Effects of commercial oils on the camel tick Hyalomma dromedarii (Acari: Ixodidae) and their enzyme activities

Hyalomma dromedarii is the predominant tick species parasitizing camels in Egypt. This study aimed to evaluate the acaricidal activity of selected oils against H. dromedarii and determine their effects on enzyme activities. A screening test was performed against unfed adults using 30 oils at a concentration of 20%. Rosemary, garlic, neem, and Cyperus oils were evaluated against semi-engorged females in a bioassay experiment. Semi-engorged females were exposed to LC50 that was calculated after two days to estimate enzyme activities of Glutathione S-transferase (GST), Acetylcholinesterase (AChE), and Catalase (CAT). Results of the screening test showed that the most effective oils against unfed adults were rosemary, neem, Cyperus, and garlic. In the bioassay experiment, rosemary oil exhibited the highest toxicity on the 2nd day (LC50: 12.3%) followed by garlic oil (LC50: 17.4%). Neem and Cyperus oils revealed approximately the same toxicity recording an LC50 of around 29% on the 2nd day. The four selected oils exhibited a significant increase or decrease in the activity of GST, AChE, and CAT enzymes (P < 0.001) during 48 h post-treatment. In conclusion, rosemary and garlic oils have strong acaricidal effects against H. dromedarii. Therefore, these two oils could be recommended in the control program of ticks as safe alternatives to chemical acaricides.