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Chronic Bronchitis This term covers a group of conditions that all present with persistent coughing in the absence of other pulmonary disease. Small breeds in late middle or old age, often carrying excessive weight are predisposed to this condition. To qualify for this diagnosis an animal must have been coughing for a period of 2 months within the previous year. The precise cause is unknown, as in man it is thought that chronic exposure to inhaled allergens (environmental pollutants and smoke) may play a part. Bacterial pathogens such as Bordetella spp are often isolated but their significance is poorly understood. The prolonged course eventually results in irreversible changes to the airway wall with an increased mucus production and fibrosis of the mucosal lining. The clinical signs vary from mild intractable coughing to severe respiratory difficulty, exercise intolerance and substantial production of mucus when coughing. Also apparent may be changes such as increased rate of respiration, wheezing or crackling when breathing and weight loss in some severely affected individuals. Most animals are however bright and alert with a healthy appetite and no fever. Sequels to this condition may include some right sided heart enlargement or slight liver enlargement due to a raised pulmonary blood pressure. Periods of acute flare ups can occur if secondary infection with organisms such as Bordetella, Pseudomonas, and Pasteurella develops. Thorough investigation of this condition is required as it is often complicated by concurrent conditions such as tracheitis, tracheal collapse, heart failure, and bronchopneumonia. It is important to identify the primary problem in order to prescribe appropriate treatment. The changes that can be seen on x-ray include thickening of the bronchial passages and indications of cellular infiltration and fibrosis in the peribronchial region. If evidence of heart disease is present then an ECG or ultrasound heart scan is useful to assess its significance. Blood tests can help identify allergic lung disease or pneumonia, most purely bronchitic animals have no changes on their haematology profiles. Bronchoscopy can show a narrowing of the bronchi and inflammation of the lining mucosa. This condition is not curable, by the time the disease develops and is diagnosed irreversible change has occurred in the lung passages, however it is usually possible to control the problem with palliative treatment and management changes. No single drug is always effective in all animals, treatment needs to be tailored for each individual. It is important to eliminate such factors as smoke, environmental pollutants, dust and excessive exercise. Antibiotics play a role in controlling secondary infection, courses of sulphonamides, tetracycline's, or amoxycillin-clavulanate should be continued for 14 days. Bronchodilators such as theophylline or etamiphylline can be used to relieve constriction of the lung passages, the response to these agents can only be determined by trial treatment. The physical condition of the animal is of importance since obesity compromises respiratory function and weight loss will ease respiratory effort. Mucus build up in the lungs also hinders air flow, the viscosity of the mucus (and therefore the ease with which it is cleared) depends on its water content. It is easy to increase the water content by simple methods such as air humidification (in a steamy bathroom). Chest physiotherapy (percussion of the chest with the palm of the hand) also helps to shift mucus. If the animal is producing mucus when coughing then cough suppressants should not be used. |
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