title: Efficacy of amitraz (Taktic 12.5% EC) as a dip for the control of Boophilus microplus (Canestrini) (Acari: Ixodidae) on cattle.
abstract: Four groups of cattle infested with Boophilus microplus (Canestrini) were each dipped in a different concentration of amitraz diluted from a 12.5% EC formulation to determine the efficacy and performance of the product in an 11,400 l dipping vat. Except for the period when heifers were dipped, animals were restrained in stanchions placed individually inside 3.3 x 3.3 m2 stalls within an open-sided barn. The amitraz in the vat was stabilized with hydrated lime to maintain a pH of ca. 12. Analyses of vat samples showed that concentrations of amitraz in the vat were 7.6 to 13% lower than the targeted concentrations of 0.010, 0.015, 0.020, and 0.025% active ingredient (AI) for dilutions prepared according to instructions on the manufacturer's label. The large quantity of hydrated lime added to the vat (10 kg/1000 l) interfered with the HPLC analysis of vat samples. Therapeutic efficacy of each of the four observed concentrations (0.0088, 0.0131, 0.0174, and 0.0231% AI) of amitraz was excellent (> 99% control). However, the rapid detachment of all ticks from an animal within a few hours after treatment with amitraz, that has been frequently observed, was not pronounced in the present study. Only 47% of the B. microplus detached in the first 4 h post-treatment, and 84% detached within the first 24 h. All of the treatments, except the lowest concentration, provided protection of cattle against re-infestation by B. microplus larvae for 14 days post-treatment. Possibly as a result of the formation of a compact layer of lime and amitraz on the bottom after the vat was undisturbed for six weeks, intense agitation was required to re-suspend the active ingredient.
authors.affiliation: U.S. Department of Agriculture, Knipling-Bushland U.S. Livestock Insects Research Laboratory, Kerrville, TX 78028-9184, USA.
authors.forename: J E
authors.initials: JE
authors.lastname: George
authors.forename: R B
authors.initials: RB
authors.lastname: Davey
authors.forename: E H
authors.initials: EH
authors.lastname: Ahrens
authors.forename: J M
authors.initials: JM
authors.lastname: Pound
authors.forename: R O
authors.initials: RO
authors.lastname: Drummond
mesh_terms: D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy*; D004305:Dose-Response Relationship, Drug; D005260:Female; D007306:Insecticides / Q000008:administration & dosage / Q000627:therapeutic use*; D013984:Tick Infestations / Q000188:drug therapy / Q000662:veterinary*; D013987:Ticks / Q000187:drug effects; D014052:Toluidines / Q000008:administration & dosage / Q000627:therapeutic use*
chemical_list: D007306:Insecticides; D014052:Toluidines; C014983:amitraz