THEILERIOSES & WILDLIFE

Theilerias are tick-borne, protozoal parasites that occur worldwide and infect a wide range of mammals, including wild and domestic ruminants, equines, canines and marsupials. The organisms are transmitted by different species of ixodid ticks and have a complex life cycle in both the mammalian host and tick vectors.

Theileria organisms most likely evolved as tick-borne parasites in wild ruminants and equids. With the emergence of domesticated species, such as cattle, sheep and goats that are also hosts of the vector ticks, some Theileria species would have initially caused disease and death until the new host population became adapted to the parasite. Not all Theileria species are pathogenic but the non-disease-causing species cause confusion during outbreaks of disease in livestock, when diagnostic testing is needed to aid control.

The three important theilerial diseases of cattle in Southern Africa are caused by Theileria