Efeitos da lectina de Canavalia marítima (CONM) sobre parâmetros reprodutivos de fêmeas de Rhipicephalus sanguineus e Rhipicephalus microplus

Abstract

The indiscriminate use of synthetic acaricides has contributed to the emergence of resistance in ticks of the genus Rhipicephalus, compromising treatment efficacy. In this context, there is a growing interest in bioproducts with antiparasitic activity. Among these, plant lectins have emerged as promising alternatives for parasite control. This study aimed to evaluate the effect of the ConM lectin, purified from Canavalia maritima seeds, on reproductive parameters of Rhipicephalus sanguineus and Rhipicephalus microplus females. ConM was purified by affinity chromatography using a Sephadex G-50 column, and purity was confirmed by SDS-PAGE. Bioassays were performed at concentrations of 0.5, 0.75, 1.0, and 1.25 mg·mL−1, evaluating engorged female weight and mortality, egg mass weight, and hatching percentage, to calculate the Egg Production Index (EPI), Oviposition Reduction, Reproductive Efficiency Index (REI), and Product Efficacy (PE). Exposure of females to ConM resulted in significant reductions in egg mass weight, especially at higher concentrations (1.0 and 1.25 mg·mL−1). For R. sanguineus, mean values ranged from 0.113 ± 0.045 g to 0.119 ± 0.048 g, significantly lower than the control group (0.179 ± 0.033 g) (p < 0.05). In R. microplus, egg mass reductions were observed at 0.066 ± 0.023 g and 0.060 ± 0.026 g at the same concentrations (p < 0.05). Regarding mortality, a rate of 6.7% was recorded in females of both species treated with 1.0 and 1.25 mg·mL−1 of ConM. Product efficacy exhibited a dose-dependent pattern, reaching 86% in R. sanguineus and 88–90% in R. microplus at the highest concentrations. Statistical analysis demonstrated a strong correlation between lectin concentration and oviposition reduction, with Spearman's ρ coefficients of 0.702 for R. sanguineus and 0.752 for R. microplus. Similarly, the correlation between lectin concentration and product efficacy showed values of 0.807 for R. sanguineus and 0.749 for R. microplus, supporting a dose-response relationship. The median inhibitory concentration (IC50) indicated higher toxicity of ConM toward R. microplus (0.41 mg·mL−1) compared to R. sanguineus (0.86 mg·mL−1), corroborating the other evaluated parameters and reinforcing the potential of this lectin as an acaricidal agent. The acaricidal activity of ConM against Rhipicephalus species represents a promising approach for controlling these ectoparasites. The results highlight the potential of ConM as a natural acaricide, with significant effects on fertility and egg viability, standing out as a sustainable alternative for tick management. However, structural and functional studies, including molecular

characterization of these interactions, are essential to validate the true potential of ConM as a plant-based acaricidal agent.