On a bitter cold February night in Santa Fe, New Mexico, my husband burst into the house at 11 p.m. and told me my mare Maisie was sick. She hadn’t eaten her evening meal and seemed lethargic and dull.

I had bought Maisie, a gray mare with kind eyes, for trail riding. I had been told she was calm, a “push button” horse. But, as it turned out, she was sometimes overcome with anxiety and struggled to stay calm and connect with me. Nonetheless, I loved her and knew with time and patience we would become partners. Now she needed me.

I crawled into my long underwear, pulled on my boots and warmest down coat, and headed to the barn. I assumed Maisie was colicking, so I walked her until midnight despite the 9°F temperature. When nothing changed, my husband and I loaded Maisie into our trailer and took her to a local clinic for small and large animals where a veterinarian was on call.

When we opened the trailer, Maisie was on the floor. She was still hooked to the trailer ties, so her head was stretched upward. Her body was contorted on the floor. Before I could do anything, the veterinarian jumped into the trailer, untied Maisie, and got her up and out. She didn’t know my horse, and I was surprised and relieved by her swift and skillful handling of the situation.

The clinic was small but had a fenced outdoor corral for horses that was warmed by a large heat lamp. Maisie showed all the signs of colic, so after checking her vitals and conducting a rectal exam, the veterinarian sedated and tubed her. Meanwhile we all danced around trying to keep warm.

Back home, then to the hospital

Feeling hopeful, my husband and I trailered Maisie home and put her in a stall. I sat in my heated car in the center aisle of our barn, periodically jumping out to check on her and walk her. Maisie remained listless as the sun rose, and I was beginning to be filled with dread. I called a mobile veterinarian who came and tubed her again. When she finished, she told me “This horse needs fluids. I can’t give them to her in this freezing temperature.” She pointed to our trailer, “If you want Maisie to survive, you need to take her to the equine hospital right away.” We loaded Maisie and hauled her to Thal Equine Regional Equine Hospital, 25 minutes away.

At the hospital, Doug Thal, DVM, DABVP, examined Maisie. She was in severe pain with a distended abdomen, a heart rate of 76 (much higher than the normal range of 28 to 40 beats per minute), reddish-purple gums and a prolonged capillary refill time. Her hematocrit—the percentage of red blood cells by volume in her bloodstream—was 60. That was well above the normal range of 37 to 47 for horses.

“It tells you that she’s very dehydrated. You have to replenish that because the blood is thick and the blood pressure is low and that’s going to affect circulation to organs,” Thal said. “It’s going to affect her blood pressure. Everything relies on that.” Abdominal ultrasound confirmed a swollen large colon wall and a rectal exam confirmed inflammation and swelling in her colon.

Maisie remained uncomfortable despite treatment, and Thal, like the other veterinarians who had seen her before, suspected her colic had a mechanical cause—an obstruction. He needed to know whether, if her pain and shock worsened, I would be willing to go to the expense of exploratory colic surgery to figure out what was going on. I declined colic surgery because of the risk and expense.

The only treatment option

That left only one option: intensive care treatment. In Maisie’s case, this would include intravenous and nasogastric fluid administration, IV plasma administration, pain relief, medications to quiet the inflamed intestine, probiotics and careful monitoring to assess her response to treatment. Horses with severe mechanical causes (especially strangulating obstructions) continue to deteriorate if the problem isn’t surgically corrected. If Maisie’s problem required surgery, we could expect her condition to worsen, and she would have to be euthanized. On the other hand, if the problem was not mechanical, but more of an inflammatory problem, her condition might improve with supportive care. I parked my chair outside her stall all afternoon, watching and waiting with an agonizing pit in my stomach.

Would Maisie get worse or get better? Neither happened. . . She just stood in the stall facing the wall, tuned out and depressed. I tried petting and talking to her, but I got no response. I wasn’t even sure she was aware of my presence.

A possible diagnosis

Thal put the pieces together and surmised she might have colitis: “We’ll know if she starts to have explosive diarrhea.”

Colitis? I knew this could occur in people but had never heard of equine colitis. Thal explained that equine colitis is an inflammation of the large colon which damages the colon wall. “The healthy large colon wall is a good barrier. It doesn’t let bacterial toxins into the bloodstream. Now that it’s damaged, the blood vessels are leaky. They’re letting all the good stuff out and letting the bad stuff in,” he said. “You have to understand that the large colon in a horse Maisie’s size is the size of a large truck tire. Full, it weights 150 pounds! You can imagine if a huge organ like that gets sick, then the horse gets pretty sick, too.”

Colitis has many potential causes, both infectious and non-infectious, which makes the diagnosis and treatment tricky. Suspected causes include infectious agents such as Salmonella or Clostridium. Overuse or misuse of nonsteroidal anti-inflammatory drugs (NSAIDs) can cause direct intestinal damage. Antibiotics can trigger the condition by throwing off the balance of intestinal bacteria. Toxic substances, or even a stressful event, may also precipitate or contribute to colitis.  It is important to know that it is the sum total of the host (horse), environmental and agent (bacteria or virus) factors that either lead to disease or not.

Searching for a cause

I couldn’t imagine what had caused Maisie’s colitis, and I left the hospital and headed home to my computer to look it up. It was confusing, there wasn’t a lot of information available and some of it was very technical. Overall, however, what I found worried me.

The onset of colitis is often sudden, and the progression can be rapid. This is a life-threatening emergency and early intervention is vital. A key risk of diarrhea is dehydration, and the massive amount of fluid loss and electrolyte imbalance can cause death within hours. While lab tests can identify pathogens, often the results don’t come in time, so veterinarians must guess at the cause and start treatment immediately.

I called the hospital the next morning to learn that Maisie did have liquid diarrhea in the early hours of the morning, confirming Thal’s suspicion. She also had a fever and a low white blood cell count—hers was 1.5 and it should be around 7.

Although he didn’t know the exact cause of Maisie’s colitis, Thal stressed time was of the essence: He needed to begin aggressive treatment immediately. “This is why we do the detective work at first, figuring out whether we’re dealing with colitis or whether we’re dealing with an obstructive problem. It matters more what we do today. Once we’re behind the eight ball, once we get way behind, we’re done. It’s too late. All the damage is done. They lose all their vital fluids; they lose all these vital proteins. They lose all their electrolytes. It all shuts down and they just die. It’s a multi-organ failure.”

Treatment begins

Thal treated Maisie with 60 to 80 liters of IV fluids per day for several days, and several liters of plasma. He also used a nasogastric tube to administer smectite, a powder derived from a natural clay that absorbs toxins and bacteria. He then “transfaunated” her (that is, gave her a filtrate of several pounds of manure from a healthy horse) via nasogastric tube to reintroduce more normal microbes back into the system—the ultimate probiotic. In the meantime, Maisie was moved into quarantine. This was necessary, “especially in a hospital setting,” Thal explains, “because potentially a horse with colitis could have something they could spread to my sick patients that are in the hospital and are off and on antibiotics. Those horses are highly susceptible.”

I asked to visit her that day, but he told me to wait. He wanted to see how she was progressing. I didn’t sleep that night, as I kept going over the past few days, trying to figure out what went wrong. The day before, Maisie had been running up and down the fence whinnying, when Sierra, her barn buddy of several years, left our home to go to a new owner.

FInally allowed to visit

I called for an update the next day, the third day of her hospitalization, and Thal agreed to let me visit Maisie. The good news was that he was seeing slight improvement in her heart rate and some vital signs. The not-so-good news was that he couldn’t say she was out of the woods. “It’s pretty touch and go,” he told me.

While I thought seeing her would quell my concern, it did the opposite. I had to suit up with a facemask, apron and gloves and then soak my boots in an anti-bacterial solution before entering the quarantine area. I had never been required to take such extreme hygiene steps (this was pre-pandemic), and I realized how serious the situation was.

Possible complications

Several complications can occur with colitis, but laminitis is one of the more deadly. As I peeked over the Dutch door in Maisie’s stall, I saw big, bulky ice boots attached to the end of her slim legs. Her head was down, she couldn’t move her legs and I was told she had to remain in those boots for at least 36 more hours. While this treatment helps prevent laminitis, it is not always successful. Thal told me some horses move around, kick them off, and won’t stand with freezing cold boots on their legs, even if sedated. “We try to keep their feet cold, and it can’t just be a little bit cold.” Sadly, he said, some horses survive colitis but ultimately succumb to laminitis. I was lucky, at least Maisie accepted the boots and wasn’t overcome with anxiety.

The fourth day of her hospitalization brought better news. The treatment was working, her vitals were returning to normal and once she started to feel better, she recovered quickly. Her attitude improved, she was eating a tiny bit, and she was passing less liquid manure. Her heart rate was closer to normal, a key indicator, and her white blood cell count rose. If she continued on this track, she would be able to come home the next day.

This was a quick recovery. Many horses with colitis need monitoring in a hospital for several weeks. As Thal assessed, “Once she turned around, she turned around fast, and we were really lucky. On a scale of 1 to 10, in terms of sickness, she was about a 6. That put her on the better end of the spectrum in terms of how these horses do.”

Maisie comes home

We picked her up the next morning, and while she didn’t look distressed, she was quiet. Once home, I watched her carefully, hand-walked her several times a day and kept her in that calm state, without activity for several weeks. I fed her hay pellets and a probiotic, and then fresh hay carefully picked over to ensure it was clean. We still didn’t have the results of the tests for pathogens, so we kept her isolated from our other horses.

While at home I noticed her manure was still soft, not the normal apples we’re used to seeing. Thal told me it would take a while for her manure to come back to normal, but in fact, it never returned to that healthy-looking stool. Several years later, it’s still a bit loose and watery, and I’ve called him too many times for reassurance. He speculates she may have slight damage to her large intestine, which could be causing this. “Probably her colon wall was damaged in a way that was permanent. But it was just mild, and she can get by fine with that.”

We never did determine whether Maisie was infected with pathogens. The test was negative, but it’s not 100 percent reliable. This is sometimes how it goes, Thal explained. “It’s disappointing, but in my practice I often do not identify the precise cause of these episodes, despite the diagnostics.“

I asked if the stress of Sierra’s depar-ture might have caused Maisie’s colitis. He thought it could have been a trigger. “The situation affected her general resistance to infection,” he told me. “Cortisol release from stress causes a reduction in general immunity.” But he speculated that an imbalance in Maisie’s gut micro-biome may have also contributed.

Lessons learned

That is a key thing I’ve learned from all this: the importance of a balanced gut microbiome. As Thal explained, “There’s this intimate link between the large colon and the health of the entire animal. And it’s almost instantaneous, because of how much exchange there is back and forth between those two things.”

I am now acutely aware of the health of my horse’s gut. I check her hay carefully and don’t make abrupt feed changes. I’m careful with NSAIDs and antibiotics, always provide clean water at a drinking temperature and I give her a pre/probiotic daily. I am also aware of possible infections around other animals, and I keep Maisie’s stress level as low as possible.

As time passed, Maisie’s attitude returned to normal, and we resumed our work together. She has become a more responsive horse, willing to partner with me. She can be erratic at times, but she has learned how to bring her anxiety down. And when I look into those deep, kind eyes, I believe she knows I was there for her, every step of the way, during the biggest struggle of her life.