We report the population structure analysis of Theileria orientalis types (Ikeda, Buffeli and Chitose), the causative agent of theileriosis in cattle and its cohorts, using ITS1 and ITS2 spacers by fragment genotyping. We utilized primers flanking the two ribosomal RNA internal transcribed spacers (ITS1 and ITS2). Due to varying degrees of sequence polymorphism in the ITS regions found within and between species, we exploited the insertions and or deletions in these regions which resulted in different fragment sizes. On the basis of fragment size polymorphism, we were able to discriminate the three commonly found types of Theileria orientalis. ITS1 was capable of discriminating all three types (Ikeda-251bp, Chitose-274bp and Buffeli-269bp) in one single reaction by fragment genotyping. However, using ITS2, Ikeda (133-bp) a more pathogenic type was distinguishable from Buffeli/Chitose (139-bp). In addition, we quantified parasite load in experimental animals using ITS1. When compared with previous PCR detection method, ITS1 and ITS2 genotyping were found to be more sensitive methods with high specificity in population analysis and can be deployed in molecular epidemiology studies.Keywords: Ribosomal RNA intergenic spacer; Theileria orientalis types; genotyping, MPSP
INTRODUCTIONAsia-Pacific theileriosis is caused by a parasite known variously as T. sergenti or T.orientalis; although the name T. sergenti is now considered redundant (C. Sugimoto, pers.Comm.). Theileriosis due to T. orientalis is prevalent throughout Japan, Korea and parts of Russia and China (Chae et al., 1999;Fujisaki et al., 1991; Kawazu et al., 1992a, b;Onuma et al., 1998) and has been reported to occur in Australia (Callow, 1984;Kamau et al., 2010). The distribution of T. orientalis-buffeli appears to be worldwide, but is less frequently associated with clinical disease although some fatal cases have been reported to occur in America (Chae et al., 1999;Stockham et al., 2000; Cossio-Buyagur et al., 2002). Its transmitted by the three-hosts tick vector Haemaphysalis longicornis, and characterized clinically by anemia and weakness, leading to death, especially in animals experiencing metabolic stress such as parturition. There are eight genetic types (genotypes) currently comprising the T. orientalis complex. These types include type1 (Chitose), type2 (Ikeda), type3 (Buffeli) and type-4-8 yet to be classified with taxonomically (Kim et al., 1998;Ota et al., 2009). Mixed infection with different types of T. orientalis in cattle are common in Japan (Kim et al., 2004;Kubota et al., 1995), Korea (Baek et al., 2002) and Thailand (Sarataphan et al., 2003) but their clinical significance remain unclear. According to Shimizu et al., (1992;, at least one to two billion yen (one to two million US$) per year is spent to fight theileria infections in Japan.Diagnosis of a variety of disease syndromes caused by the T. orientalis parasites is principally based on clinical signs, knowledge of the disease, tick-vector distribution, and identification of...