| Proroptic acariasis is a kind of ectoparasite disease induced by Psoroptes cuniculi’sparasitizing on animals’ body surface or epidermis. It causes severe pruritus and exudativeinflammation of skin as well as depilation, as infection development, it leads to mentaldepression and magersucht, or even death by multiple system organ failure. The disease rateand infection rate of Proroptic acariasis is relatively high in summer and autumn, and thedisease usually causes huge financial losses to animal husbandry. At present the drugs used totreat Proroptic acariasis are mainly divided into two groups: natural medicine and syntheticmedicine. The latter operates rapidly and possesses good curative effect，while easily causesdrug residues and pollution of animal products. For this reason, natural plant medicines withlow toxicity, residue-free, resistance-free and high safety to human beings, livestocks andenvironments have become a hotspot research area in acaricides. A highly efficient acaricidalconstituent was extracted from the Chinese medicinal herb Eugenia caryophyllata Thunbwhich was identified as eugenol and could kill all tested mites in mere12min. Although thereare plenty of studies on the extraction, pharmacological action and clinical application ofeugenol, it is still lack of comprehensive and systematic researches on the acaricidalmechanisms of eugenol against Psoroptes cuniculi. By using activities of target enzymes ofnerve system as the main evaluation indicator, and along with the semiology and histologystudy, the research aimed at exploring the acaricidal mechanism of eugenol against Psoroptescuniculi and providing scientific foundation for further application.(1) The observation of subcellular structure under electron microscopy: The transmissionelectron microscopy was applied to evaluate the changes of subcellular structure of Psoroptescuniculia after treated by eugenol. Eugenol was diluted into0.6%test solution with paraffinoil and poured into a24-hole culture plate,300μL each hole. Psoroptes cuniculi wasimmersed into eugenol solution in the culture plate holes with needles, then the24-hole platewas placed in thermotank at22℃and the changes were observed every36min until180min.The mites were taken out from the solution and blotted by filter papers after3h’s treatmentwith eugenol solution, and then the subcellular structure of Psoroptes cuniculi was observed. After treatment with eugenol solution for180min, the karyotheca of Psoroptes cuniculi cellsswelled, nuclear chromatin condensed, Golgi complex and mitochondria vacuolated,endoplasmic reticulum (ER) ruptured or distorted and transverse striation of muscle cellsbecame unclear and further caused dysfunction of cells and deaths of mites.(2) The determination of the enzymes activity: The biochemical method was applied toevaluate the changes of the enzymes activity in Psoroptes cuniculi in the treated group and thecontrol group.100mites were sampled for each at the time point of36,72,108,144,180minafter treated by eugenol, and immediately homogenated in physiological saline in ice bath,and then centrifuged at2,500g for15min. The supernatant was collected and used fordetermination of the activities of acetylcholine esterase (AChE), glutathione-S-transferase(GSTs) and Ca2+-ATPase. Additionally,200tested mites were sampled to evaluate the activityof monoamine oxidase (MAO). The results showed that the activities of MAO, GSTs andCa2+-ATPase of Psoroptes cuniculi were significantly decreased after treatment with0.6%eugenol for36,72,108,144,180min respectively (P<0.05), and the activity of AChE wassignificantly decreased after treatment for108,144,180min respectively. It is concluded thateugenol can significantly inhibit the enzymes activity of Psoroptes cuniculi and causedysfunction of cells and further lead to the deaths of mites. |
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