Potential for misinterpretation of the faecal egg count reduction test for levamisole resistance in gastrointestinal nematodes of sheep
Potential for misinterpretation of the faecal egg count reduction test for levamisole resistance in gastrointestinal nematodes of sheep
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DOI：
10.1016/0304-4017(95)00874-8
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发表时间：
1996-04-01
影响因子：
2.6
通讯作者：
Hunt, KR
中科院分区：
文献类型：
--
作者：
Grimshaw, WTR;Hong, C;Hunt, KR
粪卵减少试验(FECRT)被广泛用于评估羊群胃肠道线虫是否存在左旋咪唑耐药，然而，在最近的一项研究中，FECRT似乎错误地指示了左旋咪唑耐药的存在。对这一结果的一个可能的解释是，驱虫剂未能完全消除左旋咪唑敏感菌株的所有未成熟阶段，这些菌株随后发育成产卵成虫，并在FECRT中给出了误导性的结果。人工感染对左旋咪唑敏感、苯并咪唑耐药株的环斑血吸虫、螺旋血吸虫和环状毛圆线虫，在感染后2~10日龄用左旋咪唑治疗，对这三种幼虫的有效率分别为84%、88%和98%。阳性对照伊维菌素对这三种病原菌均有99%以上的防治效果。左旋咪唑治疗后11天和20天采集的样本的粪卵计数减少率分别为80%和78%。这些结果表明，由于未成熟阶段的成熟，尽管没有对左旋咪唑耐药的胃肠道线虫株，但基于治疗后11天或更长时间的粪卵计数的FECRT可能会得出左旋咪唑耐药的结果。
The faecal egg count reduction rest (FECRT) is widely used to assess the presence or absence of levamisole resistance in gastrointestinal nematodes in sheep flocks, However, in a recent study the FECRT appeared to falsely indicate the presence of levamisole resistance. One possible explanation for this result could have been that the anthelmintic failed to completely remove all immature stages of levamisole-susceptible strains, which then developed into egg laying adults and gave misleading results in the FECRT. Artificial infection of lambs with levamisole-susceptible, benzimidazole-resistant strains of Ostertagia circumcincta, Haemonchus contortus and Trichostrongylus colubriformis was followed by treatment with levamisole when the infections were between 2 and 10 days old; Levamisole was 84%, 88% and 98% effective against these immature stages of the three species, respectively. The positive control, ivermectin, was more than 99% effective against all three species. The percentage faecal egg count reduction on samples taken 11 and 20 days post-treatment with levamisole was 80% and 78%, respectively. These results demonstrate that, due to the maturation of immature stages, the FECRT based on faecal egg counts taken 11 or more days after treatment may give results indicative of levamisole resistance despite the absence of levamisole resistant strains of gastrointestinal nematodes.