This study aimed to investigate the evolutionary status of T. annulata in Al-Diwaniyah province, Iraq. In this study, the clinical examination of 50 infected animals was performed with blood sample collection (2.5ml per animal), and drug targets cytochrome b, a vital component of the electron transfer chain in the mitochondria of the protozoan, cytb gene was targeted using a polymerase chain reaction (PCR) procedure. Also, 18S rRNA gene as a molecular target for the PCR and a partial gene

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... cing (PGS) were included. The PCR that involved using the 18S rRNA and cytb genes as genetic targets revealed amplification of the targeted pieces at 620bp and 1092bp, respectively, in all tested samples. The18S rRNA gene sequence of local T. annulata isolates were aligned with global reference strains for T. annulata recorded in the GenBank. The local strains were close, 100%, in their identity to isolates from Iran, Turkey, and Pakistan; however, they were 99% similar to a nucleotide sequences from India and Bangladesh. Diseased calves showed clinical signs such as high fever (40.3-41.5°C), decreased appetite or in appetence, asymmetrical enlargement of superficial lymph nodes particularly the prescapular ones, some cases with diarrhea, pale or icteric mucus membrane of eyes, bulging eyes, lacrimation, ecchymotic hemorrhages on the sclera, incoordination, nervous signs (Dullness, depression, lethargy), salivation, and bloated young calves. The data observed from the present inspecting work may reveal genetic evolution in the local strains with others recorded in the GeneBank. This means that our local strains might have close relationships with some global strains.