What is pneumonia?
In general terms, the respiratory system is divided into two parts. The upper respiratory tract consists of the nose, nasal sinuses, throat and trachea bronchi, bronchioles and lungs. Strictly speaking, pneumonia is an inflammation of the lungs or lower respiratory tract. In general terms, inflammation is the response of tissues or cells to injury, irritation, or infection.
Causes
In the dog, most cases of pneumonia are caused by a bacterial infection. The most common bacteria that cause pneumonia in the dog are Bordetella bronchiseptica, Streptococcus zooepidemicus, Pasteurella multocida, Pseudomonas aeruginosa, Klebsiella pneumoniae, E. coli and Mycoplasma species. Bordetella bronchiseptica is highly contagious and may spread easily to other dogs. It usually causes 'kennel cough', an infection of the trachea and bronchi, but can spread deeper into the lungs, especially in young or old dogs, or dogs with immune system compromise. Most other causes of bacterial pneumonia are not particularly contagious to other dogs. Sometimes, dogs develop bacterial pneumonia as a secondary infection.
Other most common cause of pneumonia is a viral infection of the lower respiratory tract. Canine distemper virus, adenovirus types 1 and 2, canine influenza virus, and parainfluenza virus cause damage to the airways and make the animal susceptible to the development of pneumonia.
Parasitic invasion of the bronchi can also result in pneumonia. Tuberculous pneumonia, although uncommon, is sometimes seen in dogs. Fungal pneumonia is also seen in dogs. Injury to the mucous membranes of the bronchial tubes and inhalation of irritants may cause pneumonia directly, as well as making the animal susceptible to bacterial infection.
Some risk factors include conditions that cause difficulty swallowing or problems with regurgitation such as laryngeal paralysis, megaesophagus, cleft palate, chronic vomiting, altered states of consciousness, and tumors of the respiratory system. Dogs with an immune system disease or that are on immunosuppressive drugs are at an increased risk of bacterial pneumonia, as are dogs with severe metabolic disorders such as kidney failure, uncontrolled diabetes mellitus, Cushing's disease or Addison's disease.
Symptoms
Dogs that have bacterial pneumonia usually have a high fever, have difficulty breathing, have decreased exercise tolerance (tire easily), are lethargic, and have a cough. Other symptoms that may be present include a nasal discharge, loud breathing, rapid breathing, weight loss, anorexia and dehydration.
Diagnosis
Your veterinarian will suspect bacterial pneumonia based on the presence of the symptoms listed above, combined with the results of a physical examination, especially if abnormal lung sounds are heard when listening to the chest with a stethoscope.
A series of tests may be required to confirm the diagnosis and to exclude other diseases that could be causing the symptoms, including: blood test for heart worm disease, chest x rays for changes in the lungs, and may be helpful to eliminate other types of heart or lung disease.
Treatment
"The appropriate antibiotic treatment is determined by the results of the culture and sensitivity tests." Since the results of culture and sensitivity testing will not be available immediately, your veterinarian may begin treatment with a broad spectrum antibiotic while awaiting the test results. It may be necessary to hospitalization for oxygen therapy and/or intravenous fluids and medications may be necessary.
If the dog is stable enough to be treated as an outpatient, your veterinarian may also prescribe oral drugs for a prolonged period of time, depending on the specific type of infection and the seriousness of the condition.
Home care
Animals with pneumonia benefit from a warm, dry environment. Your veterinarian may also recommend several daily sessions of brief exercise to help loosen secretions and promote coughing out of inflammatory debris. Another helpful home treatment is to place the dog in a closed bathroom with a warm shower running for about 15 minutes up to 3 times per day. This increase in humidity has the effect of thinning out the mucus in the airways so that it is coughed up more readily. Apart from these short sessions, your dog's activity should be restricted.
Prediction
The prognosis depends on the severity of disease and whether there are any predisposing factors. The prognosis is generally good for uncomplicated bacterial pneumonia. The prognosis for animals with predisposing factors depends on whether the risk factor can be treated or resolved. If the risk factors cannot be resolved, recurrent infections may occur.
Pneumonia from Inhalation of Foreign Matter in Dogs
Aspiration pneumonia is a condition in which a dog's lungs become inflamed due to the inhalation of foreign matter, from vomiting, or from the regurgitation of gastric acid contents. Aspiration pneumonia can also be a direct result of a neuromuscular disorder, which would cause difficulty with swallowing, as well as problems associated with the esophagus, with possible paralysis of the esophagus improperly administered medications, forced feeding.
(The writer is a Veterinary Surgeon and holds B.V.Sc; M.Sc Poultry Science; Master of Public Administration and Management)
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