It wasn't exactly disgust, but more like a kind of discomfort originating from the heart, a feeling that couldn't be easily described.
If it were to be analogized...it's kind of like watching a movie, where there are scenes of people murdering or torturing others in the most brutal ways possible, which doesn't seem to affect you much while watching.
But when you watch a real-life murder documentary on some social networking site, you start to feel discomfort, which might linger for several days or even a lifetime, in severe cases!
That's a shadow!
Just this kind of feeling, but for Tang Ye, it was induced by some natural attributes of the zombies. This feeling can only be vaguely described, and can't be fully portrayed.
The psychological activities of zombies vary greatly from humans, and this difference can't be accurately described from a human's perspective. Only someone like Tang Ye, who is experiencing it firsthand, can truly perceive the difference.