| As specialized blood-sucking ectoparasites,ticks are described and named 960 species in the worldwide,and 124 species have been identified in China.Ticks could transmit a variety of pathogens and toxins,such as viruses,rickettsiae,bacteria,spirochetes and protozoa,endangered human health,husbandry and wildlife.Hyalomma asiaticum belongs to the Ixodidae family and the Hyalomma genus,were found in the areas like Xinjiang,Gansu,Inner Mongolia provinces.Its ability to survive and reproduce were strong,parasitizing camels,cattle,horses,sheep and other livestock and people,posing a serious risk to public health and safety and animal husbandry.Plant essential oil,as a low-toxic and efficient environmentally friendly drug,had been application in tick control.In this study,we screened 22 essential oils to evaluate their repellent and toxic effects on H.asiaticum,used Gas Chromatography-Mass Spectrometry（GC-MS）analysis to investigate the active ingredients of the candidate oils,the activity alteraction of 4 enzymes in ticks under the plant essential oils treatment were determined by biochemical techniques,and the high-throughput sequencing was used to explore the mechanism of action.In this study,a total of 14 effective plant essential oils were screened for their main components:the maximal proportion of Cinnamomum tamala oil was 2h-Inden-2-one;the maximal proportion of Mentha hyplocalyx oil,Eucalyptus robusta oil and Rosa rugosa oil was isopropyl palmitate;the maximal proportion of Ocimum basilicum oil was tetradecanoate acid;the maximal proportion of Citrus limon oil was 3-Cyclohexene-1-acetaldehyde;the maximal proportion of Achyranthes bidentata oil was carvacrol;the maximal proportion of Mentha spicata oil was diethyl phthalate,the maximal proportion of Ilex chinensis oil was methyl salicylate;the maximal proportion of t Juniperus rigida oil wasγ-terpinene;the highest content of the essential oil of Mosla chinensis oil was cis-9-Tetradecen-1-ol;the maximal proportion of the essential oil Tagetes erecta oil was 1,6-Octadien-3-ol;the maximal proportion of Syringa oblata bud oil and Pimenta dioica oil was eugenol.The repellent effects of S.oblata bud oil,J.rigida oil,M.chinensis oil,T.erecta oil,I.chinensis oil,and P.dioica oil EC50were 12.45μg/cm2,15.50μg/cm2,17.73μg/cm2,18.87μg/cm2,22.12μg/cm2,and 23.56μg/cm2,respectively.The highest repellent efficiency was S.oblata bud oil with 57%repellent rate.8 essential oils,including C.tamala oil,R.rugosa oil,E.robusta oil,M.haplocalyx oil,O.basilicum oil,C.limon oil,A.bidentata oil,M.spicata oil were showed resultful thixotoxic effects on different life stages of H.asiaticum;among them,C.tamala oil,A.bidentata oil and C.limon oil were showed the best thixotoxic effects on unfed H.asiaticum larvae after treatment,the LC50 were 0.76 mg/ml,2.94 mg/ml and 3.38 mg/ml,respectively;R.rugosa oil,C.tamala oil and E.robusta oil were showed the best thixotoxic to unfed H.asiaticum nymph,the LC50 were 0.61 mg/ml,0.98 mg/ml and 1.07 mg/ml respectively.C.tamala oil,E.robusta oil and O.basilicum oil were showed the best thixotoxicity in treated unfed H.asiaticum adults,with LC50 of 2.43 mg/ml,2.59 mg/ml,and 2.71 mg/ml,respectively.The highly component of C.tamala oil,E.robusta oil,O.basilicum oil,like2H-Inden-2-one,eucalyptol,eugenol,showed efficient killing activity.2H-Inden-2-one,eucalyptol,eugenol the LC50 of unfed H.asiaticum nymph were 3.46 mg/ml,0.34 mg/ml,0.25 mg/ml,respectively,the LC50 of unfed H.asiaticum adult were 4.78 mg/ml、2.87 mg/ml、1.60 mg/ml,respectively.Comparing with the control group,the results of the enzyme activity of the experimental group after 24 h treatment with C.tamala oil,R.rugosa oil,E.robusta oil,M.haplocalyx oil,O.basilicum oil,C.limon oil,eugenol,eucalyptol and 2H-Inden-2-one the half lethal concentration of unfed H.asiaticum adult were determined as follows:（1）O.basilicum oil,C.limon oil,M.haplocalyx oil,C.tamala oil and eugenol had a significant effect on SOD activity,while the other treatment groups had a non-significant effect on SOD activity（P<0.05）.（2）6 plant essential oils and 3 single components exerted part effect on CAT activity,but not significantly（P<0.05）.（3）Except for C.tamala oil,all other treated groups showed significant effects on Car E activity（P<0.05）.（4）Except for C.limon oil,R.rugosa oil and C.tamala oil,all other treated groups had significant effects on Ach E activity（P<0.05）.The results of transcriptome showed that flavin monooxygenases（FMOs）was significantly up-regulated in the drug metabolism-cytochrome P450 pathway after treatment with C.tamala oil,and the results of fluorescence quantitative PCR validation were consistent with transcriptome results,indicating that FMOs was involved in the detoxification mechanism of H.asiaticum in response to C.tamala oil.In brief,C.tamala oil and E.robusta oil could be used as effective alternatives to chemical acaricides for the prevention and H.asiaticum control.This study provides a theoretical basis for the screening of anti-tick drugs and the development of new acaricides. |
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