10 Signs of Internal Illness in Horses
I walked out to check on my two horses about an hour before sunset. Solstice was in the paddock, eating hay, snorting contentedly, and swishing his tail. When I walked up to the fence, he perked his ears and looked at me with bright, cheerful eyes.

But Sabrina stood quietly in the run-in shed. She saw me approach, poked her head out, blinked, and sighed. She ambled out of the barn toward me, put her head over the fence, and waited for me to stroke her face.

Wait. She wanted her face stroked? Sabrina was not well.

As much as Solstice loves to be cuddled like a golden retriever puppy, his dam, Sabrina, acts like she has too much dignity for public displays of affection. She’d rather be chasing Solstice from every hay pile and pinning her ears when he tries to steal a bite. The last thing she’d do is hang out in the barn watching him eat her hay and then come to me for a scratch on the head.

Two hours later Sabrina was on the ground, curling her lip and groaning. I’d already called her veterinarian, who determined from my description of her symptoms that she was colicking. Fortunately, with my vet’s help, Sabrina’s colic resolved within a few hours.

Horses can give us plenty of cues when they’re dealing with early illness. The problem is they don’t; horses don’t like to show that they’re sick.

“They’re a prey species, so hiding any evidence of illness is a survival technique,” says Elizabeth Davis, DVM, PhD, Dipl. ACVIM, professor and head of the department of clinical sciences at Kansas State University’s Veterinary Health Center, in Manhattan.

But they do give subtle signs, like Sabrina’s uncharacteristic affection or her standing quietly in the barn or not eating hay. To help you recognize them and intervene accordingly, we’ve put together this 10-point list of warning signs.

1. Diminished or absent appetite

Has your horse suddenly become picky about or even completely uninterested in his food? That’s a significant sign of brewing illness, our sources say.

“A change in appetite, whether for grain or hay or both, is a big indicator to me that something isn’t quite right,” says Davis. “Whereas he used to take 15 minutes to clean up his bucket of concentrates, now it might take 45 minutes with some breaks to walk around a bit. Or he won’t eat hay as vigorously and will get picky about it.”

Appetite changes could indicate gastrointestinal upsets such as colic. In fact, waning interest in food can signal a wide variety of internal illnesses beyond the GI system, says Kari Bevevino, DVM, internal medicine resident at Texas A&M University, in College Station.

“This is among the most important signs of disease in various systems of the body,” she says.

2. Diarrhea

Any change in poop production is worth monitoring, as we’ll address in more detail on page 18. But diarrhea, in particular, deserves special attention, says Bevevino. “Diarrhea can go from not-too-bad to very bad in a very short period of time, and early intervention is beneficial to both the horse and the veterinarian treating him,” she says. 

An infectious disease—which can cause severe illness or death and can also spread to other horses—is the most alarming possible cause, Bevevino says. Salmonella and Clostridium bacteria,
for instance, cause diarrhea-related infections with varying levels of clinical signs.

“Some horses remain bright and alert while others develop very severe disease,” she says. Rapid treatment can ease discomfort, improve chances for recovery, and help the veterinarian and horse owner control disease spread.

Other causes of diarrhea include sand accumulation in the colon, inflammatory bowel disease, and, less commonly, cancer, she adds. Regardless of the cause, diarrhea can lead to rapid dehydration and electrolyte losses, sometimes requiring “pretty intensive therapy,” Bevevino says. 

3. Lethargy, uncharacteristic calm or inactivity, and separation from the group

Horses should maintain a consistent activity level and keep up with the herd, our sources say. “A sick horse might stand off by himself and stay quiet,” Bevevino says. “By quiet, I mean he’ll hang his head a little lower, hold his ears a little less perked up than usual, and not have his eyes quite as wide and bright
as usual.”

You might also notice subtle lethargy, adds Davis. “Under saddle he might need a little extra encouragement to get going, and he might run out of gas a little sooner,” she says. “Or the pasture pet suddenly isn’t keeping up with the herdmates.”

The Horse, August 2019This article continues in the August 2019 issue of The Horse: Your Guide to Equine Health Care. Subscribe now and get an immediate download of this issueincluding this in-depth feature on early warning signs that illness is brewing within your horse.

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