title: Repellent effects of Melaleuca alternifolia (tea tree) oil against cattle tick larvae (Rhipicephalus australis) when formulated as emulsions and in β-cyclodextrin inclusion complexes.
abstract: Rhipicephalus australis (formerly Boophilus microplus) is a one host tick responsible for major economic loss in tropical and subtropical cattle production enterprises. Control is largely dependent on the application of acaricides but resistance has developed to most currently registered chemical groups. Repellent compounds that prevent initial attachment of tick larvae offer a potential alternative to control with chemical toxicants. The repellent effects of Melaleuca alternifolia oil (TTO) emulsions and two β-cyclodextrin complex formulations, a slow release form (SR) and a modified faster release form (FR), were examined in a series of laboratory studies. Emulsions containing 4% and 5% TTO applied to cattle hair in laboratory studies completely repelled ascending tick larvae for 24h whereas 2% and 3% formulations provided 80% protection. At 48h, 5% TTO provided 78% repellency but lower concentrations repelled less than 60% of larvae. In a study conducted over 15 days, 3% TTO emulsion applied to cattle hair provided close to 100% repellency for 2 days, but then protection fell to 23% by day 15. The FR formulation gave significantly greater repellency than the emulsion and the SR formulation from day 3 until the end of the study (P<0.05), providing almost complete repellency at day 3 (99.5%), then decreasing over the period of the study to 49% repellency at day 15. Proof of concept is established for the use of appropriately designed controlled-release formulations to extend the period of repellency provided by TTO against R. australis larvae.
authors.affiliation: Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St Lucia, QLD 4072, Australia.
authors.forename: Wei Tsun
authors.initials: WT
authors.lastname: Yim
authors.affiliation: School of Agriculture and Food Sciences, The University of Queensland, Brisbane, QLD 4072, Australia.
authors.forename: Bhesh
authors.initials: B
authors.lastname: Bhandari
authors.affiliation: Biosecurity Queensland, Department of Agriculture and Fisheries, 39 Kessels Road, Coopers Plains, QLD 4108, Australia.
authors.forename: Louise
authors.initials: L
authors.lastname: Jackson
authors.affiliation: Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St Lucia, QLD 4072, Australia. Electronic address: p.james1@uq.edu.au.
authors.forename: Peter
authors.initials: P
authors.lastname: James
mesh_terms: D000818:Animals; D004655:Emulsions / Q000008:administration & dosage / Q000737:chemistry; D006197:Hair / Q000469:parasitology; D066298:In Vitro Techniques; D007814:Larva / Q000187:drug effects; D020011:Protective Agents / Q000008:administration & dosage / Q000494:pharmacology; D048494:Rhipicephalus / Q000187:drug effects; D020947:Tea Tree Oil / Q000494:pharmacology*; D047392:beta-Cyclodextrins / Q000737:chemistry* / Q000494:pharmacology
chemical_list: D004655:Emulsions; D020011:Protective Agents; D047392:beta-Cyclodextrins; D020947:Tea Tree Oil
keywords: Controlled release; Ectoparasite; Microparticles; Rhipicephalus microplus