This chapter focuses on the epidemiology, transmission routes, and biosecurity measures of bacterial diseases in pigs and poultry raised in intensive production systems. Bacterial pathogens are highly prevalent in these systems and cause major animal health, welfare, and production problems. There are numerous transmission routes by which bacterial pathogens may enter or spread within a pig or poultry farm. Many infections are subclinical but may result in overt clinical disease in the presence of risk factors. Typical examples are postweaning Escherichia coli infections, Brachyspira and Mycoplasma hyopneumoniae infections in pigs, and Clostridial- and E. coli infections in poultry. Proper biosecurity is of paramount importance to control or prevent bacterial infections. The biosecurity can be improved by taking further measures or adopting new habits; however, there might be limitations in farm infrastructures and a smaller impact of biosecurity regarding issues like mortality. Further research, e.g., by improved monitoring is needed to improve the biosecurity and reduce bacterial disease in pig and poultry farms.