Evaluation of β-caryophyllene(1-3) as a potential anti-tick molecule for controlling tick infestations on animals.

Ageratum conyzoides (Family: Asteraceae), a common herbaceous weed has a long history of use in traditional medicine. Rhipicephalus microplus, the cattle tick is distributed globally and causing significant economic losses to the animal husbandry sectors. Due to repeated applications of chemical acaricides to control infestation on animals, the tick species developed resistance to most of the acaricides. In the present study, to manage the problem of resistant ticks, the potentiality of β-caryophyllene (1-3) is explored for its anti-tick efficacy against three important tick species. The LC value of β-caryophyllene (1-3) against reference susceptible IVRI-I strain of R. microplus was 0.0284 % (95 % CI = 266.5-299.4) while against multi-acaricide resistant field isolates it was 0.0507 % (95 % CI = 491.4-523.0). The compound was 95 % efficacious against Hyalomma anatolicum and R. annulatus ticks. The anti-tick efficacy of the compound after oral administration at the dose rate of 7.5 mg per kg body weight was tested under challenged infestation conditions and more than 80 % efficacy was noted. In a separate experiment, a 73.3-97.7 % (mean efficacy = 77.6 %) efficacy of β-caryophyllene (1-3) was noted for three months which was comparable and not significantly lower than the efficacy (95.8 %) observed in the amitraz treatment group of animals but significantly higher as compared to the control group of animals. The present study was focused on the identification of new plant derived anti-tick molecule having the acaricidal capability for the management of resistant tick infestations on animals.