Assessment of the in vitro acaricidal activity of Bravecto® (fluralaner) and a proposed orange oil-based formulation vehicle for the treatment of Sarcoptes scabiei.

BACKGROUND: Sarcoptic mange is a serious animal welfare concern in bare-nosed wombats (Vombatus ursinus). Fluralaner (Bravecto®) is a novel acaricide that has recently been utilised for treating mange in wombats. The topical 'spot-on' formulation of fluralaner can limit treatment delivery options in situ, but dilution to a volume for 'pour-on' delivery is one practicable solution. This study investigated the in vitro acaricidal activity of Bravecto, a proposed essential oil-based diluent (Orange Power®), and two of its active constituents, limonene and citral, against Sarcoptes scabiei. METHODS: Sarcoptes scabiei were sourced from experimentally infested pigs. In vitro assays were performed to determine the lethal concentration (LC50) and survival time of the mites when exposed to varying concentrations of the test solutions. RESULTS: All compounds were highly effective at killing mites in vitro. The LC50 values of Bravecto, Orange Power, limonene and citral at 1 h were 14.61 mg/ml, 4.50%, 26.53% and 0.76%, respectively. The median survival times of mites exposed to undiluted Bravecto, Orange Power and their combination were 15, 5 and 10 min, respectively. A pilot survival assay of mites collected from a mange-affected wombat showed survival times of < 10 min when exposed to Bravecto and Orange Power and 20 min when exposed to moxidectin. CONCLUSIONS: These results confirm the acaricidal properties of Bravecto, demonstrate acaricidal properties of Orange Power and support the potential suitability of Orange Power and its active constituents as a diluent for Bravecto. As well as killing mites via direct exposure, Orange Power could potentially enhance the topical delivery of Bravecto to wombats by increasing drug penetration in hyperkeratotic crusts. Further research evaluating the physiochemical properties and modes of action of Orange Power and its constituents as a formulation vehicle would be of value.

Current perspectives and difficulties in the design of acaricides and repellents from plant-derived compounds for tick control.

Ticks and tick-borne diseases have gained increasing attention in recent years due to their impact on public health and significant losses in livestock production. The use of synthetic compounds for tick control is becoming problematic, mainly due to the resistance to commercially available products as well as their toxicity. Therefore, new alternative control methods are required. For this purpose, plant-derived extracts may be considered as effective repellents and/or acaricides. The present literature review focuses on studies evaluating the acaricidal and repellent activity of plant-derived extracts and plant secondary metabolites. We also noted recent advances in protein-ligand-docking simulation to examine the possible toxic effect of natural chemical compounds on ticks. In conclusion, plant-derived repellents/acaricides can be effective against ticks, especially in rural areas and livestock farms.

Properties of essential oils absorbed on the surface of cardboard pieces after using atmospheric-pressure plasma treatments to develop long-lasting Varroa miticides in honeybees (Apis mellifera).

The ectoparasitic mite, Varroa destructor is the most serious widespread pest of managed honeybees (Apis mellifera). Several acaricide products, which include essential oils, have been proposed for mite control. In this study, we aimed to apply atmospheric-pressure plasma to modify a cardboard piece surface in order to prolong the delivery of essential oils for controlling Varroa in honeybee colonies. Absorption capacity, release rates and evaporation rates of essential oils were determined. Cardboard piece showed a higher absorption capacity of cinnamon compared to citronella and clove. Surface modification of cardboard pieces using argon plasma at different gas flow rates and treatment durations, significantly affected the absorption of clove oil. Additionally, the release rate of cinnamon, citronella and clove was significantly enhanced after argon plasma treatments. Evaporation of cinnamon was dramatically increased by plasma treatment at 6-h of incubation. The highest evaporation rate was obtained by plasma-treated cardboard piece at a gas flow rate of 0.5 Lpm for 60 s (0.2175 ± 0.0148 µl/g•h). Efficiency of plasma-treated cardboard piece, impregnated with essential oils, was also investigated for Varroa control in honeybee colonies. In the first experiment, formic acid 65% (v/v) showed the highest efficiency of 90.60% and 81.59% with the percent of mite infestation was 0.23 ± 0.13% and 0.47 ± 0.19% at 21 and 35 days, respectively after treatment. The efficacy of cardamon oil (5% (v/v)) delivered using plasma-treated cardboard pieces was 57.71% (0.70 ± 0.16% of mite infestation) at day 21 of experiment. However, the delivery of cardamon oil at the concentration of 1% and 5% (v/v) by untreated cardboard piece had 16.93% and 24.05% of efficacy to control mites. In the 2nd experiment, the application of plasma-treated cardboard pieces impregnated with 5% (v/v) clove oil induced a 38.10% reduction in the population of Varroa mites followed by 5% (v/v) of cardamon with 30% efficiency. Although, the infestation rate of Varroa in colonies was not significant different between treatments, essential oils delivered using plasma-treated cardboard pieces tended to decrease Varroa population in the treated colonies. Hence, atmospheric-pressure plasma for the modification of other materials, should be further investigated to provide alternative control treatment applications against honeybee mites.

Impact of landscape composition on honey bee pollen contamination by pesticides: A multi-residue analysis.

The honey bee is the most common and important managed pollinator of crops. In recent years, honey bee colonies faced high mortality for multiple causes, including land-use change and the use of plant protection products (hereafter pesticides). This work aimed to explore how contamination by pesticides of pollen collected by honey bees was modulated by landscape composition and seasonality. We placed two honey bee colonies in 13 locations in Northern Italy in contrasting landscapes, from which we collected pollen samples monthly during the whole flowering season in 2019 and 2020. We searched for almost 400 compounds, including fungicides, herbicides, insecticides, and acaricides. We then calculated for each pollen sample the Pollen Hazard Quotient (PHQ), an index that provides a measure of multi-residue toxicity of contaminated pollen. Almost all pollen samples were contaminated by at least one compound. We detected 97 compounds, mainly fungicides, but insecticides and acaricides showed the highest toxicity. Fifteen % of the pollen samples had medium-high or high levels of PHQ, which could pose serious threats to honey bees. Fungicides showed a nearly constant PHQ throughout the season, while herbicides and insecticides and acaricides showed higher PHQ values in spring and early summer. Also, PHQ increased with increasing cover of agricultural and urban areas from April to July, while it was low and independent of landscape composition at the end of the season. The cover of perennial crops, i.e., fruit trees and vineyards, but not of annual crops, increased PHQ of pollen samples. Our work highlighted that the potential toxicity of pollen collected by honey bees was modulated by complex interactions among pesticide category, seasonality, and landscape composition. Due to the large number of compounds detected, our study should be complemented with additional experimental research on the potential interactive effects of multiple compounds on honey bee health.

Oxalic acid application method and treatment intervals for reduction of Varroa destructor (Mesostigmata: Varroidae) populations in Apis mellifera (Hymenoptera: Apidae) colonies.

Oxalic acid (OA) is a popular miticide used to control Varroa destructor (Mesostigmata: Varroidae) in western honey bee (Apis mellifera L.) (Hymenoptera: Apidae) colonies. Our aim was to investigate which method of OA application (dribbling, fogging, or vaporizing) was the most effective at reducing V. destructor infestations (Experiment 1) and to improve upon this method by determining the treatment interval that resulted in the greatest V. destructor control (Experiment 2). We used the product Api-Bioxal (97% OA) and maintained 40 honey bee colonies (10/treatment) in both experiments. In Experiment 1, the treatments included (i) dribbling 50 ml of 3% OA solution, (ii) vaporizing 4 g of solid OA, (iii) using an insect fogger supplied with 2.5% OA dissolved in ethyl alcohol, and (iv) an untreated control. After 3 weeks, only the vaporization method reduced V. destructor infestations (from 9.24 mites/100 bees pretreatment to 3.25 mites/100 bees posttreatment) and resulted in significantly increased brood amounts and numbers of adult bees over those of the controls. In Experiment 2, all colonies were treated with 4 applications of OA via vaporization at a constant concentration of 4 g OA/colony. In this experiment, the groups were separated by treatment intervals at either 3-, 5-, or 7-day intervals. We observed that 5- and 7-day treatment intervals significantly reduced V. destructor populations from pretreatment levels over that of the controls and 3-day intervals. Our data demonstrate the efficacy of OA in reducing V. destructor infestation, particularly vaporizing 4 g every 5-7 days as the most effective method of application.

Evaluation of synergism in essential oils against the cattle tick Rhipicephalus microplus in Burkina Faso.

The cattle tick Rhipicephalus microplus affects animal production economically by reducing weight gain and milk production and causing diseases, such as babesiosis and anaplasmosis. Using synthetic acaricides to reduce their incidence has caused the emergence of resistant tick populations. The present study aimed to assess the in vitro acaricidal activity of combinations of essential oils (EOs) from Ocimum americanum, Ocimum gratissimum, and Lippia multiflora against R. microplus larvae. In fact, numerous biological properties have been reported on EOs from these three plants, including acaricidal properties. Hence, a larval immersion test was performed using a population of R. microplus resistant to synthetic acaricides used in Burkina Faso. Results revealed that EO from O. gratissimum was the most effective on R. microplus larvae with LC50 and LC90 values at 10.36 and 15.51 mg/mL, respectively. For EO combinations, the most significant synergistic effect was obtained by combination 6 (1/3 O. americanum + 2/3 O. gratissimum +1/6 L. multiflora), with a combination index value of 0.44. All combinations presented dose reduction index >1, indicating a favorable dose reduction. According to the literature, this is the first study to determine the combination effect of EOs from the abovementioned plants in controlling R. microplus activity in vitro. Thus, the combination of these EOs is an alternative to control the resistant populations of invasive cattle ticks.

Controlling Argas arboreus and A. persicus (Acari: Argasidae) by Adiantum capillus-veneris L. extracts with phytochemical analysis.

Argas species are parasites associated mostly with birds. Their infestations of the host may cause blood loss, resulting in anemia and finally death. Egypt loses millions of tons annually from birds because of these parasites. In addition, they can transmit pathogens to animals and humans. The acaricidal effects of the ethanolic and methanolic extracts of Adiantum capillus-veneris at different concentrations (1-4%) against semi-fed adults of Argas arboreus and A. persicus were investigated during 30 days after treatments. Mobility and mortality, acaricide efficacy, and the concentration that kills 50% of specimens (LC50) were estimated. The percentage of dead adults of both Argas species appeared during 6 days considerably until 30 days was significantly increased after treatment of either ethanol or methanol extracts of Adiantum at 1-4%, versus control groups. Ethanolic extracts (100% mortality) were more effective than methanolic ones (90% mortality) for both Argas species. Argas arboreus (80% efficacy and 5.9% LC50) was more resistant than A. persicus (100% efficacy and 4.1% LC50). Generally, males were more resistant than females. The chemical profile (by gas chromatography-mass spectrometry analysis) for the ethanolic extract of Ad. capillus-veneris at 4% (the most effective extract) was provided for the first time, which showed that the major group was sugars and sugar alcohols, and the main components were thymol-ß-d-glucopyranoside, D-(-)-Tagatofuranose, D-Arabinose, D-Galactose, D-(-)-Fructofuranose and Anthracene, 1-methyl. The efficiency of all these components was discussed. Based on the findings, bioactive compounds present in Ad. capillus-veneris have the potential to be applied as substitutes for synthetic acaricides and a biological control agent in the management of A. arboreus and A. persicus ticks.

Efficacy of local essential oils against Amblyomma variegatum tick from Burkina Faso.

The native tick Amblyomma variegatum remains one of the most important tick species affecting cattle in West Africa. This hinders animal production by negatively impacting the health and reproduction of animals infested with the tick. Given the negative consequences on production quality and environmental health, the use of chemical products for tick control is increasingly being discouraged. Therefore, this study aimed to assess the acaricidal activity of essential oils such as Ageratum conyzoïdes, Cymbopogon citratus, Cymbopogon giganteus, Lippia multiflora and Ocimum gratissimum against specimens of A. variegatum from Burkina Faso. A larval immersion test was performed to investigate the larvicidal activities of these essential oils. Gas chromatography-mass spectrometry was used to determine the chemical compositions of essential oils. The chemical composition was predominantly oxygenated monoterpenes in A. conyzoïdes (48.71 %), C. citratus (99.9 %) and C. giganteus (73.63 %), while hydrocarbon monoterpenes were the most abundant in O. gratissimum (63.7 %) and hydrocarbon sesquiterpenes in L. multiflora (71.719 %). The recorded larvicidal activity, varied according to the species of plants and the dose applied. At a dose of 12.5 mg/mL, all essential oils studied, except L. multiflora (7.54 %), induced 100 % larval mortality. In this study, we highlight the promising larvicidal effects of local essential oils against A. variegatum. These essential oils can be used as bio-acaricides, which are effective and environmentally-friendly alternatives to chemical products. However, further investigations are required to determine the mechanisms of action of these essential oils for in vivo experimentation and their practical application in the control of A. variegatum ticks.

Acaricidal, larvacidal, and repellent activity of green synthesized silver nanoparticles against Hyalomma dromedarii.

We aimed at determination of acaricidal, larvacidal, and repellent activities of green synthesized silver nanoparticles (SNP) against Hyalomma dromedarii as one of the most common ticks in camels. SNP were green synthesized by reducing Lupinus albus extract through the precipitation technique. The acaricidal, larvicidal, and repellent activity of SNP against H. dromedarii was studied through the adult immersion test (AIT), the larval packet test (LPT), the vertical movement behavior of tick's larvae method, anti-acetylcholinesterase (AChE) activity, and oxidative enzyme activity. The green synthesized SNP displayed a spherical form with a size ranging from 25-90 nm; whereas the most distribution of particles size was reported at 50-65 nm. SNP dose-dependently (p<0.001) increased the mortality rate of H. dromedarii adult; whereas at 16 and 32 µg/mL completely killed the adult females. Treatment of exposure of H. dromedarii adult to SNP markedly (p<0.001) declined the mean number, weight, and hatchability of eggs. Treatment of H. dromedarii larvae with SNP reduced the viability rate of larvae with the LC50 and LC90 values of 3.1 and 6.9 µg/mL, respectively. Exposure of H. dromedarii larvae to SNP, especially at ½ LC50 and LC50, markedly (p<0.001) increased the oxidative stress and declined the level of antioxidant enzymes in H. dromedarii larvae; whereas, markedly suppressed the AChE activity of the larvae stage of H. dromedarii in comparison to the control group. These results showed that SNP green synthesized by L. albus extract had promising acaricidal, larvicidal and repellent activity against H. dromedarii adults and larvae as a dose-dependent response. SNP also considrably decreased the level of acetylcholinesterase and antioxidant activity and also provokes oxidative stress in H. dromedarii larvae. However, more investigation must be designed to clear the accurate mechanisms and the efficacy of SNP in practical use.

Natural Products as Mite Control Agents in Animals: A Review.

Mites have been a persistent infectious disease affecting both humans and animals since ancient times. In veterinary clinics, the primary approach for treating and managing mite infestations has long been the use of chemical acaricides. However, the widespread use of these chemicals has resulted in significant problems, including drug resistance, drug residues, and environmental pollution, limiting their effectiveness. To address these challenges, researchers have shifted their focus towards natural products that have shown promise both in the laboratory and real-world settings against mite infestations. Natural products have a wide variety of chemical structures and biological activities, including acaricidal properties. This article offers a comprehensive review of the acaricidal capabilities and mechanisms of action of natural products like plant extracts, natural compounds, algae, and microbial metabolites against common animal mites.

Integrating In Vitro and In Silico Approaches to Assess Monotheca buxifolia Plant Extract against Rhipicephalus (Boophilus) microplus and Sarcoptes scabiei.

Tick and mite infestations pose significant challenges to animal health, agriculture, and public health worldwide. The search for effective and environmentally friendly acaricidal agents has led researchers to explore natural alternatives. In this study, we investigated the acaricidal potential of the Monotheca buxifolia plant extract against Rhipicephalus microplus ticks and Sarcoptes scabiei mites. Additionally, we employed a computational approach to identify phytochemicals from the extract that could serve as drug candidates against these ectoparasites. The contact bioassay results demonstrated that the M. buxifolia plant extract exhibited significant efficacy against R. microplus and S. scabiei, with higher concentrations outperforming the positive control acaricide permethrin in terms of mite mortality. Time exposure to the extract also showed a positive correlation with better lethal concentration (LC50 and LC90) values. Similarly, the adult immersion test revealed a notable inhibition of tick oviposition via the plant extract, especially at higher concentrations. The two-protein primary structure, secondary structure and stability were predicted using the Expasy's ProtParam server, SOPMA and SUSUI server, respectively. Using Homology modeling, the 3D structure of the protein was obtained and validated through the ERRAT server, and active sites were determined through the CASTp server. The docking analysis revealed that Alpha-Amyrenyl acetate and alpha-Tocopherol exhibited the highest docking scores for S. scabiei and R. microplus aspartic protease proteins, respectively. These phytochemicals demonstrated strong binding interactions, suggesting their potential as acaricidal drug candidates. In conclusion, the M. buxifolia plant extract displayed significant acaricidal activity against R. microplus and S. scabiei. Moreover, the computational approach identified promising phytochemicals that could serve as potential drug candidates for controlling these ectoparasites.

Novel acaricidal and growth-regulating activity of Aloe vera and Rheum rhabarbarum extracts and their oil/water nanoemulsions against the camel tick, Hyalomma dromedarii.

Hyalomma dromedarii is an important tick species infesting livestock. This work evaluated the novel adulticidal, insect growth-regulating, and enzymatic efficacy of ethanol plant extracts of Aloe vera and Rheum rhabarbarum and their nanoemulsions against males and engorged females of the camel tick, H. dromedarii. The physicochemical properties of nanoemulsions were evaluated. The High-Performance Liquid Chromatography (HPLC) analyses indicated that the extracts contained polyphenols and flavonoids, which could enhance their acaricidal effect. Dynamic light scattering (DLS) of the nanoemulsions of A. vera and R. rhabarbarum were 196.7 and 291 nm, whereas their zeta potentials were - 29.1 and - 53.1 mV, respectively. Transmission electron microscope (TEM) indicated that nanoemulsions showed a regular spherical shape (less than 100 nm). Fifteen days post-treatment (PT) with 25%, the mortality% of A. vera and R. rhabarbarum were 88.5 and 96.2%, respectively. Five days PT, the median lethal concentration values of A. vera, R. rhabarbarum, and their nanoemulsions were 7.8, 7.1, 2.8, and 1.02%, respectively, and their toxicity indices were 91.02, 100, 36.4, and 100%, respectively. Their median lethal time values PT with 3.5% were 6.09, 5.09, 1.75, and 1.34 days, respectively. Nanoemulsions enhanced the efficacy of the crude extract 1-7 folds, 5 days PT, and accelerated their speed of killing ticks 2-4 times. The total protein and carbohydrates, Acetylcholinesterase, Alpha esterase, and Amylase were affected PT. The reproductive potential of engorged females was adversely impacted. In conclusion, the novel A. vera and R. rhabarbarum extracts were promising acaricides, and their nanoformulations enhanced their efficacies.

Efficacy of hydroethanolic extract of Randia aculeata seed against the southern cattle tick Rhipicephalus (Boophilus) microplus (Acari: Ixodidae) on naturally infested cattle under field conditions.

The cattle tick Rhipicephalus (Boophilus) microplus is a major problem of concern for cattle industry in tropical and subtropical areas. Control of cattle tick is based mainly on the use of chemical acaricides, which has contributed to the emerging problem of selection of resistant tick lineages. Plants have been used as an alternative to conventional acaricidal drugs. On the other hand, the acaricidal activity of hydroethanolic extract of Randia aculeata seed (EHRA) has been demonstrated against R. microplus under laboratory conditions. However, the utility of EHRA seed as a potential acaricidal needs to be determined under field conditions. For this reason, the aim of this study was to evaluate the efficacy of the EHRA against R. microplus sprayed on naturally infested calves, determine the effect of the EHRA seed on acetylcholinesterase activity in R. microplus larval and identify the chemical composition of EHRA. Forty-five male calves were divided in three groups and treated with: G1 water; G2 EHRA 20% w/v and G3 coumaphos 0.2% v/v. Acetylcholinesterase (AChE) activity in R. microplus larvae was determined by a colorimetric assay. The chemical composition of EHRA was accessed through HPLC/MS. Significantly fewer ticks were observed after 24 h on the treated group compared to control group. EHRA significantly inhibited in vitro AChE activity in R. microplus at all tested concentrations. Chlorogenic acid, vanillinic acid, p-coumaric acid, caffeic acid. rutin, quercetin, (-)-epicatechin, 4-hydroxybenzoic acid, quercetin, vanillin, 2,4-dimethoxy-6-methylbenzoic acid, scopoletin and ferulic acid were identified in the extract. The results provided new data for the elucidation of the mechanisms of EHRA acaricide action and to further evaluate the use as a new alternative control agent against R. microplus under in vivo conditions.

Acaricidal activity of a 2-methoxy-clovan-9-ol rich fraction from Eugenia copacabanensis (Myrtaceae) extract on Rhipicephalus microplus (Acari: Ixodidae).

Rhipicephalus microplus (Ixodidae, canestrini, 1888) is an invasive ectoparasite of cattle which causes high economic losses in emerging countries such as Brazil. Phytochemical compounds have been tested as an alternative to synthetic acaricides due to potentially lower mammalian toxicity. This study evaluated the acaricidal activity against R. microplus of the 2-methoxy-clovan-9-ol rich fraction obtained from Eugenia copacabanensis Kiaersk.leaves, a little known Myrtaceae species from the Brazilian Atlantic Forest. This fraction was obtained by maceration with methanol, partition with n-hexane and purification by normal-phase column chromatography. GC-MS, 1H and 13C NMR and IR analysis contributed to the identification of a major compound as the sesquiterpene 2-methoxy-clovan-9-ol, reported for the first time for the Myrtaceae family. The fraction was tested against R. microplus unfed larvae and engorged females and a 93% larval mortality was observed at the concentration of 50 mg mL-1. Lower concentrations of the solution tested demonstrated a significant difference in egg mass weight, hatching and control percentage. Experiments with 50.0 mg mL-1 showed significative results, with lower concentration and maximum efficacy for both assays. The IC50 values for unfed larvae and engorged females were 21.76 and 11.13 mg mL-1, respectively. These results were similar to those obtained in other studies with isolated botanical compounds and essential oils. The lower IC50 for engorged females than for unfed R. microplus larvae had also been described for other plant materials, including plants from the same Myrtaceae family. The present result suggested different mechanisms of action of the compound on the reproductive biology of engorged females, improving its effect against egg viability. These results are important for tick control, suggesting that 2-methoxy-clovan-9-ol could be a potential natural acaricidal product against both R. microplus unfed larvae and engorged females.

Liver and spleen of hosts of Rhipicephalus linnaei exposed to synthetic (afoxolaner) and natural acaricides (esters from castor oil). A comparative clinical-morphological study.

In dogs, Rhipicephalus linnaei transmits pathogens such as Ehrlichia canis, Babesia vogeli, and Hepatozoon canis. The veterinary market has synthetic acaricides to ticks control. Esters derived from castor oil are efficient. However, there is little information about their effects on non-target organisms. This work consisted of a clinical (AST, ALT, and ALP) and histological and histochemical analysis (liver and spleen) of female rabbits exposed to these esters and afoxolaner. The rabbits were divided into three groups: control group (CG) received Bandeirante® rabbit feed; the afoxolaner treatment (TG1) received rabbit feed and two doses of afoxolaner; castor oil esters treatment (TG2) received rabbit feed enriched with esters (1.75 g esters/kg). No alterations were observed in the AST, ALT, and ALP enzymes in exposure to esters TG2. Rabbits from TG1 showed changes in AST. The liver of rabbits exposed to afoxolaner underwent histological and histochemical changes, such as steatosis and vacuolation, as well as poor protein labeling. Polysaccharides were intensely observed in the group exposed to esters. The spleen showed no changes in any of the exposure. Esters from castor oil caused fewer liver changes when incorporated into the feed and fed to rabbits than exposure to afoxolaner.

Acaricidal and repellent activities of ethanol extracts of nine chinese medicinal herbs against Rhipicephalus microplus (Acari: Ixodidae).

Rhipicephalus microplus is a major threat to the cattle industry worldwide. The intensive use of acaricides and repellents has resulted in drug resistance. Hence, effective and eco-friendly pest control alternatives are urgently needed, especially from natural plant resources. In this study, the acaricidal and repellent activities of nine herbs against the larvae and eggs of R. microplus were evaluated. The results showed that ethanol extracts of star anise (Illicium verum), chaulmoogra (Hydnocarpus anthelmintica), motherwart (Leonurus artemisia), mandarin orange peel (citri reticulatae pericarpium, i.e., peel of Citrus reticulata fruit), and stemona (Stemona sessilifolia) had good contact acaricidal activities of 100, 98, 94, 88 and 86%, respectively, whereas star anise and clove (Syzygium aromaticum) had good fumigant acaricidal activities of 98 and 96%, respectively. The hatching inhibition rate of star anise against R. microplus eggs was 100%. All nine herbs had good real-time repellent rates, but only castor bean and star anise had repellent effects after 48 h (81.3 and 79.6%, respectively). This is the first report of the acaricidal and repellent activities of these medicinal herbs against R. microplus. Ethanol extracts of these herbs might be considered as potential alternatives to chemical acaricides for control of R. microplus.

Composición química y revisión de las propiedades acaricidas de los aceites esenciales de Melinis minutiflora y Lantana camara / Chemical composition and review of the acaricidal properties of the essential oils of Melinis minutiflora and Lantana camara

The present study determined the volatile chemical components of the essential oils (EA) of the Melinis minutiflora and Lantana camara species, by means of gas chromatography coupled to a mass spectrometer, the species were collected in the cantons of Quilanga and Loja, the extraction was carried out by steam distillation. In the essential oil (EA) of M. minutiflora, 20 compounds were identified, representing 93.21%, the compounds in the highest concentration: 1-tetradecanol (16.30%), (E) -cariophylene (12.44%), germacrene D (10.99%), (E) -nerolidol (8.28%), δ-cadinene (5.61%), α-humulene (5.36%), viridiflorol (4.78%) and (Z) -ß-farnesene (4.76%). In the AE of L. camara, 68 compounds were identified, representing 96.54%, the compounds with the highest concentration (E) -caryophyllene (15.46%), germacrene D (12.21%), α-humulene (9.92%), bicyclogermacrene (7.06 %), γ-terpinene (5.97%) and germacrene B (4.66%). The species M. minutifloraand L. Camarahave repellent, acaricidal properties in adult larvae of Amblyomma cajennense and Rhipicephalus (Boophylus) microplus.

El presente estudio determinó los componentes químicos volátiles de los aceites esenciales (AEs) de las especies Melinis minutiflora y Lantana camara, mediante cromatografía de gases acoplado a espectrómetro de masas, las especies se recolectaron en los cantones de Quilanga y Loja, la extracción se hizo mediante destilación por arrastre de vapor. En el aceite esencial (AE) de M. minutiflora se identificaron 20 compuestos, representan el93,21%, los compuestos en mayor concentración: 1-tetradecanol (16,30%), (E)-cariofileno (12,44 %), germacreno D (10,99%), (E)-nerolidol (8,28 %), δ-cadineno (5,61 %), α-humuleno (5,36 %), viridiflorol (4,78 %) y (Z)-ß-farneseno (4,76 %). En el AE de L. camara se identificaron 68 compuestos, representan el 96,54%, los compuestos en mayor concentración (E)-cariofileno (15,46%), germacreno D (12,21%), α-humuleno (9,92%), bicyclogermacreno (7,06%), γ-terpineno (5,97%) y germacreno B (4,66%); las especies M. minutiflora y L. cámara, presentan propiedades repelentes, acaricidas en larvas, adultas de Amblyomma cajennense y Rhipicephalus (Boophylus) microplus.

Natural Clerodendrum-derived tick repellent: learning from Nepali culture.

Ticks attaching to ear canals of humans and animals are the cause of otoacariasis, common in rural areas of Nepal. The plant Clerodendrum viscosum is used in multiple indigenous systems of medicine by ethnic communities in the Indo-Nepali-Malaysian region. Visiting the Chitwan National Park, we learned that in indigenous medicine, flower extract of C. viscosum is utilized to treat digestive disorders and extracts from leaves as tick repellent to prevent ticks from invading or to remove them from the ear canal. The objective of our study was to provide support to indigenous medicine by characterizing the in vivo effect of leave extracts on ticks under laboratory conditions and its phytochemical composition. We collected plant parts of C. viscosum (leaves and flowers) and mango (Mangifera indica) leaves at the Chitwan National Park, previously associated with repellent activity to characterize their effect on Ixodes ricinus ticks by in vivo bioassays. A Q-ToF high-resolution analysis (HPLC-ESI-QToF) was conducted to elucidate phenolic compounds with potential repellent activity. Clerodendrum viscosum and M. indica leaf extracts had the highest tick repellent efficacy (%E = 80-100%) with significant differences when compared to C. viscosum flowers extracts (%E = 20-60%) and phosphate-buffered saline. Phytochemicals with tick repellent function as caffeic acid, fumaric acid and p-coumaric acid glucoside were identified in C. viscosum leaf extracts by HPLC-ESI-QToF, but not in non-repellent flower extracts. These results support the Nepali indigenous medicine application of C. viscosum leaf extracts to repel ticks. Additional research is needed for the development of natural and green repellent formulations to reduce the risks associated with ticks resistant to acaricides.

Essential oil Ageratum conyzoides chemotypes and anti-tick activities.

Rhipicephalus (Boophilus) microplus represents a significant obstacle to animal productivity in tropical and subtropical areas, leading to considerable economic losses for the dairy and meat production industries. Essential oils (EO) extracted from Ageratum conyzoides are known to cause death and induce morphogenetic abnormalities in several insect species. This plant, however, presents morphological flower variations, which range from white to purple, associated to different chemotypes. In this context, this study aimed to conduct a novel assessment on the effects of EO extracted from two A. conyzoides chemotypes in the control of the bovine tick R. microplus. The primary constituents of the oil obtained from white flower samples (WFs) were precocene I (80.4 %) and (E)-caryophyllene (14.8 %), while purple flower oil samples (PFs) contained predominantly ß-acoradiene (12.9 %), γ-amorphene (12.3 %), α-pinene (9.9 %), bicyclogermacrene (8.9 %), α-santalene (8.7 %), and andro encecalinol (5.6 %). Interestingly, only the EO chemotype from A. conyzoides PFs displayed acaricidal activity towards R. microplus larvae, with an LC50 of 1.49 mg/mL.

Development and Validation of a Gas Chromatography-Mass Spectrometry Method for Determining Acaricides in Bee Pollen.

Pesticides can be found in beehives for several reasons, including contamination from surrounding crops or for their use by beekeepers, which poses a risk to bee ecosystems and consumers. Therefore, efficient and sensitive methods are needed for determining pesticide residues in bee products. In this study, a new analytical method has been developed and validated to determine seven acaricides (atrazine, chlorpyrifos, chlorfenvinphos, α-endosulfan, bromopropylate, coumaphos, and τ-fluvalinate) in bee pollen using gas chromatography coupled to mass spectrometry. After an optimization study, the best sample treatment was obtained when using a modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) method employing an ethyl acetate and cyclohexane as the extractant mixture, and a mixture of salts for the clean-up step. A chromatographic analysis (<21 min) was performed in an Agilent DB-5MS column, and it was operated under programmed temperature conditions. The method was fully validated in terms of selectivity, limits of detection (0.2-3.1 µg kg-1) and quantification (0.6-9.7 µg kg-1), linearity, matrix effect (<20% in all cases), trueness (recoveries between 80% and 108%), and precision. Finally, the proposed method was applied to analyze commercial bee pollen samples, and some of the target pesticides (chlorfenvinphos, α-endosulfan, coumaphos, and τ-fluvalinate) were detected.