Animal herds can contract infectious disease from outside or within a region. Even if biosecurity efforts reduce the risk of external infection, a herd may remain at risk from intra-region spread. We provide a simple discrete cost over expected benefit decision model of disease management in which an action can eliminate the risk of external infection and may reduce the risk of infection through intra-region spread. For simultaneous moves by herd-owners, the model is solved to show that insufficient protection is provided. Dominant strategy solutions apply when the action protects against extra-regional entry but not against intra-region spread. Mixed strategy solutions may emerge when the action provides partial protection against intra-region spread. In addition to directly reducing social loss, partial protection is shown to increase the private incentive to act. We then discuss animal healthcare action characteristics and what they mean for the appropriateness of public sector intervention. Many actions exhibit non-rivalry to the point of being anti-rivalrous, and so do not fit into the traditional definition of a public good. Many also generate positive externalities. Various policy options are possible, including subsidies and assignment of biosecurity action mandates to a set of herd-owners