Phylogenetic Analysis by rRNA Comparison of the Highly Pathogenic Sheep‐Infecting Parasites Theileria lestoquardi and a Theileria Species Identified in China

Abstract: In the Northwestern part of China there have been reports of clinical cases in small ruminants of a hæmoparasite with the characteristics of Theileria hirci (T. lestoquardi). However, some properties of this parasites argue against its classification as T. lestoquardi. In this paper, we present evidence that T. lestoquardi and the Chinese Theileria isolate are distinct parasite species. Phylogenetic analysis of determined nucleotide sequences of small subunit ribosomal RNA (srRNA) genes of T. lestoquardi and the Chinese Theileria parasite show that they belong to different clades within the phylogenetic tree of piroplasms. The srRNA sequence of the Chinese parasite was found to be most closely related to T. buffeli, which, with T. sergenti, belongs to an evolutionary lineage of non‐lymphoproliferative Theileria species. On the other hand, it was clearly divergent to a lineage of lymphoproliferative Theileria species: T. annulata, T. parva, T. taurotragi, and T. lestoquardi, the latter being most closely related to T. annulata.