This issue
Glossary of medical terms
A review of recent veterinary literature:
Cat vaccinations, a new recommendation:
What about dog vaccinations?
Lawsuits, a potential worry among vets:
Don't forget the yearly physical exam, though!
Christmas Day, 1981
Diabetic Cats -- a "new" option:
Perianal Fistulas
We decided that it would be a good idea to include a glossary of veterinary medical terms that are used in our newsletter. Please let us know if we can help with other medical terms or if we forget to include an important one or fail to explain it carefully enough.
hypo- this prefix is used to indicate a condition in which less than the expected quantity of something is present
hypothyroidism - have less thyroid hormone than is necessary to meet normal physiologic needs
DVM -- Doctor of Veterinary Medicine, the degree conferred by most of the veterinary degree programs in the United States.
VMD -- Veterinary Medical Doctor (I am presuming this) -- the degree conferred by the University of Pennsylvania. It is easy to spot a vet who graduated from this veterinary school due to this.
megaesophagus -- abnormal dilation of the esophagus, the tube which conducts food from the mouth to the stomach
peripheral neuropathy -- a nerve disorder affecting nerves after they exit the spinal cord
gastric dilitation -- commonly referred to as "bloat", this is excessive air accumulation in the stomach causing it to enlarge
volvulus -- a twist in the stomach which sometimes occurs after gastric dilitation. The syndrome in which these two symptoms occur at the same time is usually referred to as gastric dilitation - volvulus or GVD
A review of recent veterinary literature:
There have been several interesting studies in the veterinary literature this month. A brief review of these articles follows.
From the December 1, 1997 edition of the Journal of the American Veterinary Medical Association, Volume 211, Number 11:
Measurement of serum total thyroxine, triiodothyronine, free thyroxine, and thyrotropin concentrations for diagnosis of hypothyroidism in dogs. Mark E. Peterson DVM, Carlos Melian DVM, and Rhett Nichols DVM, pages 1396-1402
The authors reviewed the use of a thyroid panel including the newest available test, TSH concentration, to diagnose hypothryoidism in dogs. It is generally expected that a dog with hypothyroidism would have low total thyroxine (T4), low free thyroxine (FT4) and high thyroid stimulating hormone levels (TSH). An exception to this would be dogs that can not produce TSH due to lack of pituitary secretion. These dogs would also be hypothyroid but would have very low or undetectable levels of TSH. Most dogs with hypothyroidism in the study (98%) had FT4 levels below the normal range and the remaining dog's level was low normal. This was a very sensitive indicator of hypothyroidism. About 7% of normal dogs also fit this criteria, though. Most dogs with hypothyroidism also had high TSH concentrations (76%). This combination is very useful in determining whether a dog truly has hypothyroidism.
It should be noted that the authors pointed out that sick dogs have lower than normal FT4 levels in many instances and care must be taken to correct recognizable underlying disease prior to evaluation of a thyroid panel. Since this is a lifelong illness that requires supplementation of a medication that can have adverse effects if taken unnecessarily, care in testing is best. When possible, it appears it would be best to test for both free thyroxine and thyroid stimulating hormone levels.
Risk factors for acquired megaesophagus in dogs, Alison R. Gaynor, DVM, Frances S. Shofer, PhD, Robert J. Washabau, VMD, PhD
This article was a review of the risk factors for megaesophagus, determined by reviewing records from the University of Pennsylvania for dogs treated for this condition, tested for hypothyroidism by TSH response testing and from the general hospital population in numbers sufficient to serve as controls for the other groups.
A predisposition to megaesophagus was noted in three breeds, German shepherds, golden retrievers and Irish setters.
Despite a strong presumption among veterinarians that hypothyroidism may contribute to megaesophagus, no correlation between the two disorders was found in this review.
Underlying cause of megaesophagus noted in the paper were peripheral neuropathies, laryngeal paralysis, acquired myasthenia gravis, esophagitis, and chronic or recurrent gastric dilitation, with or without volvulus.
About 28% of the dogs in this study with megaesophagus also had myasthenia gravis, which was presumed to be the underlying cause. This was the most commonly identified cause for megaesophagus.
Risk factors for acquired myasthenia gravis in dogs: 1,154 cases (1991 - 1995), G. Diane Shelton, DVM, PhD, Alan Schule, BS and Philip H. Kass, DVM, PhD
Acquired myasthenia gravis is an immune mediated disease characterized by excessive fatiqability and muscular weakness due to interference in neuromuscular transmission caused by antibodies against the acetylcholine receptors at the nerve to muscle junction. Generalized weakness with megaesophagus and megaesophagus without any other signs were the two most common clinical signs or illness leading to testing for myasthenia gravis in this study.
Breeds with an increased predisposition to myasthenia gravis (MG) were Akitas, terriers, Scottish terriers, German shorthaired pointers and chihauhaus.
Breeds with a lower than normal risk for MG were the rottweiler, doberman pinscher, dalmatian and Jack Russell terrier.
German shepherds and golden retrievers had the highest numbers of affected members but this was due to high numbers of these dogs in the population, not due to a higher than expected incidence of myasthenia gravis in the breed.
Dogs are more prone to MG as they age. Dogs that are sexually intact (both males and females) had a slightly lower incidence of myasthenia gravis.
We can not provide a comprehensive review of the veterinary literature but when there are interesting articles we will try to provide the information from them when possible.
Cat vaccinations, a new recommendation:
The newest recommendation for cat vaccinations is to vaccinate every three years, after the initial vaccination series and the first year booster, for all of the common viral infections. This is a change from the yearly schedule that has been traditionally recommended. Researchers have been studying this issue, particularly at Cornell University, and it seems pretty clear that the vaccines do provide protection of at least a three year duration in most cats. Since there is also evidence to suggest that about 1 in 3000 to 10,000 cats develop cancer at vaccination sites it seems prudent to extend the vaccination interval if it is safe to do so.
These are new guidelines from the American Association of Feline Practitioners and they do not match the label recommendations. For some time this issue will be controversial among veterinarians due to this conflict and the dependence of veterinarians on vaccination income to subsidize other practice areas. It is going to be very hard for veterinarians to re-educate their clients and many will choose not to do so and to just continue with their current vaccination strategies. Some veterinarians do have sincere reservations about extending the interval between vaccinations. They fear the return of diseases that seem to be well controlled now by the current vaccination schedule. In time it will be evident if this is a problem. Until then it will be a dilemma for veterinarians and their clients. The new studies do not support the view the increasing vaccine intervals will be a problem but you may feel the same way. Fortunately, you have a choice in this matter, no matter how you feel. Our recommendation is to extend the vaccination interval.
What about dog vaccinations?
I am pretty confident that we will be recommending a similar vaccination interval for dogs soon. At present there is not a published study that I am aware of that establishes vaccination protection intervals for dogs but that will come soon. There is a complication in dog vaccinations that doesn't seem to be as much of a problem in cat vaccinations, though. Canine distemper vaccines are made from differing strains of distemper virus. One strain provides nearly lifelong immunity, one strain provides immunity that seems to vary from dog to dog but probably lasts about 1.5 to 2 years on the average and there is a new recombinant vaccine strain that I have not been able to find any duration of immunity information on. It would seem to make sense to just use the most potent vaccine strain except that my understanding is that it also has the most potential to cause adverse side effects. It may turn out that yearly vaccination for distemper will remain the standard due to this. Parvovirus vaccination appears to confer immunity of very long duration, perhaps lifelong, after the inital vaccine series. This is also true of the canine hepatitis vaccine.
At present, we are going to stick with yearly vaccinations for dogs since there is no evidence that dogs have the problem with cancer formation at vaccination sites. If research indicates a longer interval is safer we will go to longer intervals, though. I see no reason to give medications or vaccinations unnecessarily since there is always a small risk associated with their use.
Lawsuits, a potential worry among vets:
The label and package insert for most vaccinations call for yearly boosters. In states in which it is allowable by law, rabies vaccinations are usually given every three years which is in accordance with the label directions. I have spoken with several veterinarians who are very reluctant to change vaccine protocols until the manufacturers change the label claims, fearing that a pet will get sick from a disease that a vaccination should have worked for, leading to a lawsuit. You might find that your veterinarian wants you to sign a release form if you (or even if he or she) wishes to extend the intervals between vaccinations.
Don't forget the yearly physical exam, though!
Pets age at a faster rate than humans. It is estimated that a yearly physical exam for a pet is roughly equivalent to an every three year examination for a person. It is surprising how many times we find problems on physical exams that owners are completely unaware of. In fact, I bring my pets to my clinic and put them up on my examination table two or three times a year to ensure that I really take a good look at them. I know that I don't really look at them like patients when I am playing with them or taking them for a walk in the woods.
It can make a big difference in a pet's lifespan when certain health problems are caught early. Don't skip the yearly physical exam for your pets. Consider putting any money you save by extending the vaccine interval into other preventative health care measures like dental cleanings or an occasional routine blood chemistry exam.
Christmas Day, 1981
I know that this newsletter is coming to you after the rush of the Christmas season is over but I thought I'd tell a story about Christmas Day in 1981, anyway.
My wife, Moe, was my chief assistant in 1981 on any call that was after-hours. She has a degree in Animal Science and was always good help. This particular Christmas she was a little hampered by being thirty-four weeks into her second pregnancy but gamely offered to go along to help when I received a call from a local dairy. They had a cow who was having great difficulty delivering a calf. I knew it was going to be a tough call because the farm manager was pretty adept at delivering calves and not very prone to calling a vet. He told me that he had been trying to figure out how to deliver the calf for several hours and he and the cow were both pretty worn out.
When we arrived at the farm the cow was just barely able to stand. I cleansed her rear end and reached in to see if I could figure out how to deliver this calf. Almost immediately I realized that there were two calves and that they were now hopelessly tangled up. I decided to do a cesarean section. We clipped and cleansed her side and then injected a local anesthetic in her left side. The muscles were separated to allow entry into ther abdomen and her uterus identified. Moe held the uterus up against the body wall while I fished out the two calves. It took an unexpectedly long time because they really were thoroughly entwined. They had probably started out tangled but the efforts to deliver them almost certainly made it worse. Moe gritted her teeth and continued to hold on. Finally, I was able to deliver the second calf and take over the job of holding the uterus while I sutured it and then closed the incision in the body wall. Moe sat on a bale of hay and watched. Every now and then an odd expression crossed her face. We finished up with the cow and started on the ride home.
"You might want to just keep going on the hospital," Moe said suddenly. Our first child had been born prematurely and the doctor had just taken Moe off of medications to prolong her pregnancy. He had assured us that it would take several days for the effect to wear off. I don't think he calculated on his pregnant patient spending an hour holding on to the uterus of another pregnant patient, though! Moe's water had broken. I stopped by my house and we changed clothes, convinced that it would be a little while before the baby really came. But we did set out for the hospital.
About halfway there Moe suggested I might want to drive faster, "unless you want to deliver another baby today". Needless to say, I sped up. Like many fathers faced with this situation I ran into the hospital with the simple message, "Help me, my wife is about to have a baby." This didn't seem to impress anyone there. At least not until the first nurse examined Moe for a few seconds and said, "We're heading straight for the delivery room."
The obstetrician wasn't there. Christmas Day is not the best time to need emergency assistance. In the whole hospital there was only one doctor, a dermatology resident. He strode confidently into the delivery room and picked up Moe's chart. After reading about the previous emergency cesaerian, the premature nature of the delivery and taking stock of the advanced stage of the delivery he did the sensible thing for a dermatology resident to do. He started to cry a little and to chant in a non-ending mantra "Don't push, don't push, come on now, don't push".
Just as I decided I really did need to deliver the third baby that day, our obstetrician arrived. Within minutes we had a wonderful Christmas present, our youngest daughter, Lauren. She was perfect despite the early delivery.
I heard our obstetrician mutter to one of the nurses as he was leaving, "Remind me never to stop Utopar on a holiday again!" We never did have the heart to tell him what Moe had done that day. Somehow it seemed better to let him think it was all his fault.
(just a note - some of you know that Moe is a veterinarian, too. She went to veterinary school from 1985 to 1989. She had more experience in the field than most of her classmates)
Diabetic Cats -- a "new" option:
Most veterinarians consider cats to be the most difficult diabetics among the domestic species. It can be very hard to regulate insulin in cats and they usually require twice daily injections of insulin as well as three or four times a day feeding to really successfully regulate their insulin requirements. Many vets feel that cats were a little easier to regulate when protamine zinc insulin (PZI) was available because it was a little more likely that a cat could be regulated on once daily injections with this product. Hopefully, this is true because PZI insulin is available again. If your vet has a hard time finding a distributor of this insulin the company making it is Anthony Products and their phone number is 1-800-423-7153. I liked PZI insulin but can't remember too many cats that stabilized on once daily injections with it, despite its reputation.
We try to teach clients to use blood glucose monitors to help us assess the insulin requirements of their cats. I believe this works better than trying to monitor urine glucose. Most of our clients can get enough blood from their cats by pricking an ear vein or the cat's lip to do the blood test. Urine glucose does not give a very accurate picture of insulin peaks and valleys but it is possible to tell if there is no sugar in the urine, meaning that the blood sugar is in the normal or low range and whether there is sugar in the urine, indicating that at least part of the day it is higher than normal. A simple way to monitor the presence or absence of sugar is to take a teaspoonful of the wet litter, put it in a small paper cup and add a teaspoonful of water. Swirl the mixture around, pour off a little liquid and test the sugar level. Obviously this isn't super accurate but it does at least let you know if sugar is present or not. That can help some in evaluating whether insulin regulation is going well.
Another potential problem with regulation of insulin in cats is concurrent chronic pancreatitis. If your cat is not responding well to insulin therapy despite rigorous attempts to acheive good regulation it is possible that pancreatitis may be a complicating factor. Pancreatitis can be hard to diagnose in a cat but blood tests can give some hint as to its presence.. Since many cats that have chronic pancreatitis also have exocrine pancreatic insufficiency (inability to produce sufficient digestive enzymes) it is a good idea to consider a test for this. A blood test is available for cats that tests for trypsin-like immunoreactivity in the serum which can help your vet determine if an insufficiency is present.
If your cat is diabetic you really have to have a good working relationship with your vet. Make sure you understand what your vet is telling you and do your best to follow directions accurately. Be patient if initial regulation is difficult. Give your vet a little time to work out a dose as long as your cat is doing reasonably well.
Perianal Fistulas
Perianal fistulas are infected tracts that occur around the rectum of medium to large size dog breeds, especially the German shepherd. These have traditionally been treated by surgery with varying success. A recent study reported in the Nov. 15th, 1997 issue of the Journal of the AVMA by Mathews, et. al., found that treatment with cyclosporin, an immunosuppresive agent normally used to prevent rejection of transplanted organs, was very successful in treating perianal fistulas. It was most effective when combined with surgical removal of the anal sacs. This is definitely an option to discuss with your vet if this problem ever occurs in your dog.
We wish you the best in 1998 and continue to thank you for supporting out web site and our newsletter. We are hoping to find enough subscribers to return to the original format of answering questions on a daily basis, to continue to write and revise the dog and cat health encyclopedias and to add information geared towards veterinarians and pet owners looking for more in depth information. Your subscriptions help us make progress towards these goals.
Thank you
This page was last edited 06/15/04
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