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Background to the disease

Theileria annulata is an apicomplexan protozoan parasite of cattle and is transmitted by ticks of the Hyalomma genus. The parasite undergoes sequential development in leukocytes and erythrocytes of the mammalian host and causes an acute, often fatal disease (tropical theileriosis) that occurs from North Africa and Southern Europe, through the Middle East and across Southern Asia.

Distribution of T. annulata (click to enlarge) >

Distribution of Theileria annulata

Life-cycle of Theileria annulata

Improved dairy breeds of cattle and their crosses, which are being used throughout the region to satisfy demands for increased milk and meat production, are highly susceptible and suffer high levels of mortality.

Compared to other tick-borne diseases such as babesiosis and anaplasmosis, tropical theileriosis poses a particularly serious constraint to livestock production due to the lack of obvious age resistance to T. annulata.

< Life-cycle of T. annulata (click to enlarge)


The livestock industry plays a vital role in the agricultural economies of most of the countries affected by tropical theileriosis and improvements in productivity are required to meet increasing demands for food production in these countries. A large proportion of the livestock producers throughout the region are small-holder farmers, who often have limited access to disease control measures. Hence, in poor rural communities the disease is not only an important cause of direct production losses but also a serious constraint to the alleviation of poverty and creation of wealth through selling produce.

Cattle in Tunisia

Improvement in the standard of living and nutrition of such farmers can be achieved by improving productivity through cattle breeding. However, this proves very difficult in endemic regions, since current control measures suffer from a number of limitations.