Role of cytokines in the clinical manifestation of exophthalmia in newborn calves with tropical theileriosis.

The present study aimed to evaluate the pathology of the exophthalmia and the host-immune response in naturally Theileria annulata-infected calves. The newborn calves detected positive for theileriosis were grouped into calves with theileriosis and absence of exophthalmia (n = 30), and calves with theileriosis and the presence of exophthalmia (n = 13). Sixteen healthy calves, free from any haemoprotozoal infection, were kept as healthy controls. A significantly (P ≤ .001) higher circulating levels of tumour necrosis factor-α (TNF-α) and interleukin-10 (IL-10) were estimated in diseased calves with and without exophthalmia as compared to healthy controls. Contrarily, significantly (P ≤ .01) lower interferon-γ (IFN-γ) level was estimated in diseased calves. The diseased calves with exophthalmia revealed significantly higher levels of TNF-α (P ≤ .001) and IL-10 (P ≤ .006) as compared to the diseased calves without exophthalmia. The diseased calves were not found to have an elevated intraocular pressure; rather they had significantly (P ≤ .001) lower intraocular pressure compared to the healthy controls. An elevated systemic TNF-α level might be attributed to the exophthalmia in calves with tropical theileriosis. The elevated circulatory IL-10 and reduced IFN-γ levels could be one of the strategies of Theileria annulata to escape the host immunity.