closantel and disophenol. in the case of ivermectin, a mean of 5.2% of the h. contortus was not removed at a dosage of 200 micrograms kg-1 live mass. a second strain of h. contortus, from amsterdam in the south-eastern transvaal, sh ...19892696916
changes in anthelmintic resistance status of haemonchus contortus and trichostrongylus colubriformis exposed to different anthelmintic selection pressures in grazing sheep.this experiment was designed to study, over a 5-year-period, the effect of different frequencies of treatment with three different anthelmintic groups, namely, benzimidazoles, levamisole and ivermectin, and different frequencies of alternation between them, on existing levels of anthelmintic resistance in the nematode parasites haemonchus contortus and trichostrongylus colubriformis of grazing sheep. no evidence of ivermectin resistance emerged, even in suppressively treated groups. likewise, h. ...19892707967
helminth parasites of intermingling axis deer, wild swine and domestic cattle from the island of molokai, hawaii.helminth infections of axis deer (cervus axis), wild swine (sus scrofa) and domestic cattle (bos taurus) were studied among intermingling herds on the puu-o-hoku ranch, molokai, hawaii. twenty-four species of helminths were collected from the 10 deer, 10 swine and 10 cattle. capillaria bovis, cooperia punctata, haemonchus contortus and trichostrongylus axei infected both axis deer and cattle, whereas gongylonema pulchrum infected both axis deer and wild swine. none of the species of helminths oc ...19892716106
a preliminary evaluation of factors affecting an experimental system for vaccination-and-challenge with haemonchus contortus in sheep.a preliminary evaluation of factors affecting an experimental system for vaccination-and-challenge with haemonchus contortus in sheep. international journal for parasitology 19: 169-175. studies were made with haemonchus contortus in sheep to ascertain the influence of a range of factors in the domain of the host, the parasite or the vaccine on the formulation of protocols for vaccination-and-challenge to be used in identifying protective immunogens. the results corroborate earlier findings that ...19892722389
the problem of escalating resistance of haemonchus contortus to the modern anthelmintics in south africa.during the past decade in south africa there has been a continual increase in sheep of strains of gastrointestinal helminths resistant to the modern anthelmintics. five strains of haemonchus contortus are described in this paper. despite the fact that 2 of the 5 strains were tested for susceptibility only to ivermectin, a total of 10 instances of resistance were found. four of the 5 strains were resistant to ivermectin, 2 to closantel, 2 to rafoxanide and 2 to the benzimidazoles. one of these st ...19892726192
parasites of south african wildlife. iii. helminths of common reedbuck, redunca arundinum, in natal.twenty-six common reedbuck, redunca arundinum, were shot in pairs at monthly intervals for 13 consecutive months in the himeville region of natal. ten nematode species, 2 cestodes and 1 trematode were recovered from these animals. cooperia yoshidai was both the most numerous and most prevalent worm and peak burdens occurred during summer. thirty-one reedbuck, killed at different intervals in various localities within the st. lucia reserve, harboured between 4 and 11 nematode species, 1 cestode a ...19892726193
haemonchus contortus: infectivity and resistance to benzimidazoles. 19892728285
seasonal prevalence of gastrointestinal nematodes of goats in pernambuco state, brazil.during each of 36 1-month periods from april 1979 to march 1982, 3-4 goats selected from typical farms were necropsied and examined for gastrointestinal nematodes. the goats were male, 12 months old, born on the farm and raised without any anthelmintic application. at the beginning of each month, from april 1981 to march 1982, three 12-month-old male goats shown to be free of gastrointestinal nematodes after anthelmintic treatment were grazed with a flock of naturally infected goats (tracer goat ...19892728324
colorimetric assay for the detection of benzimidazole resistance in trichostrongyles.a modified version of the aphid tile-test, which is used to detect insecticide resistance in single adult aphids that are resistant or susceptible to organophosphate or carbamate insecticides, was used to compare the levels of non-specific esterases in strains of the trichostrongyle nematodes haemonchus contortus, ostertagia circumcincta and trichostrongylus colubriformis which were known to be resistant or susceptible to benzimidazole (bz) anthelmintics. this colorimetric assay has shown that t ...19892740631
experimental haemonchus contortus infections in guinea pigs.approximately 40% of exsheathed haemonchus contortus larvae administered to guinea pigs established in the stomach and developed into fourth stage larvae. most worms were then lost between 5 and 7 days after infection and the guinea pigs were resistant to a second infection. haemorrhage, oedema and infiltration with inflammatory cells, especially eosinophils, developed in the stomach wall of infected guinea pigs and reactive hyperplastic changes occurred in the gastric lymph node. h. contortus i ...19892759770
efficacy of nitroxynil against a benzimidazole-resistant strain of haemonchus contortus in sheep. 19892763432
motility response of levamisole/benzimidazole-resistant haemonchus contortus larvae.electronic measurements of the motility of third stage larvae of a susceptible and a levamisole/benzimidazole-resistant strain of haemonchus contortus were made after incubation in solutions of anthelmintics for 24 h. results confirmed the resistance to benzimidazoles, but failed to show differences in response to levamisole. visual observations of paralysis of first and third stage larvae in solutions of levamisole also failed to show significant differences between the two strains. the tests a ...19892763445
the epidemiological control of nematodes in new england lambs.epidemiological control of nematodes in weaned lambs in new england was investigated over three grazing seasons (n = 58, n = 52 and n = 62 lambs, respectively). spring prophylactic treatment, clean pasture and mid-summer treat-and-move to hayfield strategies were compared to traditional fall treatments (control). in these studies when lambs were weaned prior to grazing, the most abundant nematodes were nematodirus sp. under these conditions, where only low levels of haemonchus contortus were pre ...19892766746
development and survival of free-living stages of gastrointestinal nematodes of sheep and goats on pasture in the nigerian derived savanna.four grass plots were sequentially contaminated with goat faeces containing known numbers of unembryonated eggs of predominantly haemonchus contortus and trichostrongylus spp. between october 1982 and april 1983. four other plots were similarly contaminated with sheep faeces between february and may 1987. an additional plot was repeatedly contaminated with sheep faeces from february to april 1987. populations of free-living stages in faeces and of infective larvae (l3) in the herbage were subseq ...19892773307
efficacy of levamisole against immature and mature nematodes in goats with induced infections.anthelmintic efficacy of levamisole against induced infections with 7- and 21-day-old haemonchus contortus, ostertagia circumcincta, trichostrongylus axei, and t colubriformis was evaluated as an oral drench in goats. group 1 (n = 8) was not treated, group 2 (n = 8) was given 3.96 mg of levamisole/kg of body weight, group 3 (n = 8) was given 7.92 mg of levamisole/kg, and group 3 (n = 7) was given 11.88 mg of levamisole/kg. efficacy against all worms was low in goats given 3.96 mg of levamisole/k ...19892774328
effects of irrigation on appearance and survival of infective larvae of goat gastro-intestinal nematodes in guadeloupe (french west indies).in guadeloupe (french west indies), faeces from naturally infected goats were deposited during the dry season on three plots, irrigated with long (plot a) or short herbage (b) and non-irrigated with long herbage (c). microclimatic data and the evolution of l3 population size in faeces, on soil surface and on herbage were followed over a period of 26 days. the initial nematode egg population was comprised of 58% haemonchus contortus (hc), 25% trichostrongylus colubriformis (tc) and 17% oesophagos ...19892777463
lack of reversion of a benzimidazole resistant strain of haemonchus contortus after six years of levamisole usage.the resistance level of haemonchus contortus was studied on a farm where benzimidazole resistance had been detected in 1980 and where, since 1982, only levamisole had been used for worm control. egg development tests gave ld50 values of 0.18, 0.19 and 0.21 microgram ml-1 thiabendazole for samples taken from ewes in 1988 compared with 0.21 microgram ml-1 in 1981. studies on sheep experimentally infected with larvae cultured from the faeces of these ewes confirmed the continued resistance of h con ...19892799086
controlled dosage titration of febantel paste in naturally parasitized cattle.a controlled anthelmintic trial was conducted to determine the efficacy of febantel paste (45.5%) at dosages of 2.5, 5.0, 7.5, and 10.0 mg/kg in calves harboring natural gastrointestinal nematode infections. dosages of 5.0, 7.5 and 10.0 mg of febantel/kg of body weight were greater than 96% effective in removing adults of haemonchus contortus, ostertagia spp, cooperia spp, and oesophagostomum radiatum. the 2.5 mg/kg dosage was considered suboptimal because of low efficacy against ostertagia and ...19892802334
no association between the ovine leucocyte antigen (ola) system in the australian merino and susceptibility to haemonchus contortus infection.a genetic analysis has been made of the ovine leucocyte antigenic (ola) system in australian merinos. the animals consisted of sires, dams and their progeny. the typing data were consistent with previous findings of a high degree of polymorphism. at least two closely linked loci with several alleles at each are necessary to explain the data. no evidence was found for an association between ola types and three measures of susceptibility to infection by the blood-sucking parasite haemonchus contor ...19892807725
post-mortem changes in the abomasal mucosae of sheep infected with haemonchus contortus compared with those in uninfected sheep.progressive post-mortem changes were observed, with fibre optic endoscopy, in the abomasum of uninfected sheep and sheep infected with h. contortus. loss of epithelial cells was observed 14 to 16 min after death in the uninfected sheep. the loss exposed the underlying lamina propria. this loss became more widespread as the time after death increased. epithelial cell loss was observed earlier (as early as 6 min after death) in the infected sheep. three of the infected sheep also displayed dispers ...19892918107
anthelmintic resistance by haemonchus contortus to ivermectin in brazil: a preliminary report. 19892929090
the efficacy of albendazole against some gastrointestinal nematodes in goats.on the basis of worm counts in naturally infected angora-x goats, albendazole at either 3.8 mg/kg repeated after 24 hours or as a single dose at 7.6 mg/kg, was >99% effective in removing adult ostertagia and trichostrongylus spp. small numbers of adult haemonchus contortus, cooperia sp. and chabertia ovina were present in control but not treated animals. the single dose of 7.6 mg/kg removed >99% of adult oesophagostomum venulosum whereas the repeated dose of 3.8 mg/kg removed only 96%.198816031461
field trials with closantel and haemonchus contortus in sheep in papua new guinea.sheep treated once with closantel at 7.5 or 15.0 mg/kg and grazing with untreated sheep remained free of haemonchus contortus for at least 4 to 5 weeks and 6 to 7 weeks respectively after treatment. when the whole flock was treated with 15.0 mg/kg, h. contortus began to become re-established 7 to 8 weeks later. maximum benefit of the residual anthelmintic effect of closantel against h.contortus was obtained only when all sheep in the flock were treated; it took 10 weeks longer for h.contortus to ...19883056375
the effect of selenium supplementation on immunity, and the establishment of an experimental haemonchus contortus infection, in weaner merino sheep fed a low selenium diet.immunity in 12 weaner merino sheep fed a low selenium (se) diet (low se sheep) was compared with that in 10 matching sheep fed the same diet but each given an intraruminal se pellet (high se sheep), while the sheep were housed in individual, sheltered pens. all sheep were challenged with killed brucella abortus cells (days 0 and 28), rabbit red blood cells (days 0, 7 and 28) and corynebacterium pseudotuberculosis toxoid (days 0 and 28), and serum antibody titres were measured weekly for 8 weeks ...19883138968
the effect of dexamethasone on a single and a superimposed infection with haemonchus contortus in sheep. 19883170067
resistance of field strains of haemonchus contortus to ivermectin, closantel, rafoxanide and the benzimidazoles in south africa.after a first description in 1975 of a strain of haemonchus contortus resistant to the benzimidazole anthelmintics in south africa, further strains of the same species developed resistance to rafoxanide and closantel, and a strain of ostertagia species became resistant to the benzimidazoles. recently five further strains of h contortus have been found which show resistance to these anthelmintics. of these, four showed varying degrees of resistance to ivermectin and one was resistant to three ant ...19883176284
field observations on the control of ovine parasitic gastroenteritis in south-east england.three worm control strategies, on a commercial farm in south east england, were monitored parasitologically for a grazing season. three peaks of larval infection in june, late august and late october/early november occurred on paddocks grazed by dosed ewes and lambs on a new ley (preventive strategy). lambs dosed and moved on to a hay aftermath in july (evasive strategy), had a mean egg count of 2090 by late august, attributable to infection with haemonchus contortus. three weekly drenching of l ...19883188346
evaluation of haemonchus contortus infections in sexually intact and ovariectomized ewes.three experiments were conducted to investigate experimentally the occurrence of periparturient nematode egg rise in ewes and the hormonal modulation of haemonchus contortus infections. in the first experiment, fall-bred and winter-bred pregnant (n = 4 and 14, respectively) and nonpregnant (n = 5 and 29, respectively) ewes were treated with anthelmintic and were pastured together on fields that were contaminated with h contortus. three weeks before lambing, all ewes were placed in concrete pens; ...19883189989
haemonchosis in sheep and goats in sierra leone.the incidence of haemonchosis in sheep and goats in sierra leone showed a seasonal variation with a high peak in the dry season (october to january) and a low one from march to may. mean relative densities were significantly higher in young hosts and showed two peaks, a high one from august to december and a low one from april to june while the mean relative densities of old hosts were low and exhibited an irregular seasonal pattern with no defined peaks. the peak seasons in young hosts coincide ...19883192917
size of inoculum dose regulates in part worm burdens, fecundity, and lengths in ovine haemonchus contortus infections.density-dependent factors frequently have been shown to regulate population parameters of free-living and parasitic helminths. to test the effects of various infection levels of haemonchus contortus on fecundity and worm size, lambs were inoculated with 3,000, 10,000, and 30,000 infective larvae. daily eggs per gram (epg) and daily total fecal production per lamb were monitored continuously. worms were collected from abomasa on 6, 15, 22, and 30 days postinfection (pi). female worms were smaller ...19883193336
the influence of cryopreservation on a benzimidazole-resistant isolate of haemonchus contortus conditioned for inhibited development.larvae of a fenbendazole (fbz)-selected, benzimidazole-resistant strain of haemonchus contortus were conditioned for inhibited development during 7 weeks at 15 degrees c. sheep raised nearly worm-free were infected with nonfrozen larvae (l3). larvae from the same batch were exsheathed and cryopreserved over liquid nitrogen for 1 year, and another group of sheep was infected with the same dose of these l3 larvae after thawing. egg hatch assays for all sheep were done between 21 and 30 days post i ...19883194369
in vitro response of haemonchus contortus larvae harvested during different times of the patent period to anthelmintics.three commercially available ruminant anthelmintics and an investigational drug were evaluated for effects on the motor function/motility of third stage (ensheathed) haemonchus contortus. helminth ova were collected at one, five, nine and 13 weeks during the patent period, cultured to the third larval stage and assayed for sensitivity to four different drugs. all four drugs (100 and 10 micrograms ml-1) significantly affected the motility of third stage h contortus larvae cultured from eggs passe ...19883194601
lymphocyte phenotypes in the abomasal mucosa of sheep infected with haemonchus contortus.lymphocyte subpopulations in the abomasal mucosa of worm-free and parasitized sheep were assessed in situ. a preponderance of t-lymphocytes, with approximately equal numbers of cells expressing cd5, cd4 and cd8 antigens, was found. most of the lymphocytes expressing cd8 lacked cd5. using a panel of 15 monoclonal antibodies to ovine leucocyte antigens, abomasal lymphoid follicles in the mucosa were shown to resemble lymph node follicles phenotypically. abomasal epithelial cells contained major hi ...19883217127
the effect of immunosuppression with dexamethasone on haemonchus contortus infections in genetically resistant merino sheep.the effect of immunosuppression with the glucocorticosteroid, dexamethasone, on the susceptibility to haemonchus contortus infection of a highly resistant merino genotype was investigated. higher faecal egg counts, larger worm burdens and heavier worms were recorded in immunosuppressed wethers. the characteristic globule leucocyte infiltrate in the abomasum of resistant wethers (12-month-old castrated males) was absent in immunosuppressed animals. treatment with dexamethasone abolished differenc ...19883217128
infection with haemonchus contortus in sheep and the role of adaptive immunity in selection of the parasite. 19883220647
resistance of young lambs to haemonchus contortus infection, and its loss following anthelmintic treatment. 19883220652
hypergastrinaemia of sheep infected with haemonchus contortus.radioimmunoassay of plasma gastrin has shown that a hypergastrinaemia occurs in yearling sheep, after infection with 10(6) infective third stage larvae of haemonchus contortus. plasma gastrin concentrations began to rise two to four days after infection, that is, at about the same time as, or slightly before, the abomasal ph was observed to increase.19883222544
influence of dietary protein on the pathophysiology of haemonchosis in lambs given continuous infections.mixed-sex groups of three-month-old finn dorset and dorset horn lambs were given complete diets containing either high or low protein. a trickle infection with haemonchus contortus of 200 larvae, given three times a week, began one month later for a 17 week period. erythrokinetic, metabolic, digestibility and balance studies were conducted with the male lambs during weeks 12 to 14 of the infection. clinical signs of haemonchosis became evident only in the low protein diet group. the infection wa ...19883222552
larval development test for detection of anthelmintic resistant nematodes.the growth, using freshly cultured escherichia coli with ampicillin or heat-treated lyophilised e coli as a food source, of the larvae of the mouse nematode nematospiroides dubius and the infectivity of resulting third stage larvae were determined. concentrations of e coli between 0.5 and 1 mg dry weight ml-1 permitted optimal larval development for both n dubius and trichostrongylus colubriformis. development of larvae of susceptible and cambendazole-resistant strains of haemonchus contortus in ...19883222553
a field evaluation of benzimidazole and nonbenzimidazole drugs in a herd of dairy goats.a study was conducted to investigate the efficacy of six anthelmintics in a herd of dairy goats. pretreatment larval cultures indicated that the goats were infected with haemonchus contortus and trichostrongylus colubriformis. three separate treatment regimens were administered. in each trial, mature nonlactating goats were allocated into two treatment groups and a control group. treatment groups received thiabendazole (tbz) or levamisole (lev), mebendazole (mbz) or fenbendazole (fbz), and moran ...19883225804
selection of ivermectin-resistant trichostrongylus colubriformis in lambs.a mixed population of haemonchus contortus, teladorsagia circumcincta and trichostrongylus colubriformis was passed for four generations through lambs. in successive passages and on day 6 (d6), lambs were dosed subcutaneously with ivermectin at 100, 200, 250 and 225 micrograms kg-1 body weight, respectively. no larvae of h. contortus were recovered after the first passage and following the third drug exposure only t. colubriformis was present. larvae of the selected strain of t. colubriformis de ...19883245107
the effect of haemonchosis and blood loss into the abomasum on digestion in sheep.1. an experiment was conducted to determine the effect of the abomasal parasite, haemonchus contortus, on the pattern of digestion and nutrient utilization in merino sheep. there were three groups of sheep: infected with h. contortus (300 larvae/kg live weight) (n 5), sham-infected by transferring blood from the jugular vein to the abomasum, and uninfected (control) sheep (n 9) which were fed daily rations equal to amounts consumed by 'paired' animals in the two other treatment groups. a diet co ...19883257884
anthelmintic activity of continuous low doses of fenbendazole into the rumen of sheep.fenbendazole (fbz) was continuously infused for 30 days into the rumen of 103 lambs which had mature or developing benzimidazole-susceptible or thiabendazole-resistant haemonchus contortus and susceptible trichostrongylus colubriformis infections. ovicidal, larvicidal and adulticidal activities were exhibited against benzimidazole-susceptible and benzimidazole-resistant h. contortus worms by fbz at a dose level of greater than or equal to 0.2 mg kg-1 body weight day-1. reasonably consistent high ...19883347991
interactions between the predacious fungus arthrobotrys oligospora and third-stage larvae of a series of animal-parasitic nematodes.interactions between the predacious hyphomycete arthrobotrys oligospora and third-stage larvae of nine animal-parasitic nematodes were tested in vitro. the trap-inducing capabilities of the ruminant trichostrongylus cooperia oncophora, c. curticei, haemonchus contortus and ostertagia ostertagi and of equine cyathostomes were almost comparable to those of free-living soil nematodes, and significantly higher than those of the porcine oesophagostomum dentatum and oe. quadrispinulatum and of the mur ...19883347992
epidemiology of ovine helminthiasis in haryana, india.tracer lambs were used to study the pasture contamination with infective stages of helminth parasites during one annual cycle in a subtropical climate. post-mortem worm counts indicated that low infections with haemonchus contortus occurred throughout the year except in june. however, twenty five or more h. contortus per lamb were recorded in january, april, may and august. trichostrongylus colubriformis infection was detected throughout the year and 150 or more worms per lamb were recorded duri ...19883354055
the population biology of the parasitic stages of haemonchus contortus.the population biology of the parasitic phase of the haemonchus contortus life-cycle is discussed within the context of a mathematical model of those processes which regulate population density. parasite death is assumed to be attributable to at least three processes: failure of the 3rd-stage larvae (l3) to exsheath following ingestion, failure to become established following exsheathment (immune exclusion), and mortality of 4th- and 5th-stage worms on the mucosal surface. the proportion of worm ...19883362575
a routine diagnostic assay for the detection of benzimidazole resistance in parasitic nematodes using tritiated benzimidazole carbamates.resistance to benzimidazoles (bzs) in parasitic nematodes has recently been shown to be due to a reduction in the ability of bzs to bind the structural protein, tubulin, in resistant isolates. based on these observations the development and standardisation of a routine diagnostic assay has been undertaken by measuring the binding of tritiated mebendazole to crude supernatants of l3 larvae. the assay is rapid, requiring less than 2 h, and is robust, highly reproducible and sensitive to minor chan ...19883369079
regulation of haemonchus contortus populations in sheep: mortality of established worms. 19883372130
laboratory selection of haemonchus contortus for resistance to ivermectin.the eighth generation of adult haemonchus contortus, selected by subjecting infected pairs of sheep to suboptimal ivermectin treatment once per generation from parent (p; bbh isolate) through f7 (iv-a; selected isolate), required an approximate 4-fold increase in the ivermectin dose to produce 95% efficacy compared with its contemporary parent isolate. in a dose titration experiment the dose-response curve of the drug pressure-derived isolate, iv-a, was significantly (0.02 less than p less than ...19883397823
immune exclusion of haemonchus contortus larvae in sheep: dose dependency, steroid sensitivity and persistence of the response.naive and immune sheep, treated with anthelmintic, challenged directly into the abomasum and killed 48 hours later were used to examine the steroid sensitivity, persistence and dose dependency of immune mechanisms which result in the failure of incoming haemonchus contortus larvae to establish (immune exclusion). immune exclusion was almost totally abolished by corticosteroid treatment, the mean percentage of larvae establishing in the mucosa of immune sheep was 1.4 per cent of the challenge inf ...19883406527
serial passage of haemonchus contortus in resistant and susceptible sheep.a recently isolated field strain of haemonchus contortus was passaged through resistant (repeatedly reinfected) and susceptible (immunosuppressed) sheep for six and nine generations, respectively. infectivity of the resulting serially passaged strains was not significantly different when tested in groups of 1-year-old susceptible sheep.19883420791
the comparative efficacy of four broad spectrum anthelmintics against some experimentally induced trichostrongylid infections in sheep and goats.a controlled slaughter trial was undertaken to compare the efficacies of oxfendazole (5 mg/kg), morantel citrate (10 mg/kg), levamisole (8 mg/kg) and ivermectin (0.2 mg/kg) against experimentally induced infections of adult haemonchus contortus, ostertagia spp., trichostrongylus colubriformis and cooperiacurticei in sheep and goats. ivermectin and oxfendazole achieved similar levels of efficacy in both hosts against all four worm genera as did levamisole and mortantel against h. contortus and c. ...198716031344
removal of haemonchus contortus, ostertagia circumcincta and trichostrongylus spp. from goats, by morantel citrate, levamisole hydrochloride, fenbendazole, and oxfendazole.young feral goats harbouring 3, 7 and 36 day old experimental infections of strains of gastrointestinal nematodes, known to be susceptible to anthelmintics in sheep, were dosed orally with commercially available anthelmintics at the manufacturers' recommended rates for sheep. the drugs and overall removals of ostertagia circumcincta and trichostrongylus spp. (t. colubriformis and t. vitrinus) respectively were: morantel citrate 69% and 68%; levamisole hydrochloride 55% and >99%; fenbendazole 98. ...198716031353
genetic resistance to haemonchosis in sheep.parasitic nematodes cause huge economic losses to the domestic livestock industry. control requires skilled farm management and heavy use of anthelmintics, but breeding for resistant animals has long been held a possibility. for about 20 years after world war ll, the genetics of association between sheep breeds and haemonchus contortus - the main parasite of importance in sheep - was studied in the usa and europe. since the early 1970s, however, such studies have received greater emphasis in aus ...198715462974
the genetics of resistance and resilience to haemonchus contortus infection in young merino sheep. 19873429127
lipid biosynthesis from 14c-glycerol in haemonchus contortus (nematoda: trichostrongylidae), in vitro. 19873434509
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