This has results of Brexit written all over it.
We import infected animals. No checks - thanks Brexit.
We don't test because it's not been an issue before but now we can't export or make our own eat it if we admit there is an issue. Farmers are not in the mood to cull given the wider Brexit problems they are having and protests.
Remember when they decided to stop tracking the 9 initial Covid cases that were discovered and Boris decided instead to say we would sacrifice the old people and never lockdown? I don't think they learnt anything from that.