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ARS Home » Plains Area » Kerrville, Texas » Knipling-Bushland U.S. Livestock Insects Research Laboratory » Cattle Fever Tick Research Unit » Research » Research Project #444919

Research Project: Evaluation of Injectable Eprinomectin Treatment Regimens for Cattle Fever Tick Management on Pastured Cattle

Location: Cattle Fever Tick Research Unit

Project Number: 3094-32000-042-100-N
Project Type: Non-Funded Cooperative Agreement

Start Date: Jan 21, 2024
End Date: Jan 20, 2029

The overall objectives of this project are to 1) evaluate the efficacy two dosing regimens using eprinomectin for cattle fever tick control in weaned cross-bred beef cattle; and 2) evaluate plasma values of eprinomectin to improve knowledge about the relationship between cattle fever tick control and eprinomectin levels within the animal.

A total of 26 weaned cross-bred beef heifers and steers (~500 lbs), purchased by USDA-ARS, will be infested twice weekly for two weeks prior to the start of the study with 125mg of CFT larvae (approx. 2500 larvae). Within gender, cattle will be randomly assigned to one of three groups and tagged with additional colored flap tags; 84d (n=10), 56d (n=10), and control (n=6) so that approximately equal numbers of each gender are enrolled in each protocol. Briefly, the 84d and 56d protocols will be administered the recommended label dose of injectable eprinomectin rounded up to the nearest half ml per manufacturer instructions, scratch inspected by trained staff, and bled accordingly (max 30 ml blood at each time point) as indicated in the figures. Cattle will also be re-infested with 125mg of CFT larvae (approx. 2500 ticks) every other week (± 3 days) and scratch inspected prior to each re-infestation. The controls will also be infested and scratch inspected on the same schedule but will not be bled during the study. If the tick burden on any control animal creates health concerns, that animal will be treated for CFT with injectable doramectin at 28 ± 3 day intervals until they appear healthy and excluded from the study. USDA-ARS staff will monitor animals for health concerns and provide veterinary care according to the treatment protocol provided by Cooperator. If any animal requires veterinary care for a health concern outside of the approved treatment protocol, the IACUC attending veterinarian will be consulted. Any animal requiring humane euthanasia as determined by the attending IACUC veterinarian will be euthanized per USDA-ARS approved protocols. Up to 10 animals from the 84d protocol will be randomly chosen for euthanasia via captive bolt and pithing under veterinary supervision at 280 days (n=5) and 308 days (n=5) and transported to a facility in College Station for necropsy and tissue sampling for residue analysis. The remaining animals will finish out their regimens on day 308 and be dipped off study after the day 308 sampling and scratch inspection.