University of Neuchâtel, Institute of Biology, Laboratory of Parasitology, 2000 Neuchâtel, Switzerland.
Vet Parasitol. 2013 Jan 31;191(3-4):323-31. doi: 10.1016/j.vetpar.2012.09.011. Epub 2012 Sep 15.
Acaricide resistance of the cattle tick Rhipicephalus (Boophilus) microplus is widespread in most of the countries where this parasite is present. Bioassays are used to diagnose the level and pattern of resistance in tick populations. In the present study, we describe a detailed protocol of the Larval Tarsal Test (LTT) using simplified equipment and data on the resistance of 17 tick field populations originating from 5 Brazilian states. Nine acaricidal compounds from 5 major classes were tested: organophosphates (OP), synthetic pyrethroids (SP), macrocyclic lactones (ML), phenylpyrazols (PYZ) and amidines. For comparison, four of the tick populations were also tested with the Larval Packet Test (LPT) with one compound per class. The most common resistances were to SP, amitraz and OP, with frequencies of 94%, 88% and 82%, respectively. Resistance to PYZ was also found to be widespread (65%), suggesting a rapid development of fipronil resistance in Brazil. One case of ML resistance and 2 cases of suspected ML resistance were identified with the LTT. The LTT led to higher resistance ratios to all compounds than the LPT, reflecting its high sensitivity to detect resistance. Finally, the LTT allowed testing a larger number of compounds and doses with reduced labour in comparison to the LPT and turned out to be a reliable bioassay to detect resistance in field populations.
牛蜱（Boophilus）微小牛蜱的杀蜱剂耐药性在大多数存在这种寄生虫的国家都很普遍。生物测定用于诊断蜱种群的耐药水平和模式。在本研究中，我们描述了使用简化设备和来自巴西 5 个州的 17 个蜱田间种群的耐药数据进行幼虫跗节测试（LTT）的详细方案。测试了来自 5 个主要类别的 9 种杀蜱化合物：有机磷（OP）、合成拟除虫菊酯（SP）、大环内酯（ML）、苯基吡唑（PYZ）和脒。为了比较，还使用每个类别的一种化合物对其中的 4 个蜱种群进行了幼虫包测试（LPT）。最常见的耐药性是对 SP、阿米曲唑和 OP，分别为 94%、88%和 82%。还发现 PYZ 的耐药性也很普遍（65%），表明巴西的氟虫腈耐药性迅速发展。LTT 鉴定出 1 例 ML 耐药和 2 例疑似 ML 耐药。与 LPT 相比，LTT 导致所有化合物的耐药比值更高，反映了其检测耐药性的高灵敏度。最后，与 LPT 相比，LTT 允许测试更多数量的化合物和剂量，并且减少了劳动力，事实证明它是一种可靠的生物测定法，可以检测田间种群的耐药性。
