theileriosis noun4 •Any disease caused by Theileria parasites, transmitted by species of ticks. •East Coast fever, a disease of cattle, sheep, and goats caused by the parasite Theileria parva, transmitted by Rhipicephalus appendiculatus •Human theileriosis, caused by Theileria microti, transmitted by deer ticks. •Tropical theileriosis, a theileriosis of cattle from the Mediterranean and Middle East area, from Morocco to Western parts of India and China, caused by Theileria annulata, transmitted by ticks of Hyalomma. formstheilerioses