The difficulties of diagnosis

The stain of the disease that afflicted Britain last year is notoriously difficult to detect and diagnose in sheep.

Frequently, the only symptoms are mouth lesions, and these are similar to those from other possible causes such as eating brambles or other illnesses.

There have been a number of scares since the last case was confirmed in September. In several of those cases, suspicion was strong enough to slaughter entire flocks, only for test results to be negative.

It is exactly one year and one week since the first case of the epidemic was confirmed. Britain was declared formally free of the disease only on 5 February.

Nearly six million animals were killed either directly as a disease control measure, or because movement restrictions prevented humane husbandry.

The suspect sheep were two of 400 restocked on a farm where all the animals were culled in August. The new flock had come from four other farms in the area and animals on these farms are also being tested for the disease.