That's easy -- horses don't sue.

It doesn't infect deer. Here is a nice piece on it:

http://www.mswildlife.org/westniledeer.html

Ex, is right about the horses not being well connected with malpractice attorneys, but there is a bit more to the story. The wall street journal (thursday or friday) had a nice piece on it.

The gist is that Wyeth (the vaccine maker) noticed in 1999 that there were 26 cases of horse west nile and because it had entered migratory birds, researchers at Wyeth speculated that it would rapidly spread across the country. So in late '99 they started a crash program to create the vaccine getting an inital doorway into a solution because they already had a vaccine for a virus that was similar to west nile.

The critical difference between animal and human vaccine development as that you can take an experimental vaccine inject, then after anti-body formation inject with live virus to test effectiviness of the vaccine. For obvious reasons nobody wants to be a guinea pig (and no well intending doctor wants to inject a person because of thug lawyers) thus the whole development cycle is much longer for people.

The good news is the horse vaccine is wicked effective. 50% of horses in CO have the vaccine and none of those that have come down with west nile have had the vaccine.

Also the rapid development of a vaccine in equines suggests that a human vaccine should be possible.

thanks bitmasher, I was hoping that it didn't effect the wildlife I love to hunt.