During oral experimental C. baileyi infection, IL-17 and related cytokine expression were up-regulated in trachea and spleen of chickens after infection, with the highest levels in tracheas at day 10 pi when the peak oocyst shedding and pathogenic lesions were observed, which suggested that IL-17 may play a role in immunity against Cryptosporidium infection. The gene discussed is IL17A; the disease is infection.