MU Equine Veterinarians Solve
Ashley French, a fourth-year veterinary student at the University of Missouri College of Veterinary Medicine is pictured with one of her favorite MU horses. French won a second place award for a paper she authored that documented a puzzling illness that caused seizure-like symptoms in a horse she helped care for at the Veterinary Medical Teaching Hospital.
When a yearling American quarter horse was brought to the University of Missouri Veterinary Medical Teaching Hospital with what seemed to be colic, the Equine Clinic team found itself piecing together a diagnostic puzzle.
The colt had recently been shown in Texas during extremely hot conditions. Upon his return to Missouri, he began demonstrating agitated behavior, such as rolling, sweating, lying down, circling and pawing at the ground. His owners suspected that he had consumed too little water for the Texas heat and they consulted their local veterinarian. However, despite receiving five liters of mineral oil and an intravenous treatment of saline solution, the horse continued to demonstrate discomfort.
His owners transported him to the MU College of Veterinary Medicine where his condition continued to worsen. He alternated between lying down and walking in circles. His heart rate became elevated and he began having muscle spasms that would last up to 30 minutes. During the most severe episodes, his symptoms were described as seizure-like.
As the equine team continued to rule out possible causes behind the colt’s distress – encephalitis, tetanus, West Nile, influenza – they turned their focus on the possibility that hyperkalemic periodic paralysis (HyPP), a genetic disease found in quarter horses and for which the horse was known to be heterozygous, was at the root of his clinical symptoms.
After several days of therapy targeting HyPP, no improvement was seen. “It was confounding,” said CVM fourth-year veterinary student Ashley French, “because the treatment for HyPP was not working. There would be an episode every two hours or so. A 1,200-pound horse flailing in his stall can be very dramatic.” French helped treat the colt under the direction of MU CVM Assistant Teaching Professor Alison LaCarrubba, DVM, ABVP, and intern Kirsty Husby, DVM.
As HyPP seemed less and less plausible as a diagnosis, the equine clinicians and veterinary students expanded their search for a cause to include muscle disorders and neurological diseases. However, muscle biopsies and an electromyography performed by a CVM board certified neurologist revealed no abnormalities. Further adding to the mystery – the colt’s herd mates began to display similar symptoms.
Undeterred in their quest to help the young horse, they sent the muscle biopsies and a video of the horse to a muscle specialist. While the MU equine team had already performed an examination of the ailing colt’s ears, the specialist recommended that a deep ear examination be performed under sedation.
Deep within the horse’s ear canals the problem was found – multiple spinose ear ticks. While the ticks are rare in Missouri, they are endemic in the Southwest United States. The parasites feed in the host’s ears causing pain, inflammation, convulsions and muscle spasms. They can also spread to other horses, as well as deer, big horn sheep, domestic cats, dogs and even humans.
The ticks were removed and the horse’s ears were treated to kill any ticks that evaded the forceps. Back home, the colt’s regular veterinarian sedated the MU patient’s herd mates and discovered they too had been infected. Within 72 hours of treatment, the colt’s symptoms disappeared and he was cleared to return home.
French found the unusual case so interesting she wrote a paper about it. That report, “Case Study of the Spinose Ear Tick in an HYPP Yearling American Quarter Horse” captured second place honors in the American Board of Veterinary Practitioners 21st Annual Case Report Contest. The contest is sponsored by Merial and Elanco. According to the ABVP, winning case reports include appropriate diagnostic workups, as well as medical or surgical managements, a clear demonstration of veterinary expertise, the application of sound medical principles in diagnosis and treatment, and the communication of medical observations and data in an organized manner.
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