No detectable changes in serum IFN-γ (mean 0.009 ng/ml) or IL-4 (mean 0.059 ng/ml) were identified in the uninfected (negative control) sheep during the experiment, except for an elevated IFN-γ response (mean 0.719 ng/ml, range 0.329–1.566 ng/ml), which was present prior to the study and throughout the time course (−3 dpi to 14 dpi) in sheep 30, likely caused by a pre-existing bacterial/viral infection. The gene discussed is IL4; the disease is viral infectious disease.