Question: “I have two questions. The first question is regarding testing for Gastric Ulcers. I have been reading about the “Sucrose Permeability Test,” for a couple of years, but still haven’t heard of any (Local) vets offering this test in lieu of traditional endoscopy. I was wondering what the reason may be for this, since it sounds, easier, cheaper, and less stressful to the horse, as well as being accurate?
My next question is regarding Lyme disease. I was reading a hot debate on whether or not “Lyme” is caused by borrelia burgdorferi, and if we aren’t treating for a disease that at this time is still unproven to cause illness in horses. What’s your take on this idea? Then if you do treat for Lyme, what’s the best course of testing, treatment? I have also read that the “SNAP” test is very accurate, but again, haven’t heard any local Vets using this test.”
That’s a lot to tackle in a relatively short blog entry. I would direct you to an article I wrote on Lyme Disease previously (link) for some answers to your questions. The controversy surrounding the existence of Lyme is too complex to tackle here, at least right now. I will focus on your questions regarding testing — both for gastric ulcers and on the SNAP Lyme test.
There was a paper presented at the 2003 AAEP convention which discussed Sucrose Permeability Testing as an alternative to scoping a horse’s stomach for the diagnosis of gastric ulcers (link, PDF 116k). The paper found that horses with gastric ulceration, when given sucrose in high levels on a fasted stomach, have higher levels of sucrose in their urine versus horses with healthy stomachs.
There are a number of important points to know about this study and the suitability of Sucrose Permeability Testing for gastric ulcers in horses. 1) The study only looked at 13 horses. The researchers were only able to induce gastric ulceration in 11 of those horses. The study size is small and it may be unwise to draw broad conclusion on such a small sample size. 2) The study showed an 83% and 90% correlation between gastric ucleration and urine sucrose concentrations of .7 mg/ml and 1.0 mg/ml, respectively. These percentages represent a reasonably strong correlation, but also leave a lot of room for error. 3) The performance of Sucrose Permeability Testing requires a 24 hour period of fasting, the administration of sucrose via nasogastric intubation, and then the collection of urine form the horse via catheterization at time intervals post sucrose administration (2 hours and 4 hours in the study). In other words, the test cannot be performed by an owner, and is ideally suited to a controlled clinic (non-ambulatory) environment. The test is also more time consuming and as invasive as scoping and it may not even be cheaper than traditional scoping. 4) Scoping gives information about the state of the esophagus, sphincters, proximal small intestine and more information about the state of a horse’s stomach. I have scoped horses fitting the profile of a gastric ulcer afflicted horse to a T, only to find horrendous esophageal ulceration or congenital outflow problems in the pyloric sphincter and small intestine.
You can find a good, general and fairly technical discussion of Equine Gastric Ulcer Syndrome (EGUS) here (PDF 168k).
As for the Lyme test, you are referring to the IDEXX Laboratories SNAP 3Dx Test (link). The test is actually labeled for use in dogs, though I and other veterinarians have used it with good results in horses (i.e. I have seen good correlations between reported positive titers on the SNAP test and full ELISA titers performed by outside laboratories). I use the test to screen for the potential of Lyme infection. The test only looks for the presence of antibodies to the Lyme bacterium and cannot tell you if a horse does or does not have active Lyme infection. On a positive SNAP Test result I send the horse’s blood to an outside lab for a full ELISA titer and Western Blot.
If a horse is negative on the SNAP test it probably means that the horse does not have active infection with the Lyme bacterium. I have not found that the strength of color change on the SNAP test to be a good indicator of the strength of Lyme infection. I use the SNAP test as a reasonably reliable and inexpensive screening test, only.
Horses threatened by the California wild fires in the Malibu area are finding refuge at Pierce College in Woodland Hills, CA. As of yesterday afternoon 120 horses had been sheltered. The facilities at Pierce College can accomadate 200 horses and additional shelters are being set up in Los Angeles County. 
