Deer blindness virus?

I was over at a friend's barn today to play with the horse she boards. I was helping the BO while I was out (waiting for friend to get there) and she mentioned 3 of her horses are either blind or partially blind. One was completely blind, another had moon blindness and another I didn't see was going blind. When my friend finally arrived the BO offered her a vaccine to prevent blindness due to a deer disease.

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?

O.O I need info on this too, so subbing!
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My first horse did develop sight problems from what I think my vet said was Lyme disease, but I was super young and it has been about 11 years so do not quote me on it. I think he said it was like moon blindness. I am also pretty sure Lyme disease is transferred by deer ticks, but again do not quote me on it. Maybe she meant that?

She offered a vaccine to me for a low fee. I didn't take it since I didn't know what exactly it was for...and for the life of me, I can't remember what its called. Its for cattle though and I think it had the number 6 in the title.

Moon blindness is not necessarily caused by just one organism. It is the reaction of the immune system to the organism. The most common cause seems to be leptospirosis.

If you have references to the uses of leptospirosis vaccines to prevent this, I would like to see them. I would not use an off label vaccine without documented evidence that it is both safe and effective.

This article has some interesting information on the subject.

New Hope For Moon Blindness | The Chronicle of the Horse

I'm trying to figure out what she was referring to and if anyone had heard of this deer disease. She seemed very adamant that it existed which is why she was using a cattle vaccine in her horses to prevent it. Apparently the deer transmit the disease through a water source (to her understanding) and when contracted, the horse or cow goes blind. She also said the blindness starts out in a spiderweb form across the eyes?

I am assuming that she is referring to leptospirosis. There are cattle vaccines for it. Wildlife can carry leptospirosis. Rodents are notorious for carrying it. If it is something else, I am waiting to hear about it.

Thats why I'm a little confused. She had a horse who has moon blindness (we disussed it) but when she described this disease, she forgot it's name. I guess I could find the name of the vaccine to help. She told me it but I wasn't interested in the purchase so I quickly forgot what it was called.

She was probably vaccinating for Lepto (Leptospirosis) Lepto can cause spontaneous abortion and blindness. I have seen it in mares that ran with cattle and goats. Deer, elk and bison can also carry it. Dogs can get it and I have heard that it can spread to people.

They do not make a specific vaccine labeled for horses (or at least they didn't when I ran horses and cattle together and it was very prevalent) so our Vet had us vaccinate our mares for it with cattle vaccine. If I remember right, there are several different strains of it and the vaccine for one strain does not protect against another.

Horses that have carried it for several years all go blind and will not carry a foal to term.-- or at least that is what I have seen.

Would it be safe for a horse who is blind (possible carrier) to be vaccinated for it? I know you aren't supposed to give the strangles vaccine to a horse who already has strangles. Is there a downside to vaccinating a horse for this is they already have the disease?