Ducks vaccinated with inactivated R. anatipestifer plus levamisole as an adjuvant showed increased secretion of Th1-type (interferon [IFN]-γ and interleukin [IL]-2) and Th2-type (IL-4 and IL-10) cytokines and enhanced survival following challenge infection with a homologous R. anatipestifer strain [14]. This evidence concerns the gene IL10 and infection.