Babesia, also called Nuttallia, is an apicomplexan parasite that infects red blood cells and is transmitted by ticks. Originally discovered by the Romanian bacteriologist Victor Babeș in 1888, over 100 species of Babesia have since been identified. Babesia comprises more than 100 species of tick-borne parasites that infect erythrocytes (red blood cells) in many vertebrate hosts.