Infectious animal diseases raise serious challenges for both public health and the livestocksector. We develop an original principal-multiple agent model for preventing these diseases thatexplicitly considers the heterogeneity of risk-averse farmers in addition to production externalitiesandex anteinformational asymmetries. Our results confirm that failing to consider farmers'heterogeneity generates Pareto-inefficient solutions. When using individual-based instruments,the government should cope with heterogeneity by increasing guaranteed payments and reducingaverage payments. However, when population-based instruments are the only available policytools, increasing average payments is better for reducing moral hazard issues.