A Spontaneous Model of Tourette Syndrome in Horses

Grant Type
Grant Year
Institution Location
Institution Organization Name
Tufts University
Investigators Name
Shuster, Louis, PhD

In studying various behavior disorders in horses we have encountered symptoms that have many resemblances to TS in humans. These horses have a tendency to bite themselves when they are confined or frustrated. This problem is the primary reason that drives owners to seek treatment or to dispose of their animals. However, self-inflicted injury is only one component of their symptoms. We have observed tics of the head and neck, and sideways-directed kicks that are often accompanied by a characteristic squeal. Exaggerated grooming may take the form of licking or hair pulling. Onset often occurs around the age of two years, equivalent to 6 years in humans. It is much more common in stallions than in mares, and in some cases symptoms have been alleviated by castration. Affected horses have normal intelligence. All have undergone basic training, and many have gone on to be successful show or race horses. Attacks rarely occur while the animal is being worked or engaged in absorbing activity. They can be brought on by anticipation of eating or by frustration and excitement, e.g., when a male horse is exposed to a mare. Symptoms occur daily, and the condition is persistent. Temporary remissions have been produced by treatment with some drugs that have been used to treat TS or obsessive-compulsive behavior in humans. There seems to be a genetic predisposition in horses. In quite a few instances, the condition has been found in the sire, offspring or siblings of the affected animal. While we have accumulated 57 reports by questioning horse owners around the country, there is an immediate need to observe and examine affected animals under carefully controlled conditions. We propose to admit 10 affected horses to the large Animal Hospital at Tufts University School of Veterinary Medicine. Their behavior will be recorded on videotape for standardized scoring by neutral observers. During a one-month observation period, each horse will be injected with drugs that are known to activate or block defined receptors in the brain. The quantitative response to these injections should cast light on the neurotransmitter systems that are involved. They should also indicate whether the horse model is suitable for testing new drug treatments as well as old ones. Louis Shuster, Ph.D. Tufts University, Boston, MA Award $25,110 Tourette Association of America Inc. – Research Grant Award 1993