Louicidal Efficacy of Essential Oils against The Dog Louse, Trichodectes canis (Mallophaga: Trichodectidae)

Biting lice are widespread ectoparasites of dogs and other animals. Their management is complicated because of growing levels of resistance to commonly applied pediculicides. Thus, the development of novel approaches to their control is of primary clinical interest. Therefore, we examined the chemical composition of garlic, clove, pumpkin, onion and marjoram essential oils through gas chromatography-mass spectrometry (GC-MS) and their individual toxicity against the dog lice Trichodectes canis using a contact filter paper bioassay. GC-MS analysis revealed the presence of 45 compounds in garlic oil, 15 compounds in clove oil, 24 compounds in pumpkin oil, 16 compounds in onion oil and 22 compounds in marjoram oil. 2,3,3-trimethyl Hexane (5.33%), (+-) -(1S, 3R)-4(S)(a)-Methyladamantan (44.35%), 2,6,10,14,18,22-Tetracosahexane, Ethyl-2,6,10,15, 19,23-Hexane (31.67%), (E, E)-2,4-Decadienal (18.64%) and 4-methyl-1-(1-methylethyl)-3-Cyclohexen-1-ol (CAS) (21.01%) were the most abundant compounds in garlic, clove, pumpkin, onion and marjoram oils, respectively. All treated groups except marjoram oil showed high levels of toxicity. Clove, garlic and pumpkin oils demonstrated the best loucidal activity reaching 100% mortality within 15 and 20 minutes. The LC50 values were 10.757, 9.156, 11.325, 27.296 and 15.059 % for garlic, clove, pumpkin, marjoram and onion oils. Based on the LC50 values, the relative efficacies of the tested oils after 35 minutes compared with that of the marjoram oil as a reference material indicated that, clove, garlic, pumpkin and onion oils were 3.0, 2.5, 2.4 and 1.8, respectively more effective than marjoram oil. The LT50 values, post-treatment with 25% were 40.659, 48.335, 39.261, 45.744, and 47.974% respectively. The relative speed of killing lice is almost similar in all tested oils. It could be concluded that clove, garlic and pumpkin oils may offer eco-friendly alternatives of veterinary pediculicides for the control of the dog lice T. canis.