Ardelli B F, Prichard R K
Institute of Parasitology, Macdonald Campus, McGill University, 21 111 Lakeshore Road, Ste. Anne de Bellevue, Quebec H9X 3V9, Canada.
Trans R Soc Trop Med Hyg. 2007 Dec;101(12):1223-32. doi: 10.1016/j.trstmh.2005.03.019. Epub 2007 Sep 29.
In some trichostrongyloid nematodes, the early stages of ivermectin (IVM) resistance have been characterized by a shift in allele frequency and reduced polymorphism at loci of P-glycoprotein genes, glutamate-gated chloride channel genes and gamma-aminobutyric acid receptor genes. Mass treatment with IVM is an integral component of the onchocerciasis control programmes. Genetic variation of an Onchocerca volvulus ABC transporter homologue (OvABC-3) from several populations in Africa was examined to determine whether an association exists between alleles of this gene and IVM treatment. Allelic variation in a non-treated population from Ghana showed this locus to be highly polymorphic. However, variability was reduced in IVM-treated populations. chi2 analysis of polymorph frequencies showed significant differences between untreated and treated samples collected in Ghana in 1999. There was less variability in this gene in samples collected in 2002 compared with the 1999 samples. In some treated populations, there appeared to be selection on OvABC-3-C. The observed reduction in variability could be expected in a control programme in which prevalence and intensity of infections are markedly reduced after years of vector control and IVM distribution. The reduction in polymorphism may not in itself indicate that these O. volvulus are IVM resistant, although it could indicate that selection for resistance is occurring.
在一些毛圆科线虫中，伊维菌素（IVM）抗性的早期阶段表现为P-糖蛋白基因、谷氨酸门控氯离子通道基因和γ-氨基丁酸受体基因位点的等位基因频率变化以及多态性降低。IVM群体治疗是盘尾丝虫病控制项目的一个重要组成部分。对来自非洲几个群体的盘尾丝虫ABC转运蛋白同源物（OvABC-3）的遗传变异进行了检测，以确定该基因的等位基因与IVM治疗之间是否存在关联。来自加纳的一个未治疗群体的等位基因变异表明该位点具有高度多态性。然而，在接受IVM治疗的群体中变异性降低。对多态频率的chi2分析显示，1999年在加纳采集的未治疗样本和治疗样本之间存在显著差异。与1999年的样本相比，2002年采集的样本中该基因的变异性较小。在一些治疗群体中，似乎对OvABC-3-C存在选择。在经过多年病媒控制和IVM分发后感染率和感染强度显著降低的控制项目中，可以预期会出现观察到的变异性降低。多态性的降低本身可能并不表明这些盘尾丝虫对IVM具有抗性，尽管这可能表明正在发生抗性选择。
