Your vet may recommend the fecal occult blood test, but hell also do a thorough exam.

Human fecal blood testing is used as a screening test for cancer in the bowel. There’s a considerable amount of debate in human medicine over the value of the test for many reasons (e.g. false positives) and how well it actually reflects the presence of cancer. Basically, the medical community agrees, though, that it’s not 100% reliable and, most importantly, that all it tells you is that there are traces of blood in the feces. It can’t tell you why. Could be cancer, could be a hemorrhoid, could be the patient ate meat too close to the time when the test was done.

Before going into the equine fecal blood test for ulcers and information about it we obtained from the manufacturer, let’s take a look at why a horse might have blood in its intestinal tract. Sources would include:

• Trauma to the gums or tongue from sharp/irritating feed and hay, swallowed blood
• Bit trauma, swallowed blood
• Nosebleed or gutteral-pouch bleed, swallowed blood
• Gum trauma from sharp teeth or dental work, swallowed blood
• Gum trauma from wood chewing, swallowed blood
• Lung bleeding following heavy exercise, swallowed blood
• Severe bleeding gastric ulcers
• Trauma from parasites in the gastro-intestinal tract
• Irritation from sand collections or enteroliths
• Irritation from impaction or dry, hard stool
• Colonic ulceration from phenylbutazone or following some larvicidal dewormings
• Inflammatory bowel disease
• Intestinal tract malignancy.

With all these possible sources, we think a positive test alone means little, especially considering the test is said to be potentially sensitive. We learned from the manufacturer that the sensitivity of the test has been set at 5 ml of blood in 26.4 pounds of manure, or about 3/100ths of a teaspoon per pound. This level was chosen based on past studies of baseline blood loss in the manure of normal horses and does help with the problem of oversensitivity and false positives, but it’s still sensitive and doesn’t tell you how or why there is evidence of blood in the manure, only that it’s there.

The Need For The Test
The press releases for this product, and the product’s web site, focus on some scary figures for ulcer disease in horses. From the American Horse Publications press release: "By using the Succeed Equine Fecal Blood Test, owners and trainers are able to detect occult blood within the GI tract—one obvious indicator of digestive distress. Studies have shown that 97 percent of horses involved in competition sports, from dressage to racing, suffer from either gastric or colonic ulcers, and 63 percent of these performance horses have colonic ulcers."

However, we learned that the "studies" referred to here is only one study, which was done by examining the digestive tracts of horses at a slaughterhouse. It’s no secret that horses intended for slaughter are under considerable stress, including long periods without food or water. It’s also no secret that horses sent to auction are often given high doses of phenylbutazone in an attempt to mask lameness so that hopefully they will bring better than killer prices.

Let’s take a look at what the literature as a whole shows. It has been recognized since the earliest endoscopic ("scoping") studies that 52% of perfectly normal horses with no symptoms whatsoever can be found to have gastric ulcers (Murray et al, Equine Vet J, 1989).

Seventeen years later (Dukti et al, Equine Vet J, 2006) the significance of gastric ulcers in relation to abdominal symptoms is still being questioned: "The clinical relevance of ulceration is still unclear and further studies are required to differentiate between incidental and clinically important gastric ulceration."

Endoscopic examination of racehorses has found from 70 to 82% have gastric (stomach) ulceration. One preliminary survey of endurance horses found 67% while show horses had only 58% (McClure et al, JAVMA, 1999), similar to the background level of 52% of normal horses with no symptoms. Further complicating the picture is that horses are fasted for 24 to 48 hours prior to scoping, which itself could induce some damage or worsen existing damage.

As for colonic ulceration, only phenylbutazone use, parasite damage or reaction to larvicidal deworming and inflammatory bowel disease (rare) have been associated with colonic ulceration in horses. Life-threatening intestinal infections such as Salmonella, Clostridia or Potomac horse fever may damage the colon lining as well but these horses would be obviously ill. We know of nothing in pathology textbooks, medicine textbooks, surgical textbooks or the published literature to suggest that 65% of performance horses or over 50% of pleasure horses without the known risk factors (e.g. bute) have colonic ulceration. We don’t think figures that came from examination of the intestinal tracts of horses that had gone through slaughterhouses is representative of the horse population in general.

There is a page on the web site suggesting the fecal occult blood test results could help your vet in diagnosing parasites, but we don’t see how. A positive test would not be any more specific for parasites than it is for anything else. If fecal egg and larvae examinations are equivocal, but your vet strongly suspects parasitism, the logical next step is simply to deworm the horse. Even the priciest dewormers are under $15.

Bottom Line
The test is available only through your veterinarian at this point. If your vet has a specific reason for wanting to perform it in your horse’s case, that’s one thing. As for general usefulness, beyond being simple to perform, we don’t see much to recommend this test. In our opinion, there are more specific ways to diagnose parasites, gastric ulcer disease and colonic ulcers.