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PubMed2001

Sensory neuroanatomy of a passively ingested nematode parasite, Haemonchus contortus: amphidial neurons of the third-stage larva.

The sensory neuronal ultrastructure of the amphids of the infective larva (L3) of Haemonchus contortus was analyzed, compared, and contrasted with that of the first-stage larva (L1). As in L1, each amphid of the L3 is innervated by 12 neurons. Thirteen ciliated dendritic processes of 10 neurons, 3 with double processes, lie in each amphidial channel. The dendritic process of each finger cell neuron ends in a large number of digitiform projections or "fingers," many more than in the L1. Processes of another pair of specialized neurons, probable homologs of wing cells in Caenorhabditis elegans, extend into the extreme anterior tip of the larva; they are much longer than those in L1. In L3, the neurons exit through the posterior wall of the amphidial chamber individually rather than in a bundle, as in L1. Cell constancy between L1 and L3 was confirmed, and the neurons were individually identified. Significant neuron-specific variations, presumably related to functional differences between the 2 stages were observed. In contrast, species-specific differences are surprisingly small. Haemonchus contortus is closely related to hookworms and has amphidial structure nearly identical to that in hookworms and similar to that in C. elegans, to which it is also closely related.

Animals↗

PubMed2001

Haemonchus horaki n. sp. (Nematoda: Trichostrongyloidea) from the grey rhebuck Pelea capreolus in South Africa.

In the course of a revision of species of Haemonchus Cobb, 1898 (Nematoda), commonly referred to as large stomach worms and significant pathogens of ruminants, a new species was discovered in the grey rhebuck Pelea capreolus, and the bontebok Damaliscus pygarthus, in South Africa. The new species, Haemonchus horaki, was previously reported as a long-spicule form of H. contortus (Rudolphi, 1803) Ransom, 1911. The new species, compared with H. contortus, can be distinguished by significantly longer spicules (555-615 microm vs. 383-475 microm); a synlophe with fewer ridges (26 vs. 30 in the region of the posterior part of the esophagus) that extend more posteriorly (within 1 mm of the copulatory bursa in males and postvulvar in females, vs. 2/3 to 3/4 of prebursal and prevulvar lengths); and an asymmetrical dorsal lobe with a long dorsal ray divided for more than half of its length, forming 2 branches of unequal length (vs. a dorsal ray divided for less than half of its length and forming 2 equal branches in H. contortus).

Animals↗

PubMed2002

Haemonchus spp. in sheep farmed under resource-poor conditions in South Africa--effect on haematocrit, conjunctival mucous membrane colour and body condition.

A longitudinal study was conducted on the differential faecal egg counts, haematocrits and body condition scores of sheep belonging to resource-poor farmers at Rust de Winter, Gauteng province, and Kraaipan, North West Province, South Africa. The animals were scored for level of anaemia using the FAMACHA method, an assay for the clinical evaluation of anaemia caused by Haemonchus spp. Periods of higher Haemonchus egg counts occurred from October to March for sheep at Rust de Winter and from September/October to February or April for sheep at Kraaipan. Lower haematocrit values were registered during these periods as was a higher incidence of anaemic conjunctival mucous membrane colour scores compared to the period April to September. No clear relationship between the faecal egg counts and the body condition scores was evident. Although wider application of the FAMACHA system in sheep raised by resource-poor farmers should be investigated, the present study indicates that this method may certainly prove to be a valuable worm control strategy for such livestock owners.

Anemia↗

PubMed1979

Studies on Haemonchus contortus. II. The effect of abomasal nematodes on subsequent challenge with H. contortus.

Fifty-thousand infective larvae of Trichostrongylus axei dosed to 7-9-month-old Merinos protected them against a subsequent challenge with 50 000 infective larvae of Haemonchus contortus. Protection varied with the period between an initial dosage of T. axei and challenge with H. contortus as follows: After 90 days it was more than 80% effective in more than 80% of sheep; at 119 and 180 days there was still a significant reduction in the numbers of H. contortus recovered (P < 0,05 and P < 0,001, respectively). Prior infestation with either Ostertagia circumcincta or with Haemonchus placei was ineffective against challenge with H. contortus.

Abomasum↗

PubMed1980

Thiabendazole-resistant strains of Haemonchus and Ostertagia in California lambs.

Ten parasite-free experimental lambs were inoculated intraruminally with a mixed-larvae inoculum which contained approximately 5,000 Haemonchus contortus infective larvae. Five lambs were treated with thiabendazole (66 mg/kg of body weight) and 5 were untreated controls. All lambs were killed 35 days after inoculations were done, and parasites present were recovered. Reduction in numbers of recovered Haemonchus contortus (25.7%) and Ostertagia spp (26.8%) were not significant (P greater than 0.05).

Animals↗

PubMed1981

Experiments on inhibited development of Haemonchus contortus and Ostertagia circumcincta in sheep in The Netherlands.

Inhibited development of Haemonchus contortus and Ostertagia spp was studied in sheep. Exposure of infective Haemonchus contortus larvae for five weeks to 15 degrees C or 16 degrees C very effectively induced inhibited development but exposure to lower temperatures was much less effective. Infection with fresh larvae cultured for seven or 12 days at 25 degrees C in the dark resulted only in very low rates of inhibited development. This was not much influenced by the age of the host or the month of infection. Exposure of infective Ostertagia spp larvae for five weeks to 4 degrees C was fairly effective in inducing inhibited development while exposure to 16 degrees C was not effective. On two occasions inhibited development of Ostertagia spp was observed in lambs after a primary infection with fresh infective larvae cultured for seven days at 25 degrees C in the dark. This implies that a conditioning for inhibited development of Ostertagia spp is possible within this seven day culture period.

Animals↗

PubMed1994

Purification and characterization of surface-associated proteins from adult Haemonchus contortus.

Extrinsic radioiodination experiments have shown that male and female adults of Haemonchus contortus (BPL strain) express a stage-specific set of surface-associated proteins with apparent molecular mass values of 30, 58, 81, and 143 kDa. A quantitatively different pattern of iodinated surface proteins is expressed by adults of the PPR strain of H. contortus, whereas the pattern of iodinated proteins expressed by Haemonchus similis is qualitatively distinct (38, 68, and 121 kDa). The 58-, 81-, and 143-kDa proteins of the BPL strain are glycosylated, whereas the 30-kDa protein is not. The binding of wheat germ agglutinin to the surface glycoproteins was inhibited by the trimer of N-acetylglucosamine (N,N,N-triacetylchitotroise) but not by the monosaccharide, indicating the presence of chitin-like homopolymers. The carbohydrate portion of the 58-kDa protein is N-linked and accounts for 30% of its apparent mass. Under nonreducing conditions, the 58-kDa glycoprotein forms a high molecular mass polymer that is unable to penetrate a 10% acrylamide gel. The 143- and 81-kDa surface glycoproteins were not hydrolyzed by either N- or O-glycanase, indicating unusual modifications to the saccharide-linkage and rendering it resistant to glycosidase digestion. The 30-, 58-, and 143-kDa purified surface proteins produced distinct peptide maps with Staphylococcus aureus V8 protease.

Abomasum↗

PubMed1994

Sublateral hypodermal chords in Haemonchus (Nematoda: Trichostrongyloidea): description and potential as a systematic character.

Prominent sublateral hypodermal chords (SHC) are described in Haemonchus spp. Four large SHC are located 1 muscle cell away from the lateral chords from the level of the middle of the esophagus to midbody. The SHC are largest in midbody and merge with the lateral chords at about 65% of the body length from the anterior end. With the aid of transmission electron microscopy, a band of nerve tissue was located parallel and medial to the SHC. Haemonchus spp. and Mecistocirrus digitatus have SHC that are so large they can be identified in thick freehand midbody cross sections cut with a cataract knife. Because SHC have not been described in other Trichostrongylidae, their presence in members of the Haemonchinae may have value as a systematic character.

Animals↗

PubMed2005

Comparative efficacy of the nematode-trapping fungus Duddingtonia flagrans against Haemonchus contortus, Teladorsagia circumcincta and Trichostrongylus colubriformis in goat faeces: influence of the duration and of the temperature of coproculture.

Amongst the alternative strategies to the use of anthelmintics, the administration of Duddingtonia flagrans spores has already proved its efficacy in reducing the number of developing larvae of several nematode species in goat faeces. In this trial, the efficacy of this fungus against the larvae of the three major nematode species of goats was compared in various conditions of coproculture. Twelve strongyle free goats were experimentally infected with either Trichostrongylus colubriformis, Teladorsagia circumcincta or Haemonchus contortus larvae. Half of the animals received an oral dose of 5x10(5) Duddingtonia chlamydospores/kg BW daily for 27 days, whereas the remaining was kept as control goats. From the 7th day of administration onwards, individual coproscopical examinations as well as coprocultures, which were incubated 4, 7, 10 or 14 days at 21 or 28 degrees C, were performed. The reduction in developing larvae due to the activity of Duddingtonia ranged from 62.8 to 99.5% compared to control. The trapping efficacy depended on temperature (better activity of the fungus at 21 than at 28 degrees C) and on duration (larval reductions lower after 4 days than after 7, 10 and 14 days of coproculture). Teladorsagia larvae were the least trapped, and Haemonchus larvae were the most trapped.

Animals↗

PubMed1995

Efficacy of pyrantel tartrate against experimental infections with Haemonchus contortus, Teladorsagia circumcincta and Trichostrongylus colubriformis in goats.

The efficacy of pyrantel tartrate was evaluated in goats against induced infections with Haemonchus contortus, Teladorsagia circumcincta and Trichostrongylus colubriformis. All the strains were of sheep origin and tested for susceptibility to pyrantel tartrate in sheep at the standard dose rate (20 mg kg-1) prior to the infection of goats. Fifteen French Alpine female goats were inoculated with the three nematode species. On Day 25 post-infection, goats were randomized into an untreated control group and two pyrantel treatment groups (20 mg kg-1 bodyweight once, and 40 mg kg-1 bodyweight as two doses 24 h apart). The goats were killed and processed for worm recovery 10 days after treatment. The two dose rates achieved high and similar levels of efficacy (> 96%) against Haemonchus contortus and Teladorsagia circumcincta. Against Trichostrongylus colubriformis, however, pyrantel tartrate was less effective at both dose rates as worm reductions ranged from 55 to 62%.

Animals↗

PubMed1990

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 glutamate of 0.1 microM, in close agreement with the findings for the membrane associated binding protein. 5. Quisqualate was capable of displacing glutamate from the soluble C. elegans receptor, again in agreement with previous findings for the membrane bound receptor. 6. The fact that a parasitic nematode, Haemonchus contortus, also possesses this putative glutamate receptor, strengthens the case for using C. elegans as a model system for the study of parasitic nematode neuromuscular physiology.

Animals↗

PubMed1997

Response to challenge infection with Haemonchus contortus and Trichostrongylus colubriformis in dairy goats. Differences between high and low-producers.

The objective of the study was to analyse the influence of the level of milk production in dairy goats on the ability to develop resistance to gastrointestinal nematode infection. Two groups of 50 goats were initially exposed (Group 'Previously Infected' PI) or not exposed (Group 'Not Previously Infected' NPI) to repeated infections with a mixture of Haemonchus contortus and Trichostrongylus colubriformis. After anthelmintic treatment, goats from both groups remained free of parasites for 2 months around kidding. One month after kidding, 24 lactating goats in each group were challenged with Haemonchus contortus and Trichostrongylus colubriformis. Parasitological, pathophysiological and milk production parameters were then examined fortnightly for 3 months following challenge. Within the PI and NPI group, the response to challenge was compared between the 25% goats exhibiting the lowest level of milk production and the 25% with the highest level of production. In the low producers, previous contact with the parasites was associated with a decrease in egg excretion which was not apparent in the high producers. Previous exposure to parasites was also associated with more severe pathophysiological disturbances in the high producers. Lastly, the response to challenge also induced more severe depression in milk production after previous infection in the animals with the highest productive potential. These results confirmed that the level of milk production in dairy goats could influence the resistance and/or resilience to parasitism with more severe consequences detected in the high producers. In addition, the results suggest that such differences could in fact be mainly related to differences in the host response to parasites.

Animals↗

PubMed1985

A strain of Haemonchus contortus resistant to thiophanate.

The occurrence of a field strain of Haemonchus contortus resistant to thiophanate is reported for the first time in New Zealand. In a controlled anthelmintic trial with experimentally infected animals, thiophanate at 50-100 mg/kg had no appreciable effect on the Haemonchus burden. Albendazole reduced faecal strongylate egg counts by 95% in animals with naturally acquired 59 infections.

Journal Article↗

PubMed1987

Efficacy of levamisole and netobimin against Haemonchus contortus in lambs in Louisiana.

Efficacy of levamisole was evaluated in a suspected levamisole-resistant population of Haemonchus contortus in the Louisiana State University sheep flock. The efficacy of netobimin also was evaluated against this population of Haemonchus. In trial 1, 5 lambs naturally infected with H contortus were given 8 mg of levamisole/kg of body weight as a drench, and 5 lambs were not treated (controls). Nematode recovery after slaughter indicated 0% efficacy against H contortus. In trial 2, 30 nematode-free lambs were each given 8,300 F1 generation infective larvae of H contortus, which were derived from parent H contortus that survived 2 levamisole treatments in lambs being maintained in a nematode-free environment. Ten lambs were treated with 8 mg of levamisole/kg as a drench, 10 were treated with 20 mg of netobimin/kg as a drench, and 10 were not treated (control). Nematode recovery after slaughter revealed 62.3% and 99.8% efficacy for levamisole and netobimin, respectively, against H contortus.

Animals↗

PubMed1982

The anthelmintic efficacy of Artemisia herba-alba against Haemonchus contortus infection in goats.

The anthelmintic activity of the powdered shoots of Artemisia herba-alba was investigated in experimental haemonchosis in six Nubian goats which had been infected with single doses of 800 to 1,000 infective Haemonchus larvae. The clinical signs of caprine haemonchosis included inappetence, dullness and soft faeces and were correlated with the pathological findings. None of these changes were observed in four of the six goats following the treatment with 2, 10 or 30 g of Artemisia shoots. This successful therapy was supported by the absence of eggs in the faeces, of adult worms in the abomasum at necropsy and of significant lesions in the tissues of the goats and return of the concentrations of serum ammonia, sodium, potassium, total protein and creatinine and of the activity of aspartate aminotransferase (GOT) to normal. In two goats, treated with either 10 or 30 g of Artemisia shoots, egg production was not completely suppressed and a few adult Haemonchus worms were found in the abomasum.

Animals↗

PubMed1993

Monoclonal antibody to CD4+ T cells abrogates genetic resistance to Haemonchus contortus in sheep.

The roles of CD4+ and CD8+ T cells in genetically determined resistance of sheep to Haemonchus contortus (a natural host-parasite relationship) was investigated by selectively depleting genetically resistant merino lambs of their CD4+ or CD8+ T cells by treatment with mouse monoclonal antibody (mAb) specific for the appropriate determinant before and during challenge infection. Administration of anti-CD4 mAb to genetically resistant lambs completely abrogated their expression of genetic resistance as indicated by significantly higher faecal egg output and worm burdens found in the CD4+ T-cell-depleted lambs compared with those of controls. Host responses associated with resistance to H. contortus including mucosal mast cell hyperplasia and tissue eosinophilia were also significantly suppressed in CD4-depleted lambs. The development of anamnestic anti-parasite antibody responses were also significantly inhibited by anti-CD4 mAb. Furthermore, anti-CD4 mAb abolished differences in host responses between genetically resistant and random-bred (susceptible) lambs. In contrast, depletion of CD8+ T cells had no effect on genetic resistance; faecal egg output, worm counts, mast cells and eosinophil responses in CD8-depleted lambs were not significantly different from those in controls. Together, these results suggest that CD4+ T cells play a pivotal role in mediating genetic resistance to H. contortus, and in the generation of mucosal mast cell hyperplasia, tissue eosinophilia and anti-Haemonchus antibody. CD8+ T cells appear to play no protective role. The possible mechanisms by which CD4+ T cells might mediate anti-parasite resistance are discussed.

Animals↗

PubMed2000

Thermotaxis and thermosensory neurons in infective larvae of Haemonchus contortus, a passively ingested nematode parasite.

As a basis for studies of thermal behavior of infective larvae (L3) of Haemonchus contortus resulting from ablation of amphidial neurons, the locations of the amphidial cell bodies in the hatchling larva (L1) were compared with their locations in the L3. We sought to verify that killing each targeted cell body in L1 destroys the putative corresponding dendrite of the L3. These comparisons confirmed the predicted cell body-to-dendrite connections, as well as similarities in the general amphidial structure of the two stages. We then conducted a series of studies using laser microbeam ablation of amphidial cell bodies in the L1 to determine the role of specific neurons in the thermal behavior of the L3. In a thermal gradient, normal L3 of H. contortus migrate to the temperature at which they were cultured and/or maintained. Larvae grown at 16 degrees or 26 degrees C migrate appropriately to either of these temperatures. Larvae grown to the L3 stage at 16 degrees C and then moved to 26 degrees C become acclimated to this temperature and thereafter migrate to it. However, when the putative thermosensory neurons, the finger cell neurons (AFD), were ablated in hatchling larvae with a laser microbeam, and these were grown to the L3 stage and tested on a radial thermal gradient, they failed to migrate to their culture temperature. Instead, they moved actively and continuously over much of the assay plate surface, with no obviously oriented cryo- or thermotactic movement. Ablation-control larvae, those in which putatively chemosensory neuron classes ASE or AWC were killed, migrated normally to their culture temperature. When the RIA interneurons (identified by positional homology with those of Caenorhabditis elegans) were ablated, the operated larvae moved actively, but circled near the initial placement point; control larvae, in which other nonamphidial neurons were killed, migrated normally. These results indicate that the finger cell neurons (AFD) are the primary thermosensory class in H. contortus. The RIA-class neurons integrate thermal responses in H. contortus, as do their putative structural homologs in C. elegans, but the behavior of H. contortus subsequent to RIA ablation is strikingly different.

Animals↗

PubMed2003

Distribution of glutamate-gated chloride channel subunits in the parasitic nematode Haemonchus contortus.

Glutamate-gated chloride channels (GluCl) are related to gamma-aminobutyric acid-A (GABA(A)) receptors and are the target sites for the avermectin/milbemycin (A/M) anthelmintics, drugs that cause paralysis of the somatic and pharyngeal muscles in nematodes. We have previously identified four GluCl subunits, HcGluClalpha, HcGluClbeta, HcGluClalpha3A, and HcGluClalpha3B from the sheep parasite Haemonchus contortus. We raised specific antisera against all of these subunits and used them in immunofluorescence experiments on adult parasites. All of the subunits were expressed in the motor nervous system, especially motor neuron commissures. Double-immunostaining experiments suggested that HcGluClalpha and HcGluClbeta were expressed on the same commissures; these were also stained with an anti-GABA antibody, suggesting that they may be inhibitory motor neurons. The HcGluClbeta subunit was also detected in lateral and sublateral nerve cords. The HcGluClalpha3A and -B subunits, products of an alternatively spliced gene, were expressed in different neurons. We found HcGluClalphaA in a pair of sensory, possibly amphid, neurons in the head, in addition to the motor neuron commissures. HcGluClalpha3B was detected in three cell bodies, probably of pharyngeal neurons, and to ventral and lateral cords. These results indicate that the GluCl are widely distributed in the H. contortus nervous system and suggest that they have critical roles controlling locomotion, pharyngeal function, and possibly sensory processing in parasitic nematodes. They also provide an explanation for the observed effects of the A/M anthelmintics.

Amino Acid Sequence↗