The aim of the present study was to test the in vitro acaricidal activity of saturated fatty acids (hexanoic, octanoic, decanoic, lauric, myristic, palmitic, octadecanoic, eicosanoic, docosanoic and tetracosanoic) against Rhipicephalus microplus and select a candidate compound for the subsequent determination of its clinical safety for mice and bovines as well as its in vivo efficacy (ethical clearance number 507/2013). None of the compounds exhibited in vitro larvicidal effectiveness, but acaricidal effectiveness was greater than 95 % in the adult immersion test at 40 mg/ml (hexanoic, octanoic, decanoic, lauric, myristic, palmitic and eicosanoic acids). After a second AIT evaluation of serial concentrations of the fatty acids, lauric and myristic acids were selected for the safety and in vivo efficacy assays. No adverse effect was found in the local lymph node assay in mice treated with lauric or myristic acid. Moreover, no clinical signs of systemic poisoning or dermatological, hematological or biochemical abnormalities were found in cattle after the topical application of 1 % lauric acid. In the dose determination test, the 1% solution of this compound exhibited 86% efficacy in cattle naturally infested by a field population of Rhipicephalus microplus susceptible to all chemical groups, except synthetic pyrethroids. The efficacy of 1 % lauric acid was 53.4 % in the dose confirmation test performed on another herd with a field R. microplus population resistant to all chemical groups of acaricides. In conclusion, fatty acids are potential bioactive compounds for the control of R. microplus. Topically applied lauric acid (C12) exhibits in vivo acaricide activity against adults, nymphs and larvae of R. (B) microplus and is safe for cattle.

中文翻译：

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月桂酸对牛的临床安全性及其对微小头蛇耳的体内和体外疗效。

本研究的目的是测试饱和脂肪酸（己酸，辛酸，癸酸，月桂酸，肉豆蔻酸，棕榈酸，十八烷酸，二十烷酸，二十二烷酸和十四烷酸）对微小头蛇耳螨的体外杀螨活性，并为后续的筛选选择候选化合物确定其对小鼠和牛的临床安全性以及体内功效（伦理批准编号507/2013）。在成人浸入试验中，在40 mg / ml（己酸，辛酸，癸酸，月桂酸，肉豆蔻酸，棕榈酸和二十烷酸）成人浸没试验中，没有一种化合物显示出体外杀幼虫剂的功效，但杀螨功效高于95％。在对脂肪酸的系列浓度进行第二次AIT评估后，选择了月桂酸和肉豆蔻酸进行安全性和体内功效分析。在用月桂酸或肉豆蔻酸治疗的小鼠的局部淋巴结试验中未发现不良反应。此外，在局部应用1％月桂酸后，在牛中未发现全身中毒或皮肤病，血液学或生化异常的临床体征。在剂量测定试验中，该化合物的1％溶液在牛中受到了对所有化学基团敏感的除实际拟除虫菊酯外的所有微小化学裂头cephal自然侵染的牛的功效为86％。在另一场对所有杀螨剂化学基团都具有抗药性的R. microplus种群进行的剂量确认试验中，1％月桂酸的功效为53.4％。总之，脂肪酸是潜在的生物活性化合物，可用于控制微小芽孢杆菌。