Around 60% of microorganisms causing human disease are passed between animals and humans (“zoonotic” pathogens). Changing farming practices in New Zealand are creating conditions promoting pathogen transfer between species. This project aims to identify interventions to control transmission to humans. Two zoonotic bacteria will be examined: Shiga-toxin producing Escherichia coli (STEC) and Staphylococcus aureus. STEC causes severe diarrhoea, while S. aureus causes serious skin and bloodstream infections. Data will be collected in a dairy-farming community about the frequency of STEC and S. aureus in cattle and humans, and about how humans interact with cattle and the environment. Data will be included in a mathematical model simulating transmission of bacteria within and between species. Intervention effects will be tested in the model. Identifying effective interventions will reduce the STEC disease burden, particularly in young rural New Zealanders, and reduce transfer of antibiotic resistant S. aureus to humans, maintaining treatment options for infections.