共查询到20条相似文献，搜索用时 15 毫秒
1.
Resistance of Teladorsagia circumcincta in goats to ivermectin In 2005, suspected ivermectin resistance of gastrointestinal nematodes was investigated in 17 goats on a farm in the Netherlands, using a faecal egg count reduction test combined with faecal larval cultures. Eight goats were treated orally with 0.2 mg/ kg ivermectin on 1 August 2005 and the other nine goats served as untreated controls. Faeces were collected from all goats on 1 August and on 12 August. Faecal egg counts were reduced by 80.6% in goats receiving ivermectin. On the basis of faecal larval cultures and the egg counts, ivermectin was found to be 100% effective against Haemonchus contortus, 15.0% effective against Teladorsagia circumcincta, and 93.3% effective against Trichostrongylus spp. The effect of levamisole and oxfendazole on gastrointestinal nematodes was also evaluated. Nine goats were treated subcutaneously with 5 mg/kg levamisole and seven goats orally with 4.5 mg/kg oxfendazole on 12 September On the basis of faecal egg counts performed on 12 and 22 September, levamisole reduced the total egg count by 95.4% and oxfendazole reduced the egg count by 85.8%. Differentiation of pooled faecal larval cultures revealed that levamisole was 99.9% effective against H. contortus, 81.9% effective against T. circumcincta, and 99.5% against Trichostrongylus spp. Oxfendazole was 75.5% effective against H. contortus, 33.2% effective against T. circumcincta, and 100% effective against Trichostrongylus spp. On 28 October the nine goats that were still present on the farm were orally treated with 0.4 mg/kg ivermectin. Faecal egg counts and differentiation of pooled larval cultures of faecal samples collected on 28 October and 9 November, respectively, revealed that total egg counts were reduced by 93.1%. Ivermectin was 49.1% effective against T. circumcincta but 100% effective against H. contortus and Trichostrongylus spp. Thus H. contortus appears to be resistant to oxfendazole and T. circumcinta appears to be resistant to oxfendazole and ivermectin. This is the first documented case of ivermectin resistance of a gastrointestinal nematode of small ruminants in the Netherlands. 相似文献
2.
Multiple resistance to albendazole, thiophanate, levamisole and orally administered ivermectin was detected in an isolate of Haemonchus contortus in sheep on a farm where benzimidazole resistance had already been identified. Following a faecal egg count reduction test, this was confirmed by both critical and controlled anthelmintic tests. Different groups of sheep infected naturally or given an experimental infection with the benzimidazole-resistant isolate were treated with the recommended doses of various anthelmintics. Compared to the control group, the percentage reductions in the faecal egg counts of sheep treated with albendazole, thiophanate, levamisole and ivermectin varied between 38.2% and 79.1% and the residual worm counts between 27.3% and 57.5%. The results indicate the presence of multiple anthelmintic resistance in this isolate of H. contortus. Sheep treated with closantel showed 100% reductions in faecal egg and worm counts, indicating that this drug was very effective against the population of H. contortus on the farm. 相似文献
3.
J A van Wyk P C van Schalkwyk H M Gerger E L Visser R M Alves L van Schalkwyk 《The Onderstepoort journal of veterinary research》1989,56(4):257-262
A strain of Haemonchus contortus from the Pietermaritzburg district of Natal was found to be resistant to levamisole (geometric mean efficacy 76.5%), morantel (41.9%), the benzimidazoles (oxfendazole: 33.7%) and rafoxanide (82.0%), but apparently fully susceptible to closantel and disophenol. In the case of ivermectin, a mean of 5.2% of the H. contortus was not removed at a dosage of 200 micrograms kg-1 live mass. A second strain of H. contortus, from Amsterdam in the south-eastern Transvaal, showed reduced susceptibility to levamisole (80.8%) and morantel (46.2%), the only 2 drugs tested. This is apparently the first report of resistance to the levamisole/morantel group of anthelmintics in sheep in South Africa. 相似文献
4.
The faecal egg count reduction test (FECRT) was conducted on 39 sheep farms and 9 goat farms located in Peninsular Malaysia. The anthelmintic groups used in these tests were the benzimidazoles, levamisole, the benzimidazole/levamisole combination, macrocyclic lactones and closantel. Results indicated that the prevalence of resistance to the benzimidazole group was high, with approximately 50% of the sheep farms and 75% of the goat farms having resistant nematode parasite populations present. Resistance to levamisole, closantel and ivermectin was also detected. Differentiation of the infective larvae derived from faecal cultures indicated that by far the most predominant parasite species was Haemonchus contortus. 相似文献
5.
Four experiments, two with sheep and two with goats, were carried out to determine the efficacy of ivermectin, fenbendazole, levamisole, closantel and some of their combinations by faecal egg count reduction tests. In the first experiment, injectable ivermectin, oral ivermectin, fenbendazole and levamisole were tested in 6-month-old lambs, and their reduction percentages were 77%, 13%, 42% and 92%, respectively. In the second experiment, with yearling sheep, the reduction percentages were 35% for injectable ivermectin, 32% for fenbendazole, 99% for levamisole, 48% for closantel, 92% for injectable ivermectin combined with fenbendazole, 99% for injectable ivermectin combined with levamisole, and 100% for fenbendazole combined with levamisole. In the study with 18-month-old goats given the same dose rates as those recommended for sheep, the reduction percentages were 73% for injectable ivermectin, 25% for fenbendazole, and 78% for levamisole. Another group of 14-month-old goats was treated with dose rates 1.5 times those recommended for sheep and the reduction percentages were 93% for levamisole, 92% for injectable ivermectin, and 97% for a combination of levamisole and ivermectin. In all experiments with sheep and goats the gastrointestinal nematode parasites identified by larval cultures were Haemonchus contortus, Trichostrongylus spp. and Oesophagostomum spp. The gastrointestinal nematodes of both sheep and goats on this farm are resistant to ivermectin and fenbendazole, whereas levamisole is still effective in sheep, but not in goats. The results are discussed in relation to the farm as a source of breeding stock to smallholder farmers and its potential to spread anthelmintic resistance. 相似文献
6.
Multiple resistance to benzimidazoles (fenbendazole, albendazole and mebendazole) in a strain of Haemonchus contortus in sheep was detected on a farm where fenbendazole resistance had already been identified. Following a faecal egg count reduction test, this was confirmed by both critical and controlled anthelmintic tests. Different groups of sheep infected naturally or given an experimental infection with the fenbendazole-resistant strain were treated with the recommended doses of various anthelmintics. Compared to the control group, percentage reductions in faecal egg counts of sheep treated with fenbendazole, albendazole, mebendazole, levamisole and morantel varied between 56% and 81% and worm counts between 71% and 86%. The results indicate the presence of multiple anthelmintic resistance in this strain of H. contortus on this farm. Sheep treated with ivermectin and closantel showed 100% reductions in faecal egg and worm counts, suggesting high efficacy of these drugs against the population of H. contortus on this farm. 相似文献
7.
Multiple species of nematodes resistant to ivermectin and a benzimidazole-levamisole combination on a sheep farm in New Zealand 总被引：1，自引：0，他引：1
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
8.
J A Van Wyk F S Malan H M Gerber R M Alves 《The Onderstepoort journal of veterinary research》1989,56(1):41-49
During the past decade in South Africa there has been a continual increase in sheep of strains of gastrointestinal helminths resistant to the modern anthelmintics. Five strains of Haemonchus contortus are described in this paper. Despite the fact that 2 of the 5 strains were tested for susceptibility only to ivermectin, a total of 10 instances of resistance were found. Four of the 5 strains were resistant to ivermectin, 2 to closantel, 2 to rafoxanide and 2 to the benzimidazoles. One of these strains was concurrently resistant to 3 different anthelmintic groups, namely, the ivermectins, the benzimidazoles and the salicylanilides. Resistance to ivermectin developed in 2 strains of H. contortus after a history of only 3 treatments with this compound in one instance and 11 treatments in the other. In the latter case drenching with ivermectin was well interspersed with that of other anthelmintics. This rapid development of resistance suggests that there may be cross-resistance between ivermectin and another anthelmintic group. Two of the ivermectin resistant strains were recovered from separate properties in the south-western Cape Province, where Ostertagia circumcincta, which is usually the dominant parasite in this region, was virtually eliminated by the anthelmintic treatment. On each of these properties it was apparently replaced by a resistant strain of H. contortus. A serious threat to control is the dissemination of worm strains with multiple resistance to anthelmintics. The strain of H. contortus resistant to 3 anthelmintic groups has already been widely dispersed, as the farmer concerned suddenly decided to give up farming with sheep and to sell his flock. 相似文献
9.
Electronic measurements of the motility of third stage larvae of a susceptible and a levamisole/benzimidazole-resistant strain of Haemonchus contortus were made after incubation in solutions of anthelmintics for 24 h. Results confirmed the resistance to benzimidazoles, but failed to show differences in response to levamisole. Visual observations of paralysis of first and third stage larvae in solutions of levamisole also failed to show significant differences between the two strains. The tests as conducted failed to demonstrate levamisole resistance, suggesting that nematode strains may vary in their mechanisms of resistance to levamisole. 相似文献
10.
11.
The efficacy of benzimidazoles and ivermectin was tested in 14 pilot farms in eastern Algeria. Resistance was detected in strongyle nematodes against benzimidazoles (five farms) and ivermectin (one farm). The main genera in the region were resistant: Teladorsagia, Trichostrongylus, Marshallagia and Nematodirus. The evaluations based on FECRT (faecal egg count reduction tests) were not always consistent due to the low-level of infection, and we developed a simplified, repeated treatment strategy to investigate resistance. The results obtained with repeated treatment faecal egg counts match globally those obtained with conventional faecal egg count reduction tests. This simplified, repeated treatment method should be investigated further since it is quicker, and this could make it possible to test larger farm samplings. 相似文献
12.
J A van Wyk G F Bath H M Gerber R M Alves 《The Onderstepoort journal of veterinary research》1990,57(2):119-122
A strain of Trichostrongylus colubriformis from Nottingham Road, in Natal, was found to be solidly resistant to levamisole and morantel at the recommended dose levels. Untreated control sheep in fact harboured fewer worms at slaughter than either of the 2 treated groups. In contrast, the benzimidazoles and ivermectin were more than 99.9% effective against this worm strain. The possible implications of escalating resistance to anthelmintics in the gastrointestinal nematodes of sheep are discussed. 相似文献
13.
A strain of Haemonchus contortus resistant to the benzimidazoles, ivermectin and salicylanilides was used to study the effect of exposure to ivermectin or oxfendazole on the number of eggs produced by adult female parasites. After anthelmintic administration there was a reduction in the faecal egg count of the infected lambs. Ivermectin caused a reduction in the number of eggs within adult parasites for up to 72 hours but this returned to higher than pre-treatment levels at 168 hours after treatment. After oxfendazole treatment there was an increase in the number of eggs stored in the adult parasites at 24 hours and then a significant reduction in the number of eggs for over 168 hours. This suggested that both ivermectin and oxfendazole have a deleterious effect on the reproductive potential of female H contortus although the parasites are resistant to these drugs. These results confirm the importance of allowing up to 10 days to elapse between the time of administration of an anthelmintic and the collecting of faecal samples when using the faecal egg count reduction test to identify anthelmintic resistance, especially when using benzimidazoles. The more prolonged effect on fecundity produced by oxfendazole may reflect the antimitotic action of the benzimidazole anthelmintics. 相似文献
14.
The resistance level of Haemonchus contortus was studied on a farm where benzimidazole resistance had been detected in 1980 and where, since 1982, only levamisole had been used for worm control. Egg development tests gave LD50 values of 0.18, 0.19 and 0.21 microgram ml-1 thiabendazole for samples taken from ewes in 1988 compared with 0.21 microgram ml-1 in 1981. Studies on sheep experimentally infected with larvae cultured from the faeces of these ewes confirmed the continued resistance of H contortus to benzimidazoles, and demonstrated the absence of benzimidazole resistance in other nematode species together with the susceptibility of all species to levamisole. 相似文献
15.
N. J. BARTON B. L. TRAINOR J. S. URIE† J. W. ATKINS† M. F. S. PYMANS‡ I. R. WOLSTENCROFT§ 《Australian veterinary journal》1985,62(7):224-227
Cases of anthelmintic resistance on 3 goat farms in Gippsland were investigated. On the first farm Haemonchus contortus, Trichostrongylus colubriformis and Ostertagia (Teladorsagia) circumcincta were found to be resistant to fenbendazole, but the first 2 species were fully susceptible to levamisole. On the second farm a population of T. colubriformis, resistant to concurrent full doses of levamisole and a benzimidazole, was found to retain this resistance when transferred to sheep. On the third farm, heavy mortality due to Ostertagia and Trichostrongylus spp burdens was arrested only by the use of concurrent full doses of levamisole and oxfendazole; no single anthelmintic was found to be effective. A disturbing rise in the incidence of clinical helminthiosis, often accompanied by anthelmintic resistance, occurred on goat farms in Gippsland early in 1984. 相似文献
16.
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
17.
Bauer C 《DTW. Deutsche tier?rztliche Wochenschrift》2001,108(2):49-50
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
18.
Swarnkar CP Sanyal PK Singh D Khan FA Bhagwan PS 《Tropical animal health and production》2001,33(4):305-312
Monitoring anthelmintic resistance in strongyle nematodes by the faecal egg count reduction test and a commercial larval development assay on an organized sheep farm in the semi-arid area of Rajasthan revealed the emergence of resistance to benzimidazoles and rafoxanide and a potential risk of the development of levamisole/tetramisole resistance. A benzimidazole/levamisole combination, avermectins and closantel were each found to be efficacious. 相似文献
19.
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. 相似文献
20.
Borgsteede F Verkaik J Moll L Dercksen D Vellema P Bavinck G 《Tijdschrift voor diergeneeskunde》2010,135(21):782-785
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