Equine Anatomy & Disease

Question: My 29-year-old Trakehner mare died suddenly in her stall this year. When found in the morning, there was dried blood at her nostril, her ears and on her stall wall and door. She was laying on her side and the shavings in her stall did not look like she struggled. She had been on a med./supplement regimen. The only daily med was for Cushing's, which she had taken for two years. Her daily supplement was Focus Senior and she was on a shot of Adequan monthly. The night before her death, she was hand walked and lightly lunged as she had been the previous three nights. Thank you for any light you can shed on this "mystery." My hope is that she did not suffer.

Answer: Sudden death, in which the owner does not see any warning signs, is actually not uncommon from the veterinarian's point of view, especially in an elderly horse. There are many possible explanations, including internal bleeding, fulminating (severe and sudden) infections, certain tumors and metabolic conditions like potassium or calcium imbalance. Even though sudden death may be explainable, it's still a terrible shock for the owner to lose an animal so unexpectedly. The fact that the bedding in the stall was not disturbed, is a good indication that her death was quick and that she did not suffer.

Question: Have you ever heard of a cancerous tumor to grow in a matter of two days in the jaw of a horse to the size of an orange? He was examined and his teeth floated just four weeks before this tumor appeared. My vet could not believe what she was seeing. It actually got bigger from when he was examined the day before, to when he was euthanized the next day. He was eating and drinking up to the last minute. I dewormed him that morning and the tumor showed up that night.

Answer: Tumors can indeed grow with great speed. Usually such tumors are malignant (spreading to other parts of the body). Abscesses and hematomas can also cause swellings that enlarge quickly, but usually you can tell the difference by the way the swelling looks and feels.

Question: I have a bad case of strangles at my barn. We are a non-profit riding center and our horses are donated. How soon can a horse be exposed to strangles after they have been given the vaccine?

Answer: I think the questions is "how long does it take for a horse to develop a protective level of immunity after the horse has been vaccinated for strangles." An exact time frame can't be predicted but 10-14 days is probably a safe estimate. Bear in mind that no vaccine is 100% effective, that is, even vaccinated horses can get the disease if they are "overwhelmed" by too many bacteria or other stresses. It's important to remember that horses that are vaccinated after they have been infected with Strangles are at an increased risk to develop an autoimmune problem called "purpura," which can be more dangerous than Strangles.

Question: I have a 12-year-old mare that has a crack down the center of each of her front hooves. It looks like it goes into the coronary band but does not. She does not suffer any lameness from this and can even ride her barefoot. I have had my vet and farrier look at her and they tell me as long as she is in not in pain not to worry. My farrier suggested that she may have thyroid disease. My question is, can the cracked hooves be related to thyroid disease? What can I do to repair her hooves and should I do anything?

Answer: If the crack is only in the surface of the hoof wall, it is usually not painful. Painful cracks are the ones that go all the way through the hoof wall into the sensitive tissues underneath. "Full thickness" cracks can also lead to infections in the hoof. Hypothyroidism (low levels of thyroid hormones) is one of many things that can cause problems with the skin and adnexa. ("Adnexa" is the medical term for things that are derived from the skin, such as hair, nails and hoofs and the skin glands). Hypothyroidism usually causes other problems for the animal, including problems with thermoregulation. There are blood tests that measure the level of thyroid hormones. However, if the horse doesn't have other symptoms beside the cracks, if the cracks are not painful and not causing any problems for the horse, it's probably safe to ignore them.



Question: It seems that EVA is more of an issue lately in Texas. Our breeding veterinarian suggests to vaccinate the stallions as a prevention for the upcoming shows as well as the next breeding season. He also suggests to quarantine the vaccinated stallion for three weeks after the vaccine. We consider keeping the stallion on our ranch but all our stalls are in the same building. Is it enough to leave one stall vacant next to his? Could he be in a pasture during day time? Will this pasture be contagious to other horses in the future as we also keep pregnant mares and young horses on our ranch.

Answer: Natural cases of EVA are spread by breeding and by aerosol (coughing, breathing). Following vaccination with a live vaccine, horses can become viremic and capable of shedding the virus that could infect other horses. Bear in mind that the major problem associated with this disease is abortion, so make special efforts to keep pregnant mares away from the stallion during the time he might be viremic. In diseases that are spread by aerosol, like EVA and EHV (equine herpesvirus), horses that are in the same barn are all considered likely to be exposed. So, to quarantine your stallion during the time in which he might be viremic, separate barns would be necessary, especially for the pregnant mares you have. Regarding the pasture: Although the EVA virus can be shed in urine and feces, transmission by anything other than aerosol or breeding seems to be very uncommon. The virus itself can survive for some time at low temperatures (refrigeration) but would not be expected to survive in hot, dry conditions.

Reprinted with permission from AAEP. To view the entire article please visit www.aaep.org/ask_the_vet.php