The reason that rabies is not often detected in horses is because horses are often put down without having a necropsy. You have to take the brain out and send it off for a necropsy. Horses who are sick and stagger around and all aren’t often necropsied. People just say it is something else.
I’ve always given mine rabies shots, you can order the vaccine if your vet won’t give it, I usually have my vet give it yearly. We always had raccoons on the bluff where I grew up on the Vernon River, and rabies went thru raccoons about every 5 years. At one barn, behind Skidaway Island, I once counted 34 raccoons coming thru the marsh and out of the trees to fight for the feed given to horses in paddocks. I fed Cloudy and Callie in their stalls and made sure the vet gave them their rabies shots. Bats too are often rabid and we had bats.
Our neighbors 4 doors down, when I was growing up my horses lived at home, owned a pet and garden shop but diid not vaccinate their own dogs! One dog got rabies, was put down, was necropsied.
People are stupid. Better to vaccinate than to have a dog or cat or horse get rabies. I used to vaccinate the dogs and cats of our support staff in Atlanta every years, and yes I included the rabies shots for their dogs and cats. They bought the drugs and syringes, and I went to their homes on weekends to vaccinate, free of course.
Preventing rabies is easy with a yearly shot. Only a few people have survived rabies.
We have coyotes and foxes, too, and rabies runs thru them as well. Your horse or dog or cat can be bitten by a lot of warm blooded animals, which can carry rabies. And yes, you give a booster shot if your animal is bitten by an unvaccinated animal. It takes about a month for a rabies shot to become fully effective, so do not put it off each spring.