Abstract
Abstract
Objective
Investigate the plasma concentrations and clinical efficacy of ponazuril in short-beaked echidnas (SBEs;
Tachyglossus aculeatus
) with enteric coccidiosis.
Methods
13 SBEs at the San Diego Zoo Safari Park with enteric coccidiosis and fecal oocyst counts greater than 400 oocysts/g, determined using quantitative McMaster fecal flotations, were enrolled in this study. In October 2025, SBEs were treated with a single dose of ponazuril at 40 mg/kg via oral gavage based on the results of a dose determination pilot study. Plasma samples were collected using a sparse-sampling model at 0, 0.5, 1, 2, 4, 8, 12, 16, 24, 48, and 72 hours. The concentration of ponazuril in plasma was measured using high-pressure liquid chromatography. Quantitative McMaster fecal flotations were performed following treatment, and fecal oocyst count reduction percentage was calculated at 14 days and 6 months posttreatment.
Results
No adverse effects were observed. Ponazuril plasma concentrations were highly variable, precluding a pharmacokinetic analysis. The median maximum plasma concentration of ponazuril was 2.46 μg/mL (range, 0.74 to 11.94 μg/mL). The median fecal oocyst count reduction percentage was 99% (range, 92.3% to 100%) at 14 days posttreatment and 100% (range, 98.6% to 100%) at 6 months posttreatment.
Conclusions
Despite variable plasma concentrations following oral administration of ponazuril in SBEs, fecal shedding of coccidia was reduced by > 95% in 63% (5 of 8) of SBEs at 14 days posttreatment and 100% (7 of 7) of echidnas at 6 months posttreatment.
Clinical Relevance
The 40-mg/kg ponazuril dose reduced fecal shedding of
Eimeria
spp in SBEs with enteric coccidiosis. Although plasma concentrations were variable, we conclude that effectiveness is likely the result of high intestinal concentrations, rather than plasma drug concentrations.