Coping without farm location data during a foot-and-mouth outbreak

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Abstract
Despite increasing globalization of agriculture, the last reported outbreak of foot-and-mouth disease (FMD) in the United States was in 1929 (1). Foot-and-mouth disease virus infects cloven-hoofed animals, with cattle and pigs being particularly susceptible. The virus is highly transmissible and causes significant symptoms in many species, with substantial mortality in the young. Therefore, outbreaks of FMD in regions where it has been eliminated (Europe, North and Central America, the Pacific Nations, and the Caribbean) pose immediate challenges for policy makers concerned with animal welfare and continued agricultural productivity (2). In this issue of PNAS, Tildesley et al. (3) use a simulation approach to investigate optimal culling strategies against an outbreak of FMD in the United States. Since the 2001 outbreak of FMD in the United Kingdom (4, 5), the epidemiology of future similar outbreaks has become a popular example for the application of mathematical models of infectious disease (6–8). In particular, spatially explicit simulation models (9) have helped to quantify the relationship between farm density in the United Kingdom and transmissibility (10). Although similar approaches have been used to describe likely patterns of transmission in the United States (11), Australia (12), Korea (13), New Zealand (14), and the Netherlands (15), analysis of the 2001 United Kingdom outbreak benefits from an unusually rich dataset. Precise locations are available for both affected and unaffected farms; furthermore, the number of infected premises during 2001 was sufficient to permit accurate estimation of key transmission parameters. Together, the rich data from the 2001 United Kingdom outbreak and the development of simulation models have greatly facilitated the investigation of spatially heterogeneous intervention policies. For example, it has been shown that if a well-matched vaccine were …