All the information I read says nasal discharge and watery eyes, but ours hadn't got that.
They just went off their food a bit and looked depressed.
Although by the time we got Flossie rounded up to vaccinate her , I did notice she'd starting breathing a bit more heavily.
I see my sheep at least 3 times a day and hand feed them so it's easy to notice them being off colour, but in a flock it would be easy to miss.
J xxxx