University of Neuchâtel, Institute of Biology, Laboratory of Parasitology, 2000 Neuchâtel, Switzerland.
Vet Parasitol. 2011 Dec 15;182(2-4):269-80. doi: 10.1016/j.vetpar.2011.06.004. Epub 2011 Jun 13.
In this article we present a new bioassay to assess the resistance status of ticks to acaricides. The Larval Tarsal Test (LTT) is a sensitive, highly time-effective in vitro test. It allows the investigation of a large number of compounds and doses on the cattle tick Rhipicephalus (Boophilus) microplus in a short period of time. The ability of the LTT to assess the lethal concentration at 50% mortality (LC(50)) and resistance ratios (RRs) of a susceptible and a resistant R. microplus strain was compared with the FAO-recommended Larval Packet Test (LPT). Representative compounds of the carbamate, organophosphate (OP), synthetic pyrethroid (SP), formamidine (FOR), macrocyclic lactone and pyrazole classes were used for this comparison. The resistance status against OP, SP and FOR of the resistant R. microplus strain was confirmed in vivo. The LTT resulted in resistance ratios comparable to those obtained with the LPT. However, the lethal concentrations were up to 150-fold lower in the LTT than in the LPT. The advantage of the LTT is to simplify the methodology by avoiding the handling of larvae and using multi-well plates. The LTT is therefore a suitable test for the assessment of the level of resistance of R. microplus and is very promising to evaluate the resistance profile of field strains. Additionally, the LTT is also suitable to test other ixodid species.
在本文中，我们提出了一种新的生物测定法来评估蜱对杀蜱剂的抗性状况。幼虫跗节测试（LTT）是一种灵敏、高度有效的体外测试。它允许在短时间内对大量化合物和剂量进行研究，包括牛蜱（Boophilus）微小亚种。将 LTT 评估敏感和抗性 R. microplus 菌株的致死浓度 50%（LC(50)）和抗性比值（RRs）的能力与粮农组织推荐的幼虫包测试（LPT）进行了比较。使用了氨基甲酸酯、有机磷（OP）、合成拟除虫菊酯（SP）、脒类（FOR）、大环内酯和吡唑类的代表性化合物进行了比较。体内证实了抗性 R. microplus 菌株对 OP、SP 和 FOR 的抗性状况。LTT 得出的抗性比值与 LPT 相似。然而，LTT 的致死浓度比 LPT 低 150 倍。LTT 的优势在于通过避免幼虫处理和使用多孔板简化了方法。因此，LTT 是评估 R. microplus 抗性水平的合适测试方法，并且非常有希望评估田间菌株的抗性谱。此外，LTT 也适用于测试其他硬蜱物种。
