While tracing movements of pigs from the index farm has proved relatively straightforward, tracking movements of sheep has proved more difficult and in some cases impossible. This is partly due to unrecorded sales of sheep, which it seems took place around the edges of the various livestock markets without passing through the markets' books. Mr Speaker, over the past four weeks many comparisons have been drawn with the 1967 outbreak. The truth is that the two outbreaks are very different. The key differences between this outbreak and 1967 are the speed and geographical scale of the spread of infection, which result from a number of factors, and the species involved.
Experts agree that the current outbreak is unprecedented internationally.
First, time had elapsed before the infection at the probable source farm was disclosed. Linked to this, the second factor in the speed and scale of spread was the larger scale of animal movements nowadays compared to 1967, aided by a much improved network of roads and motorways. A third factor was the fact that the infection spread quickly to sheep, and then among sheep, which, because of the nature of sheep flocks and the way they are traded, made the course of the infection more difficult to trace. The 1967 outbreak was mainly in pigs and cattle. The strain of the virus we are currently dealing with does not manifest itself clearly in sheep, which makes detection difficult.