Ribosomal small-subunit RNA gene-sequence analysis of Theileria lestoquardi and a Theileria species highly pathogenic for small ruminants in China.

A fatal disease of sheep and goats in the northwestern part of China has been reported to be due to Theileria lestoquardi (syn. T. hirci). However, some characteristics of the causative agent are not in accordance with attributes ascribed to this parasite. We therefore determined the nucleotide sequence of the small-subunit ribosomal RNA (srRNA) gene of T. lestoquardi and the parasite identified in China and compared it with that of other Theileria and Babesia species. In the inferred phylogenetic tree the srRNA sequence of the Chinese parasite was found to be most closely related to T. buffeli and clearly divergent from T. lestoquardi, suggesting that it is an as yet unrecognized Theileria species. Extensive structural similarities were observed between the srRNA sequences of T. lestoquardi and T. annulata, revealing a close phylogenetic relationship between these two Theileria species. On the basis of the srRNA nucleotide sequence, polymerase chain reaction (PCR) primers were designed that specifically amplified genomic DNA of the Chinese Theileria species. These primers may be valuable tools in future epidemiology studies.

Phylogenetic analysis by rRNA comparison of the highly pathogenic sheep-infecting parasites Theileria lestoquardi and a Theileria species identified in China.

In the Northwestern part of China there have been reports of clinical cases in small ruminants of a haemoparasite 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.

Lymphocyte stimulatory capacity of Theileria annulata-infected ovine lymphoblastoid cells.

T. annulata, the causative agent of tropical theileriosis in cattle, is transmitted by ticks of the genus Hyalomma. Sporozoites of this parasite invade their target cells, where they differentiate to macroschizonts. T. annulata additionally invades and transforms ovine and caprine leukocytes. T. annulata infection in the ovine system is poorly studied, thus we used a mixed lymphocyte culture (MLC) to analyze the capacity of these cells to activate naïve uninfected ovine cells. The peak response was observed on day three or four and the response could not be induced by lysates of infected cells or their supernatants. The stimulated cells expressed IL-2 and secreted an IL-2-like growth factor.