Stomach Ulcers in Sled Dogs
Introduction
The tendency of racing sled dogs to suffer serious illness from
stomach ulcers, suddenly and with little warning, has been
recognized for at least a decade. At the request of the sled dog
racing officials and participants (most notably those associated
with the Iditarod Sled Dog Race), our team has conducted numerous
investigations into the causes and possible remedies for stomach
ulcers in sled dogs. The following discussion will summarize our
findings and describe the next steps we believe should be taken to
continue our efforts to solve this problem.
How Extensive is the Problem?
The goal of our initial studies (conducting in 2000 and 2001) was to
determine the extent of the problem. At that time, the only
information on what percentage of dogs had stomach ulcers was
through observation of the dogs (i.e., seeing them vomit blood) or
from post-mortem exams of dogs that had died during a race. These
techniques suggested a very low percentage of dogs had stomach
ulcers, but veterinary officials were certain that these methods
were not at all sensitive, and there were likely many more dogs with
stomach ulcers that were going undetected. The best way of
diagnosing stomach ulcers is to examine the stomach directly using
an endoscope (similar to what is done with humans). To date, we
have conducted 9 different studies that have included, in some
manner, endoscopic examination of sled dogs after exercise, and
these studies have yielded relatively consistent results:
· Approximately half of all dogs running a significant
distance (100 miles/day or more) had evidence of stomach ulcers,
provided they were not receiving any medication intended to reduce
or eliminate the problem.
· Endoscopic evidence of stomach ulcers can be found after as
little as a single 100 mile run at a modest (8-9 mph) pace.
· The severity of the stomach ulcers does not seem to be
greatly influenced by how long the dogs are working (i.e., how many
consecutive days), but may be related to how hard the dogs are
working (i.e., how many miles/day).
· In the majority of dogs, ulcers heal with 3-5 days of rest,
so that during pre-exercise exams, most dogs do not have visible
evidence of stomach ulcers.
· We have found no evidence that a particular blood line or
feeding strategy is related to stomach ulcers in sled dogs (although
these issues have not been thoroughly investigated).
· We have found minimal evidence of certain dogs being
predisposed to ulcers. Many of our studies have involved similar
groups of dogs, and there has been no tendency for the same dogs to
have stomach ulcers in different studies. However, we have found a
very small number of dogs that do not follow these "rules", i.e.,
they tend to have severe ulcers, they do not appear to heal with
rest, and they seem to develop ulcers every time they run.
What is the Cause of the Problem?
We do not have a confirmed cause of the problem yet, but it is
interesting to note that other athletic species like humans and
horses also have high occurrence rate of stomach ulcers. The
conditions between these species may not be identical, but there may
be many similarities. Biopsies (small pieces of tissue) taken from
dogs during endoscopic examination has shown that even when the
stomach appears normal (for instance, before exercise or a race), it
has extensive microscopic abnormalities that suggest an ongoing
disease process that may weaken the stomach. These microscopic
abnormalities seem to resolve during prolonged rest between seasons,
but the intervals between training runs may not be long enough to
allow all of the abnormalities to heal. Chemical tests of the
stomach have also provided evidence that the stomach is leakier
during exercise than normal, and that may be part of the overall
development of the ulcers by letting stomach acid leak into the wall
of the stomach and damage it. There is some evidence that the dog's
response to the stress of running can cause that leakiness, but this
is not a certainty, since it is possible that the leakiness causes
the stress, rather than vice versa. We are reasonably certain that
stomach ulcers in sled dogs are not caused by bacteria (like in
humans) or by the type of food being fed (like in horses) based on
tests of the stomach biopsies and analysis of the distribution of
the ulcers within the stomach.
How can We Prevent Stomach Ulcers in Sled Dogs?
One of the conclusions from our studies on the overall occurrence of
stomach ulcers in sled dogs is that most dogs effectively conceal
the stomach ulcers from the mushers and veterinarians. Since we had
little hope for detecting severe ulcers before they became a serious
problem, we focused our efforts on preventing the ulcers from
developing. The most common method for preventing ulcers in other
species is to block the secretion of stomach acid. In one study,
dogs from 3 teams running in the Iditarod received either omeprazole (Prilosec) or a placebo daily, and were examined endoscopically at
the end of the race. Omeprazole significantly improved the severity
of the stomach ulcers, but did not completely eliminate them. Some
of the drawbacks of omeprazole are that it must be given as a pill,
which proved to be troublesome for mushers when faced with pilling
16 dogs/day for 10 or more days, all the while trying to race. In
addition, there was some evidence that dogs receiving omeprazole had
a slightly higher likelihood to have diarrhea during the race. A
study to see whether omeprazole could simply be placed in the dog's
food found that food significantly impaired the absorption of the
drug. Given the frequency that sled dogs are fed during racing, we
elected to examine other drugs that inhibit acid secretion. Our
second study examined famotidine (Pepcid AC). We found that famotidine was well absorbed when administered with food, and could
simply be dropped into the dog's food (as long as the dog did not
eat around the pill). Using a brief training run of 100 miles in
approximately 18 hours, we demonstrated that famotidine was
extremely effective in blocking the development of stomach ulcers at
a dose of 20 mg/dog once daily. However, a recent study under
racing conditions found that this dose was not as effective as in
training, possibly because of the more strenuous nature of the
race. We have plans to evaluate higher doses of famotidine and
directly compare them omeprazole in a future study.
Goals of Future Studies
· Identify the best drug, dose, and duration of dosing to
prevent stomach ulcers in racing sled dogs
· Examine dogs training and competing at shorter distances to
determine whether these dogs are also at risk
· Develop a diagnostic method for detecting stomach ulcers
that does not require anesthesia
· Determine whether preventing stomach injury during training
improves resistance to stomach ulcers during racing.
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