For example, GM chickens expressing a short-hairpin RNA suppressed avian influenza transmission [5], PrPC-deficient (PRNP−/−) cattle were resistant to prions (BSE, bovine spongiform encephalopathy) [6], and GM cows that secreted lysostaphin resisted S. aureus-induced mastitis [7]. The gene discussed is PRNP; the disease is avian influenza.