When it does occur, pneumonia can be devastating. Most animals struggle with;
- Inflammation of the airways
- Inefficient oxygen exchange
- Compromised lung tissue
- Excess mucus production
What are the causes of pneumonia?
Pneumonia is usually associated with a predisposing condition, especially when that condition compromises the immune system. Some of the more common triggers include;
- Bacteria - this is most often found in young dogs and in dogs that have spent time in kennels or rehoming shelters. Bordetella bronchiseptica., Pasteurella and Streptococci are frequently isolated.
- Viruses - viral pneumonia is generally associated with the canine distemper virus and should always be considered in poorly vaccinated dogs. Other viruses linked to pneumonia include parainfluenza and adenovirus (canine hepatitis CAV-1).
- Aspiration – foods, vomit and saliva can all be inadvertently inhaled, resulting in a secondary bacterial pneumonia. A mixed population of bacteria with an anaerobic bias is common. Aspiration pneumonia is typically characterised by a distribution to the most dependent lung lobe - the right middle lobe.
- Inhaled foreign bodies – food material can trigger a foreign body reaction in the lung tissue causing significant inflammation and oedema. A secondary bacterial pneumonia will ensue.
- Allergens – common triggers include cigarette smoke, pollen, mold, aerosol sprays and dust mites .
- Lungworms – we all need to be aware of Angiostrongylus vasorum and Oslerus osleri in dogs.
- Drugs – the concurrent us of chemotherapeutic medications can have a significant impact on the immune system. Many animals will have marked suppression of their white cell count, making them vulnerable to secondary bacterial infections.
- Chronic systemic illness – any long-term illness will make an animal more at risk from secondary diseases, including pneumonia.
- Laryngeal paralysis – be aware with older breeds such as Labradors, Retrievers, St. Bernards, Newfoundlands and English Setters.
- Neoplasia - respiratory tract tumours will always make an animal more likely to develop a focal pneumonia as a result of the diseased lung tissue.
- Megaoesophagus – this condition is usually idiopathic. It can be an acquired condition secondary to oesophagitis, Myasthenia gravis, Addison’s disease, toxins (e.g. lead, organophosphates, botulism and tetanus).
15 signs of pneumonia
Most animals with pneumonia present with one or more of the following signs, though quite often the signs can be very subtle and sometimes all you’ll notice is a mild fever.
- Pyrexia – a mild fever may often be the only signs that something is wrong.
- Inappetence – most patients with pneumonia feel unwell and will lose their of appetite.
- Exercise intolerance – owners may have noticed their pet no longer wanting to go for a walk.
- Chest congestion – careful auscultation will reveal wheezes, rales and crackles.
- Weight loss – at first you may not notice, but as the disease progresses, it becomes more apparent.
- Tachypnoea – owners may notice their pet developing rapid breathing.
- Hyperpnoea – look for an increased inspiratory effort.
- Dyspnoea – the animals may be in respiratory distress on inspiration and exhalation. They often have an anxious look.
- Cough – this may or may not be present. If it is, it’s usually soft, wet and productive.
- Nasal discharge – many animals with pneumonia wont produce any discharge, but if they do, it’s usually bilateral, thick, purulent and mucoid.
- Sneezing – if there’s a nasal discharge, you may notice some sneezing.
- Tachycardia – listen for a rapid regular heart.
- Depression – animals will feel unwell and weak and may stand or walk in an unusual way. Some will hold their head down and have a wide front leg stance to allow for the hyper and tachypnoea.
- Cyanosis – the compromised lung tissue and airways will prevent normal oxygen exchange in the lungs.
- Pain – look for pain associated with breathing movements.
Treatment and prognosis
Dogs with uncomplicated pneumonia generally have a good prognosis, with most cases of bacterial pneumonia being successfully treated. Acute-onset aspiration pneumonia accompanied by severe respiratory distress however can be fatal. If the underlying cause of the pneumonia is not identified and corrected, recurrence of the disease is likely. The treatment available for pneumonia depends a lot on the primary cause.
- Cage rest – never stress or overly exert an animal with pneumonia. They will be at significant risk of anoxia and death.
- Oxygen therapy - in the acute phase, oxygen supplementation using an oxygen mask or cage can help relieve some of the respiratory distress.
- Intravenous fluids - either with or without added electrolytes, can be given in cases with dehydration.
- Antibiotics - bacterial pneumonias are treated with antibiotics based upon the results of culture and sensitivity testing. Treatment with cephalosporins, gentamycin and ampicillin are often suitable. Drugs such as doxycycline and potentiated sulphonamides also achieve good penetration into the lung tissue.
- Bronchodilators – these help open the airways to aid breathing.
- Intensive care - nursing with appropriate nutrition and fluid therapy and chest percussion, steam inhalation and mucolytic agents will all contribute to a successful outcome.