Rabies in horses is pretty rare but far from unheard of, and each case should be a reminder of the need for proper vaccination. The latest US case was a horse in Newport, New York, but I haven’t yet been able to track down more details. Presumably, human and animal contacts are being investigated, with assessment being made as to whether there was potential exposure to rabies virus. For people, that would mean a course of post-exposure prophylaxis. For animals, that would mean a quarantine, observation period or euthanasia, depending on the species and vaccination status.
The risk to people is quite low. The biggest human health risk is from being attacked or otherwise physically injured by a neurological horse, as opposed to getting rabies from an infected horse. But rabies is something with which we don’t play around, so anyone deemed to have been exposed will presumably be treated.
Rabies isn’t common in horses but it kills. Vaccinate your horses (and other animals).