Discovery of a new Theileria sp. closely related to Theileria annulata in cattle from Sri Lanka

Theileria annulata is a haemoprotozoan parasite that causes a cancer-like illness known as tropical theileriosis in cattle. In the course of analyzing the genetic diversity of T . annulata in Sri Lanka, we observed that merozoite-piroplasm surface antigen ( tams1 ) and surface protein ( tasp )-like gene sequences obtained from bovine blood DNA samples, which were PCR-positive for T . annulata , were conserved but shared low identity with T . annulata GenBank sequences. Moreover, the 18S rRNA sequences from the Sri Lankan samples contained ten unique single-nucleotide polymorphisms compared with all known T . annulata sequences. The cytochrome b ( cob ) gene sequences isolated from the Sri Lankan samples were highly conserved and shared low identity scores with similarly conserved T . annulata sequences from GenBank. Phylogenetic analysis showed that the Sri Lankan tams1 -like, tasp -like, 18S rRNA, and cob sequences clustered together and formed sister clades to the common ancestors of all known T . annulata and Theileria lestoquardi sequences. These findings demonstrated that the Sri Lankan cattle were not infected with T . annulata but with a new Theileria sp. (designated as Theileria sp. Yokoyama) closely related to T . annulata .