Anthelmintic effect of Cymbopogon citratus essential oil and its nanoemulsion on sheep gastrointestinal nematodes

Abstract The anthelmintic resistance stimulated the search for strategies for controlling gastrointestinal nematodes, including the use of free essential oils or its nanoemulsion. This study evaluated the anthelmintic efficacy of Cymbopogon citratus essential oil (CcEO) and C. citratus essential oil nanoemulsion (CcEOn). Pysicochemical analyses were performed. The in vitro effect was determined using the egg hatch test (EHT) on Haemonchus contortus and in vivo effect was evaluated in sheep infected with gastrointestinal nematodes. The animals were treated with CcEO (500 mg/kg) or CcEOn (450 mg/kg) for the fecal egg count (FEC) and the determination of worm burden. The main component of CcEO was citral. The CcEO content in the nanoemulsion was 20% (v/v), and the mean particle size was 248 nm. In EHT, CcEO and CcEOn (1.25 mg/mL) inhibited larval hatching by 98.4 and 97.1%, respectively. Three animals treated with CcEO died whereas in the group treated with CcEOn one animal died. The FEC and total worm burden of the treated groups did not differ from the negative control (p>0.05). The CcEOn showed efficacy only on H. contortus (p<0.05). In conclusion, nanoencapsulation reduced toxicity and increased efficacy on H. contortus.

摘要 抗驱虫药性的出现推动了胃肠道线虫防控策略的研发，其中涵盖游离精油及其纳米乳剂的应用。本研究评估了柠檬草精油（Cymbopogon citratus essential oil, CcEO）及其纳米乳剂（Cymbopogon citratus essential oil nanoemulsion, CcEOn）的驱虫效果。本研究开展了理化性质分析，采用体外虫卵孵化试验（Egg Hatch Test, EHT）检测其对捻转血矛线虫（Haemonchus contortus）的体外活性，并通过人工感染胃肠道线虫的绵羊模型评估其体内效果。试验动物分别以500 mg/kg剂量的CcEO或450 mg/kg剂量的CcEOn给药，随后开展粪便虫卵计数（Fecal Egg Count, FEC）与虫荷测定。CcEO的主要活性成分为柠檬醛，该纳米乳剂中CcEO的体积分数为20%（v/v），平均粒径为248 nm。在EHT试验中，浓度为1.25 mg/mL的CcEO与CcEOn分别可抑制98.4%与97.1%的幼虫孵化。CcEO给药组共有3只试验动物死亡，而CcEOn给药组仅1只动物死亡。给药组的粪便虫卵计数与总虫荷与阴性对照组均无显著性差异（p>0.05），但CcEOn仅对捻转血矛线虫表现出显著的驱虫活性（p<0.05）。综上，纳米包埋技术可降低柠檬草精油的毒性，并提升其对捻转血矛线虫的驱虫效果。