This article explores the links between biosecurity policy and rural differentiation. It attempts to show how biosecurity policy has been fundamentally affected by uncertainty over the rules of the game of policy-making – what Hajer has called the ‘institutional void’. In particular, the article attempts to show how this void has created a new political space in which the traditional practices of dealing with animal disease have been challenged and reshaped. Crucial to this is a discourse of partnership that permits new actors and forms of expertise to construct different approaches to biosecurity at new spatial scales. These actions legitimate a new spatiality of disease control, thereby contributing to the differentiation of the countryside. The article uses a case-study of policy attempts to control the spread of bovine tuberculosis in England and Wales.