In the west of the Zamora Province in Castilla y León region, one of the most rural and isolated areas of Spain, the Zamorano – Leonés donkey – a native endangered breed -is still playing a central role in the traditional daily agriculture activities practiced by the local inhabitants. In February 2010 a study was carried out to understand the prevalence of equine piroplasmosis in the population of Zamorano – Leonés Donkey, collecting blood samples from 86 animals in 13 villages in the Zamora Proviince. Equine piroplasmosis is a tick-borne disease of equids, caused by Theileria equi and Babesia caballi. These intraerythrocytic parasites are responsible for a high morbidity and mortality in equids. The cELISA tests (competitive – inhibition Enzyme-Linked Immunosorbent Assay) revealed a positive seroprevalence of 21%, with 8 of the 86 donkeys positive for Theileria equi (9.3%), 10 for Babesia caballi (11.7%) and one of these 18 animals positive for both. The results of this study clearly demonstrate the importance of equine piroplasmosis affecting the Zamorano – Leonés donkey population. As far as we know this is the first study on intra-erythrocytic parasites in endangered Iberian breeds of donkeys and the results obtained reveal its importance in order to preserve this unique genetic heritage.