EQUUS ‘Farm Calls’ episode 18: Equine rabies

Tune in as we talk to Dr. Sarah Colmer about this deadly equine disease and what you need to know about it.

“Equine rabies is a devastating disease that is largely preventable,” said Sarah Colmer, VMD, DACVIM, of the University of Pennsylvania’s New Bolton Center. “It is almost always fatal.”

In Episode 18 of EQUUS Farm Calls podcast we talk to Colmer about this deadly equine disease and what you need to know about it.

Colmer said horses are susceptible to rabies because they live outside where the wildlife vectors—including skunks, raccoons and bats—also live. While it is uncommon, equine rabies cases do happen every year. “I’ve seen three cases since 2019,” Colmer noted.

Rabies in horses is an even bigger issue because there usually are human exposures to the rabid horse. And sometimes it isn’t easy to diagnose or even suspect a horse has rabies while it is alive.

How horses get rabies

In most cases, Colmer said, horses get rabies when they are bitten by a rabid animal in their environment, such as a skunk, bat or raccoon. Most of the time owners or managers will not see that interaction happen, so they have no idea the horse has been exposed. A bite is a tiny wound, so even with meticulous grooming, an owner might not notice that bite puncture wound.

The saliva of the rabid animal gets into the bite wound and replicates the virus. It reaches the nerves and eventually the spinal cord, said Colmer. “Rabies can affect all parts of the horse’s neurologic system,” she noted. That is why rabies in horses is difficult to diagnose in the live animal with clinical signs.

Clinical signs are confusing

According to Colmer, a rabid horse can appear to be colicky, behave “abnormally,” might trip or stumble, might be more reactive to stimulus, or have neurologic signs such as an eyelid, tongue or ear droop. Some horses with “furious” rabies will self-mutilate or can become aggressive.

“If these signs occur quickly, that heightens the concern that this could be rabies,” said Colmer. “If you call your vet, you should tell him or her when the last rabies vaccination was.”

According to the American Association of Equine Practitioners (AAEP), physical signs can include:

  • Choke
  • Colic
  • Fever
  • Anorexia
  • Blindness
  • Dysphagia
  • Hyperesthesia—manifesting as self-mutilation or intense pruritus
  • Lameness
  • Paresis and/or ataxia
  • Incontinence
  • Muscle twitching
  • Paralysis—ascending
  • Sudden death

Behavioral signs can include:

  • Variable behavior changes at onset
  • Dumb form: depression/stupor; more common in horses
  • Furious form: mania; less common in horses but extremely dangerous

Diagnosis

Unfortunately, the only 100% diagnostic for equine rabies is by examining the brain of the deceased horse.

But in order to help your veterinarian include or exclude rabies from the list of differential diagnoses, horse owners need to give a veterinarian a history of the horse’s behavior, clinical signs and how fast they are progressing, and vaccination history if the practitioner doesn’t already have that. “If it is rabies, there is a severe and rabid demise once signs start,” advised Colmer.

“If rabies is suspected, [a veterinarian will usually] send the horse to a referral center where biosecurity with isolation is available and there is complete PPE [personal protective equipment],” said Colmer.

Owners who think a horse might have been exposed to rabies are advised to wear PPE—including gloves, a face shield and eye protection—when handling or being around the horse. The virus can enter mucous membranes as well as being transferred through a bite.

Colmer said to keep in mind that a rabid horse can have the rabies virus in milk and placental fluids.

Treatment

“Rabies is not treatable,” stated Colmer. “If the horse is hospitalized, they try to treat and manage it until death.”

She said if you see a vaccinated horse being bitten by a potentially rabid animal, the horse should be re-boosted immediately by a veterinarian. Then the veterinarian will clean the wound and monitor it. The horse will be monitored for 45 days. Horse owners can read the AAEP Guidelines for Equine Rabies here: https://aaep.org/document/rabies

If you suspect an unvaccinated horse has been exposed to rabies, that is more serious, said Colmer. “The state veterinarian might recommend euthanasia or several months of isolation,” she said.

Take-home message

The bottom line is that all horses should receive a rabies vaccine. It is highly recommended that a veterinarian administer the vaccine to ensure it is done according to label directions and state law.

This episode was brought to you by our partners at Farnam, the makers of SandClear Natural Psyllium Crumbles.  Horses consume small amounts of sand and dirt, regardless of location or feeding regimen.  Help prevent sand build-up and keep your horse’s intestinal tract healthy by providing a high-quality psyllium supplement.  Visit Farnam.com to learn more. 

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