Programa de Pós-graduação em Ciências Veterinárias da Universidade Federal Rural do Rio de Janeiro, BR 465, Km 7, Seropédica, RJ 23897-000, Brazil.
Departamento de Patologia, Universidade Federal do Maranhão, Av. dos Portugueses, 1966, Bacanga, São Luís, MA 65080-805, Brazil.
Vet Parasitol. 2022 Oct;310:109787. doi: 10.1016/j.vetpar.2022.109787. Epub 2022 Aug 20.
This study evaluated the acaricidal activity of thymol and carvacrol on Rhipicephalus microplus populations with different resistance profiles and investigated the synergistic effect of combinations of these monoterpenes with cypermethrin. The adult immersion test (AIT) was used to characterize the susceptibility of tick populations (45 field populations) to synthetic acaricides: deltamethrin, amitraz and chlorfenvinphos. The larval packet test (LPT) was used to determine the LC values for thymol (25 tick populations) and carvacrol (20 tick populations). The susceptible strain Porto Alegre (POA) was used as a reference for calculating the resistance ratio (RR). Subsequently, larval immersion tests (LIT) were performed with combinations of cypermethrin with thymol or carvacrol to assess a synergistic effect. In the AIT, deltamethrin showed efficacy > 90% in one (2.2%) population tested (mean: 12.1 and 11.1 for populations 1-25 and 26-40, respectively), whereas amitraz and chlorfenvinphos showed efficacy > 90% for two (4.4%) populations (mean: 61.3 and 47.3 for populations 1-25 and 26-40, respectively) and eight (17.7%) populations (mean: 69.7 and 59.7 for populations 1-25 and 26-40, respectively). In the LPT, the LC values for thymol and carvacrol varied from 0.67 to 2.12 mg/mL and 0.55-3.21 mg/mL, with an average LC for populations of 1.49 and 1.75 mg/mL, respectively. For thymol, no resistance was observed in any of the populations, values of RR > 1.5. There was no correlation between the LC values for thymol and the efficacy of the chemical acaricides tested. Regarding carvacrol, for only one tick population had the value of RR > 1.5, indicating an incipient resistance. No correlation was observed between the LC values for carvacrol and the efficacy of tested acaricides. The combination of thymol and carvacrol with cypermethrin showed a synergistic effect in the resistant population (Jaguar - thymol 4.19 and carvacrol 3.67), and no synergistic interaction were showed in the susceptible population. Answering the questions we conclude that: 1 - The comparison between the LC values for thymol and carvacrol in field populations and the susceptible strain POA suggests the absence of cross-resistance (ticks and terpenes), and the differences between the LC values for thymol and carvacrol in the different R. microplus populations are inherent to the characteristics of each population tested; 2 - the combination of thymol or carvacrol with cypermethrin showed a synergistic effect with different activity according to the population of ticks.
本研究评估了百里香酚和香芹酚对具有不同抗药性特征的无角血蜱种群的杀蜱活性，并研究了这些单萜与氯菊酯组合的协同作用。采用成虫浸浴试验（AIT）来描述 45 个田间种群对合成杀蜱剂（溴氰菊酯、甲脒和氯菊酯）的敏感性。采用幼虫包囊试验（LPT）测定百里香酚（25 个蜱种群）和香芹酚（20 个蜱种群）的 LC 值。将易感品系 Porto Alegre（POA）用作计算抗性比（RR）的参考。随后，采用氯菊酯与百里香酚或香芹酚的组合进行幼虫浸浴试验（LIT），以评估协同作用。在 AIT 中，溴氰菊酯在一个（2.2%）测试种群中表现出 >90%的功效（种群 1-25 和 26-40 的平均值分别为 12.1 和 11.1），而甲脒和氯菊酯在两个（4.4%）种群中表现出 >90%的功效（种群 1-25 和 26-40 的平均值分别为 61.3 和 47.3）和八个（17.7%）种群（种群 1-25 和 26-40 的平均值分别为 69.7 和 59.7）。在 LPT 中，百里香酚和香芹酚的 LC 值范围为 0.67-2.12mg/mL 和 0.55-3.21mg/mL，种群的平均 LC 值分别为 1.49 和 1.75mg/mL。对于百里香酚，没有观察到任何种群出现 RR>1.5 的抗性。百里香酚的 LC 值与测试的化学杀蜱剂的功效之间没有相关性。关于香芹酚，只有一个蜱种群的 RR>1.5，表明出现了初始抗性。香芹酚的 LC 值与测试杀蜱剂的功效之间没有观察到相关性。百里香酚和香芹酚与氯菊酯的组合在抗性种群（Jaguar-百里香酚 4.19 和香芹酚 3.67）中表现出协同作用，而在敏感种群中则没有表现出协同相互作用。通过回答问题，我们得出以下结论：1- 田间种群和易感品系 POA 中百里香酚和香芹酚的 LC 值比较表明不存在交叉抗性（蜱和萜烯），并且不同无角血蜱种群中百里香酚和香芹酚的 LC 值差异是种群特有的；2- 百里香酚或香芹酚与氯菊酯的组合具有不同的活性，根据蜱种群表现出协同作用。
