Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Haemonchiasis”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 541 records · Page 30Linked to original sources
PubMed2004

Esmodil: an acetylcholine mimetic resurfaces in a Southern Australian marine sponge Raspailia (Raspailia) sp.

Bioassay directed fractionation of a Raspailia (Raspailia) sp. (Order Poecilosclerida; Family Raspailiidae) collected during scientific trawling operations off the Northern Rottnest Shelf yielded as nematocidal agents the known metabolites, phorboxazoles A (1) and B (2). Further examination revealed the new natural product but known synthetic compound, esmodil (3). The structure for 3 was confirmed by spectroscopic analysis and total synthesis.

Animals↗
PubMed1995

Host movement and the genetic structure of populations of parasitic nematodes.

Mitochondrial DNA (mtDNA) sequence data were used to compare the population genetic structures of five species of parasitic nematodes from three different hosts: Ostertagia ostertagi and Haemonchus placei from cattle, H. contortus and Teladorsagia circumcincta from sheep, and Mazamastrongylus odocoilei from white-tailed deer. The parasites of sheep and cattle showed a pattern consistent with high gene flow among populations. The parasite of deer showed a pattern of substantial population subdivision and isolation by distance. It appears that host movement is an important determinant of population genetic structure in these nematodes. High gene flow in the parasites of livestock also indicates great opportunity for the spread of rare alleles that confer resistance to anthelmintic drugs. All species, including the parasite of deer, had unusually high within-population diversities (averages of 0.019-0.027 substitutions per site between pairs of individuals from the same population). Large effective population sizes (Ne), perhaps in combination with rapid mtDNA evolution, appear to be the most likely explanation for these high within-population diversities.

Alleles↗
PubMed2003

Vaccination-induced protection of lambs against the parasitic nematode Haemonchus contortus correlates with high IgG antibody responses to the LDNF glycan antigen.

Lambs respond to vaccination against bacteria and viruses but have a poor immunological response to nematodes. Here we report that they are protected against the parasitic nematode Haemonchus contortus after vaccination with excretory/secretory (ES) glycoproteins using Alhydrogel as an adjuvant. Lambs immunized with ES in Alhydrogel and challenged with 300 L3 larvae/kg body weight had a reduction in cumulative egg output of 89% and an increased percentage protection of 54% compared with the adjuvant control group. Compared to the adjuvant dimethyl dioctadecyl ammonium bromide, Alhydrogel induced earlier onset and significantly higher ES- specific IgG, IgA, and IgE antibody responses. In all vaccinated groups a substantial proportion of the antibody response was directed against glycan epitopes, irrespective of the adjuvant used. In lambs vaccinated with ES in Alhydrogel but not in any other group a significant increase was found in antibody levels against the GalNAcbeta1,4 (Fucalpha1,3)GlcNAc (fucosylated LacdiNAc, LDNF) antigen, a carbohydrate antigen that is also involved in the host defense against the human parasite Schistosoma mansoni. In lambs the LDNF-specific response increased from the first immunization onward and was significantly higher in protected lambs. In addition, an isotype switch from LDNF-specific IgM to IgG was induced that correlated with protection. These data demonstrate that hyporesponsiveness of lambs to H. contortus can be overcome by vaccination with ES glycoproteins in a strong T-helper 2 type response-inducing aluminum adjuvant. This combination generated high and specific antiglycan antibody responses that may contribute to the vaccination-induced protection.

Adjuvants, Immunologic↗
PubMedDate not supplied

Aspartyl proteases from the intestinal brush border of Haemonchus contortus as protective antigens for sheep.

A novel pepsin-like aspartyl protease was identified as a component of Haemonchus galactose-containing glycoprotein (H-gal-GP), which is an integral membrane glycoprotein complex located on the intestinal cells of Haemonchus contortus, and a highly protective antigen for sheep. This molecule, designated HcPEP2, showed 50% sequence identity with a previously described aspartyl protease from H-gal-GP known as HcPEP1. Fractions of H-gal-GP, either containing both HcPEP1 and 2 or other lower molecular weight components of the complex, were evaluated as protective antigens in immunization - challenge trials in sheep. When separated from the rest of the complex by gel filtration in 8 m urea, the HcPEP1 and 2 fraction significantly reduced H. contortus egg counts by 48% and worm numbers by 36%, but the lower molecular weight components were not significantly protective. However, the HcPEP1 and 2 fraction did not protect if electro-eluted from SDS-dissociated H-gal-GP, nor did bacterially expressed recombinant HcPEP1, suggesting that conformational epitopes are important for inducing immunity.

Amino Acid Sequence↗
PubMed1993

A search for associations between major histocompatibility complex restriction fragment length polymorphism bands and resistance to Haemonchus contortus infection in sheep.

Polymorphic bands were detected within the DQB and DRB regions of the ovine major histocompatibility complex by probing TaqI digested DNA from three large sheep half-sib families derived from a highly resistant ram. All animals were phenotypically assessed for Haemonchus contortus resistance by faecal egg counts and associations with RFLP bands and haplotypes were estimated using mixed model, best linear unbiased prediction statistical methods. Although the highly resistant sire was homozygous at the MHC, no significant associations were found between any band or haplotype and faecal egg count.

Animals↗
PubMed1993

Comparative kinetic disposition of oxfendazole in sheep and goats before and during infection with Haemonchus contortus and Trichostrongylus colubriformis.

The kinetic disposition of [14C]-oxfendazole (OFZ) and its metabolites, fenbendazole (FBZ) and fenbendazole sulphone (FBZ.SO2), in plasma and abomasal fluid were determined in Merino sheep and Angora goats before and during infection with Trichostrongylus colubriformis and Haemonchus contortus. The systemic availability (area under the plasma curve, AUC) of OFZ was significantly lower in goats (13.5 micrograms.h/ml) than in sheep (22.2 micrograms.h/ml) and was reduced with infection in goats (5.6 micrograms.h/ml) and sheep (15.1 micrograms.h/ml). The elimination of plasma [14C] was faster in goats than in sheep. The responses observed for [14C] were a reflection of the behaviour of OFZ. The concentration of OFZ and metabolites in abomasal fluid were similar in both species in the absence or presence of infection. However, as the mean flow rate of abomasal fluid was slower in goats (240 ml/h) than in sheep (488 ml/h), only 7% of the dose passed the pylorus in abomasal fluid of goats compared with 14% in sheep. The presence of gastrointestinal nematodes generally increased abomasal fluid flow rate but neither species nor infection had any effect on the rate or extent of [14C] excretion in urine or faeces. It is suggested that goats possess a faster hepatic metabolism than sheep resulting in more rapid elimination of OFZ.

Abomasum↗
PubMed1996

The effect of level of feed intake on the pharmacokinetic disposition and efficacy of ivermectin in sheep.

The kinetic disposition of orally administered [3H]-Ivermectin (IVM) was examined in sheep in which the feed intake was maintained at either 800 or 400 g/day. The [3H]-metabolites were almost completely associated with particulate digesta in the rumen. In the low feed intake group the digesta flow was slower than in sheep on high feed intake. This resulted in an extended residence time and greater availability of IVM and its metabolites. The anthelmintic efficacy of IVM was then examined in sheep in which feed intake was reduced from 800 g/day to 400 g/36 h prior to and 36 h after IVM administration. In sheep with reduced intake 97% of IVM-resistant Haemonchus contortus were removed, compared with 53% in sheep maintained on high feed intake.

Abomasum↗
PubMed2004

Interrelationships among physicochemical properties, absorption and anthelmintic activities of 2-desoxoparaherquamide and selected analogs.

The interrelationships between physicochemical properties, absorption and potency of 2-desoxoparaherquamide and five analogs, representing a new anthelmintic class, were evaluated in in vitro and in vivo assays. At pH 7.5, rates of drug absorption by the gastrointestinal nematode Haemonchus contortus and jird small intestine, parameterized by the permeability coefficient, P(e), ranged from 1.2-2.4 x 10(-4) cm/min (nematode) to 2.5-5.5 x 10(-3) cm/min (jird). In the jird intestine, absorption was pH-dependent, with P(e) at pH 7.5 being twice that at pH 4.5, reflecting the negative influence of protonation on transport of these weakly basic molecules. Each compound rapidly paralyzed H. contortus during in vitro exposure to therapeutically relevant concentrations (1-10 microm). The kinetics of drug action on motility in vivo mirrored their in vitro effects; motility concentrations were reduced in nematodes collected from jird stomach 3 h following oral drug dosing, by which time > or =50% clearance of the parasites had occurred. The nematode/medium partition coefficient K ranged from 10.1 to 16.1, consistent with the lipophilic nature of the compounds. The time required to reduce motility in vitro by 50% (t50*) and P(e) were used to determine C(n)*, the concentration of drug in the nematode at t50*, as an indicator of intrinsic potency. In the jird, the apparent potencies of the compounds were insensitive to route of administration (i.e. oral = i.v. = i.p. = i.m.) for H. contortus and two other gastrointestinal nematodes, Ostertagia ostertagi and Trichostrongylus colubriformis; topical administration, however, required three to 10-fold higher doses for equivalent efficacy.

Absorption↗
PubMed1987

Systemic release of a mast cell proteinase following nematode infections in sheep.

An enzyme-linked immunosorbent assay (ELISA) for sheep mast cell proteinase (SMCP) has been developed. Concentrations of SMCP in homogenates of abomasal tissue from parasite-immune sheep (341 micrograms SMCP/g tissues) were raised when compared to those in normal (non-infected) abomasa (0.145 micrograms SMCP/g tissue). SMCP was not detected in sera from normal animals challenged with Haemonchus contortus but was present (less than 1.0 ng SMCP/ml) in sera from 8/11 immune sheep 2 h after intra-abomasal challenge with 1 x 10(6) exsheathed Haemonchus larvae. In two further experiments, the SMCP response in gastric lymph was monitored after homologous larval challenge in sheep immune to Ostertagia circumcincta and in normal controls. SMCP (less than 1.4 ng SMCP/ml) was detected in lymph from 2/3 and 4/5 immune animals between 1 and 4 days post-challenge with 50,000 larvae, but not from normal animals. SMCP was not detected in lymph from immune animals following challenge with 1000 Ostertagia larvae. The relatively low concentrations of SMCP in blood and lymph reflect the presence of proteinase inhibitor(s) which interfered with the ELISA.

Abomasum↗
PubMed1988

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 histocompatibility complex (MHC) class II antigen. Infection or hyperimmunization of pasture-reared sheep with the gastric nematode Haemonchus contortus increased the numbers of mucosal mast cells and eosinophils but did not alter the phenotypic composition or number of mucosal lymphocytes or the pattern of expression of MHC class II antigens.

Abomasum↗
PubMed1988

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 differences between resistant and susceptible genotypes in faecal egg counts, worm weights, thymus weights and globule leucocyte responses to infection with H. contortus. These results suggest that an immunological basis underlies the high level of resistance to infection in the resistant genotype.

Animals↗
PubMed1989

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 primary infection PBMC did not respond to soluble antigens or those fractionated on SDS-PAGE, whereas T cell lines generated from these PBMC responded well. T cell lines and PBMC derived after a secondary infection responded similarly to fractionated larval antigen. This indicated that (a) the T cell lines had retained their antigen specificities (as represented by autologous PBMC reactivity) in spite of in-vitro cycles of restimulation with whole larval soluble antigen and subsequent expansion in recombinant human IL-2, and (b) proliferation of the antigen-specific PBMC was predominantly due to helper T cells. Variations between individual sheep in response to fractionated larval antigens was also observed. The pattern of helper T cell reactivity to SDS-PAGE larval antigens correlated poorly with B cell reactivity in the same animals by serum antibody Western blot analysis. These results demonstrate that helper T cell epitopes can be mapped in complex parasite antigen preparations in sheep and that this approach will be useful in the identification of parasite protective antigens in helminthiasis where the cellular or humoral nature of protection is not clearly defined.

Animals↗
PubMed1991

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 intraruminal injection. Both collagen materials induced antibodies reactive with cuticle collagens; however, neither induced reproducible protection to H. contortus infections in vaccinated/infected sheep. In the most extensive test, there were no statistical differences in mean faecal worm egg count for 56 days post worm challenge, in mean numbers of H. contortus and female fecundity ratios at necropsy of immunized and unimmunized sheep. Failure to reproducibly immunize sheep with cuticle collagens may be due to the inability of antibodies or host immune cells to reach the collagen epitopes in the nematode cuticle without prior surface coat removal as postulated in human nematode studies.

Adjuvants, Immunologic↗
PubMed1991

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. Significant reductions in adult worm numbers compared with non-treated controls, as determined 42 days after infection, were of 30%, 34%, 45%, 52%, 56%, and 55% in groups A, B, C, D, E, and F, respectively. A significant correlation, between the time of FCA administration (referred to the day of infection) and the number of worms recovered at necropsy, was also observed.

Abomasum↗
PubMed1991

Genetic control of acquired resistance to haemonchosis in Merino lambs.

Parasitological and immunological responses of genetically resistant and random-bred lambs to primary and secondary infection with H. contortus were studied. Resistant lambs had higher faecal egg counts and total worm burdens than the random-bred lambs following the primary infection. As there were no significant differences in serum and antibody levels, mucosal mast cells, circulating and tissue eosinophils between the two groups, it is inferred that what ever the underlying mechanism it was an innate characteristic. In contrast to primary infection, resistant lambs had significantly lower faecal egg counts and worm burdens than the random-bred lambs on secondary infection. Resistant lambs also exhibited significantly higher antibody levels, mucosal mast cell hyperplasia and mucosal eosinophilia in response to a challenge infection than the random-bred lambs. Furthermore, levels of mast cell hyperplasia and anti-Haemonchus antibodies correlated positively with the resistance status of the host. Taken together these results suggest that the genetic resistance of sheep to H. contortus results from the expression of an acquired immune response, and that anti-parasite antibodies and mast cell-derived mediators may play an important role in genetically determined resistance of sheep to haemonchosis.

Abomasum↗
PubMed1992

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, due to the cessation of stimulation with Haemonchus larvae 84 days previously or to treatment of sheep with corticosteroid, was associated with a marked decline in mast cell density and concentrations of SMCP in abomasal mucosal tissues. Nevertheless, larvae also failed to establish in immune sheep rested from challenge 42 days previously and in which mast cell counts were not significantly different from those of control sheep. A small, but significant, release of SMCP was demonstrated in gastric mucus from immune sheep following larval challenge, whereas little or no SMCP was detected in mucus from naïve animals.

Abomasum↗
PubMed1992

Vaccination of young Dorset lambs against haemonchosis.

Six Dorset Horn lambs were each vaccinated at age 7 weeks and 9 weeks with 50 micrograms of glycosylated integral membrane proteins, particularly enriched in the protein H11 from the intestinal brush border of adult Haemonchus. At 11 weeks of age the lambs were infected with 10,000 infective third stage Haemonchus larvae. Compared with the average for the control group the vaccinated group of lambs had a 78% reduction in parasite egg output over the patent period, with four of the six better than 93% protected. At autopsy 35 days post-infection the mean total worm burden of the vaccinated lambs was 83% reduced compared with the controls. The serum antibody titres to H11 correlated with the degree of protection.

Animals↗
PubMed1992

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 than 95% protected by all criteria. For these two groups parasite egg output was reduced 99% on average over the patent period. Two of the animals injected with 10 micrograms protein were partially protected, with 86% reduction in egg output. Two animals in the group injected with 1 microgram protein also showed partial protection. Antibody level correlated with protection.

Animals↗