Enteritis In Horses: A Source Of Colic And Of Mystery

by | 02.13.2020 | 7:52pm
California Chrome

Fan favorite California Chrome may have suffered a bout of enteritis since his arrival to Arrow Stud in Japan, but one veterinarian familiar with the illness says there's no reason to be concerned about his long-term health.

Enteritis is the inflammation of either the large or small intestine and often results in part of the intestine failing to move its contents along, which causes it to stretch out and become painful. In horses, enteritis presents as a classic colic, with symptoms of abdominal pain like elevated heart rate, lack of manure, and restlessness which could include a horse touching or kicking at its sides. Enteritis in the small intestine is most common in foals, while large intestinal enteritis is most common in adult horses.

Dr. Bryan Waldridge, veterinarian at Park Equine Hospital in Lexington, Ky., said typical presentations of enteritis will also have reflux of stomach contents through a nasogastric tube. Because the contents can't keep moving through the intestine as normal, they'll backfill into the stomach, which causes the horse discomfort. Ultrasound can also show a veterinarian where intestinal contents have backed up. 

What causes enteritis? In some cases we know, in other cases it's less clear. In foals, Waldridge said the cause is often infectious. In adult horses, there are different causes associated with different geographic regions. In Europe, enteritis is associated with another illness called grass sickness, in which part of the nervous system suffers damage, due to an unidentified toxin. Grass sickness can also be found in South America, but for some reason is not found in North America. Acute cases of grass sickness tend to be fatal, but the cases of enteritis Waldridge sees in North America usually aren't. 

“We see a few enteritis cases here [in Kentucky] but they're not like the ones in the Southwestern U.S.,” said Waldridge. “Those were idiopathic, so no one knows what was causing those. I think a lot of our cases here fall into that category.”

Many cases of enteritis are due to a bacterial infection in the intestine – but not because someone near the horse has failed to sanitize their environment or gave them spoiled food. Waldridge explained that horses (like humans and other animals) have “good” and “bad” bacteria living in their large intestine all the time, but most of the time good bacteria (which aid in digestion) outnumber the bad and keep them from taking over. If the horse experiences a change in their bacteria balance, however, the bad bacteria like salmonella or clostridium can multiply. 

“It's the same thing that happens when you're on oral antibiotics – you kill off the good stuff, and the bad stuff has a chance to populate,” said Waldridge.

Lots of things, including stress, can change an animal's bacteria balance. For that reason, Waldridge said travel is one of the biggest risk factors for enteritis in horses. 

Long hauls can also be particularly stressful for horses. A peer-reviewed study published in the online open access journal Plos One examined twelve horses on an eight hour journey and found mild but significant impacts of travel on fluid and electrolyte balance and increased inflammatory cells and mucus in the throat. Of particular interest to Waldridge was the finding that horses who lowered their heads more during travel experienced less stress evidenced by cortisol levels and heart rate compared to horses who did not lower their heads – which could be impacted by the style of trailer or box a horse travels in. 

“A horse's shock organ is its gut. If it has a bad shock, the gut ends up paying most of the time,” he said. “Travel is a whole lot bigger stress on horses that people think it is. One of the most stressful things you can do to a horse is tie it up in a trailer where it can't lower its head during travel.”

That isn't to say that every horse who takes an international trip is going to experience enteritis – the same way that not every horse who travels loses a drastic amount of weight or develops a respiratory illness. Waldridge said that many horses make long trips and do just fine, and there's no predicting which ones will fall into which category. 

As for treatment, much of enteritis is a waiting game. Waldridge typically tubes horses every couple of hours to remove reflux, runs intravenous fluids, and medicates with flunixin to manage pain. Lidocaine is also a good option because in addition to having a pain-relieving effect, it seems to increase gut motility. Surgery is not necessary in most cases. Eventually, the intestine “wakes up” and begins moving again, and then it's safe to gradually allow the horse to resume eating. 

In good news for Chrome fans, Waldridge also said unlike some other causes of colic, enteritis doesn't typically recur in the same horse, so it's improbable the big chestnut will have to face it again. 

Waldridge said the report from Japanese ownership group JS Company that Chrome is back to eating enthusiastically is a good sign that he is in the later stages of recovery. 

“That's huge,” he said. “It tells you his gut motility is back. Once the gut starts moving, it moves the fluid through, no distention, no pain. If he's eating, to me, the crisis is gone.” 

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