Le Jambre L F
CSIRO Division of Animal Health, Pastoral Research Laboratory, Armidale, NSW, Australia.
Acta Trop. 1993 May;53(3-4):331-43. doi: 10.1016/0001-706x(93)90038-d.
The application of molecular techniques such as restriction length polymorphisms, mitochondrial DNA analysis and sequence tagged microsatellite sites to determine the amount of genetic variation and population structure of trichostrongylid parasites of domestic ruminants is examined. Information already provided by these techniques indicates that the parasite populations have a large amount of genetic variation and that gene flow between populations is greater than previously expected. The implications are that parasites can rapidly respond to selection by either anthelmintics or genetically resistant hosts. Advance warning of the response to selection can be obtained, even when the trait under selection is unknown, by measuring changes in the DNA polymorphisms of the parasite populations. Resistance to the benzimidazoles in the trichostrongylids now appears to be dependent on changes at two beta-tubulin loci. The first stage in the development of benzimidazole (BZ) resistance involves selection for an allele encoding a resistant form of isotype 1 beta-tubulin. A higher level of resistance is achieved with the selection of the gene encoding isotype 2 beta-tubulin. Techniques that maintain BZs in the host for extended periods of time may select for the higher level of resistance. A DNA assay to test this hypothesis is proposed.
研究了诸如限制性片段长度多态性、线粒体DNA分析和序列标签微卫星位点等分子技术在确定家养反刍动物毛圆线虫寄生虫的遗传变异量和种群结构方面的应用。这些技术已经提供的信息表明，寄生虫种群具有大量的遗传变异，而且种群之间的基因流动比以前预期的要大。这意味着寄生虫可以通过驱虫药或具有遗传抗性的宿主迅速对选择作出反应。即使在选择的性状未知的情况下，通过测量寄生虫种群DNA多态性的变化，也可以获得对选择反应的提前预警。毛圆线虫对苯并咪唑的抗性现在似乎取决于两个β-微管蛋白基因座的变化。苯并咪唑（BZ）抗性发展的第一阶段涉及选择编码抗性形式的1型β-微管蛋白的等位基因。通过选择编码2型β-微管蛋白的基因可实现更高水平的抗性。在宿主体内长时间维持BZs的技术可能会选择出更高水平的抗性。提出了一种DNA检测方法来验证这一假设。
