Ivermectin plasma concentration in Iberian Ibex (Capra pyrenaica) following oral administration: a pilot study

Sarcoptic mange is considered the main driver of demographic declines occurred in the last decades in Iberian ibex (Capra pyrenaica) populations. Mass treatment campaigns by administration of in-feed acaricides are used as a measure to mitigate the impact of mange in the affected populations. However, there are no data on ivermectin (IVM) pharmacokinetics in this wild caprine, and the treatment through medicated feed is not endorsed by evidence on its effectiveness. The aim of this study is to determine the pharmacokinetic profile of IVM in plasma samples of ibexes after the experimental oral administration of IVM, using high performance liquid chromatography (HPLC) with automated solid phase extraction and fluorescence detection. A dose of 500 μg of IVM per body weight was orally administered in a feed bolus to nine healthy adult ibexes (seven males and two females). Blood samples were collected by jugular venipuncture into heparin-coated tubes at day 1, 2, 3, 4, 7, 10, 15, and 45 post-administration (dpa). The highest plasma concentration of IVM (Cmax = 3.4 ng/ml) was detected 24 h after the oral administration (T1), followed by a rapid decrease during the first week post-administration. Our results reveal that plasma IVM concentration drops drastically within 5 days of ingestion, questioning the effectiveness of a single in-feed dose of this drug to control sarcoptic mange. To the best of our knowledge, this is the first study on plasma availability of oral IVM in ibexes and in any wild ungulate species.

This project was funded by the Consejería de Medio Ambiente de la Junta de Andalucía (project 173/2009/M/00; 03/15/M/00; 861_11_M_00 and 2016/00014/M), and by the Spanish Ministerio de Economía y Competitividad (projects CGL2012-40043-C02-01, CGL2012-40043-C02-02, and CGL2016-80543-P). The authors' research activities are partially supported by the Plan Andaluz de Investigación (RNM-118 group). MV is supported by a FI-GENCAT Fellowship (2020_FI_B2_00049, co-financiated by Agència de Gestió d'Ajuts Universitaris i de Recerca and European Social Fund) and ES by the Spanish Ministerio de Ciencia Innovación y Universidades (MICINN) through a Ramon y Cajal agreement (RYC-2016-21120). GM is a Serra Húnter Fellow.