A few years ago in the late summertime, I received a phone call from some people with a horse showing signs of colic. When I arrived, I could see the horse was in severe pain. He would get up off the ground and walk a few steps, keeping his knees and hocks flexed, similar to a horse with a severe bellyache. His pulse was rapid, but he had pretty good bowel sounds and he would eat grain while sitting on his sternum. Occasionally, he would try to stand up and sometimes would make it up and go a step or two, then collapse. These signs were not consistant with colic and the more I watched, the more I wondered if he had a sever case of founder or laminitis, because it seemed the pain was in his feet. There was no history of any feed change or excess grain feeding, which would back up a diagnosis of founder, but I decided to block all four feet.
Several minutes after depositing some local anthestetic around the digital nerves on all four feet, the horse got up and walked over to some grass and started eating as if nothing had been wrong. We hauled him to the clinic so I could keep a close watch on hime since the diagnosis was not clear.
A couple people had called and reported some of their horses had vesicular stomatitis with the typical blister and ulcers on the lips, gums and tongue. Vesicular stomatitis can also effect the feet, causing severe inflammation at the coronet. I told the owner that night his horse could have vesicular stomatitis and the next morning he had a couple of blisters on his lips, which helped confirm the diagnosis.
In the weeks after all that, the large animal veterinarians in the area saw many cases of vesicular stomatitis. Sometimes every horse on a farm was affected, other places would only have one horse with symptoms. Cattle also were affected and economic losses to dairy farmers were enormous since the udders of the cows could also be affected. In horses the mouth lesions were the most common. At first vesicles would develop and break, leaving a raw ulcer which was very sore. Some horses had only a few sores and some had almost the entire lip and tongue involved. Vesicular stomatitis is caused by a virus and the symptoms are similar to hoof and mouth disease, which was eradicated from the United States early in the century by the federal government. There is no treatment except to use antinflammatory medication to relieve pain and try to keep the horse eating and support them through the initial and most painful few days of the disease. Mose cases occur in the summer or fall. Flies are thought to be involved in the transmission, although some cases have occured in the winter. According the the literature, vesicular stomatitis is sporadic and not epidemic, but there have been epidemics two years in Western Colorado since I have been practicing here. Most years we see a few isolated cases in the fall.
A small percentage of cases will have foot lesions. The coronet can be inflammed severly enough that as the hoof grows, the wall separates from the sensitive tissue around the coffin bone and the entire hoof and sole will come off. Some of these horses can be saved if the owner is willing to spend the money and do the necessary bandaging and care until the foot toughens, and a new hoof can start to grow from the coronet. One cowboy brought a horse in he treated himself. All four feet had sloughed. The horse had grown solid new hoof wall and soles on all four feet. He trotted sound and x-rays of the feet showed no abnormalities. Another horse sloughed a hind foot and eventually grew a new wall and sole, but as he bore weight on the foot, the toe would turn up indicating the naviciular suspensory ligaments were ruptured sometime during the disease or the healing process. Some horses would show the mouth lesions and some degree of lameness for a day or two, then have not further problems. The horse that the owner thought had colic, did not slough his feet, but he was tender footed for a few months. He eventually was able to go back to his previous use as a steer roping horse.
Because of the foot and mouth lesion, vesicular stomatitis is reportable to the government. The signs are similar to hoof and mouth disease and our first epidemic attracted a lot of attention. Federal veterinarians flew to Western Colorado from Washington, D.C. and other parts of the country to meet with area practitioners. I guess we all learned something, but there wasn't much we could do. The disease was widespread and much was unknown about transmission.
A few cases still occur almost every year. Horses salivate and go off feed. The mouth should be examined for foxtail or cheat grass awns, which can cause the same symptoms. Grass awns get stuck under the tongue or around the base of the teeth and the horse salivates and is reluctant to eat just as with vesicular stomatitis. The good thing about vesicular stomatitis is that it is sporadic. We have seen epidemics do we know the book is not always right.
We would like to take this opportunity to thank HARRIS VETERINARY CLINIC, in Grand Junction, Colorado for providing us with this information.
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