Successive treatments with ivermectin (3.15%) to control the tick Rhipicephalus (Boophilus) microplus in cattle: Pharmacokinetic and efficacy assessment

• Published in: Ticks and tick-borne diseases 2022-01, Vol.13 (1), p.101848, Article 101848
• Main Authors: Sarli, Macarena, Miró, María Victoria, Rossner, María Victoria, Nava, Santiago, Lifschitz, Adrián
• Format: Article
• Language: English
• Subjects: Drug residues; Ivermectin 3.15; Pharmacokinetics; Rhipicephalus microplus; Therapeutic efficacy
• ISSN: 1877-959X; 1877-9603
• DOI: 10.1016/j.ttbdis.2021.101848

This study aimed to evaluate the pharmacokinetics, the potential accumulation in the body of treated animals and the efficacy of ivermectin long-acting formulation (3.15%) against the cattle tick Rhipicephalus (Boophilus) microplus in a scheme of three successive treatments. Fifteen 12-month-old heifers, naturally infested with R. microplus, were divided into two groups (G). Cattle from GI (n = 10) were subjected to three treatments with ivermectin 3.15% (IVOMEC GOLD®, Merial Argentina S.A.) at a rate of 1 mL/50 kg on days 0, 35, and 70. Cattle from GII (n = 5) were not treated. From day 1 to 202 post-treatment blood samples were taken to measure ivermectin concentrations by HPLC and female ticks (4.5–8 mm) were counted to evaluate the efficacy of the treatment. The level of tick resistance to ivermectin was evaluated before and after finishing the scheme of successive treatments by larval immersion test (LIT) bioassay from engorged females collected from GI. The area under the concentration vs. time curves (AUC0–35d) obtained post-second treatment was 1.51 ± 0.39-fold higher than those observed post-first treatment (P