Diversity and Genetic Structure of Theileria annulata in Pakistan and Other Endemic Sites

Theileria annulata is a tick-borne protozoan parasite responsible for bovine theileriosis, a disease that impacts cattle population in many developing countries. Development and deployment of effective control strategies, based on vaccine or therapy, should consider the extent of diversity of the parasite and its population structure in different endemic areas. In this study, we examined T. annulata in Pakistan and carried out a comparative analysis with similar data garneted in other areas, to provide further information on the level of parasite diversity and parasite genetic structure in different endemic areas.

The present study examined a set of 10 microsatellites/minisatellites and analyzed the genetic structure of T. annulata in cattle breeds from Pakistan (Indian sub-continent) and compared these with those in Oman (Middle East), Tunisia (Africa), and Turkey (Europe).

A high level of genetic diversity was observed among T. annulata detected in cattle from Pakistan, comparable to that in Oman, Tunisia, and Turkey. The genotypes of T. annulata in these four countries form genetically distinct groups that are geographically sub-structured. The T. annulata population in Oman overlapped with that in the Indian Subcontinent (Pakistan) and that in Africa (Tunisia).

The T. annulata parasite in Pakistan is highly diverse, and genetically differentiated. This pattern accords well and complements that seen among T. annulata representing the global endemic site. The parasite population in the Arabian Peninsula overlapped with that in the Indian-Subcontinent (India) and that in Africa (Tunisia), which shared some genotypes with that in the Near East and Europe (Turkey). This suggests some level of parasite gene flow, indicative of limited movement between neighboring countries.