Bovine Theileriosis: Effects on the Status of Thyroid Hormones, Homocystein, Serum Lipids and Lipoproteins

Abstract

Tropical theileriosis of cattle is a common tick-borne disease in tropical and subtropical regions and is recognized as a disease of major economic importance. This study aimed to determine whether Theileria annulata infection influences the plasma homocystein (Hcy), thyroid activity and serum lipid status in infected cattle. Fifty crossbred Holstein cattle, naturally infected with Theileria annulata were selected and divided into 3 subgroups according to their parasitemia rates (<2, 2-4, 4-8%). Also, 10 non-infected cattle were assigned as controls. Blood samples were collected and hematological parameters, plasma Homocystein (Hcy), thyroid hormones (T3, T4, free T3 (fT3) and free T4 (fT4)) and the concentrations of serum lipid and lipoproteins (cholesterol, triglyceride and lipoproteins including HDL, LDL and VLDL cholesterol) and phosphatidylserine (PS) on erythrocytes were measured. According to the results, significant elevations were observed in the concentration of plasma Hcy (hyperhomocysteinemia) in the infected groups compared to controls. In addition, we conclude that T. annulata can interfere with the lipid metabolism, which is particularly characterized by substantial decreases in the levels of cholesterol, LDL and HDL in the serum of affected animals. In spite of remarkable influences of the parasite on Hcy and lipid contents of the serum, our study proved that tropical theileriosis did not affect the thyroid hormones during parasitemia. This study demonstrates that the infection of cattle with Theileria annulata is mainly characterized by the anemia. Also, evidenced elevation in the level of homocystein (hyperhomocysteinemia) in parasitized cattle can result in oxidative stress on erythrocytes and the probable endothelial injuries. In addition, T. annulata can induce failure in lipid metabolism which is particularly featured by a decrease in the cholesterol, LDL-cholesterol and HDL-cholesterol concentrations; however the parasite cannot implement significant influences on the thyroid hormones in the affected cattle.