Tehran University of Medical Sciences Iranian Journal of Parasitology 1735-7020 7 4 2015 10 13 91 98 EN SP. Yasini Department of Clinical Pathology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran. Z. Khaki Department of Clinical Pathology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran. S. Rahbari Parasitology Department, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran. B. Kazemi Cellular and Molecular Biology Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran. J. Salar-Amoli Department of Toxicology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran. A. Gharabaghi Department of Larg Animal Internal Medicine, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran. SM. Jalali Department of Clinical Pathology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran. 2015 10 13 2015 10 13 Background: Anaplasma ovis infections can cause clinical symptoms in acute phase and lead to huge economic losses in flocks. The aim of the present study was to investigate the hematological and par- asitological changes in experimental anaplasmosis in sheep with Iranian strain of A. ovis. Method: Five male sheep without any blood parasite infection were selected. One hundred ml hepa-rinized blood was collected from splenectomised sheep that showed 6% A. ovis parasitemia. Inocu- lums of 20 ml blood were administered intravenously to each test animal. Hematological, parasito- logical and clinical changes of experimental anaplasmosis were studied in 0-38 days post infection. Result: Parasitemia was detected 3 days post infection and reached its maximum level on the day 12 of experiment in test animals. Then the parasitemia was declined, but the organism could be found persistently until the last day of study. The red cell counts, packed cell volume and hemoglobin con- centration were decreased and mean corpuscular volume was increased significantly during the infec- tion period. Reticulocytosis and basophilic stippling were also detected. No significant changes were observed in total and differential leukocyte count and animal body temperature. Conclusion: Experimental A. ovis infection in sheep resulted in marked normocytic normochromic anemia at the beginning of the infection which became macrocytic normochromic by the develop- ment of the disease. There were negative correlations between parasitemia and RBC, PCV and Hb values, therefore hematological assessment can be considered as a practical diagnostic tool in ovine anaplasmosis. https://ijpa.tums.ac.ir/index.php/ijpa/article/view/289 https://ijpa.tums.ac.ir/index.php/ijpa/article/download/289/272