Plasma Cortisol and Thyroid Hormone Profile in Theileria equi Affected Horses

Equine theileriosis caused by Theileria equi is an endemic disease in most of the countries. The latently infected animals may exhibit low performance following physical, immunological or mental stress due to the flare-up of underlyingparasitemia leading to clinical form of the disease. In the present study, 72 horses were screened for T. equi by using polymerase chainm reaction based on equine merozoite antigen-5 and 6, which revealed 25 to be positive for theileriosis. Furtherstudy was conducted to assess the cortisol and thyroid hormone (T3 and T4) levels in healthy (n=47) and in T. equi infected (n=25) horses. In horses positive for T. equi, there was significant increase (p less than 0.05) in cortisol (42.80±0.69 vs.24.44± 0.12 ng/ml) and T4 level (47.56±4.06 vs. 38.14±2.40 ng/ml) with significant reduction (p less than 0.01) in T3 level (0.44±0.13 vs. 1.20±0.19 ng/ml) when compared to the healthy group. This may be the first report revealing that theileriosisinfected horses are under stress due to the involvement of endocrine system as well as metabolic pathways.