Protecting your sheep against footrot is extremely important, caused by the bacterium Dichelobacter Nodosus, it can cause severe lameness in sheep.
Early signs of footrot include a spreading of the infection under the horn tissue, which causes the horn to become separated from the sole. The reddened corium can become exposed causeing considerable pain. In chronic cases the hoof walls and toes become overgrown and misshapen.
Source: http://www.nadis.org.uk