title: Efficacy of eprinomectin and doramectin against Amblyomma americanum (Acari: Ixodidae) on cattle.
abstract: Steers were treated with doramectin or eprinomectin by daily oral capsule for 28 consecutive days. The level of doramectin in the serum of steers treated at 200 microg/kg/d reached a maximum of 104.0 +/- 22.1 ppb at day 21 and declined from 93.3 +/- 20.5 ppb on the final day of treatment to below detectable by day 56. Steers treated at 50 microg/kg/d reached a maximum level of doramectin in the serum of 24.7 +/- 1.2 ppb on day 21 and declined from 24.7 +/- 0.6 ppb on the final day of treatment to less than detectable on day 42. Both doramectin dosages provided 100% control of estimated larvae (EL) of Amblyomma americanum (L.) (Acari: Ixodidae) throughout the 28-d treatment period. Daily oral treatment with eprinomectin at a dosage of 200 microg/kg for 28 consecutive days produced a maximum concentration in the serum of 41.6 +/- 11.0 ppb at day 14. On the final day of eprinomectin treatment, the serum concentration was 38.3 +/- 5.9 ppb. Seven days later at day 35, eprinomectin was not detectable in the serum. For steers treated at 50 microg/kg/d for 28 consecutive days, the serum level of eprinomectin reached a maximum of 10.0 +/- 3.0 ppb on day 28 and was undetectable on day 35. Both eprinomectin dosages provided complete control of EL of A. americanum during the 28-d treatment period. Because eprinomectin is efficacious against A. americanum at lower serum levels in cattle and is eliminated from the serum at a more rapid rate than either doramectin or ivermectin, it provides advantages for use in applications such as the medicated bait for control of ticks on white-tailed deer and could have potential for use in the Cattle Fever Tick Eradication Program.
authors.affiliation: USDA-ARS, Knipling-Bushland U.S. Livestock Insects Research Laboratory, 2700 Fredericksburg Road, Kerrville, TX 78028, USA. kim.lohmeyer@ars.usda.gov
authors.forename: K H
authors.initials: KH
authors.lastname: Lohmeyer
authors.forename: J A
authors.initials: JA
authors.lastname: Miller
authors.forename: J M
authors.initials: JM
authors.lastname: Pound
authors.forename: D D
authors.initials: DD
authors.lastname: Oehler
mesh_terms: D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000517:prevention & control*; D004305:Dose-Response Relationship, Drug; D007306:Insecticides / Q000494:pharmacology*; D007559:Ivermectin / Q000031:analogs & derivatives* / Q000494:pharmacology; D026863:Ixodidae / Q000187:drug effects; D013984:Tick Infestations / Q000517:prevention & control / Q000662:veterinary*; D013997:Time Factors
chemical_list: D007306:Insecticides; D007559:Ivermectin; C101434:eprinomectin; C084101:doramectin