For many people, Empire Maker was an appropriately-named horse whose legacy as a stallion will live on well after his death this week at the age of 20. His veterinarians, Dr. Lauren Javernick and Dr. Nathan Slovis also hope the Gainesway stallion may also one day be remembered for helping other horses suffering from a rare immune disease.
Empire Maker died of common variable immunodeficiency (CVID), a disease Slovis has only seen twice in his 25 years of practice.
“It is very rare,” said Slovis, who is one of the top internal medicine practitioners and director of the McGee Center at Hagyard Equine Medical Institute. “One of the white blood cells, called a B cell, is part of what makes antibodies in your bloodstream. Unfortunately, in this disorder, the B cells stop producing antibodies. It just stops, and there's no rhyme or reason to it.”
Brian Graves, general manager at Gainesway Farm, said the farm first became concerned in September, when Empire Maker dropped weight suddenly for no obvious reason. Slovis tested the stallion for Cushings and other common diseases.
“The vets (Dr. Javernick and Dr. Slovis) who were on this case were sharp enough to recognize what it was,” said Graves. “Unfortunately, it's incurable, and not something they can battle for very long. It's about giving the horse as much quality of life as you can in the face of a disease like that.”
Once a horse contracts CVID, the disease reduces their immunity to that of a newborn foal – one who hasn't gotten colostrum.
“Pretty much, Empire Maker's antibody levels were like a brand newborn foal, next to nothing,” Slovis said. “[His antibody level] was down to 50 or 60 but consider that a newborn foal, after it's had colostrum, is above 800. Aggressive medical treatment kept him from getting a life-threatening infection, but there's only so much you can do. You can't keep a horse in a bubble.”
CVID is characterized by a horse repeatedly contracting illnesses, particularly minor fevers and respiratory bugs but also hoof abscesses, diarrhea, gingivitis, skin problems, and neurologic disorders, until something more serious like pneumonia develops.
Slovis said regenerative treatments like bone marrow transplants in horses do not “take” the way they do in humans and are not a viable option for CVID. Plasma transfusions may create a temporary improvement on lab results, but they will not actually address the problem of antibody production. Managers are left to provide the horse with supportive care to keep them as comfortable as possible, but horses rarely live more than six months past diagnosis.
Unfortunately, scientists know more about what doesn't cause CVID than what does cause it. It's not viral or bacterial. Slovis said so far researchers have ruled out diet, stress, location, and exposure to other horses. Horses with CVID do not seem to catch it from others, and do not pass it along to others. CVID is not limited to a particular breed, gender, or age of horse, and travel (like Empire Maker's trip to Japan and back in the middle of his stud career) does not impact a horse's likelihood of contracting it. There's also no connection between the amount of colostrum a horse gets as a foal and its likelihood of getting CVID later.
Slovis said CVID may be a result of a particular gene, one responsible for ordering the B cells to produce antibody becoming “turned off” by something. This does not mean relatives or offspring of Empire Maker are bound to get it – research indicates it does not get passed along through families – but rather something has stopped the genetic code from doing its job.
“I'm getting calls already from people have foals by him, wondering what to do,” Slovis said. “They don't need to worry.”
Cornell University's College of Veterinary Medicine has led the charge into CVID research, and Slovis just happens to know Cornell's Dr. Maria Julia Bevilaqua Felippe Flaminio, who heads those research efforts. Samples of Empire Maker's bone marrow will be stored and maintained for future testing, in hopes his tissue can help Flaminio or others crack the code of CVID.
“He may be able to save horses' lives and help us figure this out,” said Slovis.
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