An investigation of the acaricidal activity of benzyl alcohol on Rhipicephalus annulatus and Rhipicephalus sanguineus and its synergistic or antagonistic interaction with commonly used acaricides.

The most economically significant ectoparasites in the tropics and subtropics are ixodid ticks, especially Rhipicephalus annulatus and Rhipicephalus sanguineus. Years of extensive use of the readily available acaricides have resulted in widespread resistance development in these ticks, as well as negative environmental consequences. Benzyl alcohol (BA) has been frequently used to treat pediculosis and scabies, and it may be an effective alternative to commonly used acaricides. The main aim of the present study was to evaluate the acaricide activity of BA and its combination with the regularly used chemical acaricides against R. annulatus and R. sanguineus. Different concentrations of BA alone and in combination with deltamethrin, cypermethrin and chlorpyrifos were tested in vitro against adult and larvae of both tick species. The results showed that BA is toxic to R. annulatus and R. sanguineus larvae, with 100% larval mortality at concentrations of ≥50 mL/L, and LC50 and LC90 attained the concentrations of 19.8 and 33.8 mL/L for R. annulatus and 18.8 and 31.8 mL/L for R. sanguineus, respectively. Furthermore, BA in combination with deltamethrin, cypermethrin and chlorpyrifos exhibited synergistic factors of 2.48, 1.26 and 1.68 against R. annulatus larvae and 1.64, 11.1 and 1.14 against R. sanguineus larvae for deltamethrin + BA, cypermethrin + BA and chlorpyrifos + BA, respectively. BA induced 100% mortality in adult R. annulatus at concentrations of ≥250 mL/L with LC50 and LC90 reached the concentrations of 111 and 154 mL/L, respectively. Additionally, BA had ovicidal activity causing complete inhibition of larval hatching at 100 mL/L. The combination of BA with deltamethrin and cypermethrin increased acetylcholinesterase inhibition, whereas the combination of BA with chlorpyrifos decreased glutathione (GSH) activity and malondialdehyde levels. In the field application, the combination of BA 50 mL/L and deltamethrin (DBA) resulted in a significant reduction in the percentage of ticks by 30.9% 28 days post-treatment when compared with groups treated with deltamethrin alone. In conclusion, BA causes mortality in laboratory and field studies alone and in combination with cypermethrin or deltamethrin. BA can be used for control of ticks of different life stages, that is, eggs and larvae, through application to the ground.

D-limonene nanoemulsion: lousicidal activity, stability, and effect on the cuticle of Columbicola columbae.

The current study was conducted to investigate the efficacy and stability of D-limonene (DL) and its nanoemulsion (DLN) against pigeon feather lice (Columbicola columbae) and their mode of action. DL pure form and DLN were prepared and characterized freshly and after storage for 50 days. In vitro bioassay on live lice was conducted with different concentrations of DL, DLN, and deltamethrin (DM). The results revealed significant mortality rates in the DL-, DLN-, DM-treated groups when compared with the control (p < 0.05). The scanning electron micrographs of lice treated with DL and DLN revealed collapsed bodies with destruction in the cuticle of the mouthparts and damaged antennae. The 50 days stored DLN showed stability in their effectiveness when compared with the freshly prepared formulation. DL and DLN caused significant inhibition (p ≤ 0.05) in acetylcholinesterase activity (AchE). Malondialdehyde level (MDA) was significantly increased while glutathione was significantly decreased in DL- and DLN-treated lice. In conclusion, DL and DLN have significant lousicidal activities. DLN showed better stability than DL after storage for 50 days. In addition, the mode of action of DL may associate with its effect on the cuticle of the lice body, inhibition of AchE, and increasing oxidative stress in the treated lice.

Toxicity and Repellency Efficacy of Benzyl Alcohol and Benzyl Benzoate as Eco-Friendly Choices to Control the Red Flour Beetle Tribolium castaneum (Herbst. 1797).

Tribolium castaneum is a damaging pest of stored grains, causing significant losses and secreting lethal quinones, which render the grains unfit for human consumption. Chemical insecticides are the most commonly used approach for control; however, they create insecticide resistance and affect the health of humans, animals, and the environment. As a result, it is critical to find an environmentally friendly pest-management strategy. In this study, two naturally occurring chemicals, benzyl alcohol (BA) and benzoyl benzoate (BB), were investigated for insecticidal activity against T. castaneum using different assays (impregnated-paper, contact toxicity, fumigant, and repellency assays). The results showed that BA had a significant insecticidal effect, with the LC50 achieved at a lower concentration in the direct-contact toxicity test (1.77%) than in the impregnated-paper assay (2.63%). BB showed significant effects in the direct-contact toxicity test, with an LC50 of 3.114%, and a lower toxicity in the impregnated-paper assay, with an LC50 of 11.75%. Furthermore, BA exhibited significant fumigant toxicity against T. castaneum, with an LC50 of 6.72 µL/L, whereas BB exhibited modest fumigant toxicity, with an LC50 of 464 µL/L. Additionally, at different concentrations (0.18, 0.09, 0.045, and 0.0225 µL/cm2), BA and BB both showed a notable and potent repelling effect. BA and BB significantly inhibited acetylcholinesterase, reduced glutathione (GSH), and increased malondialdehyde (MDA) in treated T. castaneum. This is the first report of BA insecticidal activity against the red flour beetle. Also, the outcomes of various assays demonstrated that the application of BA induces a potent bio-insecticidal effect. BA may be a promising eco-friendly alternative to control T. castaneum due to its safety and authorization by the EFSA (European Food Safety Authority).

Efficacy and safety of geranium-oregano-thymol formulations to control of dog tick Rhipicephalus sanguineus sensu lato under laboratory and field conditions.

The present study evaluated, in laboratory and field, the efficacy and safety of formulations of Pelargonium graveolens (geranium - G), Origanum majorana (oregano - O) commercial essential oils (EO) and thymol (T) to control of Rhipicephalus sanguineus sensu lato. In the laboratory, three formulas (A: 2% tween 80%, B: powder and C: nanoemulsion) by a mixture of these components (GOT) were prepared and evaluated, and the best one was used to assess its safety and field application against R. sanguineus s. l. on naturally infested dogs. Besides the major compounds of the EO used were identified. The results of the lab study showed that formula A (2.5 g of each G + O + T + 2% tween 80 to complete 100 mL) was significantly more effective than the other two formulas tested and exhibited highly effective adulticidal, larvicidal, and ovicidal activity against R. sanguineus s.l. Significant LC50 and LC90 values of GOT were evaluated (13.4 and 21.5 mg/mL, respectively) for the adulticidal activity, (2.81 and 4.46 mg/mL, respectively) for ovicidal activity and (2.44 and 4.45 mg/mL, respectively) for larvicidal activity. The safety of formula A has been proven by the absence of its cytotoxicity on a cell line of human epidermoid carcinoma. Citronella and carvacrol were the major compounds identified in the commercial essential oils of P. graveolens and O. majorana, respectively. Formula A was used in a field control trial for almost 8 months, during the tick infestation season (April to November, 2022). Fourteen naturally infested dogs were divided into two groups, each with seven dogs. One group received formula A spraying five times during an experiment that continued for 8 months, while the other group received treatment with commercially available malathion acaricide. The animals were sprayed on five occasions throughout the experiment (April, June, July, August, and September). The results showed a substantial percentage of effectiveness after the first application of formula A with a 99.3% reduction in tick count at day 28 post-application (PA). In the case of severe infestation 60 days after the first application of formula A (more than 180 ticks per dog), the second application was done, achieving an efficacy of 54.9% at day 3 PA, so an emergency spray was done at day 5 PA to combat the rest of the tick infestation, achieving efficacy of 99% after 3 days. Consequently, a regular spray (third, fourth, and fifth application) was done every 35 days. This regular spray revealed 100% effectiveness at 14 days PA. Biochemical parameters of treated dogs were evaluated to confirm the safety of formula A. Creatinine, ALT, and albumin of the dogs treated with formula A were within the normal range of dogs, while urea and AST were higher than the normal range. In conclusion, formula A can safely treat R. sanguineus s.l. infestations in dogs with regular application every 5 weeks.

Benzoate Derivatives Toxicity to Musca domestica Results in Severe Muscle Relaxation and Body Distortion.

The house fly, Musca domestica (Linnaeus) (Diptera: Muscidae), is a significant threat to human and animal health and is also resistant to a variety of insecticides. Plant-derived benzoates are known to have insecticidal activities against various insects. In this study, the larvicidal, pupicidal, and adulticidal activities of benzoate derivatives (benzyl alcohol BA, benzyl benzoate BB, and methyl benzoate MB) were assessed and investigated for their effects on larval structure and acetylcholinesterase activity. Six concentrations (2.5 to 100 mg/mL) of benzoate derivatives were applied to larvae and pupae through the residual film method and topical application, respectively. Meanwhile, concentrations from 0.625 to 50 mg/L air were applied to adult flies through a fumigation assay. BA and MB achieved promising results against larvae with LC50 values of 10.90 and 11.53 mg/mL, respectively. Moreover, BA killed 100% of the larvae at a concentration of 25 mg/mL, and MB achieved the same effect at a concentration of 50 mg/mL. Regarding the pupicidal activity, MB showed a percentage inhibition rate (PIR) of 100% at a concentration of 100 mg/mL, while the same effect was achieved by BA at a concentration of 50 mg/mL. Meanwhile, BB did not show any effect on the larvae or pupae at any of the tested concentrations. Moreover, the scanning microscopy observations on the treated larvae by BA and MB estimated flaccid and deformity in the larva body with a shrunken cuticle. Additionally, both BA and MB suppress nerve signal transmission by inhibiting acetylcholinesterase. In conclusion, the results of this study indicate that BA and MB may be useful in control housefly populations. These substances cause severe muscular relaxation and deformities in insects.

Safety and Efficacy of Pure and a Nanosuspension of D-limonene for Controlling Pigeon Lice.

This study investigated the safety and efficacy of two forms of D-limonene (DL) against Columbicola columbae (pigeon feather lice); pure and a nanoemulsion formulation (DLN). The cell cytotoxicity of the prepared forms of DL/DLN was investigated using skin cell lines. In vitro and ex vivo bioassays were applied on lice. The ex vivo bioassay was done on cut feathers containing lice eggs. The in vivo experiment was conducted on pigeons naturally infested by lice. The infested pigeons were treated with DL, DLN, or deltamethrin (D) as a positive control. Both forms of D-limonene were found to be safe when applied to the normal human skin fibroblast cell line, but DLN was toxic to skin cell carcinoma. The in vitro and ex vivo results of both DL and DLN forms were similar. All eggs treated with DL, DLN, and D failed to hatch (100%). The in vivo results showed complete elimination of lice 24 h post-treatment (PT), and biochemical analysis showed that the treated birds retained normal kidney and liver functions. Treated groups also showed improved productivity in the 4 months PT. In conclusion, DL and DLN are safe and effective in controlling feather lice infestation in pigeons and successful treatment encourages bird productivity.

Synthesis of Carvacrol-Loaded Invasomes Nanoparticles Improved Acaricide Efficacy, Cuticle Invasion and Inhibition of Acetylcholinestrase against Hard Ticks.

Carvacrol is a monoterpenoid phenol found in many essential oils that has antibacterial, antifungal and antiparasitic activities. Drug loaded-invasome systems are used to deliver drugs utilizing nanoparticles to improve bioavailability, efficacy, and drug release duration. As a result, the present study developed carvacrol-loaded invasomes and evaluated their acaricidal effect against Rhipicephalus annulatus (cattle tick) and Rhipicephalus sanguineus (dog tick). Carvacrol loaded-invasome (CLI) was prepared and characterized using UV/Vis spectrophotometer, zeta potential measurements, Scanning Transmission Electron Microscopy (STEM), Fourier Transform Infrared (FT-IR) Spectroscopy, and Differential Scanning Calorimetry Analysis. CLI (5%) induced significant mortality (100%) in R. annulatus adult ticks with LC50 of 2.60%, whereas the LC50 of pure carvacrol was 4.30%. Carvacrol and CLI were shown to have a significant larvicidal action on both tick species, with LC50s of 0.24 and 0.21% against R. annulatus and 0.27 and 0.23% against R. sanguineus, respectively. Carvacrol and CLI (5%) induced significant repellent activities for 24 h against R. annulatus and R. sanguineus, as evidenced by the rod method and the petri-dish selective area choice method, respectively. High-performance liquid chromatography (HPLC) demonstrated that the CLI form had 3.86 times the permeability of pure carvacrol. Moreover, carvacrol and CLI inhibited acetylcholinesterase activity and decreased glutathione and malonedealdehyde levels in the treated ticks. In conclusion, invasomes significantly improved adulticidal and repellency activities of carvacrol against both tick species.

Efficacy of D-Limonene Nanoemulsion Against Rhipicephalus annulatus and Rhipicephalus sanguineus Ticks.

PURPOSE: Ticks infestation has a negative impact against human and animal health through blood sucking, transmission of blood-borne diseases and also caused economic losses. METHODS: In the present study the adulticidal, ovicidal and larvicidal activity of D-limonene nanoemulsion (DLN) were evaluated against two tick species; Rhipicephalus annulatus and Rhipicephalus sanguineus. Nanoemulsion form of D-limonene was prepared, and its characteristics were evaluated using a UV spectrophotometer and zeta droplet size measurement. Acetylcholinesterase activity was determined. RESULTS: The results revealed significant adulticidal effect with low LC50 and LC90 for D-limonene pure form (DL) against both adult tick spp. (R. annulatus and R. sanguineus) ((0.958 and 1.559%) and (2.26 and 3.51%), respectively). DLN LC50 and LC90 values were ((1.277 and 2.396) and (3.97 and 7.28), respectively) against R. annulatus and R. sanguineus, respectively. DL and DLN showed significant ovicidal effect against R. sanguineus at high concentrations (10 and 5%). In larval packet test, LC50 and LC90 values of DL were ((1.53 and 2.22%) and (6.81 and 12.07%), respectively) against R. annulatus and R. sanguineus, respectively, while LC50 and LC90 values of DLN were ((6.48 and 11.26%) and (7.82 and 13.59%), respectively) against R. annulatus and R. sanguineus, respectively. Significant acetylcholinesterase inhibition percentage was detected for both ticks spp. which treated by DL and DLN. CONCLUSION: Pure DL is more effective than DLN form against R. annulatus and R. sanguineus.

Evaluation of deltamethrin-loaded Zn-Fe, Zn-Al-GA layered double hydroxide, and Fe-O nanoparticles against resistant Rhipicephalus annulatus ticks.

The over use of deltamethrin has resulted in the development of resistance. Thus, the search for a new method to improve its acaricidal effect is the target of the present study. Layered double hydroxide (LDH) compounds are now used as drug delivery systems. Deltamethrin (Butox®) was loaded on Zn-Fe LDH, Zn-Al-GA layered double hydroxide (LDH), and Fe-oxide nanoparticles NPs. Then its acaricidal efficacy was evaluated. The nanocomposites (NCs) were prepared by the co-precipitation method and characterized before and after deltamethrin loading. The deltamethrin-loaded NCs were applied against the phenotypically resistant Rhipicephalus annulatus tick (adult and larvae). The adult ticks treated by Butox® alone or Butox® loaded nanocomposites at different concentrations showed no mortality. A significant (P≤0.05) reduction in egg production index was observed at the recommended dose (X) (1 µl/ml distilled water) and its bi-folds (2X, 3X, and 4X) in ticks treated with deltamethrin/Zn-Fe LDH nanocomposites compared to deltamethrin alone. Moreover, no significant difference (P>0.05) was recorded in larval mortality between the treatments with deltamethrin alone and its loaded nanocomposites. Also, the nanomaterials alone without conjugation with deltamethrin revealed a low mortality rate. Deltamethrin-loaded nanocomposites even improve effect against adult tick but cannot overcome tick resistance to deltamethrin that needs more search. The acaricidal activity of deltamethrin was not improved after loading it with these nanocomposites.

Preparation of geranium oil formulations effective for control of phenotypic resistant cattle tick Rhipicephalus annulatus.

The aim of the present study was to evaluate in vitro and in vivo the acaricidal activity of two forms of geranium (Pelargonium graveolens) (PG). These two forms were the P. graveolens essential oil nanoemulsion (PGN), and the PG in combination with the sesame oil (SO), PGSO). These forms were first evaluated in vitro for their adulticidal, ovicidal, and larvicidal activities against the different stages of acaricide-resistant Rhipicephalus annulatus (Say). Geranium nanoemulsion was prepared and then characterized by UV-Vis spectrophotometer, and zeta droplet size measurement. The results revealed that LC50 of the PG against the adult ticks was attained at concentration of 7.53% while it was decreased to 1.91% and 5.60% for PGSO and PGN, respectively. Also, the LC50 of PGN and PGSO were reached at concentrations of 1.688 and 0.944%, respectively against the larvae while the LC50 of the PG was reached at concentration of 3.435% for. The combination of PGN with PG exhibited non-significant ovicidal effect meanwhile PGSO showed significant ovicidal effect even at the low concentration (2.5%). The PGSO and PGN formulations were applied in a field trial to control the ticks of the naturally infested cattle. PGSO and PGN significantly reduced the tick burden to 74.83% and 87.97%, respectively at 3 weeks post-application with performance better than the deltamethrin (29.88%). In conclusion, the two PG forms can be used as suitable alternatives to control R. annulatus tick and they need further modifications for effective field application.

Acaricidal Activity of Tea Tree and Lemon Oil Nanoemulsions against Rhipicephalus annulatus.

Tick infestation is a serious problem in many countries since it has an impact on the health of animals used for food production and pets, and frequently affects humans. Therefore, the present study aimed to investigate the acaricidal effects of nanoemulsions of essential oils of Melaleuca alternifolia (tea tree, TT) and Citrus limon (lemon oil, CL) against the different stages (adult, eggs, and larvae) of deltamethrin-resistant Rhipicephalus annulatus ticks. Three forms of these oils were tested: pure oils, nanoemulsions, and a binary combination. Tea tree and lemon oil nanoemulsions were prepared, and their properties were assessed using a zeta droplet size measurement and a UV-Vis spectrophotometer. The results showed that TT and CL exhibited higher adulticidal effects in their pure forms than in their nanoemulsion forms, as demonstrated by the lower concentrations required to achieve LC50 (2.05 and 1.26%, vs. 12.8 and 11.4%, respectively) and LC90 (4.01% and 2.62%, vs. 20.8 and 19.9%, respectively). Significant larvicidal activity was induced by the TTCL combination, and LC50 was reached at a lower concentration (0.79%) than that required for the pure and nanoemulsion forms. The use of pure CL oil was found to have the most effective ovicidal effects. In conclusion, pure TT and CL have potent acaricidal effects against phenotypically resistant R. annulatus isolates. It is interesting that the activity levels of TT and CL EOs' binary and nanoemulsion forms were lower than those of their individual pure forms.

New insight on some selected nanoparticles as an effective adsorbent toward diminishing the health risk of deltamethrin contaminated water.

Deltamethrin is a widely used insecticide that kills a wide variety of insects and ticks. Deltamethrin resistance develops as a result of intensive, repeated use, as well as increased environmental contamination and a negative impact on public health. Its negative impact on aquatic ecology and human health necessitated the development of a new technique for environmental remediation and wastewater treatment, such as the use of nanotechnology. The co-precipitation method was used to create Zn-Fe/LDH, Zn-AL-GA/LDH, and Fe-oxide nanoparticles (NPs), which were then characterized using XRD, FT-IR, FE-SEM, and HR-TEM. The kinetic study of adsorption test revealed that these NPs were effective at removing deltamethrin from wastewater. The larval packet test, which involved applying freshly adsorbed deltamethrin nanocomposites (48 hours after adsorption), and the comet assay test were used to confirm that deltamethrin had lost its acaricidal efficacy. The kinetics of the deltamethrin adsorption process was investigated using several kinetic models at pH 7, initial concentration of deltamethrin 40 ppm and temperature 25°C. Within the first 60 min, the results indicated efficient adsorption performance in deltamethrin removal, the maximum adsorption capacity was 27.56 mg/L, 17.60 mg/L, and 3.06 mg/L with the Zn-Al LDH/GA, Zn-Fe LDH, and Fe Oxide, respectively. On tick larvae, the results of the freshly adsorbed DNC bioassay revealed larval mortality. This suggests that deltamethrin's acaricidal activity is still active. However, applying DNCs to tick larvae 48 hours after adsorption had no lethal effect, indicating that deltamethrin had lost its acaricidal activity. The latter result corroborated the results of the adsorption test's kinetic study. Furthermore, the comet assay revealed that commercial deltamethrin caused 28.51% DNA damage in tick cells, which was significantly higher than any DNC. In conclusion, the NPs used play an important role in deltamethrin decontamination in water, resulting in reduced public health risk. As a result, these NPs could be used as a method of environmental remediation.

Effect of high concentrations of lufenuron, pyriproxfen and hydroprene on Rhipicephalus (Boophilus) annulatus.

The activity of high doses of three insect growth regulators (IGRs), lufenuron (MATCH®), pyriproxfen® and hydroprene (Gentrol®), were tested on Rhipicephalus(Boophilus) annulatus adult females, eggs and larvae. Different concentrations of the IGRs were tested on eggs, larvae and adult ticks through immersion, larval packet and adult immersion bioassays, respectively. The tested IGRs did not show adulticidal activity against female ticks even at very high concentration. However, both hydroprene and pyriproxfen caused a significant decrease (P<0.05) in the reproductive indices of adult female ticks. Both lufenuron and pyriproxefen showed considerable ovicidal activity delaying the hatchability of the treated eggs until the 21st day and decreasing the hatchability percentages to 37.7% and 60.6% at concentrations ≥10X and ≥4X, respectively. Lufenuron (≥10X dose), hydroprene (≥4X dose) and pyriproxyfen (≥4X dose) induced highly significant larvicidal activity as they caused 100% mortality after 72 h of exposure. The oxidative profile of the hydroprene treated ticks had decreased glutathione peroxidase and increased malonaldehyde in comparison to the other IGR- treated and control untreated ticks. It is concluded that the IGRs did not show R. annulatus adulticidal effect, however, the deposited egg mass and its hatching percent decreased significantly when treated with hydroprene and pyriproxfen. The tested IGRs showed larvicidal activity against R. (B.) annulatus.