1. Overview The term asthma comes from human medicine and refers to chronic airway inflammation involved in a variety of cells, especially mast cells, eosinophils and T lymphocytes. In susceptible people, this inflammation can cause repeated symptom...
1. Overview
The term asthma comes from human medicine and refers to chronic airway inflammation involved in a variety of cells, especially mast cells, eosinophils and T lymphocytes. In susceptible people, this inflammation can cause repeated symptoms such as wheezing, shortness of breath, chest tightness and cough, which often occur at night or in the early morning. Such symptoms are often accompanied by widespread and variable expiratory flow rate limitations, but can be partially relieved or treated. This symptoms are also accompanied by increased airway response to various stimulators. But it should be remembered that a possible crisis of severe asthma can be life-threatening at any time. Asthma with airway contraction can be divided into spontaneous or allergic reaction types. Treatment is fundamentally based on reducing and preventing airway contraction.
The definition of cat asthma is difficult to determine. We often call chronic bronchitis, bronchial asthma or allergic bronchitis, etc., which are mostly caused by allergies and belong to the allergic reaction type. When cats are stimulated by allergens, serotonin present in platelets and mast cells will be released, causing tracheal smooth muscle to contract, and usually the symptoms will gradually worsen, eventually leading to bronchodilation and emphysema.
The main allergies that cause cats asthma are pollen, grass seeds, smoke, sprays (perfume, deodorant, hair gel, etc.), cat litter dust, dry cleaning powder or food allergies. But the difficulty is that these allergens often cannot be accurately diagnosed, and asthma symptoms will continue to occur and the frequency of attacks will become more dense. Although it can be controlled well with drugs, airway problems may accompany the cat for a lifetime.
At present, all clinical diagnostic standards for cat asthma are applied to human standards, and veterinary clinical needs to be improved one step further. In human asthma, we know the specific time of asthma attack and the lesion process of the respiratory tract. However, when cats show asthma symptoms, we cannot yet clarify the specific time of asthma onset and pathological changes in the trachea. Therefore, most of the research is based on human asthma.
2. Cause
Causes, cats, are hypersensitivity reactions to environmental allergens, and in most cases it is difficult to identify specific stimulus sources. Through clinical diagnosis and treatment records, the stimulus sources of asthma can be divided into the following categories.
1. Smoke: candles, cigarettes, fireplaces, various incense, outdoor burning
2. Perfume: perfume, air freshener, fragrance cat litter
3. Chemicals: new carpet, paint, furniture dye
4. Environmental factors: pollen, mold, humid and cold air
5. Dust: dust mites, Lingyan cat litter, bedding (especially when cleaning the house)
6. Stress: overwork, long-distance travel, stress, fear (causing shortness of breath and irregular heart rate)
7. Microorganisms: parasites, mycoplasma
8. Overweight.
These reasons may stimulate the airway and cause asthma. Sometimes it is a separate stimulus, but more often it is a mixture of multiple stimulus sources to work together. This is why it is difficult to identify stimulus sources in clinical practice.
III. Pathophysiology
1. Uncertain stimulus sources cause chronic active infection, resulting in the following results.
(1) Epithelial cells fall off and proliferate.
(2) Goblet cells hypertrophy and hyperplasia.
(3) Submucosal gland hypertrophy, hyperplasia, and excessive secretion.
(4)Edema and cell infiltration into the mucosa and submucosa.
(5)Smooth muscle hypertrophy (rare).
(6) Submucosal fibrosis (occasionally). [page]
2. Stimulate (cough) receptor excitation and produce cough, and tracheal-bronchial mucus secretion increases.
3. Airway obstruction is caused by mucus, edema and cell infiltration in the cavity and accompanied by reversible smooth muscle contraction.
4. When exhaling, especially during exercise, the airway in the chest collapses during excitement or coughing and for a period of time afterwards.
5. Cat asthma belongs to allergic reaction type (type 1) allergic reaction.
When the various stimulus sources mentioned above enter the body for the first time, they cause an immune response, that is, under the action of APC and TH cells, they stimulate IgE-producing B cells distributed in the mucosal lamina propria or local lymph nodes. The latter proliferates and differentiates and secretes IgE antibodies. IgE binds to the surface Fc receptor (FcεR) of mast cells and eosinophils, making it sensitized and the body is in a sensitized state. When the allergen enters the body again, it binds to specific IgE antibodies on the surface of mast cells and eosinophils. Mast cells and eosinophils are sensitized after binding to IgE. As long as the sensitized cells are cross-linked, the cells are activated, degranulated, and release active mediators of pharmacological effects, such as histamine, slow reactants A, serotonin, allergic toxins, leukotrienes and prostaglandins. These media can act on tracheal tissue, causing capillary dilation, increased permeability, mucosal edema, tracheal spasm, tracheal obstruction, etc.
4. Clinical symptoms
This disease has no obvious age and breed tendency, but Siamese cats are usually more susceptible and have the most serious attacks.
Sick cats may experience standard asthma symptoms, squat in a hen, stretch their necks and cling to the ground, and then have thick and cracked wheezing sounds (available throughout the lungs). Sometimes it also occurs with the symptoms of cough, mostly dry cough or phlegm, and there will be vomiting at the end of the cough. With the severity or frequency of allergens, some cats will continue to occur within a day, others will occur once a few days, and mildly or even once a few months to years.
Because of the lesions in the airway during cats during asthma, the amount of gas exhaled and inhaled by cats each time is much less than normal, and the exhalation time is significantly longer. Breathing is superficial and rapid. Some cats even open their mouths to breathe so as to get the maximum air flow. In severe cases, cyanosis will occur.
Asthma cats may also experience symptoms such as exercise intolerance, decreased appetite, and depression.. If oral corticosteroids are effective in the early stage, it is generally recommended to take medication for a long time. However, long-term use of corticosteroids will definitely have certain side effects, even if cats are highly resistant to corticosteroids. For a cat with severe asthma symptoms, taking oral medication may be difficult, so you can choose to inject long-acting steroids to control the symptoms. However, since the efficacy of injected drugs is stronger than that of oral drugs, all the side effects will be stronger than that of oral drugs. This means that injecting drugs can only be given periodically to avoid the risk of metabolic diseases such as diabetes. If a cat needs multiple injections of medication within a month, an inhaler should be considered (see below for details).
The key point of using oral corticosteroids is to find a minimum controlled dose over time. If frequent use of high doses is required, cats may become resistant to steroids. At this time, you also need to consider changing the drug or changing the method of administration.
(1) The initial dose of prednisolone is 1 mg/kg, po, bid, 10~14d;
(2) Maintenance dose 0.1~0.25 mg/kg, po, bid, bid, once every other day or the lowest effective dose to control cough;
(3) The dosage of corticosteroids should be gradually reduced within 2~3 months.
3. Other treatment options besides corticosteroids
(1) Antibiotics should be used when bacterial cultures are confirmed to have bacterial infections to avoid prophylactic or long-term antibiotic treatment.
① There is no fact that bacterial infection plays a major role in chronic bronchitis in cats.
② The bacterial culture results determine the treatment with antibiotics, and the choice of antibiotics is the same as other respiratory inflammations.
(2) Cough relieving drugs are only used when animals faint after coughing, when they are unable to sleep, or when animals are unable to sleep due to coughing, etc.
① Butorphinol 0.05~0.1mg/kg, po, sq, sid~tid.
② Hydrocodone (heavy tartrate) 0.22mg/kg, po, sid~tid.
(3) Tracheal dilation drug.
Boliconi and theophylline are ideal tracheal dilators and are often used to deal with airway stenosis in asthma. If tracheal stenosis is the main problem in sick cats, applying this medicine will be of great help. Both terbutalin and theophylline can be taken orally or injected. It is recommended that the owner of a sick cat keep some at home so that it can be used in critical situations. The doctor should tell the owner the correct way to use the medicine and teach the owner how to give the medicine.
① Boliconi 0.625mg/cat, po, bid.
②Aminophylline 4~6mg/kg, po, sid.
(4) Antihistamine drug
Histamine is an inflammatory substance released in an allergic reaction. Histamine has always been thought to be associated with the airway contraction mechanism, and antihistamine drugs are also widely used in prescriptions for cats asthma. But recent studies have shown that there is a receptor called H3 in the cat's airway, which will produce an expansion reaction when it feels histamine in place of a contraction reaction. This is also why sometimes antihistamine drugs do not produce ideal results. Basically, antihistamines are ineffective for cats asthma.
(5)Cyclosporin[page]
Cyclosporin is relatively new in the treatment of asthma. It is often used as an immune modulator in human organ transplant surgery. It is occasionally given with other drugs when inflammation cannot be controlled with a separate drug. Or when cats cannot use steroids for some reason (complex diabetes, history of calcium oxalate stones, etc.), cyclosporine can be used.
4. Inhaler treatment
Just like human asthma control, cats can also be controlled with inhaler. In order for the cat to use inhaler smoothly, special equipment is needed. Some veterinarians use asthma inhalers for children with medical masks, but the effect is not ideal. Currently, there is a cat-specific asthma inhaler (AEROKET) available for use.
The inhaled drugs are mainly steroids and tracheal dilatation drugs, and human inhaled drugs can be selected, such as Flixotide and Serevent. Inhaled drugs are limited to the respiratory system and do not have serious side effects like those taken orally or injected drugs.
Serevent is a long-acting β2 antagonist that only starts to take effect 15 to 30 minutes after inhalation, but the effect can last for more than 12 hours. This agent is not recommended for acute bronchial contraction, but when used with steroid inhaler daily, the dosage of steroids can be reduced and the symptoms of asthma can be alleviated and control the symptoms of asthma.
Flixotide is considered to be the most effective and longest-acting inhaler. Steroid inhaler is the most effective anti-inflammatory inhaler. It can help control asthma symptoms, normalize lung function, and prevent irreversible airway damage. It can produce benefits within 24 hours after inhalation, but to achieve the best control effect, it may require continuous use for 1 to 2 weeks or more; after stopping the medication, the control effect on asthma can last for several days.
8. Prognosis and monitoring
For cats with asthma, minimize air irritants. Don’t let the cats get smoke everywhere, try to use dust-free cat litter. If you need to remove insects, try not to use spray insect removal agents. Consider using an air purifier at home to keep it ventilated. Control your weight and weight loss can also slow down asthma. For food, you can choose a prescription recipe with hypoallergenicity.
Tell the owner of the cat that once the cat has abdominal breathing and mouth-opening breathing, he must seek medical treatment as soon as possible. The owner should explain to the owner that it is clear that the treatment of cat asthma is only to do everything possible to improve the quality of life of the cat, and it is impossible to completely cure it. Although the frequency of coughing decreases over time, it rarely eliminates completely. Exercise intolerance will increase, and the degree of collapse of the airway in the tracheal lumen can be seen through the bronchoscope. Obese animals can reduce weight and improve physical tolerance and oxygen partial pressure. The physical condition and medication treatment status of the animals were re-evaluated every 3-6 months. If the cough is severity or the number of times increases, exercise tolerance is reduced or the animal develops into systemic disease, the animal's status needs to be re-evaluated.
