She said that the deer who carry this disease (to which she forgot the name) can contaminate the water that the horses use. The horses become infected and go blind. She hasn't had any of her horses tested for this disease but is putting 2 and 2 together and she's getting everyone vaccinated with the shot.
This apparently happens in cattle too and though there isn't a vaccine for equines, people commonly use the cattle vaccine for their horses since its safe for them as well.
Anyone have any insight to what I just witnessed?