Molecular report of resistant isolates of Theileria annulata by targeting the cytochrome b gene in cattle and ticks in Babylon, Al-Qasim city of Iraq

Background: Ticks are the carriers of the deadly animal illness theileriosis. Theileria annulata in cattle is an obligatory intracellular protozoan parasite carried by ticks (Hyalomma spp.) that infects hosts with mild, severe, and fatal illnesses. Theileria annulata, also known as tropical theileriosis, is a lymphoproliferative illness that causes severe mortality and morbidity in calves. Currently available antiparasitic medications work well in animals, but owing to developing resistance, animals may die or continue to be carriers. Treatment works best while the disease is still in its early stages.Methods: In the current study, 2.5 mL of blood was drawn from the jugular vein and placed in an EDTA anticoagulant tube. Tick samples from each animal suspected of having Theileria annulata infection were placed in plastic tubes and sent straight to the laboratory for microscopic diagnosis using a blood smear and, later, PCR testing, which yielded a positive result.Results: PCR targeting the 18S rRNA gene showed amplification in all tested blood samples (100%), confirming infection with T. annulata. In ticks, 81.25% (13/16) was positive for T. annulata. Furthermore, the cytochrome b gene (resistant gene) was detected in 100% of the calves’ samples and 81.25% of the tick samples tested using PCR.Conclusion: The cytochrome b gene was detected in all (100%) calf samples and 81.25% of tick samples, which may be a contributing factor to mortality in infected calves. Sequencing analysis is a necessary method for the identification of mutations in the ticks and calves' blood samples.Keywords: Theileria annulata, Cytochrome b gene, Tick, Buparvaquone, Sequencing