Animal infectious diseases threaten food security, livestock production and public health. While disease prevention strategies typically target risk factors associated with high-competence hosts or environmental conditions, we hypothesise that lower-competence species can reduce disease risk by diluting effective contact rates between farms. Using spatial statistical models calibrated on three successive French high pathogenicity avian influenza (HPAI) epidemics (2020-2023), we show that greater local diversity of livestock farms, including cattle and pig farms, is associated with significantly lower HPAI risk. Moreover, we show that the positive association between duck houses and HPAI risk weakens as the number of less-competent non-duck poultry houses increases, revealing a dilution effect within poultry production systems. These findings suggest that livestock diversity is a previously overlooked determinant of disease spread and open new research avenues on territorial diversification to complement traditional approaches for the long-term control of high-impact animal infectious diseases.