Laboratory of Parasitology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820, Merelbeke, Belgium.
Biometrics Research Center, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820, Merelbeke, Belgium.
Parasit Vectors. 2019 Aug 29;12(1):425. doi: 10.1186/s13071-019-3654-x.
Treatment of Psoroptes ovis in cattle is limited to topical acaricides or systemic treatment with macrocyclic lactones. Treatment failure of macrocyclic lactones has been reported. The aim of this study was to evaluate a potential alternative treatment against P. ovis.
The acaricidal activity against P. ovis of four plant-derived essential oil components, i.e. geraniol, eugenol, 1,8-cineol and carvacrol, was assessed in vitro and in vivo. In vitro contact, fumigation and residual bioassays were performed. In addition, 12 Belgium Blue cattle were artificially infested and treated topically once a week for three successive weeks with carvacrol in Tween-80 (treatment group) or with Tween-80 alone (control). The efficacy of carvacrol was determined by the reduction in lesion size and mite counts. Six additional animals were topically treated with carvacrol to assess local adverse reactions.
Three components showed a concentration-dependent acaricidal activity in a contact assay, with LC of 0.56, 0.38 and 0.26% at 24 h for geraniol, eugenol, and carvacrol, respectively. However, 1,8-cineol showed no activity at any of the tested concentrations in a contact bioassay. In a fumigation bioassay, carvacrol killed all mites within 50 min after treatment, whereas geraniol, eugenol and 1,8-cineol needed 90 to 150 min. Following a 72 h incubation period in a residual bioassay, carvacrol killed all mites after 4 h of exposure to LC while geraniol and eugenol killed all mites only after 8 h exposure. Based on these results, carvacrol was further assessed in vivo. Mite counts in the treatment group were reduced by 98.5 ± 2.4% at 6 weeks post-treatment, while in the control group the mite population had increased. Topical application of carvacrol only caused mild and transient erythema 20 min after treatment. No other side effects were observed.
Considering the strong acaricidal activity of carvacrol in vitro and in vivo and the mild and transient local side effects, carvacrol shows potential as an acaricidal agent in the treatment of P. ovis in cattle.
牛皮蝇蛆病的治疗仅限于局部杀螨剂或全身性大环内酯类药物治疗。据报道，大环内酯类药物治疗失败。本研究旨在评估一种针对牛皮蝇蛆的潜在替代治疗方法。
评估了四种植物源精油成分，即香叶醇、丁香酚、1,8-桉叶油醇和香芹酚，对牛皮蝇蛆的体外和体内杀螨活性。进行了体外接触、熏烟和残留生物测定。此外，12 头比利时蓝牛被人工感染，并每周用香芹酚在吐温-80 中（治疗组）或仅用吐温-80（对照组）局部涂抹一次，连续三周。通过减少病变面积和螨虫计数来确定香芹酚的疗效。另外 6 只动物局部用香芹酚处理，以评估局部不良反应。
三种成分在接触测定中表现出浓度依赖性杀螨活性，香叶醇、丁香酚和香芹酚的 LC 分别为 24 小时时为 0.56%、0.38%和 0.26%。然而，1,8-桉叶油醇在任何接触生物测定的测试浓度下均无活性。在熏烟生物测定中，香芹酚在处理后 50 分钟内杀死了所有螨虫，而香叶醇、丁香酚和 1,8-桉叶油醇则需要 90 至 150 分钟。在残留生物测定中孵育 72 小时后，香芹酚在暴露于 LC 4 小时后杀死了所有螨虫，而香叶醇和丁香酚仅在暴露 8 小时后杀死了所有螨虫。基于这些结果，进一步在体内评估了香芹酚。治疗组的螨虫数量在治疗后 6 周时减少了 98.5%±2.4%，而对照组的螨虫数量增加了。香芹酚局部应用仅在治疗后 20 分钟引起轻度和短暂的红斑。未观察到其他副作用。
考虑到香芹酚在体外和体内的强烈杀螨活性以及温和和短暂的局部副作用，香芹酚在牛皮蝇蛆病的牛治疗中具有作为杀螨剂的潜力。
