Susceptibilidad in vitro de rhipicephalus microplus frente a mezclas ixodicidas de uso ganadero en Ecuador In vitro susceptibility of rhipicephalus microplus to ixodicide mixtures used in livestock production in Ecuador

Abstract

Acaricide resistance in Rhipicephalus microplus is an increasing problem in tropical livestock systems due to the intensive, continuous, and non-rotational use of ixodicides, which reduces the effectiveness of control programs and justifies the need to evaluate the biological response of the ectoparasite. The objective of this study was to determine the in vitro susceptibility of R. microplus to two commercial acaricide combinations: Flumethrin + Fluazuron (TA) and Fipronil + Ivermectin (TB). An inductive–deductive and analytical–synthetic methodological approach was applied to interpret the evidence, complemented by an experimental laboratory method based on dose–response assessment. A total of 360 adult ticks were collected from cattle in La Piñuela (Canuto, Manabí, Ecuador). The adult immersion test was performed, exposing individuals to five concentrations (0.0125–0.100% and pure concentration) of each treatment. Mortality was recorded after 24 hours of incubation under controlled conditions. The comparative analysis followed a completely randomized design, analysis of variance, and Tukey’s test (p < 0.05). Results showed that treatment TA significantly increased mortality at concentrations of 0.050% and 0.100%, forming the group with the highest efficacy. In contrast, TB concentrations presented low mortality rates with no statistical differences among them. It is concluded that R. microplus exhibits reduced susceptibility to Fipronil + Ivermectin, whereas Flumethrin + Fluazuron maintains superior dose-dependent efficacy, highlighting the need to strengthen resistance surveillance and promote rotational control programs.