Predictive spatial modelling of alternative control strategies for the foot‐and‐mouth disease epidemic in Great Britain, 2001

Abstract

A spatial simulation model of foot-and-mouth disease was used in March and early April 2001 to evaluate alternative control policies for the 2001 epidemic in Great Britain. Control policies were those in operation from March 20, 2001, and comprised a ban on all animal movements from February 23, 2001, and a stamping-out policy. Each simulation commenced with the known population of infected farms on April 10, 2001, and ran for 200 days. For the control policy which best approximated that actually implemented from late March, the model predicted an epidemic of approximately 1800 to 1900 affected farms, and estimated that the epidemic would be eradicated between July and October 2001, with a low probability of continuing beyond October 2001. This policy included the slaughter-out of infected farms within 24 hours, slaughter of about 1.3 of the surrounding farms per infected farm within a further 48 hours, and minimal interfarm movements of susceptible animals. Delays in the slaughter of animals on infected farms beyond 24 hours after diagnosis slightly increased the epidemic size, and failure to achieve pre-emptive slaughter on an adequate number of at-risk farms substantially increased the expected size of the epidemic. Vaccination of up to three of the most outbreak-dense areas carried out in conjunction with the adopted control policy reduced the predicted size of the epidemic by less than 100 farms. Vaccination of buffer zones (designed to apply available vaccine and manpower as effectively as possible) carried out in place of the adopted control policy allowed the disease to spread out of control, producing an epidemic involving over 6000 farms by October 2001, with no prospect of immediate eradication.

Modeling spatial and temporal transmission of foot-and-mouth disease in France: identification of high-risk areas

“…The last major epidemic was in 1981 and at this time the cattle were vaccinated but no account of which farm were vaccinated and where it was located was kept. Thus no validation of the model was possible using French data and the only way to explore the consequences of FMD was to use parameters estimated from other epidemics, as it done previously with the epidemic from 1967-1968 [11] and more recently in 2001 [9,10,18,19,22,23]. Furthermore, Keeling et al [19] argue that the epidemic trend was not sensitive to the precise shape of the infection Kernel.…”

“…Transmission kernel: it was estimated by the Department of Environment, Food and Rural Affairs (DEFRA) 2 and can be represented as a continuous function [17] or as a histogram [23]. It represents the multiplicative relative risk of transmission as a function of the distance from an IP.…”

A mobility model for classical swine fever in feral pig populations

“…These models are generally focused on domestic animals, with some models capturing explicit animal movement between farms, saleyards and other locations where disease transmission may readily occur. The significant movement of animals between different farms via markets was a key factor in the rapid, country-wide dissemination of foot-and-mouth disease in the United Kingdom in 2001 [10,21,26].…”

“…A challenge faced in this task is to capture the movement characteristics of the wild animal subpopulation. It is this spatio-temporal mobility which contributes substantially to long-range spread of animal diseases [4,26]. Domestic animal populations may be readily modelled using accurate records of animals located on farm premises, with some countries (e.g.…”

“…Due to the significance to disease spread of spatial heterogeneity and movement on the landscape, spatially explicit models and their attendant simulation software have been developed, such as those developed for footand-mouth disease [4,10,11,21,26,32]. These models are used to examine the effects of various containment or eradication strategies, namely culling, vaccination and movement bans.…”