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1.
Worm egg counts of yearling Angora or Merino wethers grazing in mixed flocks at either 4/ha or 8/ha were observed over a 5 month period. Based on faecal egg counts infection levels in the sheep increased for the first 3 months and then decreased as the animals developed resistance. Egg counts in the goats did not decrease during the experiment. Post mortem worm counts indicated that there was a significant host species--stocking rate interaction on worm burdens of Haemonchus contortus adults and Ostertagia circumcincta adults and larvae. Goats had more H. contortus and O. circumcincta adults than sheep at the 8/ha stocking rate. At 4/ha goats had fewer O. circumcincta fourth stage larvae than sheep. There was no stocking rate effect on the numbers of Trichostrongylus axei or T. colubriformis. Sheep had more T. axei and fewer T. colubriformis than goats.  相似文献   

2.
The efficacy of ivermectin (0.08 per cent w/v oral solution) at different dose levels was evaluated against induced infections of adult Haemonchus contortus (21 days old) and Trichostrongylus colubriformis (21 days old) and fourth stage larvae of Oesophagostomum columbianum (17 days old), Ostertagia circumcincta (five days old) and Strongyloides papillosus (five days old). Twenty-five Boergoats (mutton goats) were randomly allocated by bodyweight within each sex to an untreated control group and four ivermectin treatment groups; ivermectin was administered at either 25, 50, 100 or 200 micrograms/kg orally, once. The goats were killed and processed for worm recovery 25 to 27 days after treatment. At 25 micrograms/kg the efficacy of ivermectin varied from 43 per cent for adult T colubriformis to more than 99 per cent for fourth larval stage O columbianum. Ivermectin at 50 micrograms/kg or higher was 99 per cent or more effective against all induced parasite infections with the exception of ivermectin at 50 micrograms/kg against S papillosus (97 per cent). For all parasites there was a statistically significant (P less than 0.05) difference between the control group and the pooled treated groups. No adverse reactions to ivermectin treatment were observed in the goats.  相似文献   

3.
In Autumn 2009, a faecal egg count reduction test (FERCT) was carried out on three sheep farms. Groups of 8-11 lambs were treated with ivermectin or moxidectin, with a 14-day interval between treatment and sampling. Ivermectin resistance was present on all three farms. Treatment with ivermectin resulted in a reduction in faecal egg numbers of 94.6%, 63%, and 59%. On two farms, 14 days after treatment pooled faecal samples yielded predominantly larvae of Hamonchus contortus (100% and 98%, respectively). On the third farm, H. contortus and (probably) Teladorsagia circumcincta were resistant to ivermectin (64% and 36% of the larvae, respectively). Treatment with moxidectin resulted in a 100% reduction in egg output in sheep on all three farms. More sensitive culture techniques failed to detect any larvae in samples taken from two farms, but a few Ostertagia-type larvae, probably of T. circumcincta, were detected in samples from the third farm. It can be concluded that gastrointestinal nematodes in sheep from these three farms were resistant to ivermectin, whereas resistance to moxidectin was not detected.  相似文献   

4.
Two experiments investigated the efficacy of the legume Hedysarum coronarium (sulla), which contains condensed tannins (CTs), for reducing gastrointestinal nematode infections relative to lucerne. Experiment 1 was aimed to show whether the lower faecal egg count (FEC) and larval establishment previously reported in lambs grazing sulla were due to direct effects of the forage on Ostertagia circumcincta and Trichostrongylus colubriformis or were mediated through an enhanced immune response. Experiment 2 evaluated the impact of feeding sulla relative to feeding lucerne (Medicago sativa), before, at, or after larval challenge on subsequent FECs and nematode burdens. In experiment 1, 64 Romney lambs were fed either freshly cut lucerne or sulla (32 lambs per herbage) for the duration of the trial. Within each herbage there were four treatment groups (n=8 per group). Initial levels of immunity were assessed in uninfected (UN) lambs which were maintained parasite-free until challenged with 15,000 O. circumcincta and 15,000 T. colubriformis larvae on day 63, and slaughtered on day 81. The other three treatment groups were trickle-infected with each of 5000 O. circumcincta and 5000 T. colubriformis larvae three times per week from day 1 to 35. Non-steroid infected (CONTROL) and steroid-treated (STER) groups were treated with anthelmintic on day 49 and challenged with 15,000 O. circumcincta and 15,000 T. colubriformis on day 63 and slaughtered on day 81. The STER lambs were given dexamethasone trimethylacetate from day 49 to 81 to determine effects of immunity on parasite infection. From day 35 an establishment group (EST) on each herbage was fed a common pelleted lucerne diet and slaughtered on day 56 to determine nematode establishment during trickle-infection. Diet did not affect FECs but feeding lucerne increased (P<0.05) numbers of T. colubriformis in CONTROL lambs compared to those fed sulla. O. circumcincta numbers were lower (P<0.05) in UN lambs fed sulla than lucerne. The sulla diet was associated with higher (P<0.05) antibody titres against secretory-excretory antigens to adult O. circumcincta and to adult and larval T. colubriformis, so there appeared to be some immunogenic response to the sulla diet but effects upon T. colubriformis numbers were not significant. The second experiment involved 48 Romney lambs grazing conventional pasture which were infected with 10,000 each of O. circumcincta and T. colubriformis larvae either 7 days before, 7 days after, or at the time they commenced grazing either sulla or lucerne. Lambs which grazed sulla had lower (P<0.05) FEC and lower (P<0.05) O. circumcincta burdens than lambs which grazed lucerne but timing of infection had no effect on FEC or worm burdens. T. colubriformis numbers were not affected by treatment or herbage. In conclusion, the sulla diet resulted in lower O. circumcincta numbers compared to lucerne outdoors and some evidence of an immunogenic response was obtained indoors. However, neither the herbage nor the immunogenic response reduced T. colubriformis numbers in either experiment.  相似文献   

5.
Anthelmintic resistance of nematodes to benzimidazoles and ivermectin was suspected from field observations in an Angora goat herd in northern Hesse. Larvae of the caprine trichostrongyle isolate were used for artificial infections of helminth-naive sheep. Groups of the lambs were treated with albendazole (3.8 mg/kg p.o.) or ivermectin (0.2 mg/kg s.c.) four weeks after infection or remained untreated as controls and were necropsied one week later. Albendazole reduced the mean faecal egg counts by 82% and the mean worm counts of Haemonchus contortus by 22%, Ostertagia circumcincta by 10% and Trichostrongylus colubriformis by 41% as compared with the controls. Ivermectin was 100% effective. This is the first report from Germany of multispecific resistance to benzimidazoles in a trichostrongyle population of goats.  相似文献   

6.
AIM: To confirm the presence of multiple anthelmintic resistance on a sheep farm in New Zealand. METHODS: Three groups of 10 weaned Romney-cross lambs were treated either with an oral dose of ivermectin (0.2 mg/kg), or a benzimidazole/levamisole (BZ/LEV) combination (4.75 albendazole and 7.5 mg/kg levamisole), or were left untreated. Ten days later, animals were necropsied, and adult worms recovered and identified from the abomasa and small intestines. Pre- and post-treatment faecal nematode egg counts (FEC) were recorded, and larval cultures were performed. RESULTS: In a faecal egg count reduction test (FECRT), adjusted to reflect pre- and post-treatment larval culture results, ivermectin resistance was detected in Teladorsagia (Ostertagia), Trichostrongylus and Haemonchus spp, while BZ/LEV combination- resistant Teladorsagia and Trichostrongylus spp were also present. Adult worm counts confirmed these results, and identified the species involved as Teladorsagia circumcincta, Trichostrongylus colubriformis and H. contortus. CONCLUSION: Multiple, multi-generic anthelmintic resistance was confirmed on a sheep property in New Zealand. This included the first confirmed case of ivermectin resistance in T. colubriformis from sheep in New Zealand.  相似文献   

7.
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/kg, but was high against adult H contortus (99%) and adult T colubriformis (99.7%) in goats given 7.92 mg of levamisole/kg. Although efficacy against adults of all species was high in goats given 11.88 mg of levamisole/kg, some immature worms of all species remained in the abomasa of goats.  相似文献   

8.
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. curticei. Against Ostertagia spp. and T. colubriformis, however, the latter two drugs were less effective in goats than sheep. Neither the numbers of Ostertagia spp. removed from goats by levamisole (81% reduction) nor the numbers of T. colubriformis removed from goats by morantel (56% reduction) were statistically significant (P>0.05).  相似文献   

9.
The efficacy of the pour-on formulation of eprinomectin, at a dose rate of 0.5 mg/kg bodyweight, was assessed in sheep against three main species of gastrointestinal nematodes and against the nasal bot fly, Oestrus ovis, and some pharmacokinetic parameters were determined for 21 days after the treatment. By comparison with untreated control sheep, infected experimentally with Haemonchus contortus, Teladorsagia circumcincta and Trichostrongylus colubriformis, eprinomectin was 100 per cent effective against the two abomasal species and 99.5 per cent effective against T. colubriformis. In ewes naturally infected with the nasal bot fly, the efficacy of the drug against O. ovis was 97.7 per cent. The mean (se) systemic area under the curve (AUC) was 56.0 (26.2) ng/day/ml and the mean residence time was 5.3 (1.0) days, but there were wide variations between individual sheep.  相似文献   

10.
Weight gain costs due to infection were higher in sheep than goats, 28 and 17.5%, respectively, for Trichostrongylus colubriformis and 48.7 and 32.2%, respectively, for Haemonchus contortus. The extent of bodyweight cost attributed to anorexia in sheep infected with H. contortus was higher (13.5 g/day) than in sheep infected with T. colubriformis (2.3 g/day). On the other hand, bodyweight cost due to the other pathogenic effects in sheep infected with T. colubriformis were higher (35.6 g/day) compared to sheep infected with H. contortus (10.9 g/day). A strong relationship between faecal egg count and worm count (r=0.79, P=0.006) was shown only in sheep infected with T. colubriformis. About half of the infected sheep and goats had low or zero faecal egg counts throughout the study. In about 40% the egg count rose initially but became low by weeks 10-16, whereas in about 10% counts increased progressively throughout the period of observation and these animals also had the highest numbers of worms at slaughter. Packed cell volume was reduced in sheep and goats infected with H. contortus but serum protein and haemoglobin levels were unaffected. Sheep infected with T. colubriformis had a higher level of eosinophilia after 8 weeks (18.4%) than sheep infected with H. contortus (11.4%), whereas this pattern was reversed in goats and levels were also lower (4.1 and 8.9%, respectively). There was no apparent relationship between eosinophilia and resistance to infection with H. contortus or T. colubriformis.  相似文献   

11.
From autumn (April) to spring (November), groups of pregnant and dry Merino ewes grazed pasture contaminated with infective larvae of Haemonchus contortus, Ostertagia circumcincta and Trichostrongylus colubriformis. A periparturient rise in faecal egg counts occurred in the pregnant ewes, following the maturation in early spring of arrested fourth-stage larvae of H. contortus and failure of pregnant ewes to expel the resulting adult worms. Peak egg counts were seen in September, just before lambing. In dry ewes, egg counts were slightly elevated at the time of the rise in the pregnant ewes, but fell to very low levels as adult worms developing from previously arrested larvae were expelled. Lactating ewes acquired greater burdens of O. circumcincta and T. colubriformis than did dry ewes, but were equally refractory to new infections with H. contortus. It is therefore suggested that the impairment of immunity to helminth infection seen in reproductive ewes may be more specific than was previously envisaged.  相似文献   

12.
Twenty-four lambs of mixed breeding with mixed experimental infections of Haemonchus contortus, Ostertagia circumcincta, Trichostrongylus axei, and T colubriformis were allotted to 4 groups. One group (control) was given the vehicle propylene glycol, and the others were given 100, 200, or 300 micrograms of ivermectin/kg of body weight by mouth. Twelve days after treatment, the sheep were necropsied. The compound was greater than 99% effective against immature stages of 4 nematode species at all dosages, except at the 100 micrograms/kg dosage, where efficacy was 96% against H contortus.  相似文献   

13.
Sera from 53 sheep belonging to Castellano, Churro, Manchego, and Merino breeds were analyzed to test the diagnostic value of a 26-kD antigen from adult Haemonchus contortus at prepatency and early and late patency of experimental haemonchosis. Animals that received zero, 1, or 2 infections with the parasite were tested. In addition, sera from 20 experimentally infected and 10 noninfected Texel sheep were used to test the antigen. Sera from 37 infected animals at prepatency as well as at patency in primary and secondary infection were found positive with the 26-kD antigen. However, sera from 10 animals with the lowest worm burdens (second infection) did not recognize the antigen during early patency (day 28 postinfection). IgG1 was the only isotype implicated in antigen recognition because IgG2, IgA, and IgM, in the same sera, showed no reactivity with the peptide. Antigen specificity was confirmed because hyperimmune sera against infective larvae and adult stages of the most common gastrointestinal nematodes found in natural infections in sheep (Trichostrongylus colubriformis and Teladorsagia circumcincta) did not recognize this peptide. The antigen was recognized only by anti-adult H. contortus hyperimmune sera and appeared to be absent in the L3 parasite stage. In addition, the partial N-terminal amino acid sequence of the diagnostic peptide is reported.  相似文献   

14.
Small ruminants are affected by gastrointestinal nematode (GIN) infection. A promising alternative strategy for control of GIN infection is to increase the level of resistance in the population by taking advantage of the host's immune response. Immunoglobulin A (IgA) and E (IgE) are known to be involved in immune response to GIN. The aim of this study was thus to investigate genetic parameters of IgA and IgE responses against Haemonchus contortus in Creole kids naturally challenged at pasture and to determine the relationship with other resistance criteria such as faecal egg counts, packed-cell volume, eosinophil counts and bodyweight. Variance and covariance components for genetic and residuals effects for each trait were estimated on 3862 males at 11 months of age. Heritability estimates for IgA and IgE ranged between 0.15 and 0.57. Strong positive genetic correlations were observed between either IgE or IgA responses against L3 and adult excretory/secretory products (ESP) antigens of H. contortus, suggesting that the humoral immune response is not specific to the life cycle stage of the parasite suggesting that there is substantial cross recognition between the different parasite antigens. Heritability estimates for faecal egg count (FEC), packed-cell volume (PCV) and bodyweight (BW) were in accordance with previous results in Creole kids. Blood eosinophil counts were found moderately heritable and negatively correlated with FEC, suggesting that this cell population plays a role in resistance to nematode parasite infection in Creole goats. IgA response was positively correlated to FEC, in contrast with the negative correlation between IgE against L3 of H. contortus and FEC. In Creole goats, IgA response against L3 or ESP of H. contortus would rather be associated with the worm burden than an immune protective response. The immune response involving activity of IgE against L3 of H. contortus may be one important pathway for development of resistance to gastrointestinal nematode infections in Creole goats.  相似文献   

15.
One of three groups of sheep was challenged twice-weekly with infective-stage larvae (L3) of the sheep parasite O. circumcincta, another with the cattle parasite O. ostertagi while the third received no larval challenge. Positive faecal egg counts (FEC) and a rise in plasma pepsinogen levels were observed only in those animals given O. circumcincta. Anti-O. circumcincta L3 IgG titres were rapidly elevated during parasite challenge with either O. circumcincta or O. ostertagi. Throughout the experiment, no rise in anti-adult IgG titres or eosinophil numbers was observed in peripheral blood in any group. On evidence of self-cure of the trickle-infection, determined by a reduction in FEC, all groups were drenched and challenged with 15,000 O. circumcincta L3. No effect of previous challenge on parasite establishment or FEC was observed, although egg viability was significantly reduced in both groups given prior challenge. Significant differences in adult female worm length were observed between groups. Those recovered from animals previously challenged with O. circumcincta were shorter than from those given O. ostertagi which were in turn shorter than those from previously unchallenged animals. In utero egg counts were significantly lower in worms from animals previously challenged with O. circumcincta than in those from unchallenged control animals. The results indicate that a level of immunity to O. circumcincta can be conferred by exposure to O. ostertagi.  相似文献   

16.
In vitro and in vivo studies were conducted to determine possible direct anthelmintic effects of condensed tannins towards different ovine gastrointestinal nematodes. A larval development/viability assay was used to investigate the effect of a condensed tannin extract (Quebracho) towards larvae of Haemonchus contortus, Teladorsagia circumcincta and Trichostrongylus vitrinus. The development to infective larvae and their viability was assessed in all three species and LD 50 values were calculated. The presence of Quebracho extract in the cultures decreased the viability of L3 in all species; the LD 50 were not significantly different for the different species. Forty-eight sheep were allocated to one of eight groups and were infected with a single dose of either 4000 L3 H. contortus (groups 1 and 2) or 5000 L3 T. colubriformis and 5000 L3 Nematodirus battus simultaneously (groups 3-6) or 10,000 L3 of T. circumcincta (groups 7 and 8). From day 28 until day 31 of the experiment, sheep infected with the intestinal species were drenched with Quebracho extract at 4, 8 or 16% w/w of food intake, or remained as undrenched controls; sheep infected with the abomasal species were either drenched with Quebracho extract at 8% w/w of food intake or remained as undrenched controls. All sheep were slaughtered 4 days after the end of the drenching period. Sheep infected with the intestinal species and drenched with 16% w/w Quebracho had lower FEC compared to sheep drenched with 8% w/w (P<0.05), which in turn were lower than in sheep either drenched with 4% Quebracho or which remained undrenched (P<0.05). The lowest intestinal worm burden was recovered from sheep drenched with 8% w/w Quebracho extract (P<0.05). The administration of Quebracho extract at 8% of food intake for 3 days did not affect FEC or worm burdens in sheep infected with the abomasal species compared to controls.  相似文献   

17.
Infection with gastrointestinal nematodes (GIN), particularly Haemonchus contortus, is the biggest constraint to profitable goat production in the United States (US). Due to widespread prevalence of anthelmintic resistance in goat GIN, alternative, non-chemical control methodologies are needed to increase profitability of small ruminant industries. A study was designed to test the efficacy of a high condensed tannin (CT) legume, sericea lespedeza [SL, Lespedeza cuneata (Dum.-Cours. G. Don)] against GIN of goats fed in confinement. The goats were given a trickle infection of 500 H. contortus larvae/animal three times per week during the trial to simulate natural infection. Twenty Boer bucks (6-8 months old) were fed bermudagrass [BG, Cynodon dactylon (L.) Pers.] hay plus concentrate for 5 weeks in confinement and then 10 animals were switched to SL hay for an additional 7 weeks. Throughout the trial, feces and blood were collected weekly from individual animals to determine fecal egg count (FEC) and blood packed cell volume (PCV). Fecal cultures were made weekly from pooled samples to determine treatment effects on GIN larval development. All goats were slaughtered at the end of the trial, with adult worms in the abomasum and small intestine of each goat recovered, counted, and identified to species. Feeding SL hay to goats significantly (P<0.01) reduced FEC and increased PCV compared with BG hay. In addition, a lower percentage of ova in feces from SL-fed goats developed into infective (L3) larvae. There was a direct effect of SL hay on adult worms, with significantly (P<0.01) lower numbers of both abomasal (H. contortus, Teladorsagia circumcincta) and small intestinal (Trichostrongylus colubriformis) nematodes compared with goats fed BG hay. Feeding SL hay to goats is an effective means of controlling parasitic nematodes and may be a potential supplement/replacement for chemical anthelmintics.  相似文献   

18.
Sheep infected with benzimidazole resistant strains of Haemonchus contortus and Trichostrongylus colubriformis were used to compare the anthelmintic efficacy of fenbendazole given as a single dose or administered in a divided dose regime over five days. Statistical analysis showed no significant difference between the two methods of administration for H contortus. On the other hand, divided dose fenbendazole was significantly less effective than single doses against adult T colubriformis at dose rates of 5 and 7.5 mg/kg. In the case of H contortus a highly significant correlation coefficient between post treatment egg counts and worm counts (r = 0.789) was obtained. This suggests that reduction in faecal egg output following drug treatment would provide a useful field indication of anthelmintic performance of fenbendazole (and possibly related compounds) against benzimidazole resistant strains of this parasite.  相似文献   

19.
The efficacy of fenbendazole against the following gastrointestinal nematodes was tested in experimentally infected lambs: O circumcincta, H contortus, T colubriformis and N filicollis. As low a dose as 0.5 mg per kg reduced the egg output of a patent infection with H contortus and T colubriformis by 85 per cent to 100 per cent. A dose of 3.5 mg per kg has a 100 per cent effect on three or 10-day-old stages of H contortus and one of more than 99 per cent or 100 per cent T colubriformis. The same dose reduces seven-day-old stages of O circumcincta and N filicollis by more than 94 per cent or 100 per cent, while 10 mg per kg produces a 100 per cent elimination of seven-day-old stages of O circumcincta. In field trials and efficacy of more than 99 per cent was determined after oral dosage with 5.0 mg per kg against Ostertagia, Haemonchus, Trichostrongylus, Cooperia, Nematodirus and Chabertia. Fenbendazole has a wide therapeutic-toxic dose ratio. Discoloration of the wool does not occur. Fenbendazole can be administered as a drench or with the feed.  相似文献   

20.
Two field trials were conducted in two farms (farms A and B) in southern Italy, to assess the efficacy of eprinomectin applied topically at the dose rate of 500 micro g/kg to sheep with naturally occurring infections of gastrointestinal nematodes (GIN). The nematode population determined by necropsy consisted of Teladorsagia circumcincta, Haemonchus contortus, Trichostrongylus vitrinus, T. capricola, Nematodirus sp., and Chabertia ovina in sheep from farm A, and of T. circumcincta, T. vitrinus, T. capricola, T. colubriformis, and C. ovina in sheep from farm B. In each farm, 42 female sheep were assigned to a eprinomectin treated group (E-group) and a control untreated group (C-group) of 21 animals each. On farm A, the percentage reductions in strongyle faecal egg counts from E-group compared to C-group were 99.1% on day 10; 97.4% on day 30; and 67.0% on day 60. On farm B, on the same days, they were 95.4, 84.9, and 69.4%, respectively. In the course of the two trials, eprinomectin was well tolerated by all the animals with no adverse reactions following the topical treatment.  相似文献   

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