Introduction: Malignant ovine theileriosis is a fatal disease of sheep caused by the pathogenic species of protozoans of the genus Theileria. This study was designed to estimate the levels of plasma homocysteine (Hcy), serum thyroid hormones, the serum trace elements and to evaluate their correlations in different parasitemia rates in naturally Theileria infected sheep.
Materials and Methods: 50 Iranian sheep, about 1-2 years old, naturally infected with T. lestoquardi were selected and divided into 2 subgroups according to parasitemia rates (<2%, 2-4%). 10 non-infected animals were also selected as controls. Blood samples were collected and Hcy, thyroid hormones and major trace elements were measured.
Results: Significant decrease in the values of red blood cell count (RBC), packed cell volume (PCV) and hemoglobin confirmed that anaemia had occurred in the infected sheep. Significant increase in Hcy and some trace elements (Mn, Fe and Zn), significant decrease in the values of thyroxine (T4) and free tri-iodothyronine (fT3) were observed.
Conclusion: Substantial elevations in plasma Hcy can potentially produce endothelial injuries and consequently help the formation of anaemia. On the other hand, significant decrease in T4 and fT3 and increase in some trace elements (Mn, Fe and Zn) besides the lack of any changes in the other related factors, indicate that the infection of sheep with lower than 4% parasitemia rates, can induce negative effects on the secretion and concentrations of thyroid hormones, but the infection could not cause reverse effects on important trace elements.