University of Neuchâtel, Institute of Biology, Laboratory of Parasitology, Neuchâtel 2000, Switzerland ; Novartis Animal Health Research Center, St. Aubin (FR) 1566, Switzerland.
USDA-ARS Knipling-Bushland U.S. Livestock Insects Research Laboratory, Kerrville, TX 78028, USA.
Int J Parasitol Drugs Drug Resist. 2012 Sep 3;2:216-24. doi: 10.1016/j.ijpddr.2012.08.001. eCollection 2012 Dec.
Resistance to synthetic pyrethroids (SP) in the cattle tick Rhipicephalus (Boophilus) microplus is widespread throughout its distribution area. Three single nucleotide substitutions identified in Domains II and III of the sodium channel gene of R. (B.) microplus are known to be associated with target site pyrethroid resistance. We developed a multiplex PCR using allele-specific primers to amplify wild type or mutated genotypes of the three mutations simultaneously. This assay was used to screen tick samples originating from Brazil, Argentina, Mexico, South Africa and Australia whose phenotype to flumethrin and cypermethrin had been determined by the use of the Larval Tarsal test (LTT) or the Larval Packet Test (LPT). These mutations were found to have distinct geographical distributions and result in different resistance phenotypes. The L64I Domain II mutation conferring resistance to several SP compounds was found in all the Brazilian, Argentinean and Australian populations and in one South African population, with frequencies between 38% and 100% in flumethrin and cypermethrin resistant populations. In contrast, this mutation was not found in samples from Mexico, while the Domain III mutation was found exclusively in this country. The G72V Domain II flumethrin-specific mutation was found in a single Australian population, with a very low resistant allele frequency (3%). The homozygous resistant RR genotype of the L64I Domain II mutation correlated significantly with the survival rates at the discriminating doses of flumethrin and cypermethrin. This survey shows the widespread distribution of the L64I Domain II mutation and provides evidence of its geographic separation from the Domain III mutation.
抗合成拟除虫菊酯（SP）的牛蜱（Rhipicephalus）（Boophilus）微丝虫在其分布区内广泛存在。已知钠离子通道基因的 II 区和 III 区的三个单核苷酸取代与靶位拟除虫菊酯抗性有关。我们使用等位基因特异性引物开发了一种多重 PCR，可同时扩增三种突变的野生型或突变基因型。该测定法用于筛选源自巴西，阿根廷，墨西哥，南非和澳大利亚的蜱样本，其对氟氯氰菊酯和氯氰菊酯的表型已通过幼虫跗节试验（LTT）或幼虫包测试（LPT）确定。这些突变具有明显的地理分布，并导致不同的抗性表型。赋予对几种 SP 化合物抗性的 L64I 区 II 突变存在于所有巴西，阿根廷和澳大利亚人群以及南非的一个人群中，在氟氯氰菊酯和氯氰菊酯抗性人群中，其频率在 38％至 100％之间。相比之下，在来自墨西哥的样本中未发现该突变，而在该国家中仅发现了 III 区突变。在一个澳大利亚人群中发现了 L64I 区 II 氟氯氰菊酯特异性突变的 G72V 突变，其抗性等位基因频率非常低（3％）。 L64I 区 II 突变的纯合抗性 RR 基因型与氟氯氰菊酯和氯氰菊酯的区分剂量的存活率显着相关。该调查显示了 L64I 区 II 突变的广泛分布，并提供了其与 III 区突变的地理分离的证据。
