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In my book Pets on the Couch, I discuss several psychological and psychiatric conditions that I have found over the years that afflict both animals and humans. But stumbling an equine version of Tourette’s Syndrome (TS) was the most unexpected discovery of all.
The journey toward discovery started with a road trip to see an Arabian stallion that was, according to his owner, exhibiting some extremely bizarre behavior. The horse, Migdol, would intermittently spin in tight circles, sometimes trying to bite his own flank or would make sudden downward deflections of his head and neck as if to swat something off his chest. It looked for all the world as if he was being attacked by biting flies during these sudden attacks and was doing his best to fend them off - but there were no flies around. There could be as many as 20 of these “attacks” per hour and in between times he would do a lot of sniffing and checking the periphery of the stall or arena in which he was enclosed.
After observing Migdol in action in his own barn, we arranged to have him brought to our large animal hospital for a few days to make some more detailed observations and see if we couldn’t come up with a treatment for him. While he was with us, right out of the trailer, we noted some other strange behaviors. First, he had obvious issues with thresholds, baulking or rearing up on his hind legs when traversing any junction between two different-looking surfaces. His reaction was so sudden and violent that once, while rearing up at a threshold, he dislocated the shoulder of the student holding him. It was a painful lesson for the student to learn that if ever a horse rears let go of the lead shank. We are no match for a horse’s sheer strength.
Another thing we noticed was that he would frequently strike out with a forelimb or hind limbs double barreled kick, especially after sniffing some manure.
During a study in which Migdol’s behavior was largely reined in following treatment with an opioid antagonist, he broke out of control when we (purposely) led a mare in estrus past his stall.
Determined to learn more about this puzzling behavior, we did a nationwide survey of 57 horses with the same condition and pondered the results. See: http://europepmc.org/abstract/med/8014092. We learned that it affected horses of various breeds, either sex (though it was predominant a male phenomenon), the age of onset was 18 months of age, it was often ameliorated by castration, and responded to antipsychotic medication. In a later in-house study we encountered horses that made odd barking sounds, which I called “harumphing.” With these additional findings and the obvious physical expression of the condition, we began to put two and two together. We could be looking at an equine version of TS.
Tourette’s syndrome in people develops at a young age. It affects mainly males, is associated with motor tics (often head and neck or shoulder jerking), and may express as sniffing or touching objects, jumping, bending, or twisting. Vocal tics include sniffing/snorting, grunting, or barking. Some of the most dramatic and disabling tics involve sudden movements that lead to self-harm. The parallels with the equine condition are compelling.
One of the horses in our 57 horse study – Pepper Belle, a quarter horse mare - lived fairly close to us at the veterinary school. His owner was impressed by the TS analogy and felt a calling to take things further. He wanted to contact the TS Foundation to see if “Pepper” would be of any interest to them as perhaps an educational opportunity for children. His concept was Pepper may have a behavioral issue but is a winner at the track. He caught the TS Foundation’s attention and we all met at his farm to discuss our options.
The result of his determination was a series of school visits in which Pepper was displayed in all her glory, drawing a sulky around the high school running track with a jockey in full silks at the reins. We would then retire to the auditorium where video of Pepper winning race after race was shown, followed by her in her worst moments twisting and shouting (metaphorically) in her stall. A person with TS would then address the crowd as did a leader of the TS Foundation. The students got the message and loved everything about the presentation.
One of the upshots of this gathering was that the TS Foundation agreed to fund a study to investigate which drugs could be used to treat TS in our equine model. We conducted the study at the veterinary school and confirmed that 1) there was no medical explanation for the behavior (no stone was left unturned) and 2) that horses with the equine version of TS respond in a similar way to people with TS. We even made some novel findings -- including the benefit we saw of employing high doses of opioid antagonists for treatment -- which we hoped would translate into another option for treatment of human TS patients.
Tourette’s syndrome is just one of several animal versions of human psychological or psychiatric conditions that I illustrate and discuss in my book. The take home message is that animals are much like us in terms of the mental afflictions that may affect them. Just as veterinarians can learn much about treatment of their patients’ behavioral disorders from studying equivalent human conditions, so psychologists and psychiatrists can learn much about the underlying biology of such conditions by studying animals. There’s more to fathoming the basic workings of such conditions than is currently gleaned from the numerous contrived rodent models. Spontaneously occurring veterinary behavioral issues are much more closely related to their human equivalents than any manufactured model. It’s time for psychologists and psychiatrists to warm up to this notion. To conclude, it is clear that there is only one medicine and that we should learn from shared disclines.
