Prevalence and phylogenetic analysis of Theileria equi in Iranian dromedaries

Considering the importance of Theileria equi infection in horse breeding industry and marketing, in the present study, we aimed to determine the prevalence of T. equi among dromedaries in central Iran, where a considerable number of camels and horses are raised and equine theileriosis is quite prevalent. For this purpose, a total of 161 blood samples from camels were examined in terms of T. equi infection, using parasitological and molecular methods. For molecular detection of T. equi, primers targeting the 18S rRNA gene were selected. Microscopic examination revealed that 0.6% of camels were positive for the intraerythrocytic stage of Theileria species, while polymerase chain reaction (PCR) method detected T. equi in 7 (4.3%) out of 161 camels. Sequences of 18S rRNAs from all the isolates showed more than 99% homology to each other and T. equi isolates in the GenBank. With respect to the single-nucleotide substitution in 18S rRNA gene of the studied camels, three different genotypes were identified and submitted to the GenBank. Considering the homology between 18S rRNA sequences of T. equi in the studied samples and those available in the GenBank, the phylogenetic tree formed three distinct, but highly-related clusters. In this study, age, gender, and locality were not determined as risk factors for T. equi infection in camels. In conclusion, this study demonstrated that T. equi is present among Iranian camels.