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Tick control mainly depends on using chemical acaricides that have led to the emergence of resistant tick populations along with environmental hazards. Natural alternatives including essential oils are now widely used to avoid the undesirable effects of chemicals on human, animals and environment. In this study, three commercial oils (myrrh, patchouli, and cypress) and their nanoemulsions (NEs) were tested against Rhipicephalus sanguineus sensu lato unfed adults. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) were used to characterize the nanoemulsions. Four concentrations with three replicates were used in the bioassay of oils and NEs against ticks using an adult immersion test. Furthermore, a toxicity study of the three oils and their NEs using normal fibroblast cells (BJ-1) was performed. TEM revealed particle size ranges from 29 to 211 nm with spherical droplets. The droplet size and polydispersity index were (29.30 nm & 0.367), (211.6 nm & 0.221) and (164.2 nm & 0.237) for myrrh NE, patchouli NE, and cypress NE, respectively. Myrrh and patchouli oils recorded high acaricidal activity followed by cypress oil with LC 50 value 5 days after treatment of 9.01, 12.40, and 15.21%, respectively. The acaricidal efficacy of oil was potentiated in the NEs form which was proved by the reduction in LC 50 values that were recorded 7 days after treatment 4.17, 8.57, and 5.04%, for myrrh, patchouli, and cypress NE, respectively. As an alternative for lab animals, we applied the cytotoxicity of myrrh, patchouli, and cypress on normal fibroblast cells. The oils showed low cytotoxic activity of 10.6, 21.5, and 23.6% for Myrrh, Patchouli, and Cypress, respectively. The nanoemulsion was revealed to be safe for normal cells up to a concentration of 0.62% (cytotoxicity%= 24.4, 34.4, and 16.3%, respectively), and the moderate cytotoxic effect appeared at around a concentration of 1.25% (cytotoxicity%= 42.2%, 57.0%, and 36.8% respectively). In conclusion, the three oils and their NEs have good acaricidal activity against Rhipicephalus sanguineus unfed adults. Further toxicity studies on mammals are needed to ensure the safe use of these formulations for the control of ticks on infested animals.

The poultry red mite (PRM), Dermanyssus gallinae , a potential vector of pathogens to animals and humans, causes impaired bird welfare. A study investigated changes in behavioural variables, physiological biomarkers, and health parameters following acaricidal treatment of PRM infestation of laying hens on a commercial farm. Mite traps determined the challenge to 12,700 hens before and after drinking water administration of the acaricide, fluralaner (Exzolt ® , 0.5 mg/kg; Weeks 0 and 1). Weekly daytime direct observations and night-time video recordings monitored bird behaviours from Weeks -6 through +6. Blood samples were collected from randomly-selected birds (Weeks -6, -1, and +6). Following treatment, mite count reductions (>99%) were statistically significant ( P < 0.0001), as were night-time reductions in the percent of hens showing activity, preening, head scratching (all P < 0.0001), and head shaking ( P = 0.0007). Significant daytime reductions were observed in preening and head scratching (both P < 0.0001), head shaking ( P = 0.0389), severe feather pecking ( P = 0.0002), and aggressive behaviour ( P = 0.0165). Post-treatment, comb wounds were significantly reduced ( P = 0.0127), and comb colour was significantly improved ( P < 0.0001). Heterophil/lymphocyte ratio was significantly reduced at Weeks 1 and 6 ( P = 0.0009 and P < 0.0001, respectively). At Week 6, blood corticosterone ( P = 0.0041) and total oxidant status ( P < 0.0001) were significantly reduced, and haemoglobin and mean corpuscular haemoglobin significantly increased ( P < 0.0001). Farm production records indicated that those post-treatment improvements were accompanied by significant reductions in weekly mortality rate ( P = 0.0169), and significant recovery in mean weekly egg weights ( P < 0.0001) and laying rate (P < 0.0001). The improvements in behavioural variables, physiological biomarkers, and health parameters that were observed following the elimination of PRM on a commercial farm indicate that infestations can be a cause of reduced hen welfare.

The current work evaluated the efficacy of 10 commercial acaricides in different pHs (4.5, 5.5, and 6.5) in laboratory (adult immersion tests (AIT), pH evaluation over time) and field assays (tick counts and efficacy). In the AIT ( n =70), higher efficacies were obtained when the acaricide emulsion had a more acidic pH (4.5), mainly for two combinations of pyrethroids + organophosphate (acaricide 3 and acaricide 9). For amidine, a higher pH (6.5) showed a higher efficacy. Over time, there was a trend in the pH of these emulsions increasing. When the efficacy of chlorpyrifos + cypermethrin + piperonyl butoxide (acaricide 3) at different pHs was evaluated over time (0, 6, 12, and 24h) by AIT, the less acidic pH (6.5) showed a strongly variation in the acaricide efficacy range. The mean pH of the water samples from different regions of Brazil was 6.5. In the field, the association of pyrethroid + organophosphates (acaricide 9) with pH of 4.5 and 5.5 were more effective in tick control than the emulsion prepared with this same spray formulation at pH 6.5. The pH of the acaricide emulsions is an important point of attention and is recommended that the veterinary industry start to develop/share information regarding how the pH can affect the acaricide efficacy.

The acaricide propargite has been widely used for over 50 years without significant resistance issues. Addressing to the propargite defects of poor crop safety, thirty-six novel halogenated propargite analogues were designed, synthesized, and characterized using 1 H NMR, 13 C NMR spectroscopy, and HRMS. All target compounds were screened for activity against adult Tetranychus cinnabarinus (spider mites) and Myzus persicae (aphids). Two compounds exhibiting higher insecticidal activity were further evaluated for crop safety on cowpea seedlings. Structural modifications, such as replacing the tert -butyl group on the propargite benzene ring with chlorine or trifluoromethoxy, and substituting the propargyl group with fluorinated alkyl groups (e.g., 2-fluoroethyl or 3,3,3-trifluoropropyl), significantly enhanced both acaricidal and aphicidal activity. Compound 5.16 demonstrated superior acaricidal activity (LC 50 : 14.85 mg L -1 ) on Tetranychus cinnabarinus and excellent crop safety on cowpea seedlings. Additionally, Compound 5.32 exhibited both acaricidal (LC 50 : 14.32 mg L -1 ) and aphicidal activity, which is unusual in this chemical class. The compounds 5.16 and 5.32 could be used as promising leads for the discovery of novel acaricides or insecticides.

Rhipicephalus microplus , a tick species, causes significant economic losses in livestock and presents control challenges due to the emergence of resistance to conventional acaricides. This underscores the urgent need for effective and eco-friendly alternatives. This study evaluates the acaricidal potential of Cirsium arvense using adult immersion and larval packet tests. In silico molecular docking techniques were employed to identify biologically active compounds within C. arvense . Using Chem-Draw Ultra software (version 12.0.2, 2010), we illustrated 25 compounds derived from the plant, which were subsequently tested as ligands in docking experiments against Subolesin. Among the tested compounds, Apigenin 7-O-glucosideand Pectolinarigenin 7-glucoside exhibited significant inhibitory effects on Subolesin, with docking scores of -6.6 and − 6.3 kcal/mol, respectively. In contact bioassays using Cirsium arvense extract, various concentrations (2.5, 5, 10, 20, and 40 mg/mL) were evaluated. The results indicated an LC50 of 2.907 mg/mL and an LC90 of 47.725 mg/mL after 24 h of exposure. Notably, at the highest concentration of 40 mg/mL, the extract significantly reduced egg-laying activity in adult female ticks, yielding an oviposition index of 0.09 ± 0.02, which corresponds to a 75.68 ± 0.44% reduction in reproductive capacity. Additionally, larval mortality reached 88.33 ± 2.90%, indicating that higher concentrations not only increased larval mortality but also substantially decreased the reproductive capacity of the ticks. These findings suggest that bioactive components from Cirsium arvense show promise as candidates for the control of R. microplus . Further research is warranted to evaluate their efficacy as alternative or complementary strategies to synthetic acaricides.