Posted on August 28, 2009 by Scott Weese

Chickens, Campylobacter, Ulcers and Horses

What's the link between chickens, Campylobacter, anti-ulcer drugs and horses? Well, nothing direct but a recent paper in the journal Emerging Infectious Diseases provides more evidence that the use of proton pump inhibitors for treatment and prevention of gastric ulcers can be associated with increased risks of certain types of infectious diarrhea in people. People who used this type of acid-suppressing drug were more than 3 times as likely to have Campylobacter diarrhea than people who didn't. Biologically, it makes sense. The acid barrier of the stomach is designed to kill harmful ingested bacteria, and decreasing that acid barrier through the use of acid-suppressing drugs can help bacteria survive passage through the stomach and subsequently cause diarrhea when they reach the intestines. It's been reported as a risk factor for Clostridium difficile diarrhea as well.

But does this apply to horses? We don't know. Infectious diarrhea is certainly a problem in this species, but no studies have looked at whether anti-ulcer drugs like omeprazole (Gastrogard) are a risk in horses. It makes sense that they could be but there's currently no proof. The reason I've been concerned about this is that anti-ulcer drugs are sometimes used like candy, when there's no clear evidence that they're necessary. These are important drugs for certain horses and are crucial for treatment in horses with ulcers. However, a lot of other horses receive anti-ulcer drugs prophylactically, and it's unclear whether the possible benefits of ulcer prevention therapy outweigh the potential risks of infectious diarrhea.

Without any clear evidence, the key is to weigh the potential risks and benefits. If your horse has ulcers (especially severe ones like in the gastroscopy picture above), then it certainly should be treated. If it has recurrent ulcers that keep coming back, prophylactic treatment may be useful, but management changes should also be made if possible to reduce the risks. In horses that do not or have not had problems with ulcers, I'm not convinced that routine anti-ulcer treatment is needed (or even a good idea). In certain situations where the risk of exposure to an infectious cause of diarrhea is higher (e.g. diarrhea outbreak on the farm, admission to an equine hospital) or when the horse has other risk factors for diarrhea (e.g. antibiotic treatment), I'd be especially wary.

Remember: While anti-ulcer drugs are useful, they may have a downside, like most other drugs.  You need to think about both aspects (risks and benefits) when deciding whether to treat or not.

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Posted on November 28, 2008 by Scott Weese

Anti-Ulcer Therapy and Diarrhea

Stomach ulcers are common in horses (especially race horses), and anti-ulcer medications are widely used. The most common of these drugs is omeprazole (sold under the brand name Gastrogard), which is a proton pump inhibitor. There is no doubt that gastric ulcers can cause problems in horses and treatment is necessary in these situations. However, there are a lot of horses being treated for mild ulcers or for prevention of ulcers, and it's unclear whether this is really needed, and whether it could even cause problems.

Picture (right): Endoscopic view of ulcers along the margo plicatus in the stomach of a horse.

In people, proton pump inhibitor treatment has been associated with an increased risk of diarrhea (particularly Clostridium difficile diarrhea). Biologically this makes  sense.  The acidic environment of the stomach normally helps kill harmful bacteria that a person (or a horse) may ingest. Treatment with anti-ulcer drugs to reduce the acidity of the fluid in the stomach may allow bad bacteria like Clostridium difficile and Salmonella to reach the intestinal tract in larger numbers, and therefore predispose the patient to developing diarrhea.  Theoretically the same thing could happen in horses.

Does this actually happen in horses? We don't know. It is certainly a possibility but there is no evidence either way.

Are certain horses at higher risk? We don't know. However, it's reasonable to suspect that this could be a greater concern in horses that are already at higher risk of developing diarrhea for other reasons, such as those being treated with antibiotics.

Should we avoid using anti-ulcer drugs in horses? Not always. These drugs are definitely needed for horses with clinically significant ulcers (i.e. their ulcers are actually painful or making them sick). However, we really need to consider whether treatment is necessary for horses that have very mild ulcers (i.e. that aren't causing clinical signs) or those that don't have ulcers at all and treatment is only "preventative".

Personally, I don't like to use anti-ulcer drugs in hospitalized horses unless they have severe ulcers that are causing problems. In cases where milder ulcers are present or people want to give anti-ulcer drugs for prevention, I prefer them to wait until the horse goes home. The same approach could be taken with horses that are on farms but at higher risk for diarrhea, such as those being treated with antibiotics.

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