Theileriosis is a disease caused by protozoan parasites of the genus Theileria, which primarily infects cattle and other ruminants. These parasites are transmitted through the bites of infected ticks, leading to symptoms such as fever, anemia, and swelling of lymph nodes. The disease can significantly impact livestock health and productivity. There are several species of Theileria, with Theileria annulata and Theileria parva being the most notable. Control measures include tick management and vaccination, which can help reduce the incidence of the disease. Early diagnosis and treatment are essential for improving recovery rates in affected animals.