I grazed my 12 store lambs in the woodland all winter. No contact with any other sheep.. Now two of them have a 6 X 2 inch patch on top of their backs where the wool is suffering as in the attached photos. The top half of the fleece has gone and the bottom part - while frazzeld looking as in the photos - seems otrherwise almost normal. No sign of lice or dcab on the skin, and while there is dust and dirt in the fleece all the other sheep have the same small bits of debris in the wool.
I would love any suggestion as to what this may be and how to treat it. And will it spread along the fleece or to the other sheep?
Help much appreciated.
John