An eprinomectin extended-release injection formulation providing nematode control in cattle for up to 150 days

AbstractA series of 10 dose confirmation studies was conducted to evaluate the persistent activity of an extended-release injectable (ERI) formulation of eprinomectin against single point challenge infections of gastrointestinal and pulmonary nematodes of cattle. The formulation, selected based on the optimal combination of high nematode efficacy, appropriate plasma profile, and satisfactory tissue residue levels, includes 5% poly(d,l-lactide-co-glycolic)acid (PLGA) and is designed to deliver eprinomectin at a dose of 1.0mg/kg bodyweight. Individual studies, included 16–30 cattle blocked based on pre-treatment bodyweight and randomly allocated to treatment with either ERI vehicle or saline (control), or the selected Eprinomectin ERI formulation. Treatments were administered once at a dose volume of 1mL/50kg bodyweight by subcutaneous injection in front of the shoulder. In each study, cattle were challenged with a combination of infective stages of gastrointestinal and/or pulmonary nematodes 100, 120 or 150 days after treatment and were processed for parasite recovery according to standard techniques 25–30 days after challenge. Based on parasite counts, Eprinomectin ERI (1mg eprinomectin/kg bodyweight) provided >90% efficacy (p