Equine piroplasmosis is a tick-borne protozoal disease of horses, mules, donkeys and zebra. The aetiological agents are blood parasites named Theileria equi and Babesia caballi. Approximately fourteen species of Ixodid ticks in the genera Dermacentor, Rhipicephalus and Hyalomma have been identified as transstadial vectors of B. caballi and T. equi, while eight of these species were also able to transmit B. caballi infections transovarially. Infected animals may remain carriers of these blood parasites for long periods and act as sources of infection for tick vectors. These parasites are also easily spread by blood contaminated instruments. The clinical signs of equine piroplasmosis are often nonspecific, and the disease can easily be confused with other conditions. Piroplasmosis can occur in peracute, acute and chronic forms. The acute cases are more common, and are characterised by fever that usually exceeds 40°C, reduced appetite and malaise, elevated respiratory and pulse rates, congestion of mucous membranes, and faecal balls that are smaller and drier than normal. Clinical signs in subacute cases are similar. In addition, affected animals show loss of weight, and fever is sometimes intermittent. The mucous membranes vary from pale pink to pink, or pale yellow to bright yellow. Petechiae or ecchymoses may also be visible on the mucous membranes. Normal bowel movements may be slightly depressed and the animals may show signs of mild colic. Mild oedematous swelling of the distal part of the limbs sometimes occurs. Chronic cases usually present nonspecific clinical signs such as mild inappetence, poor performance and a drop in body mass. The spleen is usually found to be enlarged on rectal examination. A rare peracute form where horses are found either dead or moribund has been reported. There are no vaccines available. Equine piroplasmosis has not been shown to be zoonotic.