LAUSR

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.