Theileria annulata is a protozoan parasite that primarily infects cattle, causing a disease known as tropical theileriosis. This parasite is transmitted through the bite of infected ticks, particularly those from the genus Rhipicephalus. The infection can lead to severe anemia, fever, and in some cases, death if not treated promptly. Theileria annulata is prevalent in tropical and subtropical regions, affecting livestock health and agricultural productivity. Control measures often include tick management and vaccination strategies to reduce the incidence of the disease. Understanding this parasite is crucial for improving cattle farming in affected areas.