Amblyomma sculptum is a species of tick in the family Ixodidae, with equids and capybaras among its preferred hosts. In this study, the acaricidal activity of the essential oil (EO) from Piper aduncum and its main component, Dillapiole, were evaluated against larvae of A. sculptum to establish lethal concentration values and assess the effects of these compounds on tick enzymes. Dillapiole exhibited slightly greater activity (LC₅₀ = 3.38 mg/mL; 95% CI = 3.24 to 3.54) than P. aduncum EO (LC₅₀ = 3.49 mg/mL; 95% CI = 3.36 to 3.62) against ticks. The activities of α-esterase (α-EST), β-esterase (β-EST), and glutathione-S-transferase (GST) enzymes in A. sculptum larvae treated with Dillapiole showed a significant increase compared to the control at all concentrations (LC₅, LC₂₅, LC₅₀ and LC₇₅), similar results were obtained with P. aduncum EO, except for α-EST, which did not differ from the control at the highest concentration (LC₇₅). The results of the acetylcholinesterase (AChE) activity show an increase in enzyme activity at the two lower concentrations (LC₅ and LC₂₅) and a reduction in activity at the two higher, lethal concentrations (LC₅₀ and LC₇₅) compared to the control. These results suggest potential mechanisms of action for these natural acaricides and can provide guidance for the future development of potential plant-derived formulations.

This study evaluated the repellent activity of DEET, eugenol, methyl eugenol, 1,8-cineole, and their combinations against Amblyomma sculptum nymphs through laboratory and field tests. Initially, the botanical compounds were tested individually in Petri dish assays to assess repellent activity over various intervals (1 min to 168 h) at concentrations of 2%. Eugenol and methyl eugenol exhibited the highest average repellent percentages (60 to 90%), with significant effects (p < 0.05) across most evaluation periods, in contrast to 1,8-cineole. Therefore, eugenol and methyl eugenol were selected for combination testing with DEET. The combinations of 7% DEET + 1% eugenol and 7% DEET + 2% methyl eugenol showed the best results, with average repellent efficacy exceeding 85%. The first combination was selected for field evaluation. In this test, volunteers wore treated socks and walked for two hours in a naturally infested area. A significant reduction (p < 0.05) in the number of ticks recovered from the socks was observed in the 7% DEET and 7% DEET + 1% eugenol treatments, with efficacies of 82.5% and 88.5%, respectively, after 120 min. Isolated eugenol showed limited field efficacy, with significant repellent activity (p < 0.05) lasting only 20 min. The results highlight the potential of eugenol and methyl eugenol as repellent compounds, especially when combined with DEET. The field study confirmed the efficacy of the 7% DEET + 1% eugenol.

Background: In 2022, a tick control product, against Rhipicephalus microplus , containing fluralaner as the active ingredient was initially launched in the Brazilian market, followed by other markets across Latin America. Once a new molecule is introduced for the control of a parasitic organism, it becomes essential to develop methods for assessing the susceptibility of target parasitic populations. In this context, discriminating dose (DD) tests represent a valuable tool. Methods: This study evaluated the susceptibility profile of 200 R. microplus populations originating from 21 federal units (20 states and a federal district) across all five regions of Brazil, using a larval immersion test (LIT) with two discriminating doses (DD) of 1.55 and 3.16 µg/mL. Populations showing mortality rates above 95% were classified as susceptible. A field trial was also conducted with one population (São José do Rio Pardo [SJRP]), which had a known history of exposure to fluralaner, to compare laboratory and field test outcomes. Results: The DD at a concentration of 1.55 µg/mL resulted in 100% mortality in 160 populations (80%), whereas the DD at a concentration of 3.16 µg/mL showed more consistent results, with 100% mortality in 182 populations (91%). In the field trial population, SJRP, fluralaner achieved 100% therapeutic efficacy (days +7 to +21) and persistent efficacy (days +28 to +42). Conclusions: LIT using DDs can provide indicative data on the susceptibility of R. microplus to fluralaner. The discriminating dose at a concentration of 3.16 µg/mL was shown to be the most appropriate for monitoring the susceptibility of R. microplus populations to fluralaner. Laboratory and field data support the classification of the SJRP population as susceptible, demonstrating consistency between the two sets of results. These results can serve as a basis for continuous spatial and temporal monitoring of the susceptibility of R. microplus populations to fluralaner. Continued research, integrating laboratory and field results, is essential to increase the reliability of laboratory-based testing.

BACKGROUND: Repellent formulations are a cost‐effective strategy for protection against disease vectors. N , N ‐diethyl‐meta‐toluamide (DEET) is widely used to repel mosquitoes and ticks, including Amblyomma sculptum , the vector of Rickettsia rickettsii (the agent of Brazilian spotted fever), and Aedes aegypti , responsible for dengue, zika, and chikungunya. This study aimed to develop cyclodextrin (CD)–DEET complexes for topical application. Phase‐solubility studies identified the most suitable CD, and hydroxypropyl‐β‐cyclodextrin (HPβCD)–DEET was selected for further investigation. In vitro release and skin permeation were evaluated. Embryotoxicity was assessed in a zebrafish model, and repellent efficacy was investigated against both species. RESULTS: Phase‐solubility studies revealed A _L ‐type profiles for αCD, γCD, and HPβCD, with slopes between 1 and 2, and K _2:1 values of 4738, 4494, and 2169, respectively. HPβCD–DEET exhibited slower DEET release compared to the control (26.7% vs 50.4% over 10 h, P < 0.05). Although DEET permeation to the receptor medium was similar ( P > 0.05), HPβCD reduced DEET retention in the stratum corneum by 2.6‐fold ( P < 0.05). HPβCD–DEET did not cause embryotoxicity in permeated DEET concentrations (69 mg L ⁻¹ ). Repellency bioassays showed HPβCD–DEET efficacy against A. sculptum for 168 h (80.5–100%) and full protection against A. aegypti for 7 h (>95%). CONCLUSION: These results highlight the potential of HPβCD–DEET complexes for safer and effective repellent formulations. © 2026 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Rhipicephalus microplus is a cattle ectoparasite responsible for economic losses in livestock systems. The present study aimed to evaluate the essential oil (EO) of Piper hemmendorffii and its major constituent, limonene, for their activity against R. microplus larvae. The EO of P. hemmendorffii and its major compound, limonene, were evaluated against pyrethroid-resistant R. microplus larvae using larval immersion bioassays, biochemical analyses of detoxification enzymes and acetylcholinesterase, and scanning electron microscopy (SEM). The EO showed higher larvicidal potency (LC₅₀ = 10.46 mg/mL; 95% CI: 9.86–11.09) compared to limonene (LC₅₀ = 31.62 mg/mL; 95% CI: 30.86–32.40). Piper hemmendorffii EO affected the following classes of enzymes investigated: α-Esterase (α-EST) activity increased at LC₂₅ and LC₅₀, reaching its highest level at LC₅₀, whereas β-esterase (β-EST) activity increased only at LC₂₅. Cytochrome P450 (CYP450)-associated heme content activity showed a significant increase exclusively at LC₅₀, suggesting a response of the surviving larvae to EO exposure, although this increase does not by itself demonstrate the activation of detoxification pathways. In contrast, limonene did not significantly affect the activity of the three evaluated enzymes. The inhibition of AChE by the EO suggests a possible effect on the cholinergic system, which may be associated with neurotoxic activity, whereas limonene had no significant effect. The absence of detectable ultrastructural changes by SEM suggests that treatment with either EO or limonene did not induce evident external morphological damage to the larval cuticle under the evaluated conditions. EO toxicity seems to be associated with changes in detoxification enzyme and AChE activities, suggesting the involvement of these biochemical pathways in larval response.