Equine piroplasmosis (EP) is a tick-borne disease of horses caused by the intraerytrocytic protozoan parasites Babesiacaballi and Theileria equi of the order Piroplasmida. Theileria equi was previously designated as Babesia equi but compelling evolutionary, morphologic, biochemical, and genetic evidence supports its reclassification as a Theileria. Infected animals may remain carriers of these blood parasites for long periods and act as sources of infection for other ticks. The introduction of carrier animals into areas where competent tick vectors are prevalent can lead to an epizootic spread of the disease. The Equine piroplasmosis multiplex polymerase chain reaction (PCR) kit detects the genes for the Babesia caballi and Theileria equi on the basis of a genetic database, so it can diagnose very fast and accurately.