This Issue
Don’t Kill Your Cat
Blood Profiles, Part I - Red Blood Cells
Causes of Non-Regenerative Anemias
 Pet Insurance, Should You or Should You Not Insure Your Pet’s health?
 Don’t Kill Your Dog, Either
 
 

Don’t Kill Your Cat

Cats are different than dogs. A lot different. Medications, flea control products and foods that are safe for dogs can be harmful to cats. Cats are also different than people. Don’t take chances. If you have not verified that a medication is reasonably safe for a cat, don’t give it to a cat. There are many medications that may be toxic to cats. Some of the medications that should not be given to cats are listed below.

Acetaminophen (Tylenol TM) is much more toxic to cats than it is to dogs or to humans. The lower end of the toxic dose for cats is about 60mg/kg of body weight which is roughly 1 regular strength Tylenol for a ten pound cat. (Michael Murphy, DVM, Journal of the American Veterinary Medical Association, August 15, 1994). The clinical signs of acetaminophen toxicity include salivation, depression, vomiting, loss of appetite, swelling of the head and ultimately death. Signs can occur in as little as two hours after administration of acetaminophen to a cat. If you have inadvertently administered acetaminophen to your cat it is imperative that you seek emergency assistance as quickly as possible. Cimetidine (Tagamet Rx) may help to reduce the speed at which acetaminophen produces toxic effects and treatment for acetaminophen toxicity can be successful using proper medications.

Aspirin can be toxic to cats but it is safer than acetaminophen and is used in cats by veterinarians in some circumstances. It is best to have your veterinarian examine your cat and determine the proper dosage before considering the use of aspirin. In most cases aspirin needs to be administered at intervals of at least 48 hours to be safe for cats.

We have treated three cats this summer for toxicity from permethrin based products (Control TM, ProTicCall TM, others). These products have recently become widely advertised as the inexpensive alternative to the new monthly flea control medications Frontline Topspot (TM) and Advantage (TM). Permethrin is relatively safe for use on dogs. It is very toxic to some cats. It causes seizures, muscle tremors, depression and sometimes death. Read the labels of any flea and tick products you are considering using on your cat very carefully. If it says "Do Not Use On Cats" don’t use it for your cat. Despite the advertising, these products are not as effective at flea control as the newer medications and are less safe as well.

Cats are obligatory carnivores. This means that their diet has to contain certain preformed amino acids that are found almost exclusively in meat. It may be possible to formulate a vegetarian diet for a cat but there is a grave risk of producing nutritional deficiencies which can lead to disability or death. Cats are meant to be carnivores. If we chose to own them we should be prepared to accept that. While vegetarian diets might seem healthier for humans and possibly even for dogs, they pose a great risk to a cat. This is the reason that your vet advises against feeding dog food to cats as their sole diet. It is less expensive to use plant proteins and dog foods often substitute plant proteins for meat proteins. This is fine for dogs but over the long term it is not OK for a cat. Stick to cat foods.

On our website I have admitted that I use Rimadyl (Rx) in cats. This is an extra-label (unapproved) use of the medication and the manufacturer, Pfizer, advises against the use of Rimadyl in cats. However, there are times when pain relief seems more important to me than a low risk of reaction. Cats are much more sensitive to the gastrointestinal effects of Rimadyl than dogs are so we limit our use of Rimadyl to one or two doses to try to avoid intestinal ulcers or other detrimental effects. It is better to use another pain reliever when it is possible to do so.

We also have published a dosage for Pepto-Bismal for cats. This medication contains salicylates, which are in the same class as aspirin. This medication should also be used with the knowledge and assistance of your veterinarian.

Don’t kill your cat. Don’t use over-the-counter remedies for cats unless you have discussed this use with your vet or at least made an effort to verify that it is safe.
 

Blood Profiles, Part I - Red Blood Cells

In the last couple of months we have tried to help with the interpretation of some of the routine laboratory tests used in veterinary medicine. We have stuck to tests that have a "positive" or "negative" value up to this point, mostly. In this issue, I will try to help you understand the red blood cell portion of the complete blood cell count, or "CBC".

Blood is red because it contains a lot of red blood cells. In one liter of blood there are usually between 5 and 10 trillion red blood cells. If red blood cells were dollars, one medium sized dog would contain enough of them to pay off the federal deficit! These sort of numbers are hard to conceptualize, even for veterinarians. So most of the time vets worry about a different number, the percentage of whole blood that is composed of red blood cells. Red cells are usually 30 to 50% of the total blood volume. The percentage of the blood made up of red blood cells is known as the hematocrit.

When blood is spun in a centrifuge it separates into a cellular layer known as the packed cell volume (PCV) and a liquid layer, which is the plasma (or serum if the blood is allowed to clot before being spun). The cell layer is red and it is easy to measure the percentage of the blood composed of cells after spinning it. The PCV is an accurate measurement of the hematocrit and is the standard measurement used by most veterinarians to determine whether or not anemia is present. The normal PCV varies by species, by sex and by age of the patient. A six week old puppy with an hematocrit of 25 is probably not anemic but an adult male dog with an hematocrit of 25 probably is anemic. Different laboratories and veterinary hospitals establish normal values based on their lab equipment but in general the PCV should be around the range listed in Table 1.
 

When the percentage of red blood cells is below the normally expected values the pet is anemic. When the percentage of red blood cells is above the normally expected value the pet is considered to be polycythemic. It should be noted that the ranges for anemia and for polycythemia vary widely in dogs. This is especially important in evaluating polycythemia in very young puppies, which sometimes occurs with congenital heart defects.

There are many causes of anemia and further examination of the red blood cells and red blood cell indices can aid in establishing a specific diagnosis.

Red blood cells do not have a nucleus. They appear to be red discs on a microscopic slide and are uniform in size in most pets. When red blood cells vary widely in size the condition is called anisocytosis. Red blood cells are also usually pretty uniform in color. When there are not the term polychromasia is used to describe the presence of different shades of red blood cells. Spherocytes are red blood cells that are smaller and more spherical in shape rather than being disc shaped. This deformity of red blood cells is commonly associated with immune mediated hemolytic anemia. It occurs when red blood cells are damaged and lose part of their mass. This usually occurs when the immune system is attempting to remove the red blood cells from the circulation for some reason. Heinz bodies are seen in cats (and sometimes dogs). These are fragments of hemoglobin that are visible in red blood cells and are found in situations in which the hemoglobin is damaged by chemicals. Onion toxicity in cats and dog can produce this and it is seen in cats with acetaminophen toxicity.

While simply observing the color, size and shape of red blood cells is useful there are also formulas that more precisely define what the average red blood cell’s size, volume and hemoglobin content are.

The MCV is the mean corpuscular volume, a measurement of the size of the average red blood cell. When the MCV is higher than normal the red blood cells are macrocytic. When the MCV is lower than normal, the red blood cells are microcytic. Immature red blood cells are larger than mature red blood cells, so an increase in the MCV usually indicates that the body is responding to an anemic state by releasing red blood cells from the bone marrow as quickly as possible. Anemias in which the MCV does not increase usually indicate an inability to produce new red blood cells, which can occur in conjunction with several systemic illnesses, such kidney failure and metastatic cancers. Iron deficiency anemia and polycythemia can cause the mean corpuscular volume to decrease. Akitas sometimes have microcytic red blood cells for no apparent reason.

The MCH is the mean corpuscular hemoglobin content. Since hemoglobin is the molecule that allows red blood cells to transport oxygen around the body it is important to maintain adequate hemoglobin levels. Low MCH values are associated with hemorrhage since hemoglobin is lost with the red blood cells. It also occurs in iron deficiency anemia.

Another way of measuring hemoglobin is the MCHC, which is the mean corpuscular hemoglobin content. This value is used mostly to evaluate the validity of the calculated MCH. An increase in MCHC without an increase in MCH can be an indication that the blood sample was exposed to too much anticoagulant. If both the MCH and the MCHC seem high in comparison to the MCV then there is a strong possibility that hemolysis (rupture of red blood cells in the blood stream or from the blood drawing and storing process) has occurred.

Immature red blood cells are called reticulocytes. They can be distinguished from mature red blood cells with special staining techniques. A reticulocyte count provides very important clues to the nature of an anemia in dogs and cats. Under normal circumstances the bone marrow releases very few immature red blood cells. When there is a very strong need for red blood cell replacement the bone marrow can release immature cells. It usually takes about three days for the bone marrow of dogs and cats to respond to an anemia by releasing reticulocytes. Cats tend to release fewer reticulocytes than dogs. The reticulocyte count is more meaningful when studied in conjunction with the protein level in the serum. While the serum protein level is not technically part of the complete blood cell count it is important in the evaluation of anemias. Decreases in serum protein occur when blood is lost from the circulation due to trauma but are less likely when red blood cells are simply not being produced or when there is destruction of the red blood cells within the circulation.

Anemias are often classified by the reticulocyte response. If the pet can not produce new red blood cells the situation is very grave. Red blood cells only live for about 120 days in a dog and 110 days in a cat. If there is a problem which prevents red blood cell production it will cause eventually cause death as red blood cells die and are not replaced. Many causes of non-regenerative anemia are treatable so the situation is not hopeless. If the bone marrow can produce red blood cells it is reassuring to the veterinarian. Destruction can still occur faster than production so finding signs of good regeneration does not ensure that the patient will live. It does help in determining what type of disease process is present, though. Assessing whether or not an anemia is regenerative is extremely important. Most veterinarians do not routinely ask for reticulocyte counts when the initial red blood cell count is run, since most dogs and cats are not going to be anemic and there is an additional cost for the test at most labs. It is important to ask for this test when anemia is discovered, though.

In a case in which anemia is occurring for no known reason in a pet, checking the reticulocyte count and serum protein levels can be very helpful. If there are no reticulocytes but a low serum protein level there is a strong possibility that hemorrhage has occurred recently. Many times hemorrhaging is missed by pet owners since it may occur outside or may occur through the digestive tract or other ways in which it is not obvious. If there are few reticulocytes in a sample and the protein level is normal then it is necessary to wonder if red blood cell production is not occurring for some reason, usually a much more serious problem. If there are lots of reticulocytes and a normal protein level then a disorder causing intravascular hemolysis is likely to be present, such as immune mediated hemolytic anemia.

Red blood cells can also be examined microscopically to see if parasites are attached to them or have invaded the cell. This occurs in haemobartonellosis (feline infectious anemia) and babesiosis in both dogs and cats. Blood parasites also occur that are not usually visible, such as Ehrlichia. Heartworm microfilaria (Dirofilaria immitis) may be seen in the blood. In some areas of the country a second microfilarial organism (Dipetalonema caninus) also occurs and must be distinquished from heartworm by size and appearance.

Anemia can occur for very many reasons. A list of some of the most likely causes of anemia in dogs and cats is included below. The list is broken down into causes of anemia for which red blood cell regeneration usually occurs (regenerative anemia) and for which regeneration is often not present (non-regenerative anemia).

Causes of Non-Regenerative Anemias

1) Recent hemorrhage (less than 3 days from the time of blood loss)

2) Chronic illness, especially kidney failure (more common in cats)

3) Ehrlichiosis (canine)

4) Cancer

5) Feline leukemia virus and panleukopenia virus infection

6) Iron deficiency

7) Vitamin B12 and folate deficiencies

8) Lead poisoning

9) Disorders of the bone marrow

10) Drug reactions (phenylbutazone, chloramphenicol, estrogen, chemotherapy drugs)

Causes of Regenerative Anemias

1) Recovery from acute traumatic hemorrhage greater than 2 to 3 days previously

2) Gastric ulcers or other gastro-intestinal blood loss

3) Hookworms (usually dogs)

4) Flea infestation, rarely tick infestation (kittens are especially prone to anemia from fleas)

5) Blood loss from the urinary tract (cystitis, bladder stones)

6) Platelet disorders (more common in dogs)

7) Babesiosis (dogs) and haemobartonellosis (cats)

8) some cancers, especially hemangiosarcoma in both dogs and cats

9) Immune mediated hemolytic anemia (more common in dogs)

10) Hemophilia (more common in dogs)

These are not complete lists of the possible anemias but do cover some of the more important ones.

There are other ways of classifying anemias. Another common way of sorting anemias out is to consider whether they occur due to hemorrhage, destruction of red blood cells or improper production of red blood cells. In general, hemorrhage and increased destruction of red blood cells are caused by the same things that cause regenerative anemias. Conversely, things that interfere with red blood production tend to cause non-regenerative anemia.

Polycythemia (too many red blood cells) occurs for fewer reasons than anemia. Except for a few pets with polycythemia vera (naturally occuring polycythemia) there is usually a primary disease causing the production of too many red blood cells. Anything that leads to hypoxia (insufficient oxygenation of the blood) can lead to over-production of red blood cells. In young dogs and cats congenital heart defects can lead to polycythemia. This is often missed by veterinarians in routine bloodwork because they are not used to drawing blood from very young pets whose PCV tends to be much lower than an adult. A puppy with a hemocrit of 40 is polycythemic while this is a normal value for an adult. Of course, most puppies and kittens with heart problems also have murmurs and most vets do notice these on the physical exam so the condition is usually diagnosed. Dehydration is the most common cause of polycythemia. As the fluid portion of the blood is depleted the concentration of red blood cells increases. This can be deceptive if there is also blood loss with the dehydration. In that case the dog or cat may appear to have normal blood values if they are taken prior to correction of the dehydration when anemia is actually present after the fluid deficit is replaced. When your vet wishes to recheck a PCV or CBC frequently, this is usually the reason. Everyone has heard of "blood-letting". Polycythemia vera is one legitimate reason to do this in modern medicine. By withdrawing red blood cells at regular intervals it is possible to keep a pet whose body is producing too many red blood cells healthy. If this isn’t done the concentration of red blood cells in pets with polycythemia vera eventually leads to blood "sludging" and death.

Has anyone noticed that blood drawn into a syringe from a vein appears to be deep purple while blood from a cut appears to be bright red? The difference is exposure to oxygen!

There is much more that could be said about red blood cells and red blood cell counts but I think we’ll have to cover some of that information in the future when we provide information about specific diseases.
 

 Pet Insurance, Should You or Should You Not Insure Your Pet’s health?

Consumer advocates tend to think that pet insurance is a bad idea. Their logic is simple. In any serious, costly illness involving a pet you have the option to select euthanasia and end the expense. For people whose focus is primarily expense and "value", the value of the money is more than the value of the pet at some point and the decision seems clear. Buying pet insurance is not a good idea when it is possible to cut the monetary loss at any pre-defined value by selecting euthanasia.

For some pet owners the pet is priceless. They know that they are going to spend whatever they have and whatever they can borrow to cure their pet. For these owners, pet insurance is a very good idea because it gives them a means of budgeting for unexpected health emergencies.

Most people are somewhere in between these two groups. They want to do what they can to help their pet but they do have a monetary limit, even if they will let it strain their budget quite a bit. For these people the decision is a little harder. Pet insurance companies tend not to cover routine care and the deductible is about 20% on most costly procedures. This still leaves considerable expense for pet health care above and beyond the cost of the insurance. On the other hand, it provides a safety net for unexpected medical expenses associated with pets. There are often differences within a family over the value of a pet. Insurance can help smooth out these differences in a crisis. In other cases there is general agreement among family members about the value of the pet. The only way to know for sure is to have a talk about the pet’s health and discuss what will happen if "Lucky" breaks a leg and needs a $900 surgery. If the answer is "fix it" then your family might want to consider pet health insurance.
 
 

 Don’t Kill Your Dog, Either

The most common toxicities that we see in dogs are to rodenticides, antifreeze, spoiled food (compost pile poisonings are becoming somewhat common in our practice) and non-steroidal anti-inflammatory medications used inappropriately.

Your dog will like the taste of the little pellets of rat poison. If you have to use a rodenticide be sure to put the pellets where your dog can not possibly reach them. Work hard at this because your dog will work hard to find them. We see at least five to ten rodenticide poisonings in dogs each year. If your dog does ingest these making him vomit immediately can decrease the chance of toxicity. This is effective up to a couple of hours after ingestion of the pellets. Vitamin K administration is antidotal for warfarin type poisonings but it must be continued for up to 28 days with the newer rodenticides.

Lots of people give their dogs ibuprofen, indocin or other non-steroidal anti-inflammatory (NSAID) products meant for humans. Ibuprofen can cause ulcers in dogs in as little as two or three doses and indocin has been reported to cause ulcers with a single dose in some cases. Don’t use any NSAID without consulting your vet. Carprofen (Rimadyl Rx) is a NSAID approved for dogs and aspirin is reasonably safe but it is still best to consult with your vet prior to using an NSAID medication.

Be careful when changing antifreeze or when adding new antifreeze to your car. Unless you are using one of the new "pet safe" antifreeze products your pet could die if it drinks antifreeze and most pets will drink it.

Compost piles are really attractive to dogs. Recently we have seen a rash of dogs with severe diarrhea after feasting on the neighbor’s compost piles. These dogs appear to have food poisoning based on their clinical signs and response to treatment. It would be a good idea to make sure your dog can not get into your compost pile or your neighbor’s compost pile, especially if they put meat scraps onto the pile.
 

 Reaching Us

Just some reminders.

To ask Dr. Mike questions write to mervet@inna.net. Please mention that you are a subcriber somewhere in the subject line or the first few lines of the email so that I know to put a high priority on your mail.

To see old issues of the VetInfo Digest check at http://www.tiercom.com/subscriber.

To reach us by phone dial 804-725-5051. That phone number is often call forwarded to the private line into my office, so we might answer the phone with a simple "Hello". Don’t let it surprise you!

Lastly, when email doesn’t seem to be working and phoning us isn’t your style, feel free to write to us at TierCom, Inc., P.O. Box 476, Cobbs Creek, VA 23035. I just read an article that said that people hated to send mail to post office boxes but in our rural county a post office box or an even stranger "hand carried route" address is all we have. There are no street numbers!

Please remember to let us know if your email or physical address changes. We have lost communication with a couple of subscribers and we would really like to honor our committment to deliver the VetInfo Digest.

As always, we truly appreciate your support of the VetInfo Digest and the VetInfo Website. We had over 1 million hits in July so you are helping us reach a great number of people.

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  06/17/04

 Subscriber homepage |Backissues  | Breed index | digestindex |

Vetinfo | vetinfo4cats| vetinfo4dogs 
| Canine  Encyclopedia |
  Feline Encyclopedia| VetInfo Digest |Links |Zoonotic info

Please do not send anything in attachment form. We will not be able to open it due to security risks. 

This page is authored by
Dr Michael Richards, DVM
and produced by TierCom, Inc.
Opinions expressed are those of  Dr. Richards.
Designed and edited by Michal Justis
copyright ©1996,1997,1998,1999,2000,2001,2002,2003,2004- TierCom, Inc