VetInfo Digest September 1998
This issueVaccination Controversy Continues...
New Stuff:
Blood Profiles, Part II - White Blood Cells
Old Cats and Old Dogs and Grooming Problems
Swamp Devil
Vaccination Controversy Continues...
There are a lot of controversial issues in veterinary medicine right now. The more we learn about medicine as it applies to pets, the more we realize what we don’t know. This creates a lot of confusion among veterinarians and their clients. Fortunately, our patients don’t worry about their health care very much. So at least we don’t have to worry about their stress levels from all the confusion. One of the biggest controversies is vaccination scheduling. Very few vets really question the need for vaccination of pets. The questions revolve around how often vaccinations should be given and which ones are important. Veterinarians are deeply divided over this issue.
Puppies and kittens need to have vaccinations. Following your veterinarian’s advice about necessary puppy and kitten vaccinations is definitely a good idea. It is important to give the first year boosters for the common diseases, as well. After that, the controversy begins.
Prior to three or four years ago most veterinarians felt that vaccinations were pretty harmless and that it was reasonable to give them every year since that is what the labels call for and no one really knew how long they would protect against disease. Veterinary clients were notified of the need for yearly vaccinations through reminder cards and brought their pets in for yearly vaccinations and physical exams. Most veterinarians admitted tacitly that the examination was more important than the vaccination but still felt that it was worthwhile to do both.
There is a small group of veterinarians who feel that vaccinations given too frequently may be causing problems such as hypothyroidism and long-term immunosuppression. There isn’t much evidence to support their claims but one veterinarian in this group, Dr. Jean Dodds, is a pretty busy speaker and fairly prolific writer, which had stirred up some controversy. On top of that it was discovered that there was a link to immune mediated hemolytic anemia and recent vaccination in dogs (a rare occurrence) and to a particularly aggressive cancer, vaccine associated sarcoma, in cats. Suddenly, vaccinations didn’t seem completely safe, anymore. The idea of risk versus benefit for vaccination has become an important concept in decision making over which vaccines to give and how frequently to give them.
Veterinarians at Cornell University studied vaccine longevity in cats and concluded that a three year vaccination interval was probably acceptable for rhinotracheitis, calicivirus and panleukopenia virus based on serologic evidence. That isn’t as good as a challenge study in which vaccinated cats are exposed to the viruses causing these diseases but it was enough to convince many veterinarians, myself included, that we could probably increase the time between vaccinations with reasonable safety. Other studies on feline leukemia show that it is hard to transmit this disease in cats over a year old. Knowing this, it seems reasonable to extend the interval between feline leukemia vaccinations in adult cats, too.
Many veterinarians are old enough to remember distemper virus outbreaks or parvovirus outbreaks in dogs. Panleukopenia is rare now but was once a pretty common cause of death in young kittens. I have been in practice long enough to have seen two severe distemper outbreaks and I was in practice when parvovirus first swept through the U.S. in the early 1980s. It is easy for me to understand why older veterinarians are reluctant to give up on yearly vaccinations without absolute proof, through challenge studies, that there is almost no chance of reviving the old days of epidemics of viral illnesses. On the other hand, I have several cat patients who developed vaccine associated fibrosarcomas. I have treated two or three cases of immune mediated hemolytic anemia that occurred one to three weeks after vaccination in dogs, making it a possible cause of the condition.
I am comfortable vaccinating on an every three year schedule. I believe that it is going to prove to be effective in preventing disease. I think I can explain to my clients the need for yearly physical exams even if I am not going to vaccinate their pet. I realize that other charges will need to rise in my practice in order to make up for lost income from vaccinations. So I recommend the longer vaccination interval. Many veterinarians are not comfortable with some aspect of the longer intervals and will continue to strongly recommend yearly vaccinations. A major sticking point is the label direction calling for yearly vaccination. Some vets feel that they would be open to lawsuits over pets that develop any of the diseases commonly vaccinated against if they go to longer vaccination intervals than the label calls for. While I think that it is defensible to use the newest information to make decisions in veterinary medicine there is some risk that a jury wouldn’t agree.
My best advice is to listen carefully to your veterinarian’s advice. He or she knows the problems in your area better than anyone else. If there seems to be a need for yearly vaccinations based on good reasoning, then it is worth considering it. I would be suspicious of recommendations to vaccinate more than once a year for distemper, parvovirus or adenovirus (hepatitis) in dogs. I am not aware of any justification for a recommendation like this other than the puppy vaccination series. For cats, I think that there is more reason to be cautious about the risk of vaccination and it would be harder to convince me to proceed with a yearly vaccination schedule. I wouldn’t skip the yearly physical exam, though.
If your vet says something different than me that wouldn’t be unusual. Your vet has as much or more training than I do. You have a brain. Think about the potential risks your cat or dog faces and follow the advice that sounds right to you. Either way, there are some risks and some benefits so you probably won’t make a bad choice.
New Stuff:
Etodolac, (Etogesic Rx) is a new analgesic being marketed by Ft. Dodge. It is similar in action to carprofen (Rimadyl Rx) but is meant to be given once a day rather than twice a day. In an odd coincidence, the price per day for Etogesic is almost exactly the same as the price per day for Rimadyl, though. It is approved for use in dogs, only. For dogs that are difficult to pill or for people who only have one time of the day they can consistently be home to give medications this may be a good choice. It is a "Cox-2" inhibitor, like carprofen, which means that it is less likely to irritate the gastrointestinal tract like older non-steroidal anti-inflammatory medications, which are "Cox-1" inhibitors. It will probably take several months of widespread use to find out if it will cause any rare side effects.
Desoxycorticostone pivulate (Percorten-V, Rx) manufactured by Novartis, has been approved for use in dogs for the treatment of Addison’s disease. This is an injectable medication made to be given once every 25 days. It replaces the use of fludrocortisone acetate (Florinef Rx), an oral tablet that was given once or twice a day as necessary but was not ever approved for use in dogs. Increased tolerance to Florinef is common over time and it is not usual to have to increase the dosage during use and to have to supplement with oral corticosteroids as well. Percorten should be a better product for most dogs.
Blood Profiles, Part II - White Blood Cells
White blood cell counts (WBCs) and differential examinations are a big topic, literally occupying nearly whole books when discussed in detail. So it is important to state up front that this will be a very general discussion of the white blood cell count and how it is used by veterinarians to help determine the nature of an illness.
The total white blood cell count is simply the number of white blood cells that are found in a microliter of blood. Usually this figure is between 5,500 and 19,500 in the cat and between 6,000 and 17,000 in the dog. Just like other lab values, the white blood cell count "normal value" varies from laboratory to laboratory and it is best to compare any individual sample against the normal values from the laboratory performing the analysis.
Total wbc: Dogs 6,000 to 17,000 wbcs/ul Cats 5,500 to 19,500 wbcs/ul There are several ways to count white blood cells, all facilitated by the fact that white blood cells have nuclei while red blood cells do not. Impedance counters are considered the most accurate method of counting white blood cells. These devices simply count the number of nuclei in the blood sample after all the cells are lysed (broken into fragments). Alternatively, it is possible to do the same thing, but by counting a portion of the cells manually and then using that count to estimate the total. Many veterinary hospitals use a QBC-V machine, which estimates white blood cell count from a specialized hematocrit tube by measuring the white blood cell layer in the spun sample. This only produces an estimated count but it correlates well with the actual counts. The QBC-V provides an estimated count in about 10 minutes from a whole blood sample which is the major reason for its popularity.
Once a total white blood cell count is obtained it is best to go one step further and to determine what types of white blood cells make up the total. There are five types of white blood cells that are most commonly encountered when examining blood smears. They are neutrophils, band neutrophils, lymphocytes, monocytes and eosinophils. Each type of white blood cell has a different "job" and by evaluating the numbers of these types of cells in the sample it is often possible to get a better idea of what type of illness or disorder is present.. Cats are particularly problematic when it comes to total white blood cell counts. Cats are prone to stress induced changes in several blood values and the white blood cell count is one of them. A cat who is obviously upset by having blood drawn or anxious just being at the veterinarian’s office can have a higher than "normal" WBC just from stress. This makes it hard to interpret borderline rises in white blood cell counts in cats. Dogs can have similar effects from corticosteroid administration. The differential count helps in discerning between abnormal white blood cell counts that are occurring for normal reasons and those that are caused by disease processes.
White blood cells that contain a nucleus and granules in the cytoplasm are called granulocytes. The granulocytes include the segmented neutrophil, band neutrophil, eosinophil and more rarely the basophil. The granules contained in these cells stain differently and allow the cells to be distinquished from one another. Neutrophil granules stain light blue on most commonly used blood stains. Band neutrophils are just immature segmented neutrophils. These two cells are distinquished by the shape of the nucleus, with the younger cell having a nucleus that looks like a "C" of uniform thickness while the segmented neutrophil’s nucleus looks like a "C" made of a chain of beads. Eosinophils have red granules and basophils have almost black granules. Basophils are seen infrequently enough that we do not usually see them at all when counting cells on a blood smear. Counting is usually accomplished in veterinary practices by examination of a blood smear and actually counting the different types of cells on the smear. Usually 100 cells are counted and the percentage of each type of cell in the count is determined. Then this is repeated and the results averaged. The QBC-V machine provides an estimate of the number of granulocytes (segmented neutrophils, band neutrophils and eosinophils) and the number of non-granulated cells (lymphocytes and monocytes) but this is not a really good substitute for observing the cells and counting them.
While the technician is counting cells he or she is also evaluating the morphology of the cells (their physical appearance). Segmented neutrophils exhibit changes as they mature or react to infectious conditions. The term "toxic neutrophils" is used sometimes to designate neutrophils with an embattled appearance from ingesting bacterial toxins. It does not imply that the neutrophil has become poisonous in some way or that there is a toxin in the body. Lymphocyte size and uniformity can be helpful in distinguishing whether an infectious or neoplastic (cancerous) disorder is causing rises in lymphocyte numbers. Platelets can be evaluated from the smear as well as white blood cells. There is a lot of variation in how different technicians identify cells, particularly in the distinction between band neutrophils and segmented neutrophils, so it is always best to check the normal values for a particular lab, if the smears are sent to a commercial lab for evaluation. Your veterinarian will have an idea of how the technicians at the practice count cells and identify morphologic changes if blood smears are examined in the clinic.
Neutrophils are the first line of defense against most foreign invaders in the body. They can migrate through the blood vessel walls and into damaged or diseased tissue. They can ingest and kill bacteria or foreign substances. They release chemicals when their granules rupture that contribute to local inflammation and fever. I tend to think of the white blood cells system as a little army inside the body. Following this line of thought, the neutrophils
are the infantry soldiers of the army, charged with putting themselves on the line to defend against foreign invaders. Like lots of armies, the neutrophils are not all on the front lines at the same time. There is a considerable reserve of neutrophils in the body which are not actively in the circulation. When the need arises for neutrophils to be activated, neutrophil counts in the circulation can rise very quickly to meet the need. Neutrophil numbers rise when there is an infection or inflammatory process. If the illness is chronic and the demand for neutrophils is high, they can be used up and a decrease in neutrophil numbers results. Neutrophils do not have a long life span in the circulation. The average neutrophil lives in the blood stream for 10 hours or so and all of the neutrophils in the body are replaced about twice a day. When a pet is sick, neutrophils live even less time, so those "old" looking neutrophils in the circulation are old only in "neutrophil years".
Segmented Neutrophils Dogs 60 to 77% 3,000 to 11,400 Cats 35 to 75% 2,500 to 12,500 Band neutrophils are just immature segmented neutrophils. Usually the bone marrow doesn't release band cells except in small quantities. When there is an excessive demand for neutrophils the bone marrow may respond to it by releasing band neutrophils. It takes a fairly serious need for neutrophils to make the body release its "baby" soldiers so a rise in bands is an important sign. When band neutrophils are increased and segmented neutrophils normal or decreased it is a sign that the body's defenses are being overwhelmed by the disease process that is occurring.
Band Neutrophils Dogs 0-3% 0-300 Cats 0-3% 0-300 Neutrophils and band neutrophils increase in the circulation under certain general conditions. These are fright (physiologic increases due to epinephrine release into the circulation), stress (increased corticosteroid levels in the blood stream) and inflammation from any cause. Specific causes of neutrophil increases include bacterial infections, viral infections, fungal infections, parasites, trauma, cancers, foreign bodies (plant awns,etc.), endotoxins and some immune system disorders.
Lymphocytes are the cells that control the white blood cell response and produce antibodies. T-Cells are lymphocytes that memorize what foreign invaders look like and identify them in some way to the body. B-Cells are lymphocytes that produce antibodies against bacteria, viruses and other microorganisms. Lymphocytes live a very long time, perhaps even a pet's entire life-span. They can divide to produce more lymphocytes so they are not totally dependent on production in the bone marrow. Only about 10% of
the lymphocytes present in the body are in the blood stream at any one time. Usually they are found in lymphatic vessels, lymph nodes and the spleen. Lymphocytes may increase in the circulation in cats when they are excited, probably due to being released from lymphatic vessels into the circulation. Lymphocyte numbers also increase in chronic infections when antibody production is in full swing. Cancer of the lymph nodes (lymphoma) is a fairly common cause of increased lymphocyte numbers in the bloodstream in dogs. Decreases in lymphocyte numbers (lymphopenia) occur when corticosteroids are administered or when natural cortisones in the body increase due to illness or chronic stress. A significant drop in lymphocyte numbers in the blood stream is a bad prognostic sign because patients with lymphopenia have a harder time surviving serious illnesses. Specific disorders leading to lymphopenia include chronic disease processes such as kidney or liver failure, chronic pancreatitis, hyperadrenocorticism (Cushing's disease), chemotherapy and prednisone or other glucocorticoid administration.
Lymphocytes Dogs 12-30% 1,000 to 4,800 Cats 20-55% 1,500 to 7,000 Eosinophils are granulocytes with a special function. These cells help to fight off parasites. They can also contribute to the control of bacterial infections. Increased numbers of eosinophils occur in allergic conditions, as well. It is not clear whether these cells help to initiate allergies or whether they are simply high in response to the preexisting allergic
condition. For parasites to cause a rise in the eosinophil count there must be prolonged infection, making heartworm disease, demodecosis and roundworm infections more likely to produce an increase in eosinophils than parasitic infections in which the contact with the parasite is less intimate and of shorter duration. Flea infestation can produce rises in the eosinophil count, too. Cats occasionally have eosinophilic granuloma complex which causes skin sores and can lead to increased numbers of eosinophils in the bloodstream.
Eosinophils Dogs 2-10% 100-750 Cats 2-12% 0-750 Monocytes are also fairly specialized cells. They migrate from the blood stream into the body and become macrophages. These cells are capable of living a pretty long time and can divide outside of the bone marrow. They are involved in cellular immunity by absorbing and digesting foreign invaders (phagocytosis). They produce some of the moderators of inflammation such as lysozyme and interferon. Low numbers of monocytes are not unusual in white blood cell counts. Not finding any monocytes is possible in normal animals. Increases in monocyte numbers occur with chronic pain, chronic illnesses of tissues that are high in macrophages, such as the lungs, tissue death from trauma or infection, hemolytic illnesses and hyperadrenocorticism.
Monocytes Dogs 3-10% 150 -1350 Cats 1-4% 0 - 850 When discussing white blood cell differential counts it is not uncommon to hear the terms "absolute number" and "relative number" of a particular cell type. Thinking back to our previous discussion it is apparent that the only actual number we know is the total white blood cell count. Then we count the number of the different types of white blood cells in a blood smear and we get a percentage of each type. It is very tempting to just use this percentage, or relative number, of the different cell types and not to bother calculating how many of each type of cell is present. This can lead to some problems in white blood cell count interpretation, though. A better method of looking at the differential is to multiply the percentage of each cell type by the total number of white blood cells to get an idea of the actual number (the absolute value) of the different cells. This number allows us to make a better estimate of whether or not there are increased or decreased numbers of a particular cell.
To illustrate this point, consider an example case:
A female dog arrives at our clinic with a history of lethargy, poor appetite and increased drinking and urinating. Her temperature is 103.5 degrees Fahrenheit. We can't find an obvious cause for the temperature or signs of illness so we draw a white blood cell count. Her total wbc is 28,500. We recognize that this is high. A smear gives us percentages of white blood cells as follows: neutrophils 89%; band neutrophils 5%; lymphocytes 4% and monocytes 2%. If we use percentages to evaluate this picture we see that there is an increase in neutrophils and band neutrophils and a decrease in lymphocytes. Since we know that a decrease in lymphocytes is a poor prognostic sign, we might be discouraged by this finding. However, if we look at the absolute numbers of the different types of cells we see that they are: neutrophils 23,565, band neutrophils 1425, lymphocytes 1140 and monocytes 570. This is reassuring, because the total number of lymphocytes is actually within the normal range. It just seemed low because the great increase in neutrophil numbers made the total count higher. X-rays help us determine that she has a pyometra (uterine infection) and treatment is initiated.
By looking at the total white blood cell count and the differential count, it is often possible to get a good idea of the type of illness is present and what sort of lab tests or physical examination findings are necessary to confirm the problem.
Old Cats and Old Dogs and Grooming Problems
Older cats frequently groom less than younger cats. They develop mats in their fur, especially around their hips and the base of their tail. It is tempting to cut these mats out with scissors but it isn’t a good idea. I have treated three cats in 1998 for lacerations of the skin due to grooming efforts. The mat pulls up a fold of skin and the scissors cut out the entire fold, leaving an oval shaped wound that can be surprisingly large. It is better to use a mat rake, available at pet stores, to get out the worst of the mat and then a fine toothed comb to get the rest of it. If that isn’t possible due to your cat’s temperament, it is best to let a groomer or your vet get the mats out.
Older cats also grow thicker nails with a tighter curve. Check your older cat’s claws occasionally to make sure they aren’t growing into a foot pad or causing difficulty walking.
Older dogs do not groom as well as they used to, either. Male dogs may develop mats around their prepuce and female dogs with long hair may have them around their vulva. In long-haired dogs of both sexes hair mats under the tail can lead to skin infections or even interfere with bowel movements. It is best to keep these areas clipped closely if mats are a problem. The nails on older dogs do not seem to get thicker like cat’s nails do but they do seem to grow a little faster and curve under a little more easily sometimes. It is a good idea to keep nails clipped, too. This can make walking easier for an older dog with arthritis.
Swamp Devil
I answer the phone at my practice more often than most veterinarians. I often have my first contact with many clients over the phone. Often, I have a mental image of the client that doesn’t fit them when we do meet.
When Mrs. Irvington called she asked for "the veterinary doctor". I told her that I was the vet and asked if I could help her.
"Do you give dogs shots?" This seems to be the standard question on the phone when people aren’t sure that they are really talking to the vet. I am not sure why but people ask it so often, since it would be hard to make a living if I didn’t vaccinate dogs and cats and most of them do know they called a veterinary clinic.
"Yes, I am the veterinarian", is my standard reply.
"Good, ‘cause my dog needs his shot. The dog warden tells me I have to get him a shot or he’s going to give me a fine and take him away." Usually this indicates a pretty low involvement with a pet. There are a number of people in our rural area that only vaccinate their dogs for rabies and only because they are required to by law. I asked Mrs. Irvington to bring her dog in.
"Devil don’t ride in no car, Doctor. Will you come to my house? None of the other vets over here will come to my house anymore. They say that Devil is too bad a dog to mess with him at my house. I’m a widow and I don’t have a car and I got to depend on my neighbors to carry me places. They don’t want Devil in their cars."
I was getting a sinking feeling in the pit of my stomach. I didn’t really want to join the ranks of vets who found Devil too much to handle but I also couldn’t see making a widow lose her dog because I wasn’t willing to give him a rabies shot. Reluctantly, I agreed to come out to her house.
Mrs. Irvington gave me very specific directions. "Doctor, you just get on Low Bottom Road and watch for a white house on the left with a dog tied out. Now when you get here don’t forget he be a bad dog. You come and knock on my door and I’ll make him listen to you."
Low Bottom road was appropriately named. It is a narrow meandering road right through a swampy marsh. At some points the road level was noticeably lower than the surrounding watery terrain but high roadside banks were keeping the road dry. Finally we started up a small rise and broke out into sunshine. Almost immediately we noticed the house on the left with Devil tied out on a chain behind it. There was a well worn circle around a very well constructed doghouse. Devil was already barking at us when we first saw him. He kept it up as we drove in the driveway and knocked on the door.
A very small woman answered the door. She had deeply wrinkled skin and was stooped over some, her left hand on a cane for support. "Are you the dog doctor?", she asked.
"Yes, ma'am, I am the vet", I replied.
"You see ol’ Devil out there? Do you think you can give him his shots?". I have always been an optimist, so I answered in the affirmative and started towards my truck. My technician, Sonja, had already gathered up a couple of leashes and put vaccinations in syringes. We eyed Devil. Ominously, he had stopped barking and was also examining us. As we planned our strategy, he seemed to be planning his.
Usually dogs on chains are not that hard to catch and hold, even if they are vicious. By letting them run to the end of the chain and then lassoing them with a leash we have them caught between two points and can deal with them. Devil was too smart to run to the end of the chain, though. He kept enough maneuvering room to allow him to attack the person trying to apply the leash. Mrs. Irvington was watching and occasionally hollering for him to be nice but it wasn’t having much effect. We withdrew to rethink our approach.
After some discussion, I decided that I could step on the chain and bring him up short if we were very quick with the other leash. Sonja walked behind me, ready to take hold of the second leash as soon as I got it on Devil. Amazingly, the plan worked. We had Devil caught between us with me standing on his chain and Sonja holding him at a safe distance with the other leash. Working carefully, I was able to get both vaccinations in and even to draw a small amount of blood for a heartworm check from his rear leg. We were feeling pretty good about the situation at that point. Devil had not resisted nearly as much as we thought. Letting us have the first round must have been Devil’s plan, though.
Sonja passed the second leash to me. Suddenly it occurred to me that as soon as I removed my foot from his chain, Devil was going to have enough chain left to get to me before I could get away from him. He grinned. Really. His upper lip pulled back and he showed his teeth in an unmistakable canine grin.
I am very fast. In fact, sometimes my reflex reactions even startle me they happen so quickly. I stepped off the chain and took off for the truck. I almost made it. Just as Devil reached the end of his chain I felt his teeth graze my buttocks and heard a loud ripping sound. I looked over my shoulder to see Devil standing there with the entire rear panel and back of the right leg of my coveralls. I began to feel a breeze up my back. Feeling around for blood, I found none. I was OK except that I didn’t have another pair of coveralls and I was forty-five miles from home with three more farm calls to go on and my right cheek just showing through a small tear in my underwear.
I walked up to the doorway, where Mrs. Irvington was still standing, careful to keep the front of me pointed towards her. "I tol’ you he be a really bad dog." was her first statement. It was true. Devil was appropriately named. "Nobody round these parts messes with my things, though. An old lady sometimes needs a little protection." I started to tell her how much she owed me when she interrupted me. "Don’t you be charging me for the aggravation, now. I remember how much you said this would cost." I laughed because I wasn’t planning on adding in the cost of the coveralls and said that I’d remember the next time what Devil was like.
We treated Devil for heartworms, vaccinated him yearly and I got to know Mrs. Irvington really well. She had six children and on her living room wall she had eight college degrees - one for each child plus two with advanced degrees. As Mrs. Irvington aged I dealt with her children more and more. She had done a great job of raising them. How she ended up with Devil, I’ll never know but he was mean until the day he died. Even after I gave up farm work I continued to drive to his house to work on him. After all, as Mrs. Irvington would say after every visit, " You’re the only dog doctor that will put up with his meanness." I didn’t do it for Devil, though. I did it for Mrs. Irvington. Something about this dignified little woman living on the edge of the swamp really appealed to me.
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Copyright, TierCom, Inc., 1998 Tiercom, Inc. P.O. Box 476 Cobbs Creek, VA 23035 The opinions expressed in this newsletter are solely those of the author, Michael Richards, DVM, unless otherwise noted in the text. Michal Justis is our web designer and graphic artist.
This page was last edited 06/20/04
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