Surely they go out in the summer? Even if the lambs are being fattened for meat, the breeding stock must graze? I thought the whole thing with sheep is that they are raised on grass, with minimal expensive hard feed, and are a very naturally produced meat. Still, that's not your question.
Another zoonosis I suggest you guard against is Orf. It's easy to catch from a scabby-faced sheep, and is very painful. Never touch your face when handling sheep, and always wash your hands before as well as after going to the toilet - that's one area you
really don't want to get orf
If you are really concerned about breathing in the bugs, you could work in a mask, but they are minimally effective unless you have total breathing apparatus. Also hard to work in as soon as you start to warm up.
Best just to take sensible normal hygiene precautions (baby wipes are indispensible
)