Sarli Macarena, Torrents Jorgelina, Toffaletti José R, Morel Nicolás, Nava Santiago
Instituto de Investigación de la Cadena Láctea (IdICaL) (INTA-CONICET), Instituto Nacional de Tecnología Agropecuaria, Estación Experimental Agropecuaria Rafaela (INTA E.E.A. Rafaela), Ruta 34 Km 227, CP 2300 Rafaela, Santa Fe, Argentina.
Instituto de Investigación de la Cadena Láctea (IdICaL) (INTA-CONICET), Instituto Nacional de Tecnología Agropecuaria, Estación Experimental Agropecuaria Rafaela (INTA E.E.A. Rafaela), Ruta 34 Km 227, CP 2300 Rafaela, Santa Fe, Argentina; Facultad de Ciencias Veterinarias, Universidad Nacional del Litoral, Esperanza, Santa Fe, Argentina.
Res Vet Sci. 2023 Nov;164:105040. doi: 10.1016/j.rvsc.2023.105040. Epub 2023 Oct 1.
The aim of this work was to comparatively evaluate the evolution of resistance in Rhipicephalus microplus tick populations exposed to successive treatments with monodrug-based formulations and combinations of them in the same commercial formulation. Thirty-six heifers, naturally infested with R. microplus, were divided into three groups (G) and subjected to three successive treatments, on days 0 (Nov-2021), 43 (Jan-2022) and 78 (Feb-2022), with the following formulations: I) ivermectin 3.15% (Ivomec Gold®) (GI), II) fipronil 1% (Ectoline®) (GII) and III) a combination of fipronil 2% and ivermectin 1% (Vaquero®) (GIII). From Nov-2021 to Dec-2022, counts of R. microplus were periodically performed to evaluate the tick infestation. Engorged females were collected at the beginning and end of the trial to determine the evolution of tick resistance to ivermectin and fipronil by in vitro bioassays. At the end of trial, GII and GIII had higher tick counts (39.18 ± 11.88 and 38.33 ± 14.31, respectively) than group I (5.11 ± 6.24) (P<0.05). The in vitro results shows that the resistance ratio (RR) values after the treatments were higher for fipronil (5.584 and 5.649 for GII and GIII, respectively) than for ivermectin (1.165 and 1.088 for GI and GIII, respectively). In the group treated with the combination (GIII), the RR increased for both drugs simultaneously. These results suggest that the successive use of drug combinations could exacerbate the problem of multi-resistance of R. microplus to chemical acaricides.
本研究的目的是比较评估微小牛蜱种群在接受基于单一药物的制剂以及相同商业制剂中它们的组合的连续处理后的抗药性演变情况。36头自然感染微小牛蜱的小母牛被分为三组（G组），并在2021年11月0日、2022年1月43日和2022年2月78日接受了三次连续处理，使用以下制剂：I）3.15%伊维菌素（伊维菌素金®）（GI组），II）1%氟虫腈（埃托林®）（GII组），III）2%氟虫腈和1%伊维菌素的组合（牧牛工®）（GIII组）。从2021年11月到2022年12月，定期对微小牛蜱进行计数以评估蜱虫感染情况。在试验开始和结束时收集饱血雌蜱，通过体外生物测定法确定蜱虫对伊维菌素和氟虫腈的抗药性演变情况。试验结束时，GII组和GIII组的蜱虫计数（分别为39.1±11.88和38.33±14.31）高于I组（5.11±6.24）（P<0.05）。体外结果表明，处理后氟虫腈的抗药率（RR）值（GII组和GIII组分别为5.584和5.649）高于伊维菌素（GI组和GIII组分别为1.165和1.088）。在接受组合治疗的组（GIII组）中，两种药物的RR同时增加。这些结果表明，连续使用药物组合可能会加剧微小牛蜱对化学杀螨剂的多重抗药性问题。
