Parasitism is a common cause of morbidity in captive-held avian species. Treatment can be difficult with some parasite species due to lack of efficacious and therapeutically safe medications. Twenty-one healthy helmeted guinea fowl (Numida meleagris) housed at the Oklahoma City Zoo were used to evaluate the pharmacokinetic parameters of topical selamectin. Study birds were divided randomly into 3 groups of 7 birds. On day 1 all birds received one dose of 20 mg/kg selamectin applied to the dorsal cervical skin. Blood was collected from group 1 at 12 hours and days 3, 7 and 14; from group 2 at 24 hours and days 4, 7, and 21; from group 3 at days 2, 5, 7, and 28. Selamectin concentrations were determined in plasma using liquid chromatography with mass spectrometry. Mean terminal half-life and maximum plasma concentrations of selamectin were 5.8 days and 16.1 ng/mL, respectively with maximum plasma levels reached at 3 days. No adverse effects were detected. Therapeutic levels of selamectin are unknown for avian species. However, the birds in this study did reach and maintain plasma levels reported as therapeutic in other species for 19 days.1 Based on these results selamectin may be a valuable antiparasiticide in some avian species although efficacy studies are needed.
1. Sarasola, P., A.D. Jernigan, D.K. Walker, J. Castledine, D.G. Smith, and T.G. Rowan. 2002. Pharmacokinetics of selamectin following intravenous, oral and topical administration in cats and dogs. J Vet Pharmacol Ther. 25:265–272.