The relationship between farm animal welfare, housing conditions, and zoonotic disease risk has become increasingly important as intensive farming is linked to pandemic pathogen emergence.
The welfare-zoonosis connection creates a rare alignment between animal welfare and human health interests that has been underutilized in policy advocacy. Animals under chronic stress from crowding, poor ventilation, and inadequate environments have compromised immune function that both increases their susceptibility to infection and creates selection pressure for pathogens to adapt to dense host populations. The extreme densities in commercial poultry and pig facilities create evolutionary pressure for increasingly virulent pathogens because individual host welfare is unimportant to a pathogen that can rapidly transmit to the next individual. Improving farm animal welfare by reducing crowding and improving housing conditions reduces both animal suffering and the conditions that favor zoonotic pathogen emergence.