Varied rabies presentation in horses make diagnosis difficult, says veterinarian

Rabies may be the last thing ranchers suspect when a horse gets sick, yet it’s important to keep rabies in mind because this is the most serious disease that humans can get from horses, according to Ann Dwyer, a veterinarian in Scottsville, N.Y. 

  Rabies can affect all warm-blooded animals and is caused by a virus that affects the nervous system, transmitted by saliva of an infected animal − via a bite or saliva coming in contact with mucous membranes, such as eyes or mouth or any opening in the skin. 

Dwyer, from Genesee Valley Equine Clinic, says skunks, foxes, bats and raccoons are the main animals that transmit this disease. 

Rabies in horses occurs infrequently, but they are still at risk.

Diagnosing rabies

Dwyer was involved in diagnosing three cases, all of which exhibited different symptoms, illustrating the fact that rabies can look like just about anything. She said one mare was acting strangely and bellowing, aggressively lunging at anyone who came near her stall.

The second case was a horse owned by a woman who didn’t believe in vaccination. 

“She called me out to see a horse that was simply dull and not eating, with a fever. I was thinking the horse had flu, so I did a physical exam with my hands in its mouth, and I didn’t wear gloves,” she says.

That horse showed no neurologic signs. It just wasn’t doing well, describes Dwyer, adding “By the next day, it lost the ability to swallow. I sent the horse to Cornell University, still not suspecting rabies.” 

“The veterinarians at Cornell didn’t suspect rabies, either, because they ended up with quite a number of people having to get the post-exposure treatment. I also had to receive the treatment,” says Dwyer. “I was vaccinated for rabies while I was in vet school and got re-treated after each one of the cases I worked on.”

Montana case

The third horse she diagnosed was a bizarre case in a horse from Montana. The new owners in New York had been told that the gelding had all his shots. 

“But later, we found he had not been vaccinated for rabies,” Dwyer says.

This horse seemed lame, and she was asked to do a lameness evaluation. 

“Then it acted colicky but not lame. The more we watched, the more puzzling it was. The horse was rapidly getting worse before our eyes,” Dwyer explains. “Children had been handling the horse, so we explained to the family about the possibility of rabies, and they were okay with euthanizing the horse.”

She and one of her interns did the post-mortem to remove its head.

“When we get the head off, there is cerebral-spinal fluid to deal with, so we use a lot of garbage bags, rubber dishwashing gloves, wearing two pairs doubled, protective suits and booties and a cap and mask. We also double-bag all the samples and put them in Tupperware containers, one inside another, to send to the lab,” she explains.

Prevention

The best prevention for rabies is annual vaccination for horses. 

In 2008, the American Association of Equine Practitioners (AAEP) included rabies as one of the core vaccines that should be given to every horse. 

“Unfortunately, some people don’t believe in vaccinating,” she says. 

People who think there isn’t any risk for their horses don’t realize that even if their horses are in stalls, rabid wildlife, including bats, may come into a barn. 

A barn cat may be bitten by a rabid animal and then pose a risk to horses or humans in the barn.

Wildlife encounters

Horses are curious, as well, says Dwyer. They’ll walk up to an animal that’s acting strangely, and get bitten. 

Last fall one of Dwyer’s clients, Mary Delton, observed one of her geldings being bitten by a skunk that was acting strangely. Delton happened to be out in the barn where she could see her horses in their paddocks. 

“My friend saw the skunk and came into the barn to tell me he saw a skunk dragging part of a dead animal into the garage,” Delton recalled. 

She and her friend decided to keep an eye on the skunk. 

“I never expected it to come to the barn where I was doing chores, but when I went to dump the wheelbarrow, I saw the skunk in the paddock with my mares. I yelled at him and ran out there, and he ran under the fence and into the geldings’ paddock. The horse kicked the skunk, and then the skunk ran back and bit the horse on the fetlock. It happened so fast I wasn’t sure what happened,” Delton said. 

“After he bit the horse and I continued to yell at him, the skunk started running towards me so I ran to the barn, closed the doors and called 911. I captured the skunk by putting a muck bucket over it,” she said. “The sheriff came and shot the skunk.”

The skunk’s brain was tested and was positive for the virus. Because the bitten horse had been vaccinated, the only action needed was a booster immunization. 

If this had been an unvaccinated horse, the authorities would have insisted on euthanasia or expensive quarantine for that horse.

“If my friend hadn’t seen the skunk, I would not have known to look for him. It just happened that I was dumping manure when it was harassing my horses,” Delton commented. “My vet and the county health department said that if the annual vaccination was within six months of when the horse was bitten, he should be fine, but for this horse, it was seven months. So he got a booster the next day.”

Heather Smith Thomas is a correspondent for the Wyoming Livestock Roundup. Send comments on this article to roundup@wylr.net.