Can orange essential oil reduce the severity of parasitic infection in sheep?

In this study, a three-step experiment was conducted to evaluate the effectiveness of orange essential oil (OEO) to reduce the severity of parasitic infection in lambs naturally infected with gastrointestinal parasites. In the first and second stages of the experiment, the lambs were distributed in groups (n = 10): without treatment (control), treated with levamisole (7.5 mg/kg), and treated either with 200, 300 or 400 mg/kg OEO in the first stage and with two doses of 300 or 350 mg/kg each of OEO with a six-hour interval in the second stage. In the third stage of the experiment, 20 lambs were distributed into control and treated groups (two doses of 350 mg/kg OEO) and slaughtered for determining the parasite count in the abomasum and small intestine. Evaluations were performed on D0, D3, D7, D10, and D14 by determining the egg count per gram of feces (EPG), and the percentage of EPG reduction was calculated in comparison to D0. Coproculture was performed on days D0 and D14 of the first and second stages of the study. In the first stage, the EPG increased by 20.90 and 100.99% and decreased by 5.54% on D14 in the groups treated with 200, 300, or 400 mg/kg OEO, respectively. At the second stage, the EPG of the OEO groups decreased by more than 96% on D3, but on D14 was decreased by 0.82% and 77.07% in the 2 × 300 and 2 × 350 mg/kg groups, respectively. Haemonchus sp. was the highest percentage of collected larvae in all coproculture tests, ranging from 90 to 100%. In the third stage, there was no difference (P > 0.05) in the mean number of parasites between the OEO groups and the control. Although the decrease in EPG of more than 96% on D3 did not persist in the other evaluations, and immature forms and adult parasites were collected at slaughter, the EPG reduction of 77.07% on D14 with the dose of 700 mg/kg (OEO2 × 350) suggests that OEO can help to reduce the severity of parasitic infection and, consequently, to diminish pastures contamination, when used together with other methods to control gastrointestinal parasites in sheep.

Adverse reactions after orange essential oil administration to lambs.

The major compound in orange essential oil (OEO) is limonene, which has in vitro anthelmintic properties; however, a safe in vivo dose has not been defined for animals. Therefore, a pilot study was conducted to evaluate the effect of an OEO formulation for the control of gastrointestinal nematodes in sheep and to investigate adverse reactions in lambs after OEO administration. A total of 17 lambs received an oral OEO formulation at a concentration of 600 mg/mL, in doses of 200, 300, and 600 mg/kg. The most common clinical signs observed were head shaking (88.8%), backward head movement (51.1%), and ataxia (74.4%). Lambs treated with 600 mg/kg of OEO showed more severe combined clinical signs and longer duration of symptoms, presenting adverse reactions for up to 2 h after OEO administration. Testing of different doses and formulations with slower release of the active ingredient is recommended to minimize or eliminate these effects.