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Asthma in Pets

  • Asthma is an inflammatory disease affecting the smooth muscle of the bronchi of cats, and rarely dogs. The inflammation causes reversible airflow obstruction through smooth muscle constriction, bronchial wall fluid buildup (edema), and thickening of the mucous glands of the airways. This inflammation, occurring as a result of a reaction (allergy) to environmental allergens (foreign proteins), causes coughing and/or wheezing. Secondary infection (pneumonia) is reported to occur in 24 to 42 percent of cats with asthma. Because feline heartworm disease can cause signs that mimic asthma, all cats with respiratory signs should be screened for feline heartworm disease. As much as possible, owners should try to minimize environmental factors (such as cigarette smoke, dust, hair spray, and perfume) that can trigger an asthmatic attack.

    Principal Natural Treatments
    The main natural treatments are designed to reduce wheezing and inflammation in pets with asthma.

    Omega-3 Fatty Acids
    Omega-3 - eicosapentaenoic acid (EPA) - and docosahexaenoic acid (DHA) - are derived from fish oils of coldwater fish (salmon, trout, or most commonly menhaden fish) and flaxseed. Omega -6 fatty acids - linoleic acid (LA) and gamma-linolenic acid (GLA) - are derived from the oils of seeds such as evening primrose, black currant, and borage. Often, fatty acids are added to the diet with other supplements to attain an additive effect.

    Just how do the fatty acids work to help in controlling inflammation in pets? Cell membranes contain phospholipids. When membrane injury occurs, an enzyme acts on the phospholipids in the cell membranes to produce fatty acids, including arachidonic acid (an omega-6) and eicosapentaenoic acid (omega-3). Further metabolism of the arachidonic acid and eicosapentaenoic acid by additional enzymes yields the production of chemicals called eicosanoids. They're produced by metabolism of arachidonic acid and are pro-inflammatory and cause inflammation, suppress the immune system, and cause platelets to aggregate and clot; the eicosanoids produced by metabolism of eicosapentaenoic acid are non-inflammatory, not immunosuppressive, and help inhibit platelets from clotting. There is some overlap and the actual biochemical pathway is a bit more complicated than I have suggested here. For example, one of the by-products of omega-6 metabolism is Prostaglandin E1, which is anti-inflammatory. This is one reason why some research has shown that using certain omega-6 fatty acids can also act to limit inflammation.

    Supplementation of the diet with omega-3 fatty acids works in this biochemical reaction. By providing extra amounts of these non-inflammatory compounds, we try to overwhelm the body with the production of non-inflammatory eicosanoids. Therefore, since the same enzymes metabolize both omega-3 and omega-6 fatty acids, and since metabolism of the omega-6 tends to cause inflammation, with the exception of Prostaglandin E1, by metabolism of omega-6 as mentioned, by suppling a large amount of omega-3, we favor the production of non-inflammatory chemicals.

    Many disorders, including asthma, are due to overproduction of the eicosanoids responsible for producing inflammation. Fatty acid supplementation can be beneficial in inflammatory disorders by regulating the eicosanoid production.

    In general, the products of omega-3 (specifically EPA) and one omega-6 (DGLA) are less inflammatory than the products of arachidonic acid (another omega-6). By changing dietary fatty acid consumption, we can change eicosanoid production right at the cellular level and try to decrease inflammation within the body. By providing the proper fatty acids, we can use fatty acids as an anti-inflammatory substance.

    However, since the products of omega-6 fatty acid metabolism are not the sole cause of the inflammation, fatty acid therapy is rarely effective as the sole therapy but is used as an adjunct therapy to achieve an additive effect.

    Note: Flaxseed oil is a popular source of alpha-linoleic acid and omega-3 that is ultimately converted to EPA and DHA. However, many species of pets (probably including dogs) and some people cannot convert ALA to these other more active non-inflammatory omega-3s. In one study in people, flaxseed oil was ineffective in reducing symptoms or raising levels of EPA and DHA. While flaxseed oil has been suggested as a less smelly substitute for fish oil, there is no evidence it is effective when used for the same therapeutic purposes as fish oil. Therefore, supplementation with EPA and DHA is important and this is the reason flaxseed oil is not recommended as the sole fatty acid supplement for pets. Flaxseed oil can be used to provide ALA and as a coat conditioner.

    Omega-3 fatty acids have been recommended for the treatment of asthma in pets as this is often a result of inflammation in the airways. While many doctors use fatty acids for a variety of medical problems, there is considerable debate about fatty acids. The debate concerns several areas:

    Dosages - What is the best dose to use in the treatment of pets? Most doctors use anywhere from two to ten times the label dose. Research in the treatment of allergies indicates the label dose is ineffective; the same theory probably holds true for treating asthma, but research is lacking. In people, the dosage that showed effectiveness in many studies was 1.4 to 2.8 gm of GLA per day, which is hard for people to obtain from the supplements currently available. If this were shown to be the correct dosage for pets, a 50-pound dog would need to take 10 or more fatty acid capsules per day to obtain a similar dosage, depending upon which supplement was used. Therefore, while the studies with omega-3s show many potential health benefits, it is almost impossible to administer the large number of capsules needed to approximate the same dosage used in these studies. The best that owners can hope for is to work with their vets and try to increase as best as possible, the amount of omega-3 fatty acids in the diet.

    Which fatty acid - What is the "correct" fatty acid to use? Should we use just omega-3 or combine them with omega-6 acids? Is there an "ideal" ratio of omega-6 to omega-3 fatty acids? Through research on pets with atopic dermatitis, the ideal dietary ratio seems to be 5:1 of omega-6: omega-3 fatty acids, although this is debated. Whether or not this "ideal" dietary ratio is ideal for the treatment of asthma and other inflammatory conditions remains to be seen.

    Fatty acid supplementation - Is supplementation with fatty acid capsules or liquids the best approach, or is dietary manipulation preferred for the treatment of inflammatory conditions? There are, in fact, diets constructed with this "ideal" ratio of fatty acids. For owners who do not like giving their pets medication, or for those pets who don't take the supplements easily, it might be wise to try some of these medically formulated diets, which are available from your pet's doctor.

    However, because these medicated diets may not be as natural as possible due to the inclusion of by-products and chemical preservatives, holistic pet owners may need to try other options. These diets, often prescribed as anti-inflammatory diets for pets with allergies, may be useful as a part of the therapy of asthmatic pets.

    Fish Oils
    Since fish oils can easily oxidize and become rancid, some manufacturers add vitamin E to fish oil capsules and liquid products to keep the oil from spoiling (others remove oxygen from the capsule).

    Since processed foods have increased omega-6s and decreased omega-3s, supplementing the diets of all pets with omega-3 fatty acids seems warranted and will not harm your pet.

    The bottom line is there are many questions regarding the use of fatty acid therapy. More research is needed to determine their effectiveness in treating various medical problems, as well as the proper doses needed to achieve clinical results. Until definitive answers are obtained, you will need to work with your doctors to determine the use of these supplements for your pet.

    Fish oil appears to be safe. The most common side effect seen in people and pets is a fish odor to the breath or skin.

    Because fish oil has a mild blood-thinning effect, it should not be combined with powerful blood-thinning medications, such as Coumadin (warfarin) or heparin, except on a veterinarian's advice. Fish oil does not seem to cause bleeding problems when it is taken by itself at commonly recommended dosages. Also, fish oil does not appear to raise blood sugar levels in people or pets with diabetes.

    Next month we'll conclude our look at asthma.