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(prostaglandin E) that is needed. This can be done with a drug called Misoprostol which is just synthetic PGE1, very similar to PGE2” says Blikslager.
“It also helps to put the horse on a low residue diet (less bulk going through the compromised colon). This would mean a pelleted ration that is mostly digested before
it reaches the right dorsal colon. This would help rest that area of the bowel. Veterinarians generally recommend doing this for up to 3 months. It’s a slow process, to heal the lining and get the protein level to come back up.” If the horse starts perking back up, moving in the right direction, this would be a sign that things are improving.
“The hard ones to deal with are the horses
that keep deteriorating in spite of treatment. The colitis is literally an ulcer of the gut. Colitis implies inflammation, but when you actually look at the lining it will be thickened (and this is why you can see it with ultrasound). The thickening is due to a lot of inflammatory cells and some scar tissue starting to form. It is missing the vital inner lining of epithelium that protects the body from what’s inside the gut. Without this protection, the horse can become endotoxemic. If we lose the horse, usually it’s because of a combination of reduced protein and endotoxemia,” he says.
With some horses, the protein just keeps dropping and this is very frustrating to deal with. “We can give back protein in the form of plasma, but it is expensive to keep doing this.” At some point the horse has to stop losing protein or he won’t survive.
“This is similar to many other colic-type problems; if it comes on quickly, they are more difficult to save. If it comes on slowly, you have a much better chance of being able to get them back to health. The rapid ones (acute cases of right dorsal colitis) are probably due to a sudden loss of gut mucosa, and the resulting endotoxemia. Horses with right dorsal colitis have a guarded prognosis, which means less than 50% of them make it,” he says.
“Serious cases that come on suddenly
might show fever and diarrhea. Others have more subtle signs, such as behavioral changes and going off feed. In a horse with fever and diarrhea, my first thought would be colitis affecting the whole colon. This is a medical emergency, and these horses are difficult to save because they lose so much fluid via the diarrhea.
“If the horse is systemically sick, there will also be some absorption of toxins into the bloodstream (endotoxin) and that will really complicate things. This would be an acute presentation, and not all cases will present with this.”
“Some veterinarians don’t use Misoprostol for treatment because it can cause horses to colic a little and they don’t feel comfortable with that. But in our hospital, in the cases we’ve treated, we’ve
found that was an important part of what enabled us to get them back to health. We felt like the benefit of getting the prostaglandins back into the horse outweighed the concern about them getting crampy. We knew we could stop the drug or lower the dose if they did,” he explains.
SUBSTITUTES FOR BUTE
There are other NSAIDs that can be used as alternatives to bute. “Bute is generally regarded as being good for treating musculoskeletal pain. The other drug labeled for osteoarthritis--and supposed to be safer for the gut--is Equioxx, but it’s a lot more expensive,” says Blikslager. Many people continue to use bute because it is cheap, and easy—putting the powder in grain, or mixed with water and molasses and squirted into the mouth if the horse won’t eat it in grain or using apple-flavored paste.
“Many people don’t even think about possible side effects of a drug like bute because it’s so commonly used, and most horses do fine with it. You can probably find it in just about every horse barn. But if people think about it and realize that not every person can take aspirin or Advil, they might understand how not all horses can tolerate bute,” he says.
“Because bute can have this side effect (and any NSAID can), there are newer NSAIDs on the market called COX2 inhibitors. The one that’s on the market for horses is Equioxx. This would be for something like arthritis (in which the horse is being treated continually) with the idea that it has a safer gut profile. In theory,
this is true. It comes in a paste formulation for horses. The same drug in a canine formulation is called Previcox. It’s a small pill, and some horse owners are using this little pill rather than the more expensive Equioxx. The trouble is that this
is off-label. When there is an FDA-approved formulation for the horse, you are not supposed to use the other,” he says.
Owners need to understand why some veterinarians are unlikely to sell them Previcox. This form has not been studied for safety and efficacy in horses. “If you use it and the horse has a problem that is thought to be related to the drug (such as any problem related to anti- inflammatory medication—like kidney, stomach or gut problem), this could be an issue. Equioxx is theoretically safer, but it is in the same class
of drugs. If the owner were to complain about a problem with use of Previcox, the veterinarian wouldn’t have any support for that, and would get into trouble.”
“In many situations there are no drugs approved for horses and in those cases, we can use drugs that are off-label. But this happens to be a situation where there is an approved drug,” he says.
CASE HISTORY OF A HORSE WITH RIGHT DORSAL COLITIS
In September 2013, Debra Stoltz (a horsewoman in Fort Lauderdale, Florida) purchased a two-year-old gelding, Mister Cool Jet (nickname Cooper). His first year of training went well, and then in October 2014 Debra noticed a change in his attitude.
“Cooper became cranky, and his coat was dull. We changed his feed and supplements, floated his teeth, and gave him two weeks off with just turnout, thinking he was exhibiting signs of stress,” she says.
Cooper was put back into training in mid- November but continued to be “off” and not his usual happy self. Debra noticed that the horse was now very sensitive to right leg cues and pressure when ridden.
EQUINE HEALTH
Right dorsal colitis
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