Quantifying foot-and-mouth disease virus transmission rates using published data

Nesya Goris

doi:10.14573/altex.2009.1.52

Abstract

Foot-and-mouth disease is an extremely infectious and devastating disease affecting all species of cloven-hoofed animals. To understand the epidemiology of the causative virus and predict viral transmission dynamics, quantified transmission parameters are essential to decision makers and modellers alike. However, such quantified parameters are scarcely available, and recently a series of animal experiments was set up to obtain such data experimentally. In this communication, however, we report on the use of data from an animal experiment conducted 10 years ago to quantify transmission of foot-and-mouth disease virus between non-vaccinated sheep and from sub-clinically infected sheep to in-contact pigs. This new analysis utilises a state-of-the-art Generalised Linear Model to estimate the transmission rate. From the obtained results it is concluded that meta-analysis of "old" experiments using newly developed techniques can provide useful data to replace, reduce and refine future foot-and-mouth disease transmission experiments, thereby minimising animal suffering for research purposes.

Highlights

Foot-and-mouth disease (FMD) is an extremely infectious and devastating disease (Goris et al, 2008)
To predict the impact of control measures on viral spread during a FMD outbreak, transmission parameters are essential to modellers and decision makers
The absence of quantified transmission parameters in sheep was the basis for recent FMD virus (FMDV) transmission experiments between lambs housed in the same stable (Orsel et al, 2007)

Summary

Introduction

Foot-and-mouth disease (FMD) is an extremely infectious and devastating disease (Goris et al, 2008). The associated reproduction ratio R (i.e. the average number of secondary infections per infectious individual during its entire infectious period) of 2.22 [95% CI: 0.46-4.33] indicates that one infected sheep can be the source of minor and major FMDV outbreaks within a susceptible sheep population (Orsel et al, 2007). This information is valuable, additional data on the spread of FMDV from sheep to other species – and especially to pigs which have the ability upon infection to excrete huge amounts of airborne virus (Alexandersen and Donaldson, 2002) – is urgently needed. Data of a study conducted 10 years ago in sheep and pigs to examine the relative sensitivity of virus isolation (VI) and of a reverse-transcription polymerase chain reaction test followed by digoxigenin ELISA detection (RTPCR-ELISA) (Callens et al, 1998), was re-analysed in terms of FMDV transmission using the statistical analysis based on the stochastic SIR model (susceptible-infectious-recovered) described by de Jong and Kimman (1994)

Findings

Experimental design and results

Discussion