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7 posts from September 2009

09/28/2009

HyperKitty : Overview of Feline Hyperthyroidism

Feline hyperthyroidism is the most common endocrine (hormonal) disorder of cats. It occurs most frequently in middle-aged and elderly cats. Cats fed fish-flavored canned cat food (particularly salmon) or liver and giblets-flavored canned cat food are at increased risk of developing this condition. Siamese and Himalayan cats are at decreased risk of hyperthyroidism compared to other breeds of cats.

Cats have two thyroid glands located in the neck. Feline hyperthyroidism is caused by the development of a growth on one or both thyroid glands. Most commonly, the growth is of a benign type called an adenoma; more rarely, a malignant tumor of the thyroid gland can occur. Affected glands produce an excess of thyroid hormones, which cause the heart to beat more rapidly and can result in heart damage and failure. Hypertension (high blood pressure) often develops. Hyperthyroidism can adversely affect the kidneys, and may cause elevated liver enzyme levels.

            Weight loss is the most common sign of feline hyperthyroidism. Increased appetite is frequently noted, and increased thirst may also be seen. Owners may feel the cat’s heart beating more rapidly. Affected cats may become restless or irritable. Diarrhea or vomiting can occur, but should raise suspicion that the cat may have gastrointestinal disease, such as inflammatory bowel disease or intestinal lymphoma.

            Veterinarians diagnose feline hyperthyroidism through blood tests and palpation of an enlarged thyroid gland. The most reliable test is measurement of a thyroid hormone called the total T4. Cats who have additional illness may have decreased levels of thyroid hormones, and this can make the diagnosis of hyperthyroidism more difficult. In this situation, it is most important to diagnose the disease which is depressing the thyroid hormone level. In cases where feline hyperthyroidism is suspected but total T4 levels are normal, a test called a free T4 level is often performed, but this test is unreliable since falsely elevated values may occur with non-thyroidal illnesses. Intestinal diseases may cause similar symptoms to hyperthyroidism, and should be suspected in cats who are losing weight and do not have elevated total T4 thyroid hormone levels.

            If a cat has a normal or low total T4 level, even if the free T4 level is elevated, it is essential to rule out intestinal disease as the cause of the cat’s symptoms. A good initial step is an abdominal ultrasound, which may show thickened intestines or enlarged intestinal lymph nodes. However, ultrasound findings can be perfectly normal in cats with even advanced intestinal disease. If a cat is losing weight and full blood work and ultrasound do not reveal a definitive cause, intestinal biopsies, such as via endoscopy, should be considered. This is particularly true if the cat does not have other signs of hyperthyroidism, such as an elevated heart rate and/or a palpably enlarged thyroid gland.

            Feline hyperthyroidism can be treated with medication, radioactive iodine therapy, or surgery. The most commonly used medication is called methimazole (Tapazole®). Use of this drug requires close monitoring of the cat’s kidney function, blood cell counts, and liver enzymes, because serious side effects can occur. Medication does not cure the disease but will decrease the hormone levels. Because the thyroid growth will continue to enlarge, the dose of medication often needs to be periodically increased. Research has shown that methimazole is more effective with fewer side effects if the dose is divided into twice-daily dosing. For example, for a cat receiving 5 mg a day, it is safer and more effective to give 2.5 mg twice a day.

            Radioactive iodine therapy (RAI) involves an injection of a radioactive isotope. Iodine is used because it is taken up by the thyroid gland. Research has shown that hyperthyroid cats receiving this treatment after initial regulation with medication have the longest lifespans. Since treatment of hyperthyroidism may affect kidney function, it is recommended that cats are treated with medication before receiving RAI, to ensure that kidney function will remain adequate when thyroid hormone levels normalize. It is also essential to closely monitor kidney values after RAI treatment.

Laws vary a bit from state to state, but it is required that cats receiving RAI are boarded in special facilities after the injection until it is deemed safe for them to be in close contact with their owners. Generally, cats thrive in these facilities, since most are designed for maximum feline comfort.

            Surgery to remove one or both thyroid glands may be performed. As with RAI, cats should first be treated with medication if possible to ensure that kidney function will remain adequate. Additionally, normalization of thyroid hormone levels before surgery with medication will decrease the risk of anesthetic complications, since elevated thyroid hormone levels can increase the risk of heart arrhythmias. Because the parathyroid glands, which control blood calcium levels, are located in close proximity to the thyroid glands, cats who have both thyroid glands removed may experience a dangerous drop in blood calcium levels. For this reason it is not generally recommended to remove both thyroid glands simultaneously; rather only the gland which is visibly enlarged is removed.

            It is essential to measure blood pressure both before and after treatment of hyperthyroidism. Hyperthyroidism can cause hypertension; additionally, research has shown that many cats with initially normal blood pressure will develop hypertension in the months following treatment.

            In cats who have severe reactions to methimazole, but who cannot be treated with RAI or surgery, perhaps due to the owner’s financial restrictions, a drug called atenolol can be used to control heart rate and blood pressure, and to improve the cat’s mood. This drug will not slow weight loss, however.

            Cats with feline hyperthyroidism who are promptly diagnosed and treated have a good prognosis. Prognosis is best in cats who receive treatment with medication followed by radioactive iodine therapy.        

09/26/2009

What is feline leukemia anyway? Does my cat need the vaccine?

Many cat lovers are aware of feline leukemia, but aren't exactly sure what it is. They know it's bad, but is it an infection, or cancer, or...?

Here's the story. There is a virus called the feline leukemia virus, often abbreviated FeLV. It's in the same family of viruses as the human HIV virus, and the feline FIV virus. They are all in the family called retroviruses.

It's confusing to folks because leukemia is a kind of cancer (cancer of the bone marrow), so when we say a cat has feline leukemia, it seems like the cat has cancer. Really it's more correct to say that a cat is "feline leukemia virus positive" which, like a person being HIV positive, means the cat is infected with the virus. The reason the virus is confusingly called the feline leukemia virus is because it can cause cancer in cats, particularly lymphoma. In fact, it is thought that lymphoma in even feline leukemia negative cats can be caused by prior exposure to the virus, and the virus has been found in feline tumors. So maybe they should have called it the feline lymphoma virus.

If possible, cats who are positive for feline leukemia on the kind of test called an ELISA should then be tested with another test called an IFA. ELISA tests can have false positives, or can be positive in cats who are infected but are going to fight off the infection. If the IFA test is positive, it means the cat is permanently infected.

The feline leukemia virus is more severe than FIV. It causes serious health issues more quickly and is more infectious. FeLV positive cats often develop anemia, infections, cancer, and other problems. The best living situation to keep an FeLV postive cat alive and healthy as long as possible is for the cat to be an only cat who is kept indoors. Unfortunately, it's hard to find homes for FeLV positive cats, much less homes where they are the only cat and never go outside. I had a friend who had a cat who was both FeLV and FIV positive; she kept him inside and he was her only cat, and he lived for many happy years before eventually developing lymphoma.

It's important to realize that while FeLV is more infectious than FIV (which is mainly transmitted by bites during fighting in unneutered males), FeLV is only transmitted by close contact such as grooming, licking, or sharing food or water. It won't be brought in on the owner's shoes or clothing, for example, or on the air, and it doesn't live a long time in the environment or on surfaces. By contrast, the panleukopenia virus (feline distemper) lives a very long time in the environment, up to a year or more, and can easily be transmitted through contaminated objects; there doesn't have to be contact between the cats themselves.

Because actual contact between cats is required for transmission of the feline leukemia virus, there is little point to vaccinating an indoor cat who never meets new untested cats. If you have a completely indoor cat who is negative for the feline leukemia virus, she just can't get it (unless you bring a strange cat home without testing him first). So this vaccine only needs to be given to cats who go outside or who will be exposed to untested cats. You should also be aware that the vaccine is not 100% protective - a vaccinated cat can still get the virus. The only way to really protect your cat from FeLV and FIV is to keep her inside.

The American Association of Feline Practitioners does recommend that vets vaccinate all kittens against feline leukemia; they are concerned that it is hard to predict what a kitten's lifestyle will be throughout his entire life. They're worried about a scenario where the vet doesn't vaccinate the kitten against feline leukemia because the kitten is being kept indoors, and then the owner gives him away to someone else who lets him go outside. From your perspective as a cat owner, you need to understand that indoor cats don't need the vaccine but if your cat's lifestyle changes at some point the vaccine may become necessary.

Unfortunately, the feline leukemia vaccine is one of those that has been associated with the development of tumors at the vaccine site. The new transdermal vaccine has been formulated to combat this problem. The other vaccine that is implicated in tumor development in cats is the rabies vaccine; the newer Purevax vaccine does not contain the ingredients that are thought to cause these tumors. It is also thought that long-acting steroid injections may cause tumors at the injection site in cats; another reason to avoid long-acting steroids when possible.

The most current thinking on vaccination of pets is that protocols should be tailored to the indiviual pet's situation. All pets should receive the core vaccines for diseases that are highly infectious and devastating, such as panleukopenia, and the other vaccines should be chosen based on the particular animal's risk factors. Pets should not routinely be given every vaccine on the market whether they need it or not; I am happy to see this happening less and less. Before your cat receives a feline leukemia vaccination, discuss with your vet whether it is necessary based on your cat's living situation.

Here is some information about the feline leukemia virus and FIV that you may find helpful.

09/21/2009

Resources for Pet Parents

Hey pet people, thought today I would share 10 of my favorite pet resources with everyone - spread the word:

1. For cats with asthma, excellent information and advice: www.fritzthebrave.com

2. To order or read about the mask to give kitties with asthma inhaled medications: www.aerokat.com

3. Great litterbox to collect urine for testing in diabetic kitties: www.smartcatbox.com

4. Fun and informative website to read about parasites and infectious diseases of pets: www.wormsandgermsblog.com

5. Where to get free or low-cost spay/neuter: www.aspca.org/pet-care/spayneuter

6. Website to find a veterinary specialist in cardiology, oncology, internal medicine, or neurology in your area: www.acvim.org

7. Help with making balanced homemade diets for pets and great nutrition info for dogs and cats: www.petdiets.com

8. To get free (!) pet behavior help: www.aspcabehavior.org

9. To learn about feline nutrition: www.catinfo.org/zorans_article.pdf

10. To find an AAHA-accredited veterinary hospital near you: HealthyPet.com

Hope you all find this info helpful! Here's to a healthy week for all animals!

09/17/2009

Pit Bull Owners: Beware of Babesia!

We need to talk about a mean little parasite called Babesia. It infects dogs' red blood cells and can cause severe anemia (decreased red blood cells) and other problems too. It has become a big problem for dogs in the US, especially American Pit Bull Terriers and American Staffordshire Terriers. Although this disease can be transmitted by ticks and other insects, it's thought that in these breeds in the US it is probably being spread when dogs bite each other, even during play or a brief disagreement. It may also be spread when dogs' tails and ears are docked.  It is likely also transmitted straight from the mom to her puppies so your dog could have Babesia even if he's never been bitten by another dog. Other dog breeds can also be infected if a dog with Babesia bites them.

It's important for Pit Bull and Staffie owners to know about Babesia because sometimes when dogs become anemic from Babesia, it is misdiagnosed as something else. Frequently it is confused with a disease called Immune Mediated Hemolytic Anemia (IMHA), which is a condition where the dog's own immune system attacks the red blood cells. If a dog with Babesia is treated with the medicines used for IMHA, which are drugs that suppress the immune system, it will make the Babesia worse. Some dogs with Babesia have vague symptoms; bottom line is that pit bulls who are anemic or mysteriously ill may need to be tested for this parasite. It's important to test for the type of Babesia that usually infects pit bulls, which is called Babesia "gibsoni" (other breeds are more commonly infected with Babesia "canis").

There are different ways to test for Babesia. Your vet can send what's called a "titer", or another test called a "PCR". The PCR is the best test, but it takes a few weeks to come back, so your vet should send both at the same time. Even if one test is negative, the other can be positive. I send my Babesia tests to to the veterinary laboratory at North Carolina State University, which I think is the best lab for this. They are very experienced with this disease, and know everything about it. There are several different kinds of Babesia and if you use a lab that doesn't do the right test for your dog, the result can be wrong. Many dogs have had "false negative" test results because they were tested for the wrong type of Babesia or with the wrong blood test instead of the PCR test. The lab at NC state tests for all the different kinds of Babesia, and they can do the PCR as long as your vet asks for it.

The best treatment for Babesia gibsoni seems to be an expensive drug called Mepron. Its other name is Atovaquone. The dogs are given Zithromax (azithromycin) at the same time. Mepron is available in the US but can be hard to find so in the meantime your vet may temporarily treat your dog with a drug called Imizol, or Imidocarb.

The bottom line: If your Pit Bull ever gets sick, make sure your vet keeps Babesia in mind!

09/11/2009

Advice For Lumpy Bumpy Dogs

Any dog parent knows: dogs love to get little lumps and bumps on their skin, especially as they reach middle age and beyond. Some older dogs are just covered with them.

Should you worry about those annoying and sometimes unsightly lumps? Some dogs seem to get a new one every month - do you need to bother going to the vet every time?

Unfortunately, yes. Dogs get plenty of benign skin lumps, such as sebaceous cysts (those greasy ones with the yucky tan toothpaste-looking stuff inside them) and lipomas (benign fatty growths). But unfortunately, skin bumps can also be malignant, and it's important to get these examined and properly removed as soon as possible.

When you go to the vet, the doctor will examine the lump and then hopefully do a simple procedure called a "fine needle aspirate", in which a small needle is inserted into the lump to draw out a cell sample. It is very important to perform this type of aspirate in order to determine which type of lump your dog has.

Once some cells have been drawn out of the lump, which takes about 30 seconds, the sample is spread on a slide. Sometimes the vet can tell right away just by looking at the material on the slide what kind of lump it is. For example, if a chunk of that yucky brown paste squirts out onto the slide, your vet may be able to say that the lump is a benign sebaceous cyst. If the sample is just perfectly clear grease, your vet may feel comfortable stating that the lump is a lipoma.

Otherwise, your vet will want to send the slide off to the lab for a veterinary pathologist to examine. The cost for this is well worth it, and may save your dog's life.

One example of a malignant skin mass is called a "mast cell tumor"; a tumor made up of the type of cells that contain and release histamine. Mast cell tumors can be any size or shape and can look like anything. I wish I had a dollar for every mast cell tumor that looked and felt so exactly like a lipoma that I almost felt silly doing the aspirate...and then was darn glad I had!

It is super important to aspirate skin bumps and find out what they are BEFORE removing them. If a skin tumor is malignant, the surgical procedure is very different than it would be for a benign lump. For example, if the surgeon is removing a benign sebaceous adenoma because it is rupturing or getting infected, he or she just needs to remove the lump itself. However, if it's a mast cell tumor or another malignancy, it is very important to get very wide and deep margins around the tumor in order to help prevent future recurrence or metastasis. Veterinary research studies have shown exactly how many centimeters of tissue must be removed around and below a mast cell tumor in order to improve the dog's chance of survival, and the surgeon needs to know this is required. You would never make such a large, deep incision for a benign lump, so you need to know beforehand what you are dealing with.

Additionally, most general vets are comfortable removing small, benign skin lumps, but if your pet has a malignant skin mass, your vet will probably refer you to a veterinary surgical specialist for the procedure, since surgeons are trained in the most effective and safest removal of tumors. It can be very tricky to get proper margins, especially in certain areas of the body, and surgical specialists are of course skilled in the best ways to accomplish this.

Take home messages:

1. Have your dog's skin lumps examined by the vet.

2. Skin lumps should be aspirated to find out what they are, BEFORE they are removed.

3. For malignant lumps or lumps that are large or in tricky areas, referral to a surgical specialist is recommended.

09/10/2009

Gotta cat? Getta screen!

The weather is gorgeous now, right? Unfortunately, beautiful weather means you don't need A/C or heating in your home. Wait - did she say "unfortunately"?? Yep, that's right, I did - because when folks don't need heat or A/C, they just open the windows. And in some cities that don't have a lot of bugs, many of the apartments don't have screens.

Guess what happens next. Beautiful day, open window, no screen, happy kitty sitting in the window watchin' the pigeons strutting about on the windowsill next door...kitty leans out to take a closer look...oh, if I could just get a little closer I could get that darn juicy pigeon...uh oh - sad kitty with broken legs and punctured lungs on the sidewalk 6 stories down.

It's called feline high-rise syndrome, and it happens all the time. Cats fall or jump (yes, jump- their kitty brains don't know they are 10 stories up!) and are horribly injured or killed. We have two to three cases a week at our hospital in nice weather and some even when the weather's bad. These cats have multiple fractured bones, bruised or punctured lungs, shattered jaws. Some don't make it.

Please please please. If you have a cat, get screens! You can buy adjustable screens at any hardware store for a couple of bucks.

Here I am demonstrating an adjustable screen on the news last night, with a cute kitten in my lap to boot!

No, cats do NOT have good instincts, people! Their instinct tells them to eat a piece of ribbon...that gets caught in their intestines. Their instinct tells them to cross the road chasing after that squirrel...and get killed by a car. Their instinct tells them to jump out a window 40 stories high when a bird flies by...and plummet to the sidewalk below.

Cats are gorgeous. They are excellent snugglers, and even better nappers. They are incredible athletes. But they are NOT good at protecting themselves (hello: "curiosity killed the cat")  - so we've gotta take care of that part!

09/02/2009

I'm not a carnivore but my cats are...

I was just reading a blog where the topic of vegetarian cats was being discussed. There was some misinformation that reminded me about the importance of understanding how unique feline physiology is.

Dogs and humans are omnivores; we are very nutritionally flexible and can adjust to a variety of diets. Cats are different! Their nutritional requirements are very strict and unforgiving. If you vary from what a cat's body needs, you can get in trouble rather quickly and cause severe effects on the cat's health and well being. Most people now know about taurine, an amino acid found in meat that dogs and humans can manufacture in their bodies but cats need to eat (they can't make it). But I think an even more striking example is vitamin A. This vitamin occurs naturally only in animal tissue. Humans can either eat vitamin A, or they can eat beta-carotene in veggies and then convert it to vitamin A. Cats? Nope, you got it - they can't convert beta carotene to vitamin A; they have to eat it in animal products.

There are lots of similar examples regarding feline nutritional needs, which are summed up beautifully in this article. If you have a cat, you should read it! It also talks about the risks of feeding cats carbs (i.e. dry food) and has tons of pretty fascinating info.

Look, if you love cats, you gotta love everything about them - including their inescapably carnivorous physiology. Sure, I wince every time I open a can of cat food, or cook my cat his (balanced!) homemade organic chicken diet. But if you wanna live with cats, you need to face that fact that you're living with a predator. Granted, a predator who loves to cuddle and is scared of strange noises and cries like a baby when he doesn't get enough attention...but inside that cute little body lies the metabolism of a tiger.

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