MS-MR-1-Equine-Rabies11by Elizabeth A. Tomlin
With all of the alarm raised over the spreading of ticks and Lyme’s Disease, equine owners should not forget the importance of another disease that is highly contagious and deadly to both horses and humans. Rabies continues to lurk in our area and our equine companions continue to need protection.
Tracy Bartick-Sedrish, DVM, of the Upstate Equine Medical Center in Schuylerville, NY, reports that she and her husband Steven Sedrish, DVM, have had two experiences with equine rabies.
“A 2-year-old horse seen as an emergency call,” Tracy explains. “The owner suspected choke as the horse seemed to have a problem drinking. A nasogastric tube was placed but no obstruction was noted.”
The veterinarian then performed an upper airway endoscopy to examine the larynx, noting left recurrent laryngeal nerve paralysis, the condition as appears in a “roarer”.
“The owner did not want to pursue anything further and did not want to hospitalize the horse,” Tracy said. “So, the veterinarian left with instructions to the owner to call if they had any other issues.”
The owners then moved the horse to another farm for easier observation. However, they did not use biosecurity methods and did not consult with the on-call veterinarian before or after the move.
The owners decided to treat the horse themselves, tubing it with water, a procedure never recommended by the Upstate Equine Medical Center, and the horse died.
When Sedrish called to check on the horse they discovered that renderers had already been called to pick up the body.
“The concern was zoonosis — disease transmissible from animal to man — with rabies being the number one differential at that time. Dr. Steve Sedrish stopped the renderer’s truck and collected a sample for rabies testing, which we personally drove to the state lab for testing.”
The sample tested positive for rabies and many people had to be immunized, including both Dr. Steve Sedrish and Dr. Tracy Bartick-Sedrish.
“The horses that were exposed to the ill animal also had to be considered — and this is a huge reason why biosecurity is such an important topic for discussion!”
The most common clinical sign of rabies is changes in behavior. Infected horses may become dull and depressed or aggressive and frantic. Symptoms of colic are often observed. Horses suspected of exposure must be isolated for 6 months. And, because of the zoonotic nature of the disease, the case must be reported to the local public health agency.
In another case of rabies, Sedrish reports, a thoroughbred race horse insured for $80,000 was involved.
The horse had been vaccinated for rabies 13 months prior to presentation and was seen by a referring veterinarian for colic/abdominal pain. The horse had become increasingly aggressive, which was attributed to pain and was referred for surgery.
However, Sedrish said, “When he arrived at the hospital he lunged off the trailer, teeth bared and striking at anyone who tried to catch him. He was corralled into a stall, became even more aggressive and lunged at the door of the stall when anyone passed by the door. He began self-mutilation behavior — biting at his forelegs. At this point he was euthanized, as rabies had now become the primary differential.”
The time from referral to euthanasia was approximately 2 hours — noting another indication rabies, which is the rapid progression of the disease.
Most horses show clinical signs of rabies 2–6 weeks after exposure to the virus. However, it can take much longer.
Philip Beaudoin, DVM of Milton MA, says this is because the rabies virus follows a nerve pathway until it reaches the brain. “For instance,” he explained, “in a bite on the leg, it has to farther travel. In rare cases it can take up to six months. But, most cases do show up in about 2 weeks.”
Beaudoin remarked veterinarians are in the most danger from rabid animal as they are the people who are examining livestock and small animals. “We’re the ones putting our hands in their mouths!”
“New York State has a high prevalence of rabies in our wild animals,” said Dr. Jill Greisman, DVM at Midvale Clinic in Montgomery Co. “Rabid animals can look like anything — they aren’t necessarily foaming at the mouth, but their behaviors are usually unexpected and out of the ordinary.”
Wild animals with rabies may enter a barn or even a house seeking water, maybe acting aggressively — and maybe not. It’s the same with domestic animals or any mammal with rabies. Aggression is not always the first sign of a rabid animal. Wild animals may show no fear of humans or other natural enemies, appearing friendly.
Staggering, convulsions, choking, frothing at the mouth and paralysis are some signs and infected animals may make abnormal sounds.
“All warm blooded animals, except birds, are susceptible. We really encourage people to vaccinate!” said Terri MacKenzie, DVM, with Midvale Clinic.
“If you shoot an animal you think is rabid, call public health and have the euthanized animal tested so you know for sure and can take appropriate precautions. Vets are vaccinated against rabies — we can remove the brains of rabies suspect animals and send them to diagnostic labs to know for sure. Many people shoot rabies suspect animals and don’t go on to have that animal tested,” Greisman stated. “So these cases go unreported. If they are never reported and tested, how do we know the actual prevalence of this disease in our area?! Have that animal tested so we have an accurate idea of the rabies risk in the area! It is, unfortunately, a higher risk than documented.”
Rabies vaccination certificates are mandatory in most states for horse related events.
Check your local public health website for the presence of active, reported rabies cases in your area.