Hyperthyroidism in cats

Hyperthyroidism in CatsVeterinary & Aquatic Services Department, Drs. Foster & Smith, Inc

Hyperthyroidism is the most common endocrine (hormone) disorder that affects cats. It creates a wide range of signs resulting from the overproduction of thyroid hormone made by the thyroid gland.

What is the thyroid gland?
The thyroid gland is a small and consists of two lobes, one on each side of the trachea (windpipe) in the neck. This gland produces the major thyroid hormone called thyroxine (T4) and a small amount of another hormone, triiodothyronine (T3). These hormones regulate the body's metabolic rate and affect every system in the body. The production of the thyroid hormones is controlled by the hormone called thyroid stimulating hormone (TSH). TSH is produced by the pituitary gland, which is found at the base of the brain.

What causes hyperthyroidism?
If the thyroid gland produces excess amounts of the thyroid hormones, the condition called hyperthyroidism results. The most common cause is benign (non-cancerous) increases in the number of cells in the thyroid gland. Groups of these abnormal cells form small nodules on the thyroid gland and are termed adenomas. Multiple adenomas may form in the same lobe, and in approximately 70% of the cases, both lobes are involved. Only 1-2% of hyperthyroid conditions in cats are caused by malignancy (cancer).

The incidence of hyperthyroidism in cats has increased remarkedly in the last 25 years. The reason for this is unknown, but probably due to multiple factors. The ingredients and types of foods fed, immunological factors, and environmental influences may be involved.

Which cats are most likely to become hyperthyroid?
Hyperthyroidism occurs most commonly in middle to old-age cats with a reported range of onset between 4 and 22 years. The median age for acquiring the disorder is just under 13 years. Only 5% of hyperthyroid cats develop the disease before 8 years of age. There does not appear to be a breed or sex predilection.

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Feline Asthma

Feline Asthma
Susan Little, DVM, DABVP (Feline)�2003

Feline asthma has been called by many other names, including chronic bronchitis, bronchial asthma, and allergic bronchitis. Regardless of the name, it is a common feline ailment. Inhaled allergens cause sudden contraction of the smooth muscles around airways, leading to typical clinical symptoms. It is usually impossible to determine which allergens cause asthma in individual cats, but common ones include grass and tree pollens, cigarette or fireplace smoke, various sprays (hair sprays, deodorants, flea sprays, deodorizers), and dust from cat litter.

Feline asthma is found in all areas of the world and in cats of all ages. The prevalence in the general adult cat population is about 1%. The most common symptoms in cats with asthma are wheezing and coughing. The coughing has been described as a dry, hacking cough that could be confused with gagging or retching. Many cats are misdiagnosed as having hairballs! Paroxysms of coughing occur frequently. In mildly affected cats, coughing and wheezing may occur only occasionally. A few cats with asthma are asymptomatic in between acute and severe bouts of airway constriction. The most severely affected cats have daily coughing and wheezing and many bouts of airway constriction, leading to open-mouth breathing and panting that can be life threatening.

The symptoms of asthma can mimic other diseases, such as heartworm, pneumonia and congestive heart failure. A diagnosis is reached by using chest x-rays, a complete blood count, a feline heartworm test, and a technique to sample cells from the lower airways (transtracheal wash, bronchial wash, or bronchoalveolar lavage). Chest x-rays may be normal in some cats with asthma, while others will have signs of bronchial inflammation, collapse of the right middle lung lobe, and over inflation of the lungs.

Unfortunately, feline asthma is a chronic progressive disease that cannot be fully cured. Medications can reduce the symptoms of asthma a great deal, but may not be able to eliminate coughing fully. In recent years, veterinarians have found that the most effective therapy for feline asthma may be to use inhalers such as human asthmatics use. A mask and spacer system, called AeroKat�, has been invented to enable cats to use inhalers or puffers. This system is similar to the mask and spacer system used to treat babies and small children.

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Feline chin acne

Feline Acne:Holly Nash, DVM, MSVeterinary Services Department, Drs. Foster & Smith, Inc.

Feline acne is a condition in which comedones (blackheads) develop on the chin of a cat.

What causes feline acne?
The exact cause of feline acne is not known, but several factors appear to be associated with its development including stress, a suppressed immune system, poor grooming habits, the presence of other diseases,
contact or atopic dermatitis, and skin conditions in which abnormal amounts of oils are produced and the hair follicles do not function properly.

What are the signs of feline acne?
Multiple comedones form on the chin and lips of the cat, and the chin may appear "dirty." The comedones can develop into small abscesses, which break open and form
crusts. In severe cases, draining tracts, hair loss, and swelling may develop on the chin. It may be itchy and cause the cat to scratch, which can lead to even more trauma to the area. Secondary bacterial infections can develop. The condition may appear only once in the life of a cat, it may come and go, or may remain for the life of the cat. In Persian cats, the condition may also affect the face and skin folds.
Feline acne occurs equally in male and female cats, and in cats of all ages and breeds.

Feline acne can be controlled, but is not really "cured." Very mild cases of feline acne in which there are no symptoms may not be treated. In other cases, antiseborrheic shampoos, such as those containing benzoyl peroxide (at a concentration of 3% or less), are used to break down the excess oils. Supplementation with fatty acids may be beneficial. Oral or topical antibiotics may be used if there is a secondary bacterial infection. Topical vitamin A (0.05% Retin-A) can often be used, but it is irritating, and needs to be applied very sparingly. Oral retinoid (Isotretinoin) therapy may be used in severe cases, but the drug is teratogenic (causes birth defects) in cats and humans, and needs to be handled very carefully. If there is a large amount of inflammation, a short course of corticosteroids, such as prednisone may be given.

It may be helpful to switch food and water dishes to a stainless steel or glass variety in the event an allergic reaction may be a contributing factor (cats can be allergic to plastics and dyes). Using a very shallow dish can also be helpful. Owners should regularly clean the chins of cats who are prone to the development of feline acne and/or have poor grooming habits.

Trimming your cats nails

Notice the pink tissue (the quick) on the inside of the claw.
Avoid the quick when you trim the claw; cutting into it will
cause pain and bleeding Remove the sharp tip below the
quick (away from the toe), clipping about halfway between
the end of the quick and the tip of claw.

Most cats are capable of' keeping their claws the proper length, either by scratching an object (preferably a scratch post rather than the leg of' your couch) or by chewing off the claw's outer layer (the usual technique for the rear claws). Only rarely (toes a cat-perhaps an old or debilitated cat, or one with extra toes-need human intervention to keep the claws from growing so long that they arc into the pad. Claw trimming 'is a matter less of length than of sharpness. The obvious advantage of keeping your cat's claws blunt is that any scratching will cause less damage.

If possible start training your cat to have her claws trimmed as a kitten. Gently stroke your cat's paws often, getting her used to having her paws held before you attempt trimming. Be sure to reward your cat with a special food treat-one that she receives only during claw trimming or some other grooming procedure-during or immediately after trimming. The best time to trim your cat's claws is when she is relaxed or sleepy. Never try to give a pedicure right after a stressful experience or an energetic round of play.

Your cat should be resting comfortably on your lap, the floor, or a table. Hold a paw in one hand and press a toe pad gently to extend the claw. Notice the pink tissue (the quick) on the inside of the claw. Avoid the quick when you trim the claw; cutting into it will cause pain and bleeding Remove the sharp tip below the quick (away from the toe), clipping about halfway between the end of the quick and the tip of claw. If your cat becomes impatient, take a break and try again later. Even if you can clip only a claw or two a day, eventually you'll complete the task. (Because cats do little damage with their rear claws and do a good job of keeping them trim themselves-by chewing them-many cat owners never clip the rear claws. Others trim their cats' rear claws three or four times a year or have them done by their veterinarian or a professional groomer.)

If you accidentally clip into the quick, don't panic. The claw may bleed for a moment, but it Will usually stop very quickly. Soothe your cat by speaking softly to tier and stroking her head. If the bleeding hasn't stopped after a minute or so, touch a styptic pencil to the claw end or pat on styptic powder to help staunch the bleeding.
How often you need to clip your cat's claws depends somewhat on how much of the tip you remove, but usually a clipping every ten to fourteen days will suffice. If' your cat absolutely refuses to allow you to clip tier claws, get help from your veterinarian or a professional groomer.

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Feline Vision

Feline Vision: A Cat�s Eye View
You and your cat see the world differently. True, your eyes are built around the same design, but each of you has specializations that make your vision best for your needs. You evolved as a fruit-eating diurnal animal; your cat evolved as a meat-eating nocturnal animal. You evolved to have good detail and color vision; your cat evolved to have good vision in the dark. Compare your eye to your cat�s eye, and you�ll understand how each of you attains the best vision for your needs.

The Pupil
Light enters through the pupil, which gets larger or smaller to let more or less light in. The cat�s pupil can get much larger than your pupil can, letting in more light, but it does so at the expense of good depth of field (the distance over which objects can be put into clear focus).
When the cat�s pupil contracts, it doesn�t stay round as a person�s does, but becomes a vertical slit. Slit pupils are seen in animals that are active in both day and night; their advantage is that they can cover a great range of sizes, getting much smaller, much faster, than can a round pupil. Their disadvantage is that when they are in their slit formation, they create optical interference that makes perfect focus difficult.

The Lens
After passing through the pupil, light is collected and focused by the lens. The cat�s lens is much larger than the human lens, which enables the lens to gather more light. But again, there�s a trade-off: while the small human lens can change shape to focus light over a great range of distances, the big cat lens can hardly change its shape at all. As a result, cats have difficulty focusing on objects very close to them, very much like an older person who needs reading glasses.

The Retina
The optics of the eye work to focus an image on the retina, the lining at the back of the eye which is made up of cells that react to light. Several factors influence how fine the detail is that a retina can pick up. First, how well is the image focused upon the retina? If the lens is too strong for the distance between it and retina, the image will come to a focus before it gets to the retina and will be defocused by the time it reaches it. If the lens is too weak for the distance to the retina, the image will still be unfocussed when it reaches it. In most cats, the lens strength is appropriate for the distance to the retina; that is, cats are neither nearsighted nor farsighted.
Second, the farther the distance to the retina, and the larger the retina, the larger the image can be on the retina. Cats have large eyes and retinas for their size.

Third, the smaller the sampling grain on the retina, the better the ability to detect details. Both cats and people have two different types of receptors in their retinas, each with a different sampling grain. Rods pool light from comparatively large areas on the retina, while cones have a very fine sampling grain. Humans have a cone-rich retina, and even have an area in the center of the visual field made up of only cones. Cats have a rod-rich retina, and no cone-only area.

Cones and Color Vision
The end result is that cats have poor detail vision compared to humans. And because cones are also responsible for color vision, cats have comparatively poor color vision. But they�re not colorblind. Instead, they have the same type of color vision as many people who are called colorblind: a type of red-green colorblindness termed deuteranopia. They can see blue versus other color fine, but tend to confuse colors on the red through brown through green continuum

Night Vision
Cats give up the ability to see fine detail and rich colors in exchange for the ability to see in the dark. The level of retina illumination is about five times higher in your cat�s eye than in yours. And all those rods pooling signals from minute amounts of light allow the cat to pick up the faintest light source. Nonetheless, some light still manages to pass between the rods and cones. Instead of letting it be absorbed at the back of the eye, as the human eye does, the cat has a structure called the tapetum lucidum that reflects light back to the receptors for a second chance to create a signal. The eye shine you see when you shine a light at a cat in the dark is the reflected light that has managed to elude the receptors in both directions and is bouncing back to you from the tapetum. The end result is that cats can see light at eight times dimmer

illumination than you can!
In summary, the cat�s eye is specialized to see in dim and changing light. To achieve this it sacrifices the ability to focus close up, detail vision, and some color vision. It is the vision of a hunter active in both day and night, enabling it to detect movement under any lighting conditions, to use binocular vision to gauge distance, and to aim correctly to catch prey.

*Article by Dr Christianne Schelling