Pharmacokinetics of oral ponazuril in kea (Nestor notabilis) support its use as a preventative for sarcocystosis.

Weekly oral ponazuril at 30 mg/kg safely maintains plasma concentrations above the inhibitory threshold for Sarcocystis in kea.

This pharmacokinetic study evaluated oral ponazuril in kea (Nestor notabilis), a critically endangered New Zealand parrot highly susceptible to fatal sarcocystosis caused by Sarcocystis falcatula. Eight adult kea received a single oral dose of 30 mg/kg ponazuril via gavage, with serial blood sampling over 192 hours analyzed by reverse-phase HPLC and noncompartmental analysis. Key pharmacokinetic parameters included a time to maximum concentration (Tmax) of 23 ± 12 hours, maximum concentration (Cmax) of 6.78 ± 1.89 µg/mL, and an elimination half-life of 128 ± 49 hours. The prolonged half-life supported investigation of weekly dosing. Following four weekly doses at 30 mg/kg, mean trough concentrations were 5.97 ± 2.15 µg/mL, meeting the target inhibitory concentration of 5 µg/mL established for Sarcocystis neurona. Long-term trough values (>1 year of weekly dosing, n=4) were notably higher at 14.06 ± 4.85 µg/mL, suggesting possible accumulation over time. No adverse effects were observed during the study or during extended weekly administration. The study supports weekly oral ponazuril at 30 mg/kg as a safe and effective prophylactic protocol for kea and potentially other susceptible psittacine species in managed care settings where complete exclusion of opossum definitive hosts is not feasible, providing a practical pharmacological strategy to reduce sarcocystosis-associated mortality.

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