Piroplasmosis is caused by blood-borne intracellular parasites that are spread naturally by a specific tick species, when they feed on a horse but may also be transmitted iatrogenically through transfer of infected blood via contaminated equipment such as re-using needles or syringes between horses. The two parasites species that cause disease in horses are Babesia caballi (B. caballi) and Theileria equi (T. equi). The parasite enters red bloods cells and destroys them and the clinical signs a horse displays are associated with the rupture of these infected blood cells. The disease is widespread and although the UK is currently considered free from endemic natural disease, cases have been occasionally confirmed and do occur in other European countries. With no formal UK requirement for pre-import screening, the international movement of horses and the demonstration of the presence of the tick species capable of transmission disease, there is a risk that the disease could be present and establish in the UK.