Intravenously infected piglets showed a peak production of Interleukin 6 (IL-6) and Interleukin 1 beta (IL-1-β) serum concentrations 1 day post-infection (p <0.001) (Fig. 4a and b) to decrease to normal levels respectively 3 and 5 days post-infection. This evidence concerns the gene IL6 and infection.