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PubMed2006

Eosinophil interactions with Haemonchus contortus larvae in the ovine gastrointestinal tract.

Sheep were immunized by weekly oral infections with Haemonchus contortus for 9 weeks followed by anthelmintic treatment. They were challenged either 9 or 22 weeks later with PBS (sham controls) or one million exsheathed L3 surgically injected in the abomasum, and killed 24 h or 48 h later. Sheep challenged 9 weeks after immunization displayed varying degrees of tissue eosinophilia that showed a significant inverse relationship with the number of intra-epithelial mast cells (globule leucocytes). Close association of eosinophils with tissue larvae was observed mainly in the gastric pits (24 h) or on the mucosal surface (48 h). All L3-challenged sheep in this group had detectable globule leucocytes and tissue IL-4 mRNA, as measured by Southern blot RT-PCR. In contrast, sheep challenged 22 weeks after immunization had no detectable globule leucocytes or IL-4 mRNA and although they exhibited consistent tissue eosinophilia, eosinophils were not closely associated with tissue larvae. Scanning and transmission electron microscopy of sheep sensitized and rested for 9 weeks before challenge showed that L3 surrounded by eosinophils were at varying stages of damage and structural collapse. These studies strongly indicate that eosinophils can damage and probably kill gastrointestinal nematode larvae in vivo. In addition, they also suggest that effective killing by tissue eosinophils may depend on other microenvironmental factors such as intra-epithelial mast cells and IL-4.

Abomasum↗
PubMed2006

Further protection studies using recombinant forms of Haemonchus contortus cysteine proteinases.

Significant levels of protection against Haemonchus contortus have been achieved in sheep by vaccination with a cysteine proteinase-enriched fraction (TSBP) isolated from the gut of adult parasites. Protection is associated with three cathepsin B-like cysteine proteinases (hmcp 1, 4 & 6). Lambs vaccinated with these proteinases, expressed in bacteria as glutathione S-transferase fusion proteins, had significantly reduced (38%) worm burdens compared to challenge controls although, intriguingly, egg output was unaffected. Here, a repeat trial with similar results is reported and protection obtained compared to that induced by vaccination with the predicted mature forms of hmcp1, 4 and 6 expressed in bacteria as non-fusion proteins. Sheep immunized with a cocktail of these non-fusion proteins had reduced faecal egg counts of 27% (P = 0.17) and worm burdens of 29% (P = 0.01) compared to controls. High levels of host serum IgG were detected in GST-hmcp and non-fusion hmcp-immunized animals, although no correlation with protection could be determined. Sera from these groups bound to the microvillar surface of the gut of H. contortus.

Abomasum↗
PubMed1998

Infection-induced protection against Haemonchus contortus in merino and manchego sheep. Relationship to serum antibody response.

Resistance to primary and secondary infections with Haemonchus contortus was studied in 10-month-old Manchego and Merino sheep. No notable interbreed differences were observed after primary infections in the parameters determined (prepatency period, faecal egg output, abomasal worm burden). Previously infected sheep (200 L-3/kg live weight (lw)) from both breeds showed notable protection after challenge (400 L-3/kg lw), evidenced by lower eggs/g faeces (epg) values and worm burdens. A protective response in the Manchego breed was associated with arrested development of fourth stage larvae in the abomasal mucosa, whereas in the Merino breed a more rapid expulsion mechanism seems to be involved. Serum antibody levels (IgG, IgA) were infective dose-dependent and protection from re-infection was not clearly related to the parasite-specific IgG response estimated by enzyme-linked immunosorbent assay (ELISA) and Western blotting.

Abomasum↗
PubMed1998

Haemonchus contortus: characterization and purification of excretory/secretory protease(s).

The activity of protease(s) has been examined separately in excretory/secretory (E/S) products from male and female Haemonchus contortus (Nematoda: Trichostrongylidae). The E/S proteolytic activity indicated the presence of preabsorptive digestion of host blood and/or tissues. Protease activity was optimum at 37 degrees C, pH 8.5 and 8.0 mg casein. These protease(s) were purified to 32.16- and 88.80-folds from male and female E/S products, respectively, by sequential purification with saturated ammonium sulphate followed by ion-exchange chromatography. The purification study revealed the presence of isomeric forms of protease(s) in the E/S products of H. contortus.

Abomasum↗
PubMed1978

Efficacy of oxfendazole against an ovine isolate of benzimidazole resistant Haemonchus contortus.

Eighteen parasite-free sheep were each infected with 6000 +/- 25 infective larvae of the AH-2, benzimidazole-resistant strain of Haemonchus contortus on each of experimental days -27, -15, -8 and -1. The sheep were subsequently randomized into 3 groups of 6 sheep each. Group 1 served as untreated controls; Groups 2 and 3 were treated orally with oxfendazole at dose levels of 5 mg/kg and 10 mg/kg body weight, respectively. At both dosage levels, oxfendazole was 100% effective against third, fourth, early fifth, and adult stages of the worms.

Animals↗
PubMed1981

The isolation of a field strain of Haemonchus contortus in Queensland showing multiple anthelmintic resistance.

Following the apparent failure of levamisole to control infections of Haemonchus contortus in sheep at Lawes in south eastern Queensland, a strain of this parasite was isolated at the Animal Research Institute, Yeerongpilly. This strain was used to infect sheep at Yeerongpilly and the Merrindale Research Station, Victoria where four experiments to classify the resistance pattern of the parasite were carried out. Resistance to thiabendazole was first suspected in 1969, and these experiments confirmed that resistance to this drug was still present. They also showed that a strong degree of resistance had been developed to both levamisole and morantel tartrate. Other benzimidazole anthelmintics and also the organophosphorus compound naphthalophos were only moderately effective against the original isolate but rafoxanide, nitroxynil and phenothiazine were almost 100% effective. Other highly effective chemicals were disophenol and closantel. After passaging the strain for four generations with both levamisole and albendazole, resistance to both naphthalophos and the newer benzimidazole anthelmintics increased dramatically. This is the first report of a field strain of H. contortus exhibiting resistance to benzimidazole, non-benzimidazole and organophosphorus anthelmintics.

Albendazole↗
PubMed1988

Abundance and survival of infective larvae of the cattle nematodes Cooperia punctata, Haemonchus placei and Oesophagostomum radiatum from faecal pats in a wet tropical climate.

Observations were made on the abundance and survival of Haemonchus placei, Cooperia punctata and Oesophagostomum radiatum infective larvae from cattle faecal pats exposed at various times of the year in north Queensland wet tropics. Pats exposed in the hot, wet season yielded abundant larvae on herbage. In the dry season, although low numbers of infective larvae were usual, considerable numbers were produced under conditions of heavy dews on dense herbage. Irrespective of season of deposition of pats, the resulting larvae persisted generally for not longer than 10 to 12 weeks, and in large numbers for only 2 to 6 weeks. The findings suggest that prevention of contamination in the wet season, and in the dry season when light rainfalls are accompanied by heavy dews on dense herbage, will result in low levels of larval infestation on herbage. Rotational grazing in the area is suggested as a means of worm control.

Animals↗
PubMed1988

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 form 50% of larval cultures when the whole flock was treated than when only a part of the flock was treated.

Administration, Oral↗
PubMed1990

The intensity of resistance by mature Merino ewes against Haemonchus contortus and Trichostrongylus colubriformis in single-species and combined-species infection.

Three-year-old, non-lactating and non-pregnant Merino ewes, raised on pasture under a program of strategic treatment with anthelmintic and found to be extremely resistant to "trickle" infection with Haemonchus contortus, were given single-dose infections with either H. contortus or Trichostrongylus colubriformis or both species together. The purpose was to ascertain the intensity of protective immunity against the 2 parasites in sheep with immunity acquired from a presumably slight exposure to infection. To provide a criterion, some infected ewes were immunosuppressed with corticosteroid, dexamethasone. Untreated ewes were extremely resistant to challenge infection with either 15,000 or 150,000 H. contortus or 15,000 T. colubriformis. Surprisingly, when mixed infection was given, egg counts for H. contortus were significantly elevated compared with infection by that species alone. Antibody to antigens from infective larval and adult H. contortus was measured in serum by enzyme-linked-immunosorbent assay (ELISA) during the course of infection. Serum titres against larval antigens were significantly depressed when infections with either H. contortus or T. colubriformis were permitted by immunosuppression with dexamethasone, whereas those against adult antigen were depressed when infection with T. colubriformis was permitted.

Animals↗
PubMed2000

Evaluation of a laboratory test to detect resistance to closantel in Haemonchus contortus.

OBJECTIVE: To evaluate a laboratory test for closantel resistance in Haemonchus contortus. PROCEDURE: Field isolates of H contortus, known to be resistant to closantel, were tested in the assay. In addition, mixtures of closantel-susceptible and closantel-resistant laboratory reference strains were tested to develop a method of predicting the proportion of resistant worms in a sample from the field. RESULTS: The assay correctly identified as resistant all of the closantel-resistant field isolates of H contortus. It also identified one isolate with an in vivo efficacy of 98% as having emerging resistance. Testing of the mixtures of laboratory reference strains revealed that an isolate would be classified as resistant when it consists of about 25% or more resistant worms. Test samples that are not fully susceptible yet contain less than 25% resistant worms may be classified as emerging resistance. CONCLUSION: The in vitro migration assay is a sensitive method of detecting closantel resistance in H contortus.

Animals↗
PubMed2001

Reduced efficacy of ivermectin, abamectin and moxidectin against field isolates of Haemonchus contortus.

OBJECTIVES: To investigate the reduced efficacy of ivermectin, abamectin and moxidectin against two field isolates of Haemonchus contortus. These isolates were identified on separate properties in the New England region of New South Wales. PROCEDURE: Reduced efficacy of macrocyclic lactone anthelmintics against two field isolates of H contortus was suspected. These isolates were obtained from sheep on separate farms and pen trials were performed to investigate the efficacy of macrocyclic lactones. The percentage efficacy was calculated for moxidectin, ivermectin and closantel against the isolate from one farm (VHR23) and for moxidectin, ivermectin and abamectin against the isolate from the second (VHR29). The persistent activity of moxidectin against both isolates was investigated. RESULTS: Ivermectin and closantel were found to have efficacies below 80% against established populations of VHR23. Moxidectin was effective against an established population of VHR23 but the persistent activity was reduced to 7 days. Moxidectin was also found to be effective against established populations of VHR29, however, ivermectin and abamectin were found to have efficacies below 80%. There was no evidence of persistent activity of moxidectin against VHR29. CONCLUSION: A reduction in efficacy of abamectin and/or ivermectin against field isolates of H. contortus was identified from two farms in the New England region of New South Wales. The persistent effect of moxidectin was reduced against both isolates.

Animals↗
PubMed2002

Effectiveness of copper oxide wire particles for Haemonchus contortus control in sheep.

OBJECTIVE: To assess the efficacy of copper oxide wire particles (COWP) for the control of H contortus infections in grazing sheep. PROCEDURE: In experiment 1, 40 worm-free Merino hoggets (11 to 12 months of age) were divided into four equal groups and allocated to separate 0.8 ha pasture plots. Two groups then received 2.5 g COWP whereas the other two groups were untreated. From 1 week after COWP treatment all lambs received a weekly infection of 2000 H contortus larvae. At week 8, six sheep from the untreated group were then allocated to two groups and treated with either 2.5 or 5.0 g of COWP to establish therapeutic efficacy of treatment. Experiment 2 followed a similar protocol but was conducted with 40 worm-free Merino lambs (3 to 4 months of age) and no assessment of therapeutic efficacy was made. RESULTS: In experiment 1 no significant difference in faecal worm egg counts was observed between treatments and faecal worm egg counts remained less than 3000 epg in all animals. Total worm counts were reduced by 37% by COWP treatment (P = 0.055). Both 2.5 g and 5.0 g doses of COWP at 8 weeks of infection reduced faecal worm egg counts by > 85% with the higher dose giving an earlier response to treatment. In experiment 2, faecal worm egg counts at 4 and 6 weeks were reduced by more than 90% in the COWP treated lambs and worm numbers were 54% lower after 6 weeks when all remaining untreated lambs had to be treated for haemonchosis. Mean faecal worm egg counts in the COWP lambs remained below 3500 epg and clinical disease did not develop in the majority of lambs before the end of the experiment at 10 weeks. CONCLUSION: Treatment with COWPs appears to have the potential to reduce establishment and worm fecundity of Haemonchus spp for an extended period and may offer livestock producers a supplementary means of reducing larval contamination of pasture particularly in areas where anthelmintic resistance is a problem and copper supplementation is likely to be beneficial.

Animal Husbandry↗
PubMed1991

Protective immunity to a blood-feeding nematode (Haemonchus contortus) induced by parasite gut antigens.

To determine the ability of gut antigens to induce a protective immune response against blood-feeding nematodes, isolated gut antigens were used to immunize goats against Haemonchus contortus. Immunization-induced antibody responses recognized parasite gut antigens which were associated predominantly with the microvillous membrane region of the parasite gut. Antibody from immune serum also recognized seven predominant gut proteins on a Western blot (immunoblot). Several of these proteins appeared to be integral membrane proteins on the basis of their solubility in the detergent Triton X-114, indicating that the presentation protocol stimulated an antibody response to microvillous membrane antigens. Three different age groups of goats ranging from less than 6 months to greater than 1 year were immunized for challenge experiments. After infection with 10(4) larvae, an 87 to 95% reduction in fecal egg counts for all age groups of goats was achieved in the immunized compared with the control group. The reduction of worms in immunized goats ranged from 65% (kids) to 89% (yearlings) compared with controls. These results indicate that gut antigens can induce significant protection against blood-feeding nematodes. Antibody to H. contortus gut antigens also cross-reacted with microvilli of other blood-feeding nematodes including Ostertagia ostertagi and small strongyles of horses, which indicates that epitopes associated with the gut are phylogenetically conserved.

Animals↗
PubMed2004

Binding of hematin by a new class of glutathione transferase from the blood-feeding parasitic nematode Haemonchus contortus.

The phase II detoxification system glutathione transferase (GST) is associated with the establishment of parasitic nematode infections within the gastrointestinal environment of the mammalian host. We report the functional analysis of a GST from an important worldwide parasitic nematode of small ruminants, Haemonchus contortus. This GST shows limited activity with a range of classical GST substrates but effectively binds hematin. The high-affinity binding site for hematin was not present in the GST showing the most identity, CE07055 from the free-living nematode Caenorhabditis elegans. This finding suggests that the high-affinity binding of hematin may represent a parasite adaptation to blood or tissue feeding from the host.

Animals↗
PubMed2006

Identification of secreted cysteine proteases from the parasitic nematode Haemonchus contortus detected by biotinylated inhibitors.

Seven cathepsin B-like cysteine proteases (CBLs) were identified from the immunoprotective excretory-secretory products of Haemonchus contortus. Two-dimensional (2-D) zymography and biotinylated inhibitors were employed to localize active CBLs in 2-D protein gels. Mass spectrometry provided the identification of AC-4, HMCP1, HMCP2, and GCP7 as well as three novel CBLs encoded by clustered expressed sequence tags.

Amino Acid Sequence↗
PubMed1988

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 anthelmintic groups. One of the strains became resistant to ivermectin very rapidly despite effective rotation of this anthelmintic with chemically unrelated anthelmintic compounds.

Animals↗
PubMed1991

Effect of development of resistance to benzimidazoles, salicylanilides and ivermectin on the pathogenicity and survival of Haemonchus contortus.

Two groups of six lambs were infected either with an anthelmintic-susceptible strain of Haemonchus contortus or with a strain resistant to benzimidazoles, ivermectin and salicylanilides. The pathogenicity of the two strains of parasite was compared by monitoring the development of anaemia, changes in plasma proteins and abomasal damage in the two groups of lambs. There were no significant differences between the groups, suggesting that the development of resistance to several anthelmintics did not correlate with an increase in the pathogenicity of the parasites. Furthermore, the establishment rates and egg production of the susceptible and resistant parasites were similar. However, fewer of the eggs of the resistant parasites survived and developed at a variety of temperatures.

Animals↗
PubMed1992

Efficacy of moxidectin, nemadectin and ivermectin against an ivermectin-resistant strain of Haemonchus contortus in sheep.

The efficacies of ivermectin, nemadectin and moxidectin were evaluated when administered orally to lambs infected with either a susceptible laboratory strain of Haemonchus contortus or a strain reported to be resistant to ivermectin. Groups of 24 Dorset cross Cheviot cross Suffolk lambs were infected with either the susceptible or resistant strain of H contortus and allocated to treatment groups according to their faecal egg counts 27 days after infection. One day later the lambs were dosed orally with one of the three anthelmintics at 0.2 mg/kg bodyweight, and they were killed and surviving worms were recovered 13 or 14 days after treatment. Against the ivermectin resistant strain, ivermectin did not significantly reduce the egg count or the numbers of adult H contortus; however, both nemadectin and moxidectin reduced the nematode egg counts and the numbers of H contortus by 99 and 100 per cent, respectively. Against the susceptible strain, all the anthelmintics reduced the egg counts by 100 per cent as early as four days after treatment and reduced the numbers of susceptible H contortus by 100 per cent. No adverse reactions to any of the drugs were observed.

Animals↗