Vijayasarathi M K, Sreekumar C, Venkataramanan R, Raman M
Madras Veterinary College (TANUVAS), Vepery, Chennai, 600 007, Tamil Nadu, India.
Postgraduate Research Institute in Animal Sciences, Kattupakkam, Kanchipuram, 603 203, Tamil Nadu, India.
Trop Anim Health Prod. 2016 Oct;48(7):1455-62. doi: 10.1007/s11250-016-1117-3. Epub 2016 Aug 10.
Anthelmintic resistance (AR) status in Madras Red sheep from selected field flocks of a government funded scheme, covered by regular, sustained anthelmintic treatment for more than 10 years was determined. Parameters such as fecal egg count reduction test (FECRT), larval paralysis assay (LPA), and allele-specific-PCR (AS-PCR) were used to test the efficacy of fenbendazole, tetramisole, and ivermectin at recommended doses, in two seasons. Sheep belonging to non-beneficiary farmers were used as controls. Mean FECRT values of beneficiary group during winter and summer seasons were 77.77 and 76.04, 93.65 and 92.12, and 95.37 and 98.06 %, respectively, for fenbendazole, tetramisole, and ivermectin. In the non-beneficiary groups, the corresponding values were 74.82 and 81.09 %, 96.05 and 97.40 %, and 97.26 and 98.23 %, respectively. The results revealed resistance to fenbendazole, suspect resistance to tetramisole and susceptibility to ivermectin in beneficiary flock. In non-beneficiary flock, while resistance was noticed against fenbendazole, both tetramisole and ivermectin were effective. FECR values were found to be significantly different between beneficiary and non-beneficiary groups against tetramisole. The results of LPA confirmed this finding, as 50 % of the Haemonchus contortus larvae were paralyzed at the concentration of 0.0156 μg/ml in the beneficiary group, while those of non-beneficiary groups required lower concentrations of 0.0078 μg/ml. AS-PCR revealed the predominance of heterozygous susceptible population of H. contortus in the beneficiary group. In this study, resistance to fenbendazole was confirmed in both the beneficiary and non-beneficiary groups and this could be attributed to frequent use of benzimidazoles as seen from the deworming records. Emergence of tetramisole resistance was detected in the beneficiary group, where the drug was used continuously for 4 years. Ivermectin was found to be effective in all the flocks. It is recommended that the practice of routine deworming of three to four times a year should be avoided, as it can lead to emergence of anthelmintic resistance.
对政府资助项目选定野外羊群中马德拉斯红羊的驱虫抗性（AR）状况进行了测定，这些羊群接受定期、持续驱虫治疗超过10年。采用粪便虫卵计数减少试验（FECRT）、幼虫麻痹试验（LPA）和等位基因特异性PCR（AS-PCR）等参数，在两个季节测试了推荐剂量的芬苯达唑、四咪唑和伊维菌素的疗效。将非受益农户的羊作为对照。受益组在冬季和夏季，芬苯达唑、四咪唑和伊维菌素的平均FECRT值分别为77.77%和76.04%、93.65%和92.12%、95.37%和98.06%。在非受益组中，相应的值分别为74.82%和81.09%、96.05%和97.40%、97.26%和98.23%。结果显示受益羊群对芬苯达唑有抗性，对四咪唑有疑似抗性，对伊维菌素有敏感性。在非受益羊群中，虽然发现对芬苯达唑有抗性，但四咪唑和伊维菌素均有效。发现受益组和非受益组在四咪唑方面的FECR值有显著差异。LPA的结果证实了这一发现，因为在受益组中，0.0156μg/ml浓度时50%的捻转血矛线虫幼虫被麻痹，而非受益组则需要0.0078μg/ml的较低浓度。AS-PCR显示受益组中捻转血矛线虫杂合易感群体占主导。在本研究中，受益组和非受益组均证实对芬苯达唑有抗性，这可能归因于从驱虫记录中可以看出的苯并咪唑类药物的频繁使用。在受益组中检测到四咪唑抗性的出现，该组连续4年使用该药物。发现伊维菌素在所有羊群中均有效。建议避免每年进行三到四次的常规驱虫做法，因为这可能导致驱虫抗性的出现。
